source: draft-ietf-httpbis/latest/p2-semantics.xml @ 799

Last change on this file since 799 was 799, checked in by julian.reschke@…, 10 years ago

latest versions of rfc2629.xslt and xml2rfc.tcl, bump up document dates

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1<?xml version="1.0" encoding="utf-8"?>
2<?xml-stylesheet type='text/xsl' href='../myxml2rfc.xslt'?>
3<!DOCTYPE rfc [
4  <!ENTITY MAY "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MAY</bcp14>">
5  <!ENTITY MUST "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST</bcp14>">
6  <!ENTITY MUST-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST NOT</bcp14>">
7  <!ENTITY OPTIONAL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>OPTIONAL</bcp14>">
8  <!ENTITY RECOMMENDED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>RECOMMENDED</bcp14>">
9  <!ENTITY REQUIRED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>REQUIRED</bcp14>">
10  <!ENTITY SHALL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL</bcp14>">
11  <!ENTITY SHALL-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL NOT</bcp14>">
12  <!ENTITY SHOULD "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD</bcp14>">
13  <!ENTITY SHOULD-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD NOT</bcp14>">
14  <!ENTITY ID-VERSION "latest">
15  <!ENTITY ID-MONTH "April">
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 caching-combining-headers  "<xref target='Part6' x:rel='#combining.headers' 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 full-date                  "<xref target='Part1' x:rel='#date.time.formats.full.date' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
30  <!ENTITY http-url                   "<xref target='Part1' x:rel='#http-url' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
31  <!ENTITY http-version               "<xref target='Part1' x:rel='#http.version' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
32  <!ENTITY use100                     "<xref target='Part1' x:rel='#use.of.the.100.status' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
33  <!ENTITY qvalue                     "<xref target='Part3' x:rel='#quality.values' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
34  <!ENTITY header-accept              "<xref target='Part3' x:rel='#header.accept' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
35  <!ENTITY header-accept-charset      "<xref target='Part3' x:rel='#header.accept-charset' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
36  <!ENTITY header-accept-encoding     "<xref target='Part3' x:rel='#header.accept-encoding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
37  <!ENTITY header-accept-language     "<xref target='Part3' x:rel='#header.accept-language' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
38  <!ENTITY header-accept-ranges       "<xref target='Part5' x:rel='#header.accept-ranges' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
39  <!ENTITY header-age                 "<xref target='Part6' x:rel='#header.age' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
40  <!ENTITY header-authorization       "<xref target='Part7' x:rel='#header.authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
41  <!ENTITY header-cache-control       "<xref target='Part6' x:rel='#header.cache-control' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
42  <!ENTITY header-content-location    "<xref target='Part3' x:rel='#header.content-location' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
43  <!ENTITY header-content-range       "<xref target='Part5' x:rel='#header.content-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
44  <!ENTITY header-etag                "<xref target='Part4' x:rel='#header.etag' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
45  <!ENTITY header-expires             "<xref target='Part6' x:rel='#header.expires' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
46  <!ENTITY header-fields              "<xref target='Part1' x:rel='#header.fields' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
47  <!ENTITY header-host                "<xref target='Part1' x:rel='#header.host' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
48  <!ENTITY header-if-match            "<xref target='Part4' x:rel='#header.if-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
49  <!ENTITY header-if-modified-since   "<xref target='Part4' x:rel='#header.if-modified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
50  <!ENTITY header-if-none-match       "<xref target='Part4' x:rel='#header.if-none-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
51  <!ENTITY header-if-range            "<xref target='Part5' x:rel='#header.if-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
52  <!ENTITY header-if-unmodified-since "<xref target='Part4' x:rel='#header.if-unmodified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
53  <!ENTITY header-pragma              "<xref target='Part6' x:rel='#header.pragma' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
54  <!ENTITY header-proxy-authenticate  "<xref target='Part7' x:rel='#header.proxy-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
55  <!ENTITY header-proxy-authorization "<xref target='Part7' x:rel='#header.proxy-authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
56  <!ENTITY header-range               "<xref target='Part5' x:rel='#header.range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
57  <!ENTITY header-upgrade             "<xref target='Part5' x:rel='#header.range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
58  <!ENTITY header-te                  "<xref target='Part1' x:rel='#header.upgrade' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
59  <!ENTITY header-vary                "<xref target='Part6' x:rel='#header.vary' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
60  <!ENTITY header-via                 "<xref target='Part1' x:rel='#header.via' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
61  <!ENTITY header-warning             "<xref target='Part6' x:rel='#header.warning' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
62  <!ENTITY header-www-authenticate    "<xref target='Part7' x:rel='#header.www-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
63  <!ENTITY message-body               "<xref target='Part1' x:rel='#message.body' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
64  <!ENTITY product-tokens             "<xref target='Part1' x:rel='#product.tokens' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
65  <!ENTITY media-type-message-http    "<xref target='Part1' x:rel='#internet.media.type.message.http' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
66  <!ENTITY status-206                 "<xref target='Part5' x:rel='#status.206' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
67  <!ENTITY status-304                 "<xref target='Part4' x:rel='#status.304' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
68  <!ENTITY status-401                 "<xref target='Part7' x:rel='#status.401' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
69  <!ENTITY status-407                 "<xref target='Part7' x:rel='#status.407' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
70  <!ENTITY status-412                 "<xref target='Part4' x:rel='#status.412' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
71  <!ENTITY status-416                 "<xref target='Part5' x:rel='#status.416' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
72]>
73<?rfc toc="yes" ?>
74<?rfc symrefs="yes" ?>
75<?rfc sortrefs="yes" ?>
76<?rfc compact="yes"?>
77<?rfc subcompact="no" ?>
78<?rfc linkmailto="no" ?>
79<?rfc editing="no" ?>
80<?rfc comments="yes"?>
81<?rfc inline="yes"?>
82<?rfc rfcedstyle="yes"?>
83<?rfc-ext allow-markup-in-artwork="yes" ?>
84<?rfc-ext include-references-in-index="yes" ?>
85<rfc obsoletes="2616" updates="2817" category="std" x:maturity-level="draft"
86     ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"
87     xmlns:x='http://purl.org/net/xml2rfc/ext'
88     xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#'>
89<front>
90
91  <title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
92
93  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
94    <organization abbrev="Day Software">Day Software</organization>
95    <address>
96      <postal>
97        <street>23 Corporate Plaza DR, Suite 280</street>
98        <city>Newport Beach</city>
99        <region>CA</region>
100        <code>92660</code>
101        <country>USA</country>
102      </postal>
103      <phone>+1-949-706-5300</phone>
104      <facsimile>+1-949-706-5305</facsimile>
105      <email>fielding@gbiv.com</email>
106      <uri>http://roy.gbiv.com/</uri>
107    </address>
108  </author>
109
110  <author initials="J." surname="Gettys" fullname="Jim Gettys">
111    <organization>One Laptop per Child</organization>
112    <address>
113      <postal>
114        <street>21 Oak Knoll Road</street>
115        <city>Carlisle</city>
116        <region>MA</region>
117        <code>01741</code>
118        <country>USA</country>
119      </postal>
120      <email>jg@laptop.org</email>
121      <uri>http://www.laptop.org/</uri>
122    </address>
123  </author>
124 
125  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
126    <organization abbrev="HP">Hewlett-Packard Company</organization>
127    <address>
128      <postal>
129        <street>HP Labs, Large Scale Systems Group</street>
130        <street>1501 Page Mill Road, MS 1177</street>
131        <city>Palo Alto</city>
132        <region>CA</region>
133        <code>94304</code>
134        <country>USA</country>
135      </postal>
136      <email>JeffMogul@acm.org</email>
137    </address>
138  </author>
139
140  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
141    <organization abbrev="Microsoft">Microsoft Corporation</organization>
142    <address>
143      <postal>
144        <street>1 Microsoft Way</street>
145        <city>Redmond</city>
146        <region>WA</region>
147        <code>98052</code>
148        <country>USA</country>
149      </postal>
150      <email>henrikn@microsoft.com</email>
151    </address>
152  </author>
153
154  <author initials="L." surname="Masinter" fullname="Larry Masinter">
155    <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
156    <address>
157      <postal>
158        <street>345 Park Ave</street>
159        <city>San Jose</city>
160        <region>CA</region>
161        <code>95110</code>
162        <country>USA</country>
163      </postal>
164      <email>LMM@acm.org</email>
165      <uri>http://larry.masinter.net/</uri>
166    </address>
167  </author>
168 
169  <author initials="P." surname="Leach" fullname="Paul J. Leach">
170    <organization abbrev="Microsoft">Microsoft Corporation</organization>
171    <address>
172      <postal>
173        <street>1 Microsoft Way</street>
174        <city>Redmond</city>
175        <region>WA</region>
176        <code>98052</code>
177      </postal>
178      <email>paulle@microsoft.com</email>
179    </address>
180  </author>
181   
182  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
183    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
184    <address>
185      <postal>
186        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
187        <street>The Stata Center, Building 32</street>
188        <street>32 Vassar Street</street>
189        <city>Cambridge</city>
190        <region>MA</region>
191        <code>02139</code>
192        <country>USA</country>
193      </postal>
194      <email>timbl@w3.org</email>
195      <uri>http://www.w3.org/People/Berners-Lee/</uri>
196    </address>
197  </author>
198
199  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
200    <organization abbrev="W3C">World Wide Web Consortium</organization>
201    <address>
202      <postal>
203        <street>W3C / ERCIM</street>
204        <street>2004, rte des Lucioles</street>
205        <city>Sophia-Antipolis</city>
206        <region>AM</region>
207        <code>06902</code>
208        <country>France</country>
209      </postal>
210      <email>ylafon@w3.org</email>
211      <uri>http://www.raubacapeu.net/people/yves/</uri>
212    </address>
213  </author>
214
215  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
216    <organization abbrev="greenbytes">greenbytes GmbH</organization>
217    <address>
218      <postal>
219        <street>Hafenweg 16</street>
220        <city>Muenster</city><region>NW</region><code>48155</code>
221        <country>Germany</country>
222      </postal>
223      <phone>+49 251 2807760</phone>
224      <facsimile>+49 251 2807761</facsimile>
225      <email>julian.reschke@greenbytes.de</email>
226      <uri>http://greenbytes.de/tech/webdav/</uri>
227    </address>
228  </author>
229
230  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
231  <workgroup>HTTPbis Working Group</workgroup>
232
233<abstract>
234<t>
235   The Hypertext Transfer Protocol (HTTP) is an application-level
236   protocol for distributed, collaborative, hypermedia information
237   systems. HTTP has been in use by the World Wide Web global information
238   initiative since 1990. This document is Part 2 of the seven-part specification
239   that defines the protocol referred to as "HTTP/1.1" and, taken together,
240   obsoletes RFC 2616.  Part 2 defines the semantics of HTTP messages
241   as expressed by request methods, request-header fields, response status codes,
242   and response-header fields.
243</t>
244</abstract>
245
246<note title="Editorial Note (To be removed by RFC Editor)">
247  <t>
248    Discussion of this draft should take place on the HTTPBIS working group
249    mailing list (ietf-http-wg@w3.org). The current issues list is
250    at <eref target="http://tools.ietf.org/wg/httpbis/trac/report/11"/>
251    and related documents (including fancy diffs) can be found at
252    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
253  </t>
254  <t>
255    The changes in this draft are summarized in <xref target="changes.since.09"/>.
256  </t>
257</note>
258</front>
259<middle>
260<section title="Introduction" anchor="introduction">
261<t>
262   This document defines HTTP/1.1 request and response semantics.  Each HTTP
263   message, as defined in &messaging;, is in the form of either a request or
264   a response.  An HTTP server listens on a connection for HTTP requests and
265   responds to each request, in the order received on that connection, with
266   one or more HTTP response messages.  This document defines the commonly
267   agreed upon semantics of the HTTP uniform interface, the intentions defined
268   by each request method, and the various response messages that might be
269   expected as a result of applying that method for the requested resource.
270</t>
271<t>
272   This document is currently disorganized in order to minimize the changes
273   between drafts and enable reviewers to see the smaller errata changes.
274   The next draft will reorganize the sections to better reflect the content.
275   In particular, the sections will be ordered according to the typical
276   processing of an HTTP request message (after message parsing): resource
277   mapping, general header fields, methods, request modifiers, response
278   status, and resource metadata.  The current mess reflects how widely
279   dispersed these topics and associated requirements had become in
280   <xref target="RFC2616"/>.
281</t>
282
283<section title="Requirements" anchor="intro.requirements">
284<t>
285   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
286   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
287   document are to be interpreted as described in <xref target="RFC2119"/>.
288</t>
289<t>
290   An implementation is not compliant if it fails to satisfy one or more
291   of the &MUST; or &REQUIRED; level requirements for the protocols it
292   implements. An implementation that satisfies all the &MUST; or &REQUIRED;
293   level and all the &SHOULD; level requirements for its protocols is said
294   to be "unconditionally compliant"; one that satisfies all the &MUST;
295   level requirements but not all the &SHOULD; level requirements for its
296   protocols is said to be "conditionally compliant."
297</t>
298</section>
299
300<section title="Syntax Notation" anchor="notation">
301  <x:anchor-alias value="CR"/>
302  <x:anchor-alias value="DIGIT"/>
303  <x:anchor-alias value="LF"/>
304  <x:anchor-alias value="VCHAR"/>
305  <x:anchor-alias value="WSP"/>
306<t>
307  This specification uses the ABNF syntax defined in &notation; (which
308  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
309  <xref target="collected.abnf"/> shows the collected ABNF, with the list
310  rule expanded.
311</t>
312<t>
313  The following core rules are included by
314  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
315  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
316  DIGIT (decimal 0-9), DQUOTE (double quote),
317  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
318  OCTET (any 8-bit sequence of data), SP (space),
319  VCHAR (any visible USASCII character),
320  and WSP (whitespace).
321</t>
322
323<section title="Core Rules" anchor="core.rules">
324  <x:anchor-alias value="obs-text"/>
325  <x:anchor-alias value="quoted-string"/>
326  <x:anchor-alias value="token"/>
327  <x:anchor-alias value="OWS"/>
328  <x:anchor-alias value="RWS"/>
329<t>
330  The core rules below are defined in &basic-rules;:
331</t>
332<figure><artwork type="abnf2616">
333  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &basic-rules;&gt;
334  <x:ref>token</x:ref>         = &lt;token, defined in &basic-rules;&gt;
335  <x:ref>OWS</x:ref>           = &lt;OWS, defined in &basic-rules;&gt;
336  <x:ref>RWS</x:ref>           = &lt;RWS, defined in &basic-rules;&gt;
337  <x:ref>obs-text</x:ref>      = &lt;obs-text, defined in &basic-rules;&gt;
338</artwork></figure>
339</section>
340
341<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
342  <x:anchor-alias value="absolute-URI"/>
343  <x:anchor-alias value="Accept"/>
344  <x:anchor-alias value="Accept-Charset"/>
345  <x:anchor-alias value="Accept-Encoding"/>
346  <x:anchor-alias value="Accept-Language"/>
347  <x:anchor-alias value="Accept-Ranges"/>
348  <x:anchor-alias value="Age"/>
349  <x:anchor-alias value="Authorization"/>
350  <x:anchor-alias value="comment"/>
351  <x:anchor-alias value="ETag"/>
352  <x:anchor-alias value="Host"/>
353  <x:anchor-alias value="HTTP-date"/>
354  <x:anchor-alias value="If-Match"/>
355  <x:anchor-alias value="If-Modified-Since"/>
356  <x:anchor-alias value="If-None-Match"/>
357  <x:anchor-alias value="If-Range"/>
358  <x:anchor-alias value="If-Unmodified-Since"/>
359  <x:anchor-alias value="partial-URI"/>
360  <x:anchor-alias value="product"/>
361  <x:anchor-alias value="Proxy-Authenticate"/>
362  <x:anchor-alias value="Proxy-Authorization"/>
363  <x:anchor-alias value="Range"/>
364  <x:anchor-alias value="TE"/>
365  <x:anchor-alias value="URI-reference"/>
366  <x:anchor-alias value="Vary"/>
367  <x:anchor-alias value="WWW-Authenticate"/>
368<t>
369  The ABNF rules below are defined in other parts:
370</t>
371<figure><!--Part1--><artwork type="abnf2616">
372  <x:ref>absolute-URI</x:ref>  = &lt;absolute-URI, defined in &uri;&gt;
373  <x:ref>comment</x:ref>       = &lt;comment, defined in &header-fields;&gt;
374  <x:ref>Host</x:ref>          = &lt;Host, defined in &uri;&gt;
375  <x:ref>HTTP-date</x:ref>     = &lt;HTTP-date, defined in &full-date;&gt;
376  <x:ref>partial-URI</x:ref>   = &lt;partial-URI, defined in &uri;&gt;
377  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
378  <x:ref>TE</x:ref>            = &lt;TE, defined in &header-te;&gt;
379  <x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in &uri;&gt;
380</artwork></figure>
381<figure><!--Part3--><artwork type="abnf2616">
382  <x:ref>Accept</x:ref>        = &lt;Accept, defined in &header-accept;&gt;
383  <x:ref>Accept-Charset</x:ref> =
384             &lt;Accept-Charset, defined in &header-accept-charset;&gt;
385  <x:ref>Accept-Encoding</x:ref> =
386             &lt;Accept-Encoding, defined in &header-accept-encoding;&gt;
387  <x:ref>Accept-Language</x:ref> =
388             &lt;Accept-Language, defined in &header-accept-language;&gt;
389</artwork></figure>
390<figure><!--Part4--><artwork type="abnf2616">
391  <x:ref>ETag</x:ref>          = &lt;ETag, defined in &header-etag;&gt;
392  <x:ref>If-Match</x:ref>      = &lt;If-Match, defined in &header-if-match;&gt;
393  <x:ref>If-Modified-Since</x:ref> =
394             &lt;If-Modified-Since, defined in &header-if-modified-since;&gt;
395  <x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in &header-if-none-match;&gt;
396  <x:ref>If-Unmodified-Since</x:ref> =
397             &lt;If-Unmodified-Since, defined in &header-if-unmodified-since;&gt;
398</artwork></figure>
399<figure><!--Part5--><artwork type="abnf2616">
400  <x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in &header-accept-ranges;&gt;
401  <x:ref>If-Range</x:ref>      = &lt;If-Range, defined in &header-if-range;&gt;
402  <x:ref>Range</x:ref>         = &lt;Range, defined in &header-range;&gt;
403</artwork></figure>
404<figure><!--Part6--><artwork type="abnf2616">
405  <x:ref>Age</x:ref>           = &lt;Age, defined in &header-age;&gt;
406  <x:ref>Vary</x:ref>          = &lt;Vary, defined in &header-vary;&gt;
407</artwork><!--Part7--></figure>
408<figure><artwork type="abnf2616">
409  <x:ref>Authorization</x:ref> = &lt;Authorization, defined in &header-authorization;&gt;
410  <x:ref>Proxy-Authenticate</x:ref> =
411             &lt;Proxy-Authenticate, defined in &header-proxy-authenticate;&gt;
412  <x:ref>Proxy-Authorization</x:ref> =
413             &lt;Proxy-Authorization, defined in &header-proxy-authorization;&gt;
414  <x:ref>WWW-Authenticate</x:ref> =
415             &lt;WWW-Authenticate, defined in &header-www-authenticate;&gt;
416</artwork></figure>
417</section>
418</section>
419</section>
420
421<section title="Method" anchor="method">
422  <x:anchor-alias value="Method"/>
423  <x:anchor-alias value="extension-method"/>
424<t>
425   The Method  token indicates the method to be performed on the
426   resource identified by the request-target. The method is case-sensitive.
427</t>
428<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/><iref primary="true" item="Grammar" subitem="extension-method"/>
429  <x:ref>Method</x:ref>         = <x:abnf-char-sequence>"OPTIONS"</x:abnf-char-sequence>   ; "OPTIONS", <xref target="OPTIONS"/>
430                 / <x:abnf-char-sequence>"GET"</x:abnf-char-sequence>               ; "GET", <xref target="GET"/>
431                 / <x:abnf-char-sequence>"HEAD"</x:abnf-char-sequence>            ; "HEAD", <xref target="HEAD"/>
432                 / <x:abnf-char-sequence>"POST"</x:abnf-char-sequence>            ; "POST", <xref target="POST"/>
433                 / <x:abnf-char-sequence>"PUT"</x:abnf-char-sequence>               ; "PUT", <xref target="PUT"/>
434                 / <x:abnf-char-sequence>"DELETE"</x:abnf-char-sequence>      ; "DELETE", <xref target="DELETE"/>
435                 / <x:abnf-char-sequence>"TRACE"</x:abnf-char-sequence>         ; "TRACE", <xref target="TRACE"/>
436                 / <x:abnf-char-sequence>"CONNECT"</x:abnf-char-sequence>   ; "CONNECT", <xref target="CONNECT"/>
437                 / <x:ref>extension-method</x:ref>
438  <x:ref>extension-method</x:ref> = <x:ref>token</x:ref>
439</artwork></figure>
440<t>
441   The list of methods allowed by a resource can be specified in an
442   Allow header field (<xref target="header.allow"/>). The return code of the response
443   always notifies the client whether a method is currently allowed on a
444   resource, since the set of allowed methods can change dynamically. An
445   origin server &SHOULD; return the status code 405 (Method Not Allowed)
446   if the method is known by the origin server but not allowed for the
447   requested resource, and 501 (Not Implemented) if the method is
448   unrecognized or not implemented by the origin server. The methods GET
449   and HEAD &MUST; be supported by all general-purpose servers. All other
450   methods are &OPTIONAL;; however, if the above methods are implemented,
451   they &MUST; be implemented with the same semantics as those specified
452   in <xref target="method.definitions"/>.
453</t>
454
455<section title="Method Registry" anchor="method.registry">
456<t>
457  The HTTP Method Registry defines the name space for the Method token in the
458  Request line of an HTTP request.
459</t>
460<t>
461  Registrations &MUST; include the following fields:
462  <list style="symbols">
463    <t>Method Name (see <xref target="method"/>)</t>
464    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
465    <t>Pointer to specification text</t>
466  </list>
467</t>
468<t>
469  Values to be added to this name space are subject to IETF review
470  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
471</t>
472<t>
473  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-methods"/>.
474</t>
475</section>
476</section>
477
478<section title="Request Header Fields" anchor="request.header.fields">
479  <x:anchor-alias value="request-header"/>
480<t>
481   The request-header fields allow the client to pass additional
482   information about the request, and about the client itself, to the
483   server. These fields act as request modifiers, with semantics
484   equivalent to the parameters on a programming language method
485   invocation.
486</t>
487<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="request-header"/>
488  <x:ref>request-header</x:ref> = <x:ref>Accept</x:ref>                   ; &header-accept;
489                 / <x:ref>Accept-Charset</x:ref>           ; &header-accept-charset;
490                 / <x:ref>Accept-Encoding</x:ref>          ; &header-accept-encoding;
491                 / <x:ref>Accept-Language</x:ref>          ; &header-accept-language;
492                 / <x:ref>Authorization</x:ref>            ; &header-authorization;
493                 / <x:ref>Expect</x:ref>                   ; <xref target="header.expect"/>
494                 / <x:ref>From</x:ref>                     ; <xref target="header.from"/>
495                 / <x:ref>Host</x:ref>                     ; &header-host;
496                 / <x:ref>If-Match</x:ref>                 ; &header-if-match;
497                 / <x:ref>If-Modified-Since</x:ref>        ; &header-if-modified-since;
498                 / <x:ref>If-None-Match</x:ref>            ; &header-if-none-match;
499                 / <x:ref>If-Range</x:ref>                 ; &header-if-range;
500                 / <x:ref>If-Unmodified-Since</x:ref>      ; &header-if-unmodified-since;
501                 / <x:ref>Max-Forwards</x:ref>             ; <xref target="header.max-forwards"/>
502                 / <x:ref>Proxy-Authorization</x:ref>      ; &header-proxy-authorization;
503                 / <x:ref>Range</x:ref>                    ; &header-range;
504                 / <x:ref>Referer</x:ref>                  ; <xref target="header.referer"/>
505                 / <x:ref>TE</x:ref>                       ; &header-te;
506                 / <x:ref>User-Agent</x:ref>               ; <xref target="header.user-agent"/>
507</artwork></figure>
508<t>
509   Request-header field names can be extended reliably only in
510   combination with a change in the protocol version. However, new or
511   experimental header fields &MAY; be given the semantics of request-header
512   fields if all parties in the communication recognize them to
513   be request-header fields. Unrecognized header fields are treated as
514   entity-header fields.
515</t>
516</section>
517
518<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
519  <x:anchor-alias value="Reason-Phrase"/>
520  <x:anchor-alias value="Status-Code"/>
521  <x:anchor-alias value="extension-code"/>
522<t>
523   The Status-Code element is a 3-digit integer result code of the
524   attempt to understand and satisfy the request. The status codes listed
525   below are defined in <xref target="status.codes"/>.
526   The Reason-Phrase is intended to give a short
527   textual description of the Status-Code. The Status-Code is intended
528   for use by automata and the Reason-Phrase is intended for the human
529   user. The client is not required to examine or display the Reason-Phrase.
530</t>
531<t> 
532   The individual values of the numeric status codes defined for
533   HTTP/1.1, and an example set of corresponding Reason-Phrase values, are
534   presented below. The reason phrases listed here are only
535   recommendations -- they &MAY; be replaced by local equivalents without
536   affecting the protocol.
537</t>
538<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"/>
539  <x:ref>Status-Code</x:ref>    =
540         "100"  ; <xref target="status.100"/>: Continue
541       / "101"  ; <xref target="status.101"/>: Switching Protocols
542       / "200"  ; <xref target="status.200"/>: OK
543       / "201"  ; <xref target="status.201"/>: Created
544       / "202"  ; <xref target="status.202"/>: Accepted
545       / "203"  ; <xref target="status.203"/>: Non-Authoritative Information
546       / "204"  ; <xref target="status.204"/>: No Content
547       / "205"  ; <xref target="status.205"/>: Reset Content
548       / "206"  ; &status-206;: Partial Content
549       / "300"  ; <xref target="status.300"/>: Multiple Choices
550       / "301"  ; <xref target="status.301"/>: Moved Permanently
551       / "302"  ; <xref target="status.302"/>: Found
552       / "303"  ; <xref target="status.303"/>: See Other
553       / "304"  ; &status-304;: Not Modified
554       / "305"  ; <xref target="status.305"/>: Use Proxy
555       / "307"  ; <xref target="status.307"/>: Temporary Redirect
556       / "400"  ; <xref target="status.400"/>: Bad Request
557       / "401"  ; &status-401;: Unauthorized
558       / "402"  ; <xref target="status.402"/>: Payment Required
559       / "403"  ; <xref target="status.403"/>: Forbidden
560       / "404"  ; <xref target="status.404"/>: Not Found
561       / "405"  ; <xref target="status.405"/>: Method Not Allowed
562       / "406"  ; <xref target="status.406"/>: Not Acceptable
563       / "407"  ; &status-407;: Proxy Authentication Required
564       / "408"  ; <xref target="status.408"/>: Request Time-out
565       / "409"  ; <xref target="status.409"/>: Conflict
566       / "410"  ; <xref target="status.410"/>: Gone
567       / "411"  ; <xref target="status.411"/>: Length Required
568       / "412"  ; &status-412;: Precondition Failed
569       / "413"  ; <xref target="status.413"/>: Request Entity Too Large
570       / "414"  ; <xref target="status.414"/>: URI Too Long
571       / "415"  ; <xref target="status.415"/>: Unsupported Media Type
572       / "416"  ; status-416;: Requested range not satisfiable
573       / "417"  ; <xref target="status.417"/>: Expectation Failed
574       / "500"  ; <xref target="status.500"/>: Internal Server Error
575       / "501"  ; <xref target="status.501"/>: Not Implemented
576       / "502"  ; <xref target="status.502"/>: Bad Gateway
577       / "503"  ; <xref target="status.503"/>: Service Unavailable
578       / "504"  ; <xref target="status.504"/>: Gateway Time-out
579       / "505"  ; <xref target="status.505"/>: HTTP Version not supported
580       / <x:ref>extension-code</x:ref>
581
582  <x:ref>extension-code</x:ref> = 3<x:ref>DIGIT</x:ref>
583  <x:ref>Reason-Phrase</x:ref>  = *( <x:ref>WSP</x:ref> / <x:ref>VCHAR</x:ref> / <x:ref>obs-text</x:ref> )
584</artwork></figure>
585<t>
586   HTTP status codes are extensible. HTTP applications are not required
587   to understand the meaning of all registered status codes, though such
588   understanding is obviously desirable. However, applications &MUST;
589   understand the class of any status code, as indicated by the first
590   digit, and treat any unrecognized response as being equivalent to the
591   x00 status code of that class, with the exception that an
592   unrecognized response &MUST-NOT; be cached. For example, if an
593   unrecognized status code of 431 is received by the client, it can
594   safely assume that there was something wrong with its request and
595   treat the response as if it had received a 400 status code. In such
596   cases, user agents &SHOULD; present to the user the entity returned
597   with the response, since that entity is likely to include human-readable
598   information which will explain the unusual status.
599</t>
600
601<section title="Status Code Registry" anchor="status.code.registry">
602<t>
603  The HTTP Status Code Registry defines the name space for the Status-Code
604  token in the Status line of an HTTP response.
605</t>
606<t>
607  Values to be added to this name space are subject to IETF review
608  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
609</t>
610<t>
611  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
612</t>
613</section>
614
615</section>
616
617<section title="Response Header Fields" anchor="response.header.fields">
618  <x:anchor-alias value="response-header"/>
619<t>
620   The response-header fields allow the server to pass additional
621   information about the response which cannot be placed in the Status-Line.
622   These header fields give information about the server and about
623   further access to the resource identified by the request-target.
624</t>
625<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="response-header"/>
626  <x:ref>response-header</x:ref> = <x:ref>Accept-Ranges</x:ref>           ; &header-accept-ranges;
627                  / <x:ref>Age</x:ref>                     ; &header-age;
628                  / <x:ref>Allow</x:ref>                   ; <xref target="header.allow"/>
629                  / <x:ref>ETag</x:ref>                    ; &header-etag;
630                  / <x:ref>Location</x:ref>                ; <xref target="header.location"/>
631                  / <x:ref>Proxy-Authenticate</x:ref>      ; &header-proxy-authenticate;
632                  / <x:ref>Retry-After</x:ref>             ; <xref target="header.retry-after"/>
633                  / <x:ref>Server</x:ref>                  ; <xref target="header.server"/>
634                  / <x:ref>Vary</x:ref>                    ; &header-vary;
635                  / <x:ref>WWW-Authenticate</x:ref>        ; &header-www-authenticate;
636</artwork></figure>
637<t>
638   Response-header field names can be extended reliably only in
639   combination with a change in the protocol version. However, new or
640   experimental header fields &MAY; be given the semantics of response-header
641   fields if all parties in the communication recognize them to
642   be response-header fields. Unrecognized header fields are treated as
643   entity-header fields.
644</t>
645</section>
646
647<section title="Entity" anchor="entity">
648<t>
649   Request and Response messages &MAY; transfer an entity if not otherwise
650   restricted by the request method or response status code. An entity
651   consists of entity-header fields and an entity-body, although some
652   responses will only include the entity-headers. HTTP entity-body and
653   entity-header fields are defined in &payload;.
654</t>
655<t>
656   An entity-body is only present in a message when a message-body is
657   present, as described in &message-body;. The entity-body is obtained
658   from the message-body by decoding any Transfer-Encoding that might
659   have been applied to ensure safe and proper transfer of the message.
660</t>
661
662<section title="Identifying the Resource Associated with a Representation" anchor="identifying.response.associated.with.representation">
663<t>
664   It is sometimes necessary to determine the identity of the resource
665   associated with a representation.
666</t>
667<t>
668   An HTTP request representation, when present, is always associated with an
669   anonymous (i.e., unidentified) resource.
670</t>
671<t>
672   In the common case, an HTTP response is a representation of the resource
673   located at the request-URI. However, this is not always the case. To
674   determine the URI of the resource a response is associated with, the
675   following rules are used (with the first applicable one being selected):
676</t>
677<t><list style="numbers">
678   <t>If the response status code is 200 or 203 and the request method was GET,
679   the response is a representation of the resource at the request-URI.</t>
680   <t>If the response status is 204, 206, or 304 and the request method was GET
681   or HEAD, the response is a partial representation of the resource at the
682   request-URI (see &caching-combining-headers;).</t>
683   <t>If the response has a Content-Location header, and that URI is the same
684   as the request-URI <cref anchor="TODO-missref-requri">(see [ref])</cref>, the response is a representation of the
685   resource at the request-URI.</t>
686   <t>If the response has a Content-Location header, and that URI is not the
687   same as the request-URI, the response asserts that it is a representation of
688   the resource at the Content-Location URI (but it may not be).</t>
689   <t>Otherwise, the response is a representation of an anonymous (i.e.,
690   unidentified) resource.</t>
691</list></t>
692<t>
693  <cref anchor="TODO-req-uri">
694   Note that "request-URI" is used here; however, we need to come up with a
695   term to denote "the URI that can be inferred from examining the
696   request-target and the Host header." (see <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196" />).
697   Also, the comparison function is going to have to be defined somewhere,
698   because we already need to compare URIs for things like cache invalidation.</cref>
699</t>
700</section>
701
702</section>
703
704
705<section title="Method Definitions" anchor="method.definitions">
706<t>
707   The set of common methods for HTTP/1.1 is defined below. Although
708   this set can be expanded, additional methods cannot be assumed to
709   share the same semantics for separately extended clients and servers.
710</t>
711
712<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
713
714<section title="Safe Methods" anchor="safe.methods">
715<iref item="Safe Methods" primary="true"/>
716<t>
717   Implementors should be aware that the software represents the user in
718   their interactions over the Internet, and should be careful to allow
719   the user to be aware of any actions they might take which may have an
720   unexpected significance to themselves or others.
721</t>
722<t>
723   In particular, the convention has been established that the GET, HEAD,
724   OPTIONS, and TRACE methods &SHOULD-NOT;  have the significance of taking an action
725   other than retrieval. These methods ought to be considered "<x:dfn anchor="safe">safe</x:dfn>".
726   This allows user agents to represent other methods, such as POST, PUT
727   and DELETE, in a special way, so that the user is made aware of the
728   fact that a possibly unsafe action is being requested.
729</t>
730<t>
731   Naturally, it is not possible to ensure that the server does not
732   generate side-effects as a result of performing a GET request; in
733   fact, some dynamic resources consider that a feature. The important
734   distinction here is that the user did not request the side-effects,
735   so therefore cannot be held accountable for them.
736</t>
737</section>
738
739<section title="Idempotent Methods" anchor="idempotent.methods">
740<iref item="Idempotent Methods" primary="true"/>
741<t>
742   Methods can also have the property of "idempotence" in that, aside
743   from error or expiration issues, the intended effect of multiple
744   identical requests is the same as for a single request.
745   The methods PUT, DELETE, and all safe methods are idempotent.
746   It is important to note that idempotence refers only to changes
747   requested by the client: a server is free to change its state due
748   to multiple requests for the purpose of tracking those requests,
749   versioning of results, etc.
750</t>
751</section>
752</section>
753
754<section title="OPTIONS" anchor="OPTIONS">
755  <rdf:Description>
756    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
757  </rdf:Description>
758  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
759  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
760<t>
761   The OPTIONS method represents a request for information about the
762   communication options available on the request/response chain
763   identified by the request-target. This method allows the client to
764   determine the options and/or requirements associated with a resource,
765   or the capabilities of a server, without implying a resource action
766   or initiating a resource retrieval.
767</t>
768<t>
769   Responses to this method are not cacheable.
770</t>
771<t>
772   If the OPTIONS request includes an entity-body (as indicated by the
773   presence of Content-Length or Transfer-Encoding), then the media type
774   &MUST; be indicated by a Content-Type field. Although this
775   specification does not define any use for such a body, future
776   extensions to HTTP might use the OPTIONS body to make more detailed
777   queries on the server.
778</t>
779<t>
780   If the request-target is an asterisk ("*"), the OPTIONS request is
781   intended to apply to the server in general rather than to a specific
782   resource. Since a server's communication options typically depend on
783   the resource, the "*" request is only useful as a "ping" or "no-op"
784   type of method; it does nothing beyond allowing the client to test
785   the capabilities of the server. For example, this can be used to test
786   a proxy for HTTP/1.1 compliance (or lack thereof).
787</t>
788<t>
789   If the request-target is not an asterisk, the OPTIONS request applies
790   only to the options that are available when communicating with that
791   resource.
792</t>
793<t>
794   A 200 response &SHOULD; include any header fields that indicate
795   optional features implemented by the server and applicable to that
796   resource (e.g., Allow), possibly including extensions not defined by
797   this specification. The response body, if any, &SHOULD; also include
798   information about the communication options. The format for such a
799   body is not defined by this specification, but might be defined by
800   future extensions to HTTP. Content negotiation &MAY; be used to select
801   the appropriate response format. If no response body is included, the
802   response &MUST; include a Content-Length field with a field-value of
803   "0".
804</t>
805<t>
806   The Max-Forwards request-header field &MAY; be used to target a
807   specific proxy in the request chain. When a proxy receives an OPTIONS
808   request on an absolute-URI for which request forwarding is permitted,
809   the proxy &MUST; check for a Max-Forwards field. If the Max-Forwards
810   field-value is zero ("0"), the proxy &MUST-NOT; forward the message;
811   instead, the proxy &SHOULD; respond with its own communication options.
812   If the Max-Forwards field-value is an integer greater than zero, the
813   proxy &MUST; decrement the field-value when it forwards the request. If
814   no Max-Forwards field is present in the request, then the forwarded
815   request &MUST-NOT; include a Max-Forwards field.
816</t>
817</section>
818
819<section title="GET" anchor="GET">
820  <rdf:Description>
821    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
822  </rdf:Description>
823  <iref primary="true" item="GET method" x:for-anchor=""/>
824  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
825<t>
826   The GET method means retrieve whatever information (in the form of an
827   entity) currently corresponds to the resource identified by the
828   request-target.
829</t>
830<t>   
831   If the request-target identifies a data-producing process, it is the
832   produced data which shall be returned as the entity in the response and not
833   the source text of the process, unless that text happens to be the output of
834   the process.
835</t>
836<t>
837   The semantics of the GET method change to a "conditional GET" if the
838   request message includes an If-Modified-Since, If-Unmodified-Since,
839   If-Match, If-None-Match, or If-Range header field. A conditional GET
840   method requests that the entity be transferred only under the
841   circumstances described by the conditional header field(s). The
842   conditional GET method is intended to reduce unnecessary network
843   usage by allowing cached entities to be refreshed without requiring
844   multiple requests or transferring data already held by the client.
845</t>
846<t>
847   The semantics of the GET method change to a "partial GET" if the
848   request message includes a Range header field. A partial GET requests
849   that only part of the entity be transferred, as described in &header-range;.
850   The partial GET method is intended to reduce unnecessary
851   network usage by allowing partially-retrieved entities to be
852   completed without transferring data already held by the client.
853</t>
854<t>
855   The response to a GET request is cacheable if and only if it meets
856   the requirements for HTTP caching described in &caching;.
857</t>
858<t>
859   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
860</t>
861</section>
862
863<section title="HEAD" anchor="HEAD">
864  <rdf:Description>
865    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
866  </rdf:Description>
867  <iref primary="true" item="HEAD method" x:for-anchor=""/>
868  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
869<t>
870   The HEAD method is identical to GET except that the server &MUST-NOT;
871   return a message-body in the response. The metainformation contained
872   in the HTTP headers in response to a HEAD request &SHOULD; be identical
873   to the information sent in response to a GET request. This method can
874   be used for obtaining metainformation about the entity implied by the
875   request without transferring the entity-body itself. This method is
876   often used for testing hypertext links for validity, accessibility,
877   and recent modification.
878</t>
879<t>
880   The response to a HEAD request &MAY; be cacheable in the sense that the
881   information contained in the response &MAY; be used to update a
882   previously cached entity from that resource. If the new field values
883   indicate that the cached entity differs from the current entity (as
884   would be indicated by a change in Content-Length, Content-MD5, ETag
885   or Last-Modified), then the cache &MUST; treat the cache entry as
886   stale.
887</t>
888</section>
889
890<section title="POST" anchor="POST">
891  <iref primary="true" item="POST method" x:for-anchor=""/>
892  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
893<t>
894   The POST method is used to request that the origin server accept the
895   entity enclosed in the request as data to be processed by the resource
896   identified by the request-target in the Request-Line. POST is designed
897   to allow a uniform method to cover the following functions:
898  <list style="symbols">
899    <t>
900      Annotation of existing resources;
901    </t>
902    <t>
903        Posting a message to a bulletin board, newsgroup, mailing list,
904        or similar group of articles;
905    </t>
906    <t>
907        Providing a block of data, such as the result of submitting a
908        form, to a data-handling process;
909    </t>
910    <t>
911        Extending a database through an append operation.
912    </t>
913  </list>
914</t>
915<t>
916   The actual function performed by the POST method is determined by the
917   server and is usually dependent on the request-target.
918</t>
919<t>
920   The action performed by the POST method might not result in a
921   resource that can be identified by a URI. In this case, either 200
922   (OK) or 204 (No Content) is the appropriate response status,
923   depending on whether or not the response includes an entity that
924   describes the result.
925</t>
926<t>
927   If a resource has been created on the origin server, the response
928   &SHOULD; be 201 (Created) and contain an entity which describes the
929   status of the request and refers to the new resource, and a Location
930   header (see <xref target="header.location"/>).
931</t>
932<t>
933   Responses to this method are not cacheable, unless the response
934   includes appropriate Cache-Control or Expires header fields. However,
935   the 303 (See Other) response can be used to direct the user agent to
936   retrieve a cacheable resource.
937</t>
938</section>
939
940<section title="PUT" anchor="PUT">
941  <iref primary="true" item="PUT method" x:for-anchor=""/>
942  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
943<t>
944   The PUT method requests that the enclosed entity be stored at the
945   supplied request-target. If the request-target refers to an already
946   existing resource, the enclosed entity &SHOULD; be considered as a
947   modified version of the one residing on the origin server. If the
948   request-target does not point to an existing resource, and that URI is
949   capable of being defined as a new resource by the requesting user
950   agent, the origin server can create the resource with that URI. If a
951   new resource is created at the request-target, the origin server &MUST;
952   inform the user agent
953   via the 201 (Created) response. If an existing resource is modified,
954   either the 200 (OK) or 204 (No Content) response codes &SHOULD; be sent
955   to indicate successful completion of the request. If the resource
956   could not be created or modified with the request-target, an appropriate
957   error response &SHOULD; be given that reflects the nature of the
958   problem. The recipient of the entity &MUST-NOT; ignore any Content-*
959   headers (headers starting with the prefix "Content-") that it does
960   not understand or implement
961   and &MUST; return a 501 (Not Implemented) response in such cases.
962</t>
963<t>
964   If the request passes through a cache and the request-target identifies
965   one or more currently cached entities, those entries &SHOULD; be
966   treated as stale. Responses to this method are not cacheable.
967</t>
968<t>
969   The fundamental difference between the POST and PUT requests is
970   reflected in the different meaning of the request-target. The URI in a
971   POST request identifies the resource that will handle the enclosed
972   entity. That resource might be a data-accepting process, a gateway to
973   some other protocol, or a separate entity that accepts annotations.
974   In contrast, the URI in a PUT request identifies the entity enclosed
975   with the request -- the user agent knows what URI is intended and the
976   server &MUST-NOT; attempt to apply the request to some other resource.
977   If the server desires that the request be applied to a different URI,
978   it &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
979   then make its own decision regarding whether or not to redirect the
980   request.
981</t>
982<t>
983   A single resource &MAY; be identified by many different URIs. For
984   example, an article might have a URI for identifying "the current
985   version" which is separate from the URI identifying each particular
986   version. In this case, a PUT request on a general URI might result in
987   several other URIs being defined by the origin server.
988</t>
989<t>
990   HTTP/1.1 does not define how a PUT method affects the state of an
991   origin server.
992</t>
993<t>
994   Unless otherwise specified for a particular entity-header, the
995   entity-headers in the PUT request &SHOULD; be applied to the resource
996   created or modified by the PUT.
997</t>
998</section>
999
1000<section title="DELETE" anchor="DELETE">
1001  <iref primary="true" item="DELETE method" x:for-anchor=""/>
1002  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
1003<t>
1004   The DELETE method requests that the origin server delete the resource
1005   identified by the request-target. This method &MAY; be overridden by human
1006   intervention (or other means) on the origin server. The client cannot
1007   be guaranteed that the operation has been carried out, even if the
1008   status code returned from the origin server indicates that the action
1009   has been completed successfully. However, the server &SHOULD-NOT; 
1010   indicate success unless, at the time the response is given, it
1011   intends to delete the resource or move it to an inaccessible
1012   location.
1013</t>
1014<t>
1015   A successful response &SHOULD; be 200 (OK) if the response includes an
1016   entity describing the status, 202 (Accepted) if the action has not
1017   yet been enacted, or 204 (No Content) if the action has been enacted
1018   but the response does not include an entity.
1019</t>
1020<t>
1021   If the request passes through a cache and the request-target identifies
1022   one or more currently cached entities, those entries &SHOULD; be
1023   treated as stale. Responses to this method are not cacheable.
1024</t>
1025</section>
1026
1027<section title="TRACE" anchor="TRACE">
1028  <rdf:Description>
1029    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
1030  </rdf:Description>
1031  <iref primary="true" item="TRACE method" x:for-anchor=""/>
1032  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
1033<t>
1034   The TRACE method is used to invoke a remote, application-layer loop-back
1035   of the request message. The final recipient of the request
1036   &SHOULD; reflect the message received back to the client as the
1037   entity-body of a 200 (OK) response. The final recipient is either the
1038   origin server or the first proxy or gateway to receive a Max-Forwards
1039   value of zero (0) in the request (see <xref target="header.max-forwards"/>). A TRACE request
1040   &MUST-NOT; include an entity.
1041</t>
1042<t>
1043   TRACE allows the client to see what is being received at the other
1044   end of the request chain and use that data for testing or diagnostic
1045   information. The value of the Via header field (&header-via;) is of
1046   particular interest, since it acts as a trace of the request chain.
1047   Use of the Max-Forwards header field allows the client to limit the
1048   length of the request chain, which is useful for testing a chain of
1049   proxies forwarding messages in an infinite loop.
1050</t>
1051<t>
1052   If the request is valid, the response &SHOULD; contain the entire
1053   request message in the entity-body, with a Content-Type of
1054   "message/http" (see &media-type-message-http;). Responses to this method
1055   &MUST-NOT; be cached.
1056</t>
1057</section>
1058
1059<section title="CONNECT" anchor="CONNECT">
1060  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
1061  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1062<t>
1063   This specification reserves the method name CONNECT for use with a
1064   proxy that can dynamically switch to being a tunnel (e.g., SSL
1065   tunneling <xref target="RFC2817"/>).
1066</t>
1067</section>
1068</section>
1069
1070
1071<section title="Status Code Definitions" anchor="status.codes">
1072<t>
1073   Each Status-Code is described below, including any metainformation required
1074   in the response.
1075</t>
1076
1077<section title="Informational 1xx" anchor="status.1xx">
1078<t>
1079   This class of status code indicates a provisional response,
1080   consisting only of the Status-Line and optional headers, and is
1081   terminated by an empty line. There are no required headers for this
1082   class of status code. Since HTTP/1.0 did not define any 1xx status
1083   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1084   except under experimental conditions.
1085</t>
1086<t>
1087   A client &MUST; be prepared to accept one or more 1xx status responses
1088   prior to a regular response, even if the client does not expect a 100
1089   (Continue) status message. Unexpected 1xx status responses &MAY; be
1090   ignored by a user agent.
1091</t>
1092<t>
1093   Proxies &MUST; forward 1xx responses, unless the connection between the
1094   proxy and its client has been closed, or unless the proxy itself
1095   requested the generation of the 1xx response. (For example, if a
1096   proxy adds a "Expect: 100-continue" field when it forwards a request,
1097   then it need not forward the corresponding 100 (Continue)
1098   response(s).)
1099</t>
1100
1101<section title="100 Continue" anchor="status.100">
1102  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1103  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1104<t>
1105   The client &SHOULD; continue with its request. This interim response is
1106   used to inform the client that the initial part of the request has
1107   been received and has not yet been rejected by the server. The client
1108   &SHOULD; continue by sending the remainder of the request or, if the
1109   request has already been completed, ignore this response. The server
1110   &MUST; send a final response after the request has been completed. See
1111   &use100; for detailed discussion of the use and handling of this
1112   status code.
1113</t>
1114</section>
1115
1116<section title="101 Switching Protocols" anchor="status.101">
1117  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1118  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1119<t>
1120   The server understands and is willing to comply with the client's
1121   request, via the Upgrade message header field (&header-upgrade;), for a
1122   change in the application protocol being used on this connection. The
1123   server will switch protocols to those defined by the response's
1124   Upgrade header field immediately after the empty line which
1125   terminates the 101 response.
1126</t>
1127<t>
1128   The protocol &SHOULD; be switched only when it is advantageous to do
1129   so. For example, switching to a newer version of HTTP is advantageous
1130   over older versions, and switching to a real-time, synchronous
1131   protocol might be advantageous when delivering resources that use
1132   such features.
1133</t>
1134</section>
1135</section>
1136
1137<section title="Successful 2xx" anchor="status.2xx">
1138<t>
1139   This class of status code indicates that the client's request was
1140   successfully received, understood, and accepted.
1141</t>
1142
1143<section title="200 OK" anchor="status.200">
1144  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1145  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1146<t>
1147   The request has succeeded. The information returned with the response
1148   is dependent on the method used in the request, for example:
1149  <list style="hanging">
1150    <t hangText="GET">
1151          an entity corresponding to the requested resource is sent in
1152          the response;
1153    </t>
1154    <t hangText="HEAD">
1155          the entity-header fields corresponding to the requested
1156          resource are sent in the response without any message-body;
1157    </t>
1158    <t hangText="POST">
1159      an entity describing or containing the result of the action;
1160    </t>
1161    <t hangText="TRACE">
1162      an entity containing the request message as received by the
1163      end server.
1164    </t>
1165  </list>
1166</t>
1167</section>
1168
1169<section title="201 Created" anchor="status.201">
1170  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1171  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1172<t>
1173   The request has been fulfilled and has resulted in a new resource being
1174   created. The newly created resource can be referenced by the URI(s)
1175   returned in the entity of the response, with the most specific URI
1176   for the resource given by a Location header field. The response
1177   &SHOULD; include an entity containing a list of resource
1178   characteristics and location(s) from which the user or user agent can
1179   choose the one most appropriate. The entity format is specified by
1180   the media type given in the Content-Type header field. The origin
1181   server &MUST; create the resource before returning the 201 status code.
1182   If the action cannot be carried out immediately, the server &SHOULD;
1183   respond with 202 (Accepted) response instead.
1184</t>
1185<t>
1186   A 201 response &MAY; contain an ETag response header field indicating
1187   the current value of the entity tag for the requested variant just
1188   created, see &header-etag;.
1189</t>
1190</section>
1191
1192<section title="202 Accepted" anchor="status.202">
1193  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1194  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1195<t>
1196   The request has been accepted for processing, but the processing has
1197   not been completed.  The request might or might not eventually be
1198   acted upon, as it might be disallowed when processing actually takes
1199   place. There is no facility for re-sending a status code from an
1200   asynchronous operation such as this.
1201</t>
1202<t>
1203   The 202 response is intentionally non-committal. Its purpose is to
1204   allow a server to accept a request for some other process (perhaps a
1205   batch-oriented process that is only run once per day) without
1206   requiring that the user agent's connection to the server persist
1207   until the process is completed. The entity returned with this
1208   response &SHOULD; include an indication of the request's current status
1209   and either a pointer to a status monitor or some estimate of when the
1210   user can expect the request to be fulfilled.
1211</t>
1212</section>
1213
1214<section title="203 Non-Authoritative Information" anchor="status.203">
1215  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1216  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1217<t>
1218   The returned metainformation in the entity-header is not the
1219   definitive set as available from the origin server, but is gathered
1220   from a local or a third-party copy. The set presented &MAY; be a subset
1221   or superset of the original version. For example, including local
1222   annotation information about the resource might result in a superset
1223   of the metainformation known by the origin server. Use of this
1224   response code is not required and is only appropriate when the
1225   response would otherwise be 200 (OK).
1226</t>
1227</section>
1228
1229<section title="204 No Content" anchor="status.204">
1230  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1231  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1232<t>
1233   The server has fulfilled the request but does not need to return an
1234   entity-body, and might want to return updated metainformation. The
1235   response &MAY; include new or updated metainformation in the form of
1236   entity-headers, which if present &SHOULD; be associated with the
1237   requested variant.
1238</t>
1239<t>
1240   If the client is a user agent, it &SHOULD-NOT;  change its document view
1241   from that which caused the request to be sent. This response is
1242   primarily intended to allow input for actions to take place without
1243   causing a change to the user agent's active document view, although
1244   any new or updated metainformation &SHOULD; be applied to the document
1245   currently in the user agent's active view.
1246</t>
1247<t>
1248   The 204 response &MUST-NOT; include a message-body, and thus is always
1249   terminated by the first empty line after the header fields.
1250</t>
1251</section>
1252
1253<section title="205 Reset Content" anchor="status.205">
1254  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1255  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1256<t>
1257   The server has fulfilled the request and the user agent &SHOULD; reset
1258   the document view which caused the request to be sent. This response
1259   is primarily intended to allow input for actions to take place via
1260   user input, followed by a clearing of the form in which the input is
1261   given so that the user can easily initiate another input action. The
1262   response &MUST-NOT; include an entity.
1263</t>
1264</section>
1265
1266<section title="206 Partial Content" anchor="status.206">
1267  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1268  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1269  <rdf:Description>
1270    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1271  </rdf:Description>
1272<t>
1273   The server has fulfilled the partial GET request for the resource
1274   and the enclosed entity is a partial representation as defined in &status-206;.
1275</t>
1276</section>
1277</section>
1278
1279<section title="Redirection 3xx" anchor="status.3xx">
1280<t>
1281   This class of status code indicates that further action needs to be
1282   taken by the user agent in order to fulfill the request.  The action
1283   required &MAY; be carried out by the user agent without interaction
1284   with the user if and only if the method used in the second request is
1285   known to be "safe", as defined in <xref target="safe.methods"/>.
1286   A client &SHOULD; detect infinite redirection loops, since such loops
1287   generate network traffic for each redirection.
1288</t>
1289<x:note>
1290  <t>
1291    <x:h>Note:</x:h> An earlier version of this specification recommended a
1292    maximum of five redirections (<xref target="RFC2068" x:fmt="," x:sec="10.3"/>).
1293    Content developers should be aware that there might be clients that
1294    implement such a fixed limitation.
1295  </t>
1296</x:note>
1297
1298<section title="300 Multiple Choices" anchor="status.300">
1299  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1300  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1301<t>
1302   The requested resource corresponds to any one of a set of
1303   representations, each with its own specific location, and agent-driven
1304   negotiation information (&content-negotiation;) is being provided so that
1305   the user (or user agent) can select a preferred representation and
1306   redirect its request to that location.
1307</t>
1308<t>
1309   Unless it was a HEAD request, the response &SHOULD; include an entity
1310   containing a list of resource characteristics and location(s) from
1311   which the user or user agent can choose the one most appropriate. The
1312   entity format is specified by the media type given in the Content-Type
1313   header field. Depending upon the format and the capabilities of
1314   the user agent, selection of the most appropriate choice &MAY; be
1315   performed automatically. However, this specification does not define
1316   any standard for such automatic selection.
1317</t>
1318<t>
1319   If the server has a preferred choice of representation, it &SHOULD;
1320   include the specific URI for that representation in the Location
1321   field; user agents &MAY; use the Location field value for automatic
1322   redirection. This response is cacheable unless indicated otherwise.
1323</t>
1324</section>
1325
1326<section title="301 Moved Permanently" anchor="status.301">
1327  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1328  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1329<t>
1330   The requested resource has been assigned a new permanent URI and any
1331   future references to this resource &SHOULD; use one of the returned
1332   URIs.  Clients with link editing capabilities ought to automatically
1333   re-link references to the request-target to one or more of the new
1334   references returned by the server, where possible. This response is
1335   cacheable unless indicated otherwise.
1336</t>
1337<t>
1338   The new permanent URI &SHOULD; be given by the Location field in the
1339   response. Unless the request method was HEAD, the entity of the
1340   response &SHOULD; contain a short hypertext note with a hyperlink to
1341   the new URI(s).
1342</t>
1343<t>
1344   If the 301 status code is received in response to a request method
1345   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1346   then the request &MAY; be automatically redirected by the user agent without
1347   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1348   request unless it can be confirmed by the user, since this might
1349   change the conditions under which the request was issued.
1350</t>
1351<x:note>
1352  <t>
1353    <x:h>Note:</x:h> When automatically redirecting a POST request after
1354    receiving a 301 status code, some existing HTTP/1.0 user agents
1355    will erroneously change it into a GET request.
1356  </t>
1357</x:note>
1358</section>
1359
1360<section title="302 Found" anchor="status.302">
1361  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1362  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1363<t>
1364   The requested resource resides temporarily under a different URI.
1365   Since the redirection might be altered on occasion, the client &SHOULD;
1366   continue to use the request-target for future requests.  This response
1367   is only cacheable if indicated by a Cache-Control or Expires header
1368   field.
1369</t>
1370<t>
1371   The temporary URI &SHOULD; be given by the Location field in the
1372   response. Unless the request method was HEAD, the entity of the
1373   response &SHOULD; contain a short hypertext note with a hyperlink to
1374   the new URI(s).
1375</t>
1376<t>
1377   If the 302 status code is received in response to a request method
1378   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1379   then the request &MAY; be automatically redirected by the user agent without
1380   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1381   request unless it can be confirmed by the user, since this might
1382   change the conditions under which the request was issued.
1383</t>
1384<x:note>
1385  <t>
1386    <x:h>Note:</x:h> HTTP/1.0 (<xref target="RFC1945" x:fmt="," x:sec="9.3"/>)
1387    and the first version of HTTP/1.1 (<xref target="RFC2068" x:fmt="," x:sec ="10.3.3"/>)
1388    specify that the client is not allowed to change the method on the
1389    redirected request.  However, most existing user agent implementations
1390    treat 302 as if it were a 303 response, performing a GET on the Location
1391    field-value regardless of the original request method. Therefore, a
1392    previous version of this specification
1393    (<xref target="RFC2616" x:fmt="," x:sec="10.3.3"/>) has added the
1394    status codes
1395    <xref target="status.303" format="none">303</xref> and
1396    <xref target="status.307" format="none">307</xref> for servers that wish
1397    to make unambiguously clear which kind of reaction is expected of the
1398    client.
1399  </t>
1400</x:note>
1401</section>
1402
1403<section title="303 See Other" anchor="status.303">
1404  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1405  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1406<t>
1407   The server directs the user agent to a different resource, indicated
1408   by a URI in the Location header field, that provides an indirect
1409   response to the original request.  The user agent &MAY; perform a GET
1410   request on the URI in the Location field in order to obtain a
1411   representation corresponding to the response, be redirected again,
1412   or end with an error status.  The Location URI is not a substitute
1413   reference for the originally requested resource.
1414</t>
1415<t>
1416   The 303 status is generally applicable to any HTTP method.  It is
1417   primarily used to allow the output of a POST action to redirect
1418   the user agent to a selected resource, since doing so provides the
1419   information corresponding to the POST response in a form that
1420   can be separately identified, bookmarked, and cached independent
1421   of the original request.
1422</t>
1423<t>
1424   A 303 response to a GET request indicates that the requested
1425   resource does not have a representation of its own that can be
1426   transferred by the server over HTTP.  The Location URI indicates a
1427   resource that is descriptive of the requested resource such that
1428   the follow-on representation may be useful without implying that
1429   it adequately represents the previously requested resource.
1430   Note that answers to the questions of what can be represented, what
1431   representations are adequate, and what might be a useful description
1432   are outside the scope of HTTP and thus entirely determined by the
1433   URI owner(s).
1434</t>
1435<t>
1436   A 303 response &SHOULD-NOT; be cached unless it is indicated as
1437   cacheable by Cache-Control or Expires header fields.  Except for
1438   responses to a HEAD request, the entity of a 303 response &SHOULD;
1439   contain a short hypertext note with a hyperlink to the Location URI.
1440</t>
1441</section>
1442
1443<section title="304 Not Modified" anchor="status.304">
1444  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1445  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1446  <rdf:Description>
1447    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1448  </rdf:Description>
1449<t>
1450   The response to the request has not been modified since the conditions
1451   indicated by the client's conditional GET request, as defined in &status-304;.
1452</t>
1453</section>
1454
1455<section title="305 Use Proxy" anchor="status.305">
1456  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1457  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1458<t>
1459   The 305 status was defined in a previous version of this specification
1460   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1461</t>
1462</section>
1463
1464<section title="306 (Unused)" anchor="status.306">
1465  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1466  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1467<t>
1468   The 306 status code was used in a previous version of the
1469   specification, is no longer used, and the code is reserved.
1470</t>
1471</section>
1472
1473<section title="307 Temporary Redirect" anchor="status.307">
1474  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1475  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1476<t>
1477   The requested resource resides temporarily under a different URI.
1478   Since the redirection &MAY; be altered on occasion, the client &SHOULD;
1479   continue to use the request-target for future requests.  This response
1480   is only cacheable if indicated by a Cache-Control or Expires header
1481   field.
1482</t>
1483<t>
1484   The temporary URI &SHOULD; be given by the Location field in the
1485   response. Unless the request method was HEAD, the entity of the
1486   response &SHOULD; contain a short hypertext note with a hyperlink to
1487   the new URI(s) , since many pre-HTTP/1.1 user agents do not
1488   understand the 307 status. Therefore, the note &SHOULD; contain the
1489   information necessary for a user to repeat the original request on
1490   the new URI.
1491</t>
1492<t>
1493   If the 307 status code is received in response to a request method
1494   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1495   then the request &MAY; be automatically redirected by the user agent without
1496   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1497   request unless it can be confirmed by the user, since this might
1498   change the conditions under which the request was issued.
1499</t>
1500</section>
1501</section>
1502
1503<section title="Client Error 4xx" anchor="status.4xx">
1504<t>
1505   The 4xx class of status code is intended for cases in which the
1506   client seems to have erred. Except when responding to a HEAD request,
1507   the server &SHOULD; include an entity containing an explanation of the
1508   error situation, and whether it is a temporary or permanent
1509   condition. These status codes are applicable to any request method.
1510   User agents &SHOULD; display any included entity to the user.
1511</t>
1512<t>
1513   If the client is sending data, a server implementation using TCP
1514   &SHOULD; be careful to ensure that the client acknowledges receipt of
1515   the packet(s) containing the response, before the server closes the
1516   input connection. If the client continues sending data to the server
1517   after the close, the server's TCP stack will send a reset packet to
1518   the client, which may erase the client's unacknowledged input buffers
1519   before they can be read and interpreted by the HTTP application.
1520</t>
1521
1522<section title="400 Bad Request" anchor="status.400">
1523  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1524  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1525<t>
1526   The request could not be understood by the server due to malformed
1527   syntax. The client &SHOULD-NOT;  repeat the request without
1528   modifications.
1529</t>
1530</section>
1531
1532<section title="401 Unauthorized" anchor="status.401">
1533  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1534  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1535  <rdf:Description>
1536    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part7</redirects-to>
1537  </rdf:Description>
1538<t>
1539   The request requires user authentication (see &status-401;).
1540</t>
1541</section>
1542
1543<section title="402 Payment Required" anchor="status.402">
1544  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1545  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1546<t>
1547   This code is reserved for future use.
1548</t>
1549</section>
1550
1551<section title="403 Forbidden" anchor="status.403">
1552  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1553  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1554<t>
1555   The server understood the request, but is refusing to fulfill it.
1556   Authorization will not help and the request &SHOULD-NOT;  be repeated.
1557   If the request method was not HEAD and the server wishes to make
1558   public why the request has not been fulfilled, it &SHOULD; describe the
1559   reason for the refusal in the entity.  If the server does not wish to
1560   make this information available to the client, the status code 404
1561   (Not Found) can be used instead.
1562</t>
1563</section>
1564
1565<section title="404 Not Found" anchor="status.404">
1566  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1567  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1568<t>
1569   The server has not found anything matching the request-target. No
1570   indication is given of whether the condition is temporary or
1571   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1572   knows, through some internally configurable mechanism, that an old
1573   resource is permanently unavailable and has no forwarding address.
1574   This status code is commonly used when the server does not wish to
1575   reveal exactly why the request has been refused, or when no other
1576   response is applicable.
1577</t>
1578</section>
1579
1580<section title="405 Method Not Allowed" anchor="status.405">
1581  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1582  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1583<t>
1584   The method specified in the Request-Line is not allowed for the
1585   resource identified by the request-target. The response &MUST; include an
1586   Allow header containing a list of valid methods for the requested
1587   resource.
1588</t>
1589</section>
1590
1591<section title="406 Not Acceptable" anchor="status.406">
1592  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1593  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1594<t>
1595   The resource identified by the request is only capable of generating
1596   response entities which have content characteristics not acceptable
1597   according to the accept headers sent in the request.
1598</t>
1599<t>
1600   Unless it was a HEAD request, the response &SHOULD; include an entity
1601   containing a list of available entity characteristics and location(s)
1602   from which the user or user agent can choose the one most
1603   appropriate. The entity format is specified by the media type given
1604   in the Content-Type header field. Depending upon the format and the
1605   capabilities of the user agent, selection of the most appropriate
1606   choice &MAY; be performed automatically. However, this specification
1607   does not define any standard for such automatic selection.
1608</t>
1609<x:note>
1610  <t>
1611    <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1612    not acceptable according to the accept headers sent in the
1613    request. In some cases, this may even be preferable to sending a
1614    406 response. User agents are encouraged to inspect the headers of
1615    an incoming response to determine if it is acceptable.
1616  </t>
1617</x:note>
1618<t>
1619   If the response could be unacceptable, a user agent &SHOULD;
1620   temporarily stop receipt of more data and query the user for a
1621   decision on further actions.
1622</t>
1623</section>
1624
1625<section title="407 Proxy Authentication Required" anchor="status.407">
1626  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1627  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1628<t>
1629   This code is similar to 401 (Unauthorized), but indicates that the
1630   client must first authenticate itself with the proxy (see &status-407;).
1631</t>
1632</section>
1633
1634<section title="408 Request Timeout" anchor="status.408">
1635  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1636  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1637<t>
1638   The client did not produce a request within the time that the server
1639   was prepared to wait. The client &MAY; repeat the request without
1640   modifications at any later time.
1641</t>
1642</section>
1643
1644<section title="409 Conflict" anchor="status.409">
1645  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1646  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1647<t>
1648   The request could not be completed due to a conflict with the current
1649   state of the resource. This code is only allowed in situations where
1650   it is expected that the user might be able to resolve the conflict
1651   and resubmit the request. The response body &SHOULD; include enough
1652   information for the user to recognize the source of the conflict.
1653   Ideally, the response entity would include enough information for the
1654   user or user agent to fix the problem; however, that might not be
1655   possible and is not required.
1656</t>
1657<t>
1658   Conflicts are most likely to occur in response to a PUT request. For
1659   example, if versioning were being used and the entity being PUT
1660   included changes to a resource which conflict with those made by an
1661   earlier (third-party) request, the server might use the 409 response
1662   to indicate that it can't complete the request. In this case, the
1663   response entity would likely contain a list of the differences
1664   between the two versions in a format defined by the response
1665   Content-Type.
1666</t>
1667</section>
1668
1669<section title="410 Gone" anchor="status.410">
1670  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1671  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1672<t>
1673   The requested resource is no longer available at the server and no
1674   forwarding address is known. This condition is expected to be
1675   considered permanent. Clients with link editing capabilities &SHOULD;
1676   delete references to the request-target after user approval. If the
1677   server does not know, or has no facility to determine, whether or not
1678   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
1679   used instead. This response is cacheable unless indicated otherwise.
1680</t>
1681<t>
1682   The 410 response is primarily intended to assist the task of web
1683   maintenance by notifying the recipient that the resource is
1684   intentionally unavailable and that the server owners desire that
1685   remote links to that resource be removed. Such an event is common for
1686   limited-time, promotional services and for resources belonging to
1687   individuals no longer working at the server's site. It is not
1688   necessary to mark all permanently unavailable resources as "gone" or
1689   to keep the mark for any length of time -- that is left to the
1690   discretion of the server owner.
1691</t>
1692</section>
1693
1694<section title="411 Length Required" anchor="status.411">
1695  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1696  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1697<t>
1698   The server refuses to accept the request without a defined Content-Length.
1699   The client &MAY; repeat the request if it adds a valid
1700   Content-Length header field containing the length of the message-body
1701   in the request message.
1702</t>
1703</section>
1704
1705<section title="412 Precondition Failed" anchor="status.412">
1706  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1707  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
1708  <rdf:Description>
1709    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1710  </rdf:Description>
1711<t>
1712   The precondition given in one or more of the request-header fields
1713   evaluated to false when it was tested on the server, as defined in
1714   &status-412;.
1715</t>
1716</section>
1717
1718<section title="413 Request Entity Too Large" anchor="status.413">
1719  <iref primary="true" item="413 Request Entity Too Large (status code)" x:for-anchor=""/>
1720  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large" x:for-anchor=""/>
1721<t>
1722   The server is refusing to process a request because the request
1723   entity is larger than the server is willing or able to process. The
1724   server &MAY; close the connection to prevent the client from continuing
1725   the request.
1726</t>
1727<t>
1728   If the condition is temporary, the server &SHOULD; include a Retry-After
1729   header field to indicate that it is temporary and after what
1730   time the client &MAY; try again.
1731</t>
1732</section>
1733
1734<section title="414 URI Too Long" anchor="status.414">
1735  <iref primary="true" item="414 URI Too Long (status code)" x:for-anchor=""/>
1736  <iref primary="true" item="Status Codes" subitem="414 URI Too Long" x:for-anchor=""/>
1737<t>
1738   The server is refusing to service the request because the request-target
1739   is longer than the server is willing to interpret. This rare
1740   condition is only likely to occur when a client has improperly
1741   converted a POST request to a GET request with long query
1742   information, when the client has descended into a URI "black hole" of
1743   redirection (e.g., a redirected URI prefix that points to a suffix of
1744   itself), or when the server is under attack by a client attempting to
1745   exploit security holes present in some servers using fixed-length
1746   buffers for reading or manipulating the request-target.
1747</t>
1748</section>
1749
1750<section title="415 Unsupported Media Type" anchor="status.415">
1751  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1752  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
1753<t>
1754   The server is refusing to service the request because the entity of
1755   the request is in a format not supported by the requested resource
1756   for the requested method.
1757</t>
1758</section>
1759
1760<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1761  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
1762  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
1763  <rdf:Description>
1764    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1765  </rdf:Description>
1766<t>
1767   The request included a Range request-header field (&header-range;) and none of
1768   the range-specifier values in this field overlap the current extent
1769   of the selected resource. See &status-416;
1770</t>
1771</section>
1772
1773<section title="417 Expectation Failed" anchor="status.417">
1774  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
1775  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
1776<t>
1777   The expectation given in an Expect request-header field (see <xref target="header.expect"/>)
1778   could not be met by this server, or, if the server is a proxy,
1779   the server has unambiguous evidence that the request could not be met
1780   by the next-hop server.
1781</t>
1782</section>
1783</section>
1784
1785<section title="Server Error 5xx" anchor="status.5xx">
1786<t>
1787   Response status codes beginning with the digit "5" indicate cases in
1788   which the server is aware that it has erred or is incapable of
1789   performing the request. Except when responding to a HEAD request, the
1790   server &SHOULD; include an entity containing an explanation of the
1791   error situation, and whether it is a temporary or permanent
1792   condition. User agents &SHOULD; display any included entity to the
1793   user. These response codes are applicable to any request method.
1794</t>
1795
1796<section title="500 Internal Server Error" anchor="status.500">
1797  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
1798  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
1799<t>
1800   The server encountered an unexpected condition which prevented it
1801   from fulfilling the request.
1802</t>
1803</section>
1804
1805<section title="501 Not Implemented" anchor="status.501">
1806  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
1807  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
1808<t>
1809   The server does not support the functionality required to fulfill the
1810   request. This is the appropriate response when the server does not
1811   recognize the request method and is not capable of supporting it for
1812   any resource.
1813</t>
1814</section>
1815
1816<section title="502 Bad Gateway" anchor="status.502">
1817  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
1818  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
1819<t>
1820   The server, while acting as a gateway or proxy, received an invalid
1821   response from the upstream server it accessed in attempting to
1822   fulfill the request.
1823</t>
1824</section>
1825
1826<section title="503 Service Unavailable" anchor="status.503">
1827  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
1828  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
1829<t>
1830   The server is currently unable to handle the request due to a
1831   temporary overloading or maintenance of the server. The implication
1832   is that this is a temporary condition which will be alleviated after
1833   some delay. If known, the length of the delay &MAY; be indicated in a
1834   Retry-After header. If no Retry-After is given, the client &SHOULD;
1835   handle the response as it would for a 500 response.
1836</t>
1837<x:note>
1838  <t>
1839    <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
1840    server must use it when becoming overloaded. Some servers may wish
1841    to simply refuse the connection.
1842  </t>
1843</x:note>
1844</section>
1845
1846<section title="504 Gateway Timeout" anchor="status.504">
1847  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
1848  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
1849<t>
1850   The server, while acting as a gateway or proxy, did not receive a
1851   timely response from the upstream server specified by the URI (e.g.,
1852   HTTP, FTP, LDAP) or some other auxiliary server (e.g., DNS) it needed
1853   to access in attempting to complete the request.
1854</t>
1855<x:note>
1856  <t>
1857    <x:h>Note</x:h> to implementors: some deployed proxies are known to
1858    return 400 or 500 when DNS lookups time out.
1859  </t>
1860</x:note>
1861</section>
1862
1863<section title="505 HTTP Version Not Supported" anchor="status.505">
1864  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
1865  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
1866<t>
1867   The server does not support, or refuses to support, the protocol
1868   version that was used in the request message. The server is
1869   indicating that it is unable or unwilling to complete the request
1870   using the same major version as the client, as described in &http-version;,
1871   other than with this error message. The response &SHOULD; contain
1872   an entity describing why that version is not supported and what other
1873   protocols are supported by that server.
1874</t>
1875
1876</section>
1877</section>
1878</section>
1879
1880
1881<section title="Header Field Definitions" anchor="header.fields">
1882<t>
1883   This section defines the syntax and semantics of HTTP/1.1 header fields
1884   related to request and response semantics.
1885</t>
1886<t>
1887   For entity-header fields, both sender and recipient refer to either the
1888   client or the server, depending on who sends and who receives the entity.
1889</t>
1890
1891<section title="Allow" anchor="header.allow">
1892  <iref primary="true" item="Allow header" x:for-anchor=""/>
1893  <iref primary="true" item="Headers" subitem="Allow" x:for-anchor=""/>
1894  <x:anchor-alias value="Allow"/>
1895  <x:anchor-alias value="Allow-v"/>
1896<t>
1897   The "Allow" response-header field lists the set of methods advertised as
1898   supported by the resource identified by the request-target. The purpose of
1899   this field is strictly to inform the recipient of valid methods
1900   associated with the resource.
1901</t>
1902<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/><iref primary="true" item="Grammar" subitem="Allow-v"/>
1903  <x:ref>Allow</x:ref>   = "Allow" ":" <x:ref>OWS</x:ref> <x:ref>Allow-v</x:ref>
1904  <x:ref>Allow-v</x:ref> = #<x:ref>Method</x:ref>
1905</artwork></figure>
1906<t>
1907      Example of use:
1908</t>
1909<figure><artwork type="example">
1910  Allow: GET, HEAD, PUT
1911</artwork></figure>
1912<t>
1913      The actual set of allowed methods is defined
1914      by the origin server at the time of each request.
1915</t>
1916<t>
1917      A proxy &MUST-NOT; modify the Allow header field even if it does not
1918      understand all the methods specified, since the user agent might
1919      have other means of communicating with the origin server.
1920</t>
1921</section>
1922
1923<section title="Expect" anchor="header.expect">
1924  <iref primary="true" item="Expect header" x:for-anchor=""/>
1925  <iref primary="true" item="Headers" subitem="Expect" x:for-anchor=""/>
1926  <x:anchor-alias value="Expect"/>
1927  <x:anchor-alias value="Expect-v"/>
1928  <x:anchor-alias value="expectation"/>
1929  <x:anchor-alias value="expectation-extension"/>
1930  <x:anchor-alias value="expect-params"/>
1931<t>
1932   The "Expect" request-header field is used to indicate that particular
1933   server behaviors are required by the client.
1934</t>
1935<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"/>
1936  <x:ref>Expect</x:ref>       = "Expect" ":" <x:ref>OWS</x:ref> <x:ref>Expect-v</x:ref>
1937  <x:ref>Expect-v</x:ref>     = 1#<x:ref>expectation</x:ref>
1938 
1939  <x:ref>expectation</x:ref>  = "100-continue" / <x:ref>expectation-extension</x:ref>
1940  <x:ref>expectation-extension</x:ref> = <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> )
1941                           *<x:ref>expect-params</x:ref> ]
1942  <x:ref>expect-params</x:ref> = ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> ) ]
1943</artwork></figure>
1944<t>
1945   A server that does not understand or is unable to comply with any of
1946   the expectation values in the Expect field of a request &MUST; respond
1947   with appropriate error status. The server &MUST; respond with a 417
1948   (Expectation Failed) status if any of the expectations cannot be met
1949   or, if there are other problems with the request, some other 4xx
1950   status.
1951</t>
1952<t>
1953   This header field is defined with extensible syntax to allow for
1954   future extensions. If a server receives a request containing an
1955   Expect field that includes an expectation-extension that it does not
1956   support, it &MUST; respond with a 417 (Expectation Failed) status.
1957</t>
1958<t>
1959   Comparison of expectation values is case-insensitive for unquoted
1960   tokens (including the 100-continue token), and is case-sensitive for
1961   quoted-string expectation-extensions.
1962</t>
1963<t>
1964   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
1965   return a 417 (Expectation Failed) status if it receives a request
1966   with an expectation that it cannot meet. However, the Expect
1967   request-header itself is end-to-end; it &MUST; be forwarded if the
1968   request is forwarded.
1969</t>
1970<t>
1971   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
1972   Expect header.
1973</t>
1974<t>
1975   See &use100; for the use of the 100 (Continue) status.
1976</t>
1977</section>
1978
1979<section title="From" anchor="header.from">
1980  <iref primary="true" item="From header" x:for-anchor=""/>
1981  <iref primary="true" item="Headers" subitem="From" x:for-anchor=""/>
1982  <x:anchor-alias value="From"/>
1983  <x:anchor-alias value="From-v"/>
1984  <x:anchor-alias value="mailbox"/>
1985<t>
1986   The "From" request-header field, if given, &SHOULD; contain an Internet
1987   e-mail address for the human user who controls the requesting user
1988   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
1989   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
1990</t>
1991<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/><iref primary="true" item="Grammar" subitem="From-v"/>
1992  <x:ref>From</x:ref>    = "From" ":" <x:ref>OWS</x:ref> <x:ref>From-v</x:ref>
1993  <x:ref>From-v</x:ref>  = <x:ref>mailbox</x:ref>
1994 
1995  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
1996</artwork></figure>
1997<t>
1998   An example is:
1999</t>
2000<figure><artwork type="example">
2001  From: webmaster@example.org
2002</artwork></figure>
2003<t>
2004   This header field &MAY; be used for logging purposes and as a means for
2005   identifying the source of invalid or unwanted requests. It &SHOULD-NOT; 
2006   be used as an insecure form of access protection. The interpretation
2007   of this field is that the request is being performed on behalf of the
2008   person given, who accepts responsibility for the method performed. In
2009   particular, robot agents &SHOULD; include this header so that the
2010   person responsible for running the robot can be contacted if problems
2011   occur on the receiving end.
2012</t>
2013<t>
2014   The Internet e-mail address in this field &MAY; be separate from the
2015   Internet host which issued the request. For example, when a request
2016   is passed through a proxy the original issuer's address &SHOULD; be
2017   used.
2018</t>
2019<t>
2020   The client &SHOULD-NOT;  send the From header field without the user's
2021   approval, as it might conflict with the user's privacy interests or
2022   their site's security policy. It is strongly recommended that the
2023   user be able to disable, enable, and modify the value of this field
2024   at any time prior to a request.
2025</t>
2026</section>
2027
2028<section title="Location" anchor="header.location">
2029  <iref primary="true" item="Location header" x:for-anchor=""/>
2030  <iref primary="true" item="Headers" subitem="Location" x:for-anchor=""/>
2031  <x:anchor-alias value="Location"/>
2032  <x:anchor-alias value="Location-v"/>
2033<t>
2034   The "Location" response-header field is used to identify a newly created
2035   resource, or to redirect the recipient to a different location for
2036   completion of the request.
2037</t>
2038<t>
2039   For 201 (Created) responses, the Location is the URI of the new resource
2040   which was created by the request. For 3xx responses, the location &SHOULD;
2041   indicate the server's preferred URI for automatic redirection to the
2042   resource.
2043</t>
2044<t>
2045   The field value consists of a single URI-reference. When it has the form
2046   of a relative reference (<xref target="RFC3986" x:fmt="," x:sec="4.2"/>),
2047   the final value is computed by resolving it against the effective request
2048   URI (<xref target="RFC3986" x:fmt="," x:sec="5"/>).
2049</t>
2050<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/><iref primary="true" item="Grammar" subitem="Location-v"/>
2051  <x:ref>Location</x:ref>       = "Location" ":" <x:ref>OWS</x:ref> <x:ref>Location-v</x:ref>
2052  <x:ref>Location-v</x:ref>     = <x:ref>URI-reference</x:ref>
2053</artwork></figure>
2054<figure>
2055<preamble>Examples are:</preamble><!--DO NOT DARE changing the vertical WSP below, it's necessary this way for xml2rfc-->
2056<artwork type="example">
2057  Location: http://www.example.org/pub/WWW/People.html#tim
2058</artwork></figure><figure><artwork type="example">  Location: /index.html
2059</artwork></figure>
2060<t>
2061   There are circumstances in which a fragment identifier in a Location URI
2062   would not be appropriate:
2063   <list style="symbols">
2064      <t>With a 201 Created response, because in this usage the Location header
2065      specifies the URI for the entire created resource.</t>
2066      <t>With 305 Use Proxy.</t>
2067   </list>
2068</t>
2069<x:note>
2070  <t>
2071    <x:h>Note:</x:h> This specification does not define precedence rules
2072    for the case where the original URI, as navigated to by the user
2073    agent, and the Location header field value both contain fragment
2074    identifiers.
2075  </t>
2076</x:note>
2077<x:note>
2078  <t>
2079    <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
2080    from Location in that the Content-Location identifies the original
2081    location of the entity enclosed in the response. It is therefore
2082    possible for a response to contain header fields for both Location
2083    and Content-Location.
2084  </t>
2085</x:note>
2086</section>
2087
2088<section title="Max-Forwards" anchor="header.max-forwards">
2089  <iref primary="true" item="Max-Forwards header" x:for-anchor=""/>
2090  <iref primary="true" item="Headers" subitem="Max-Forwards" x:for-anchor=""/>
2091  <x:anchor-alias value="Max-Forwards"/>
2092  <x:anchor-alias value="Max-Forwards-v"/>
2093<t>
2094   The "Max-Forwards" request-header field provides a mechanism with the
2095   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>)
2096   methods to limit the number of times that the request is forwarded by
2097   proxies or gateways. This can be useful when the client is attempting to
2098   trace a request which appears to be failing or looping in mid-chain.
2099</t>
2100<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/><iref primary="true" item="Grammar" subitem="Max-Forwards-v"/>
2101  <x:ref>Max-Forwards</x:ref>   = "Max-Forwards" ":" <x:ref>OWS</x:ref> <x:ref>Max-Forwards-v</x:ref>
2102  <x:ref>Max-Forwards-v</x:ref> = 1*<x:ref>DIGIT</x:ref>
2103</artwork></figure>
2104<t>
2105   The Max-Forwards value is a decimal integer indicating the remaining
2106   number of times this request message may be forwarded.
2107</t>
2108<t>
2109   Each proxy or gateway recipient of a TRACE or OPTIONS request
2110   containing a Max-Forwards header field &MUST; check and update its
2111   value prior to forwarding the request. If the received value is zero
2112   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2113   respond as the final recipient. If the received Max-Forwards value is
2114   greater than zero, then the forwarded message &MUST; contain an updated
2115   Max-Forwards field with a value decremented by one (1).
2116</t>
2117<t>
2118   The Max-Forwards header field &MAY; be ignored for all other methods
2119   defined by this specification and for any extension methods for which
2120   it is not explicitly referred to as part of that method definition.
2121</t>
2122</section>
2123
2124<section title="Referer" anchor="header.referer">
2125  <iref primary="true" item="Referer header" x:for-anchor=""/>
2126  <iref primary="true" item="Headers" subitem="Referer" x:for-anchor=""/>
2127  <x:anchor-alias value="Referer"/>
2128  <x:anchor-alias value="Referer-v"/>
2129<t>
2130   The "Referer" [sic] request-header field allows the client to specify the
2131   URI of the resource from which the request-target was obtained (the
2132   "referrer", although the header field is misspelled.).
2133</t>
2134<t>
2135   The Referer header allows servers to generate lists of back-links to
2136   resources for interest, logging, optimized caching, etc. It also allows
2137   obsolete or mistyped links to be traced for maintenance. Some servers use
2138   Referer as a means of controlling where they allow links from (so-called
2139   "deep linking"), but it should be noted that legitimate requests are not
2140   required to contain a Referer header field.
2141</t>
2142<t>
2143   If the request-target was obtained from a source that does not have its own
2144   URI (e.g., input from the user keyboard), the Referer field MUST either be
2145   sent with the value "about:blank", or not be sent at all. Note that this
2146   requirement does not apply to sources with non-HTTP URIs (e.g., FTP).
2147</t>
2148<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/><iref primary="true" item="Grammar" subitem="Referer-v"/>
2149  <x:ref>Referer</x:ref>        = "Referer" ":" <x:ref>OWS</x:ref> <x:ref>Referer-v</x:ref>
2150  <x:ref>Referer-v</x:ref>      = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
2151</artwork></figure>
2152<t>
2153   Example:
2154</t>
2155<figure><artwork type="example">
2156  Referer: http://www.example.org/hypertext/Overview.html
2157</artwork></figure>
2158<t>
2159   If the field value is a relative URI, it &SHOULD; be interpreted
2160   relative to the request-target. The URI &MUST-NOT; include a fragment. See
2161   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
2162</t>
2163</section>
2164
2165<section title="Retry-After" anchor="header.retry-after">
2166  <iref primary="true" item="Retry-After header" x:for-anchor=""/>
2167  <iref primary="true" item="Headers" subitem="Retry-After" x:for-anchor=""/>
2168  <x:anchor-alias value="Retry-After"/>
2169  <x:anchor-alias value="Retry-After-v"/>
2170<t>
2171   The response-header "Retry-After" field can be used with a 503 (Service
2172   Unavailable) response to indicate how long the service is expected to
2173   be unavailable to the requesting client. This field &MAY; also be used
2174   with any 3xx (Redirection) response to indicate the minimum time the
2175   user-agent is asked wait before issuing the redirected request.
2176</t>
2177<t>
2178   The value of this field can be either an HTTP-date or an integer number
2179   of seconds (in decimal) after the time of the response.
2180</t>
2181<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/><iref primary="true" item="Grammar" subitem="Retry-After-v"/>
2182  <x:ref>Retry-After</x:ref>   = "Retry-After" ":" <x:ref>OWS</x:ref> <x:ref>Retry-After-v</x:ref>
2183  <x:ref>Retry-After-v</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
2184</artwork></figure>
2185<t anchor="rule.delta-seconds">
2186  <x:anchor-alias value="delta-seconds"/>
2187   Time spans are non-negative decimal integers, representing time in
2188   seconds.
2189</t>
2190<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2191  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2192</artwork></figure>
2193<t>
2194   Two examples of its use are
2195</t>
2196<figure><artwork type="example">
2197  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2198  Retry-After: 120
2199</artwork></figure>
2200<t>
2201   In the latter example, the delay is 2 minutes.
2202</t>
2203</section>
2204
2205<section title="Server" anchor="header.server">
2206  <iref primary="true" item="Server header" x:for-anchor=""/>
2207  <iref primary="true" item="Headers" subitem="Server" x:for-anchor=""/>
2208  <x:anchor-alias value="Server"/>
2209  <x:anchor-alias value="Server-v"/>
2210<t>
2211   The "Server" response-header field contains information about the
2212   software used by the origin server to handle the request.
2213</t>
2214<t>
2215   The field can contain multiple product tokens (&product-tokens;) and
2216   comments (&header-fields;) identifying the server and any significant
2217   subproducts. The product tokens are listed in order of their significance
2218   for identifying the application.
2219</t>
2220<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/><iref primary="true" item="Grammar" subitem="Server-v"/>
2221  <x:ref>Server</x:ref>         = "Server" ":" <x:ref>OWS</x:ref> <x:ref>Server-v</x:ref>
2222  <x:ref>Server-v</x:ref>       = <x:ref>product</x:ref>
2223                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2224</artwork></figure>
2225<t>
2226   Example:
2227</t>
2228<figure><artwork type="example">
2229  Server: CERN/3.0 libwww/2.17
2230</artwork></figure>
2231<t>
2232   If the response is being forwarded through a proxy, the proxy
2233   application &MUST-NOT; modify the Server response-header. Instead, it
2234   &MUST; include a Via field (as described in &header-via;).
2235</t>
2236<x:note>
2237  <t>
2238    <x:h>Note:</x:h> Revealing the specific software version of the server might
2239    allow the server machine to become more vulnerable to attacks
2240    against software that is known to contain security holes. Server
2241    implementors are encouraged to make this field a configurable
2242    option.
2243  </t>
2244</x:note>
2245</section>
2246
2247<section title="User-Agent" anchor="header.user-agent">
2248  <iref primary="true" item="User-Agent header" x:for-anchor=""/>
2249  <iref primary="true" item="Headers" subitem="User-Agent" x:for-anchor=""/>
2250  <x:anchor-alias value="User-Agent"/>
2251  <x:anchor-alias value="User-Agent-v"/>
2252<t>
2253   The "User-Agent" request-header field contains information about the
2254   user agent originating the request. This is for statistical purposes,
2255   the tracing of protocol violations, and automated recognition of user
2256   agents for the sake of tailoring responses to avoid particular user
2257   agent limitations.
2258</t>
2259<t>
2260   User agents &SHOULD; include this field with requests. The field can contain
2261   multiple product tokens (&product-tokens;) and comments (&header-fields;)
2262   identifying the agent and any subproducts which form a significant part of
2263   the user agent. By convention, the product tokens are listed in order of
2264   their significance for identifying the application.
2265</t>
2266<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/><iref primary="true" item="Grammar" subitem="User-Agent-v"/>
2267  <x:ref>User-Agent</x:ref>     = "User-Agent" ":" <x:ref>OWS</x:ref> <x:ref>User-Agent-v</x:ref>
2268  <x:ref>User-Agent-v</x:ref>   = <x:ref>product</x:ref>
2269                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2270</artwork></figure>
2271<t>
2272   Example:
2273</t>
2274<figure><artwork type="example">
2275  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2276</artwork></figure>
2277</section>
2278
2279</section>
2280
2281<section title="IANA Considerations" anchor="IANA.considerations">
2282
2283<section title="Method Registry" anchor="method.registration">
2284<t>
2285  The registration procedure for HTTP Methods is defined by
2286  <xref target="method.registry"/> of this document.
2287</t>
2288<t>
2289   The HTTP Method Registry located at <eref target="http://www.iana.org/assignments/http-methods"/>
2290   should be populated with the registrations below:
2291</t>
2292<?BEGININC p2-semantics.iana-methods ?>
2293<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2294<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2295   <ttcol>Method</ttcol>
2296   <ttcol>Safe</ttcol>
2297   <ttcol>Reference</ttcol>
2298   <c>CONNECT</c>
2299   <c>no</c>
2300   <c>
2301      <xref target="CONNECT"/>
2302   </c>
2303   <c>DELETE</c>
2304   <c>no</c>
2305   <c>
2306      <xref target="DELETE"/>
2307   </c>
2308   <c>GET</c>
2309   <c>yes</c>
2310   <c>
2311      <xref target="GET"/>
2312   </c>
2313   <c>HEAD</c>
2314   <c>yes</c>
2315   <c>
2316      <xref target="HEAD"/>
2317   </c>
2318   <c>OPTIONS</c>
2319   <c>yes</c>
2320   <c>
2321      <xref target="OPTIONS"/>
2322   </c>
2323   <c>POST</c>
2324   <c>no</c>
2325   <c>
2326      <xref target="POST"/>
2327   </c>
2328   <c>PUT</c>
2329   <c>no</c>
2330   <c>
2331      <xref target="PUT"/>
2332   </c>
2333   <c>TRACE</c>
2334   <c>yes</c>
2335   <c>
2336      <xref target="TRACE"/>
2337   </c>
2338</texttable>
2339<!--(END)-->
2340<?ENDINC p2-semantics.iana-methods ?>
2341</section>
2342
2343<section title="Status Code Registry" anchor="status.code.registration">
2344<t>
2345   The registration procedure for HTTP Status Codes -- previously defined
2346   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> -- is now defined
2347   by <xref target="status.code.registry"/> of this document.
2348</t>
2349<t>
2350   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
2351   should be updated with the registrations below:
2352</t>
2353<?BEGININC p2-semantics.iana-status-codes ?>
2354<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2355<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
2356   <ttcol>Value</ttcol>
2357   <ttcol>Description</ttcol>
2358   <ttcol>Reference</ttcol>
2359   <c>100</c>
2360   <c>Continue</c>
2361   <c>
2362      <xref target="status.100"/>
2363   </c>
2364   <c>101</c>
2365   <c>Switching Protocols</c>
2366   <c>
2367      <xref target="status.101"/>
2368   </c>
2369   <c>200</c>
2370   <c>OK</c>
2371   <c>
2372      <xref target="status.200"/>
2373   </c>
2374   <c>201</c>
2375   <c>Created</c>
2376   <c>
2377      <xref target="status.201"/>
2378   </c>
2379   <c>202</c>
2380   <c>Accepted</c>
2381   <c>
2382      <xref target="status.202"/>
2383   </c>
2384   <c>203</c>
2385   <c>Non-Authoritative Information</c>
2386   <c>
2387      <xref target="status.203"/>
2388   </c>
2389   <c>204</c>
2390   <c>No Content</c>
2391   <c>
2392      <xref target="status.204"/>
2393   </c>
2394   <c>205</c>
2395   <c>Reset Content</c>
2396   <c>
2397      <xref target="status.205"/>
2398   </c>
2399   <c>300</c>
2400   <c>Multiple Choices</c>
2401   <c>
2402      <xref target="status.300"/>
2403   </c>
2404   <c>301</c>
2405   <c>Moved Permanently</c>
2406   <c>
2407      <xref target="status.301"/>
2408   </c>
2409   <c>302</c>
2410   <c>Found</c>
2411   <c>
2412      <xref target="status.302"/>
2413   </c>
2414   <c>303</c>
2415   <c>See Other</c>
2416   <c>
2417      <xref target="status.303"/>
2418   </c>
2419   <c>305</c>
2420   <c>Use Proxy</c>
2421   <c>
2422      <xref target="status.305"/>
2423   </c>
2424   <c>306</c>
2425   <c>(Unused)</c>
2426   <c>
2427      <xref target="status.306"/>
2428   </c>
2429   <c>307</c>
2430   <c>Temporary Redirect</c>
2431   <c>
2432      <xref target="status.307"/>
2433   </c>
2434   <c>400</c>
2435   <c>Bad Request</c>
2436   <c>
2437      <xref target="status.400"/>
2438   </c>
2439   <c>402</c>
2440   <c>Payment Required</c>
2441   <c>
2442      <xref target="status.402"/>
2443   </c>
2444   <c>403</c>
2445   <c>Forbidden</c>
2446   <c>
2447      <xref target="status.403"/>
2448   </c>
2449   <c>404</c>
2450   <c>Not Found</c>
2451   <c>
2452      <xref target="status.404"/>
2453   </c>
2454   <c>405</c>
2455   <c>Method Not Allowed</c>
2456   <c>
2457      <xref target="status.405"/>
2458   </c>
2459   <c>406</c>
2460   <c>Not Acceptable</c>
2461   <c>
2462      <xref target="status.406"/>
2463   </c>
2464   <c>407</c>
2465   <c>Proxy Authentication Required</c>
2466   <c>
2467      <xref target="status.407"/>
2468   </c>
2469   <c>408</c>
2470   <c>Request Timeout</c>
2471   <c>
2472      <xref target="status.408"/>
2473   </c>
2474   <c>409</c>
2475   <c>Conflict</c>
2476   <c>
2477      <xref target="status.409"/>
2478   </c>
2479   <c>410</c>
2480   <c>Gone</c>
2481   <c>
2482      <xref target="status.410"/>
2483   </c>
2484   <c>411</c>
2485   <c>Length Required</c>
2486   <c>
2487      <xref target="status.411"/>
2488   </c>
2489   <c>413</c>
2490   <c>Request Entity Too Large</c>
2491   <c>
2492      <xref target="status.413"/>
2493   </c>
2494   <c>414</c>
2495   <c>URI Too Long</c>
2496   <c>
2497      <xref target="status.414"/>
2498   </c>
2499   <c>415</c>
2500   <c>Unsupported Media Type</c>
2501   <c>
2502      <xref target="status.415"/>
2503   </c>
2504   <c>417</c>
2505   <c>Expectation Failed</c>
2506   <c>
2507      <xref target="status.417"/>
2508   </c>
2509   <c>500</c>
2510   <c>Internal Server Error</c>
2511   <c>
2512      <xref target="status.500"/>
2513   </c>
2514   <c>501</c>
2515   <c>Not Implemented</c>
2516   <c>
2517      <xref target="status.501"/>
2518   </c>
2519   <c>502</c>
2520   <c>Bad Gateway</c>
2521   <c>
2522      <xref target="status.502"/>
2523   </c>
2524   <c>503</c>
2525   <c>Service Unavailable</c>
2526   <c>
2527      <xref target="status.503"/>
2528   </c>
2529   <c>504</c>
2530   <c>Gateway Timeout</c>
2531   <c>
2532      <xref target="status.504"/>
2533   </c>
2534   <c>505</c>
2535   <c>HTTP Version Not Supported</c>
2536   <c>
2537      <xref target="status.505"/>
2538   </c>
2539</texttable>
2540<!--(END)-->
2541<?ENDINC p2-semantics.iana-status-codes ?>
2542</section>
2543<section title="Message Header Registration" anchor="message.header.registration">
2544<t>
2545   The Message Header Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> should be updated
2546   with the permanent registrations below (see <xref target="RFC3864"/>):
2547</t>
2548<?BEGININC p2-semantics.iana-headers ?>
2549<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
2550<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
2551   <ttcol>Header Field Name</ttcol>
2552   <ttcol>Protocol</ttcol>
2553   <ttcol>Status</ttcol>
2554   <ttcol>Reference</ttcol>
2555
2556   <c>Allow</c>
2557   <c>http</c>
2558   <c>standard</c>
2559   <c>
2560      <xref target="header.allow"/>
2561   </c>
2562   <c>Expect</c>
2563   <c>http</c>
2564   <c>standard</c>
2565   <c>
2566      <xref target="header.expect"/>
2567   </c>
2568   <c>From</c>
2569   <c>http</c>
2570   <c>standard</c>
2571   <c>
2572      <xref target="header.from"/>
2573   </c>
2574   <c>Location</c>
2575   <c>http</c>
2576   <c>standard</c>
2577   <c>
2578      <xref target="header.location"/>
2579   </c>
2580   <c>Max-Forwards</c>
2581   <c>http</c>
2582   <c>standard</c>
2583   <c>
2584      <xref target="header.max-forwards"/>
2585   </c>
2586   <c>Referer</c>
2587   <c>http</c>
2588   <c>standard</c>
2589   <c>
2590      <xref target="header.referer"/>
2591   </c>
2592   <c>Retry-After</c>
2593   <c>http</c>
2594   <c>standard</c>
2595   <c>
2596      <xref target="header.retry-after"/>
2597   </c>
2598   <c>Server</c>
2599   <c>http</c>
2600   <c>standard</c>
2601   <c>
2602      <xref target="header.server"/>
2603   </c>
2604   <c>User-Agent</c>
2605   <c>http</c>
2606   <c>standard</c>
2607   <c>
2608      <xref target="header.user-agent"/>
2609   </c>
2610</texttable>
2611<!--(END)-->
2612<?ENDINC p2-semantics.iana-headers ?>
2613<t>
2614   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
2615</t>
2616</section>
2617</section>
2618
2619<section title="Security Considerations" anchor="security.considerations">
2620<t>
2621   This section is meant to inform application developers, information
2622   providers, and users of the security limitations in HTTP/1.1 as
2623   described by this document. The discussion does not include
2624   definitive solutions to the problems revealed, though it does make
2625   some suggestions for reducing security risks.
2626</t>
2627
2628<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2629<t>
2630   Like any generic data transfer protocol, HTTP cannot regulate the
2631   content of the data that is transferred, nor is there any a priori
2632   method of determining the sensitivity of any particular piece of
2633   information within the context of any given request. Therefore,
2634   applications &SHOULD; supply as much control over this information as
2635   possible to the provider of that information. Four header fields are
2636   worth special mention in this context: Server, Via, Referer and From.
2637</t>
2638<t>
2639   Revealing the specific software version of the server might allow the
2640   server machine to become more vulnerable to attacks against software
2641   that is known to contain security holes. Implementors &SHOULD; make the
2642   Server header field a configurable option.
2643</t>
2644<t>
2645   Proxies which serve as a portal through a network firewall &SHOULD;
2646   take special precautions regarding the transfer of header information
2647   that identifies the hosts behind the firewall. In particular, they
2648   &SHOULD; remove, or replace with sanitized versions, any Via fields
2649   generated behind the firewall.
2650</t>
2651<t>
2652   The Referer header allows reading patterns to be studied and reverse
2653   links drawn. Although it can be very useful, its power can be abused
2654   if user details are not separated from the information contained in
2655   the Referer. Even when the personal information has been removed, the
2656   Referer header might indicate a private document's URI whose
2657   publication would be inappropriate.
2658</t>
2659<t>
2660   The information sent in the From field might conflict with the user's
2661   privacy interests or their site's security policy, and hence it
2662   &SHOULD-NOT;  be transmitted without the user being able to disable,
2663   enable, and modify the contents of the field. The user &MUST; be able
2664   to set the contents of this field within a user preference or
2665   application defaults configuration.
2666</t>
2667<t>
2668   We suggest, though do not require, that a convenient toggle interface
2669   be provided for the user to enable or disable the sending of From and
2670   Referer information.
2671</t>
2672<t>
2673   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref target="header.server"/>) header
2674   fields can sometimes be used to determine that a specific client or
2675   server have a particular security hole which might be exploited.
2676   Unfortunately, this same information is often used for other valuable
2677   purposes for which HTTP currently has no better mechanism.
2678</t>
2679<t>
2680   Some methods, like TRACE (<xref target="TRACE"/>) may expose
2681   information sent in request headers in the response entity.
2682   Clients &SHOULD; be careful with sensitive information, like Cookies,
2683   Authorization credentials and other headers that might be used to
2684   collect data from the client.
2685</t> 
2686</section>
2687
2688<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
2689<t>
2690   Because the source of a link might be private information or might
2691   reveal an otherwise private information source, it is strongly
2692   recommended that the user be able to select whether or not the
2693   Referer field is sent. For example, a browser client could have a
2694   toggle switch for browsing openly/anonymously, which would
2695   respectively enable/disable the sending of Referer and From
2696   information.
2697</t>
2698<t>
2699   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
2700   HTTP request if the referring page was transferred with a secure
2701   protocol.
2702</t>
2703<t>
2704   Authors of services should not use
2705   GET-based forms for the submission of sensitive data because that
2706   data will be encoded in the Request-target. Many existing
2707   servers, proxies, and user agents log or display the Request-target in
2708   places where it might be visible to third parties. Such services can
2709   use POST-based form submission instead.
2710</t>
2711</section>
2712
2713<section title="Location Headers and Spoofing" anchor="location.spoofing">
2714<t>
2715   If a single server supports multiple organizations that do not trust
2716   one another, then it &MUST; check the values of Location and Content-Location
2717   headers in responses that are generated under control of
2718   said organizations to make sure that they do not attempt to
2719   invalidate resources over which they have no authority.
2720</t>
2721</section>
2722
2723</section>
2724
2725<section title="Acknowledgments" anchor="ack">
2726</section>
2727</middle>
2728<back>
2729
2730<references title="Normative References">
2731
2732<reference anchor="Part1">
2733  <front>
2734    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
2735    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2736      <organization abbrev="Day Software">Day Software</organization>
2737      <address><email>fielding@gbiv.com</email></address>
2738    </author>
2739    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2740      <organization>One Laptop per Child</organization>
2741      <address><email>jg@laptop.org</email></address>
2742    </author>
2743    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2744      <organization abbrev="HP">Hewlett-Packard Company</organization>
2745      <address><email>JeffMogul@acm.org</email></address>
2746    </author>
2747    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2748      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2749      <address><email>henrikn@microsoft.com</email></address>
2750    </author>
2751    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2752      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2753      <address><email>LMM@acm.org</email></address>
2754    </author>
2755    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2756      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2757      <address><email>paulle@microsoft.com</email></address>
2758    </author>
2759    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2760      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2761      <address><email>timbl@w3.org</email></address>
2762    </author>
2763    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2764      <organization abbrev="W3C">World Wide Web Consortium</organization>
2765      <address><email>ylafon@w3.org</email></address>
2766    </author>
2767    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2768      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2769      <address><email>julian.reschke@greenbytes.de</email></address>
2770    </author>
2771    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2772  </front>
2773  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
2774  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
2775</reference>
2776
2777<reference anchor="Part3">
2778  <front>
2779    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
2780    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2781      <organization abbrev="Day Software">Day Software</organization>
2782      <address><email>fielding@gbiv.com</email></address>
2783    </author>
2784    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2785      <organization>One Laptop per Child</organization>
2786      <address><email>jg@laptop.org</email></address>
2787    </author>
2788    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2789      <organization abbrev="HP">Hewlett-Packard Company</organization>
2790      <address><email>JeffMogul@acm.org</email></address>
2791    </author>
2792    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2793      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2794      <address><email>henrikn@microsoft.com</email></address>
2795    </author>
2796    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2797      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2798      <address><email>LMM@acm.org</email></address>
2799    </author>
2800    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2801      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2802      <address><email>paulle@microsoft.com</email></address>
2803    </author>
2804    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2805      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2806      <address><email>timbl@w3.org</email></address>
2807    </author>
2808    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2809      <organization abbrev="W3C">World Wide Web Consortium</organization>
2810      <address><email>ylafon@w3.org</email></address>
2811    </author>
2812    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2813      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2814      <address><email>julian.reschke@greenbytes.de</email></address>
2815    </author>
2816    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2817  </front>
2818  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
2819  <x:source href="p3-payload.xml" basename="p3-payload"/>
2820</reference>
2821
2822<reference anchor="Part4">
2823  <front>
2824    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
2825    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2826      <organization abbrev="Day Software">Day Software</organization>
2827      <address><email>fielding@gbiv.com</email></address>
2828    </author>
2829    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2830      <organization>One Laptop per Child</organization>
2831      <address><email>jg@laptop.org</email></address>
2832    </author>
2833    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2834      <organization abbrev="HP">Hewlett-Packard Company</organization>
2835      <address><email>JeffMogul@acm.org</email></address>
2836    </author>
2837    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2838      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2839      <address><email>henrikn@microsoft.com</email></address>
2840    </author>
2841    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2842      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2843      <address><email>LMM@acm.org</email></address>
2844    </author>
2845    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2846      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2847      <address><email>paulle@microsoft.com</email></address>
2848    </author>
2849    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2850      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2851      <address><email>timbl@w3.org</email></address>
2852    </author>
2853    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2854      <organization abbrev="W3C">World Wide Web Consortium</organization>
2855      <address><email>ylafon@w3.org</email></address>
2856    </author>
2857    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2858      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2859      <address><email>julian.reschke@greenbytes.de</email></address>
2860    </author>
2861    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2862  </front>
2863  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
2864  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
2865</reference>
2866
2867<reference anchor="Part5">
2868  <front>
2869    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
2870    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2871      <organization abbrev="Day Software">Day Software</organization>
2872      <address><email>fielding@gbiv.com</email></address>
2873    </author>
2874    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2875      <organization>One Laptop per Child</organization>
2876      <address><email>jg@laptop.org</email></address>
2877    </author>
2878    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2879      <organization abbrev="HP">Hewlett-Packard Company</organization>
2880      <address><email>JeffMogul@acm.org</email></address>
2881    </author>
2882    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2883      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2884      <address><email>henrikn@microsoft.com</email></address>
2885    </author>
2886    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2887      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2888      <address><email>LMM@acm.org</email></address>
2889    </author>
2890    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2891      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2892      <address><email>paulle@microsoft.com</email></address>
2893    </author>
2894    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2895      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2896      <address><email>timbl@w3.org</email></address>
2897    </author>
2898    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2899      <organization abbrev="W3C">World Wide Web Consortium</organization>
2900      <address><email>ylafon@w3.org</email></address>
2901    </author>
2902    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2903      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2904      <address><email>julian.reschke@greenbytes.de</email></address>
2905    </author>
2906    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2907  </front>
2908  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
2909  <x:source href="p5-range.xml" basename="p5-range"/>
2910</reference>
2911
2912<reference anchor="Part6">
2913  <front>
2914    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
2915    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2916      <organization abbrev="Day Software">Day Software</organization>
2917      <address><email>fielding@gbiv.com</email></address>
2918    </author>
2919    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2920      <organization>One Laptop per Child</organization>
2921      <address><email>jg@laptop.org</email></address>
2922    </author>
2923    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2924      <organization abbrev="HP">Hewlett-Packard Company</organization>
2925      <address><email>JeffMogul@acm.org</email></address>
2926    </author>
2927    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2928      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2929      <address><email>henrikn@microsoft.com</email></address>
2930    </author>
2931    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2932      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2933      <address><email>LMM@acm.org</email></address>
2934    </author>
2935    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2936      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2937      <address><email>paulle@microsoft.com</email></address>
2938    </author>
2939    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2940      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2941      <address><email>timbl@w3.org</email></address>
2942    </author>
2943    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2944      <organization abbrev="W3C">World Wide Web Consortium</organization>
2945      <address><email>ylafon@w3.org</email></address>
2946    </author>
2947    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
2948      <address><email>mnot@mnot.net</email></address>
2949    </author>
2950    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2951      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2952      <address><email>julian.reschke@greenbytes.de</email></address>
2953    </author>
2954    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2955  </front>
2956  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
2957  <x:source href="p6-cache.xml" basename="p6-cache"/>
2958</reference>
2959
2960<reference anchor="Part7">
2961  <front>
2962    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
2963    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2964      <organization abbrev="Day Software">Day Software</organization>
2965      <address><email>fielding@gbiv.com</email></address>
2966    </author>
2967    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2968      <organization>One Laptop per Child</organization>
2969      <address><email>jg@laptop.org</email></address>
2970    </author>
2971    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2972      <organization abbrev="HP">Hewlett-Packard Company</organization>
2973      <address><email>JeffMogul@acm.org</email></address>
2974    </author>
2975    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2976      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2977      <address><email>henrikn@microsoft.com</email></address>
2978    </author>
2979    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2980      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2981      <address><email>LMM@acm.org</email></address>
2982    </author>
2983    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2984      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2985      <address><email>paulle@microsoft.com</email></address>
2986    </author>
2987    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2988      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2989      <address><email>timbl@w3.org</email></address>
2990    </author>
2991    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2992      <organization abbrev="W3C">World Wide Web Consortium</organization>
2993      <address><email>ylafon@w3.org</email></address>
2994    </author>
2995    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2996      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2997      <address><email>julian.reschke@greenbytes.de</email></address>
2998    </author>
2999    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3000  </front>
3001  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
3002  <x:source href="p7-auth.xml" basename="p7-auth"/>
3003</reference>
3004
3005<reference anchor="RFC2119">
3006  <front>
3007    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
3008    <author initials="S." surname="Bradner" fullname="Scott Bradner">
3009      <organization>Harvard University</organization>
3010      <address><email>sob@harvard.edu</email></address>
3011    </author>
3012    <date month="March" year="1997"/>
3013  </front>
3014  <seriesInfo name="BCP" value="14"/>
3015  <seriesInfo name="RFC" value="2119"/>
3016</reference>
3017
3018<reference anchor="RFC3986">
3019 <front>
3020  <title abbrev='URI Generic Syntax'>Uniform Resource Identifier (URI): Generic Syntax</title>
3021  <author initials='T.' surname='Berners-Lee' fullname='Tim Berners-Lee'>
3022    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3023    <address>
3024       <email>timbl@w3.org</email>
3025       <uri>http://www.w3.org/People/Berners-Lee/</uri>
3026    </address>
3027  </author>
3028  <author initials='R.' surname='Fielding' fullname='Roy T. Fielding'>
3029    <organization abbrev="Day Software">Day Software</organization>
3030    <address>
3031      <email>fielding@gbiv.com</email>
3032      <uri>http://roy.gbiv.com/</uri>
3033    </address>
3034  </author>
3035  <author initials='L.' surname='Masinter' fullname='Larry Masinter'>
3036    <organization abbrev="Adobe Systems">Adobe Systems Incorporated</organization>
3037    <address>
3038      <email>LMM@acm.org</email>
3039      <uri>http://larry.masinter.net/</uri>
3040    </address>
3041  </author>
3042  <date month='January' year='2005'></date>
3043 </front>
3044 <seriesInfo name="RFC" value="3986"/>
3045 <seriesInfo name="STD" value="66"/>
3046</reference>
3047
3048<reference anchor="RFC5234">
3049  <front>
3050    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
3051    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
3052      <organization>Brandenburg InternetWorking</organization>
3053      <address>
3054        <email>dcrocker@bbiw.net</email>
3055      </address> 
3056    </author>
3057    <author initials="P." surname="Overell" fullname="Paul Overell">
3058      <organization>THUS plc.</organization>
3059      <address>
3060        <email>paul.overell@thus.net</email>
3061      </address>
3062    </author>
3063    <date month="January" year="2008"/>
3064  </front>
3065  <seriesInfo name="STD" value="68"/>
3066  <seriesInfo name="RFC" value="5234"/>
3067</reference>
3068
3069</references>
3070
3071<references title="Informative References">
3072
3073<reference anchor="RFC1945">
3074  <front>
3075    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
3076    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3077      <organization>MIT, Laboratory for Computer Science</organization>
3078      <address><email>timbl@w3.org</email></address>
3079    </author>
3080    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
3081      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3082      <address><email>fielding@ics.uci.edu</email></address>
3083    </author>
3084    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3085      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
3086      <address><email>frystyk@w3.org</email></address>
3087    </author>
3088    <date month="May" year="1996"/>
3089  </front>
3090  <seriesInfo name="RFC" value="1945"/>
3091</reference>
3092
3093<reference anchor="RFC2068">
3094  <front>
3095    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
3096    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
3097      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3098      <address><email>fielding@ics.uci.edu</email></address>
3099    </author>
3100    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3101      <organization>MIT Laboratory for Computer Science</organization>
3102      <address><email>jg@w3.org</email></address>
3103    </author>
3104    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3105      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
3106      <address><email>mogul@wrl.dec.com</email></address>
3107    </author>
3108    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3109      <organization>MIT Laboratory for Computer Science</organization>
3110      <address><email>frystyk@w3.org</email></address>
3111    </author>
3112    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3113      <organization>MIT Laboratory for Computer Science</organization>
3114      <address><email>timbl@w3.org</email></address>
3115    </author>
3116    <date month="January" year="1997"/>
3117  </front>
3118  <seriesInfo name="RFC" value="2068"/>
3119</reference>
3120
3121<reference anchor="RFC2616">
3122  <front>
3123    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
3124    <author initials="R." surname="Fielding" fullname="R. Fielding">
3125      <organization>University of California, Irvine</organization>
3126      <address><email>fielding@ics.uci.edu</email></address>
3127    </author>
3128    <author initials="J." surname="Gettys" fullname="J. Gettys">
3129      <organization>W3C</organization>
3130      <address><email>jg@w3.org</email></address>
3131    </author>
3132    <author initials="J." surname="Mogul" fullname="J. Mogul">
3133      <organization>Compaq Computer Corporation</organization>
3134      <address><email>mogul@wrl.dec.com</email></address>
3135    </author>
3136    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
3137      <organization>MIT Laboratory for Computer Science</organization>
3138      <address><email>frystyk@w3.org</email></address>
3139    </author>
3140    <author initials="L." surname="Masinter" fullname="L. Masinter">
3141      <organization>Xerox Corporation</organization>
3142      <address><email>masinter@parc.xerox.com</email></address>
3143    </author>
3144    <author initials="P." surname="Leach" fullname="P. Leach">
3145      <organization>Microsoft Corporation</organization>
3146      <address><email>paulle@microsoft.com</email></address>
3147    </author>
3148    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
3149      <organization>W3C</organization>
3150      <address><email>timbl@w3.org</email></address>
3151    </author>
3152    <date month="June" year="1999"/>
3153  </front>
3154  <seriesInfo name="RFC" value="2616"/>
3155</reference>
3156
3157<reference anchor='RFC2817'>
3158  <front>
3159    <title>Upgrading to TLS Within HTTP/1.1</title>
3160    <author initials='R.' surname='Khare' fullname='R. Khare'>
3161      <organization>4K Associates / UC Irvine</organization>
3162      <address><email>rohit@4K-associates.com</email></address>
3163    </author>
3164    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
3165      <organization>Agranat Systems, Inc.</organization>
3166      <address><email>lawrence@agranat.com</email></address>
3167    </author>
3168    <date year='2000' month='May' />
3169  </front>
3170  <seriesInfo name='RFC' value='2817' />
3171</reference>
3172
3173<reference anchor='RFC3864'>
3174  <front>
3175    <title>Registration Procedures for Message Header Fields</title>
3176    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3177      <organization>Nine by Nine</organization>
3178      <address><email>GK-IETF@ninebynine.org</email></address>
3179    </author>
3180    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3181      <organization>BEA Systems</organization>
3182      <address><email>mnot@pobox.com</email></address>
3183    </author>
3184    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3185      <organization>HP Labs</organization>
3186      <address><email>JeffMogul@acm.org</email></address>
3187    </author>
3188    <date year='2004' month='September' />
3189  </front>
3190  <seriesInfo name='BCP' value='90' />
3191  <seriesInfo name='RFC' value='3864' />
3192</reference>
3193
3194<reference anchor='RFC5226'>
3195  <front>
3196    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3197    <author initials='T.' surname='Narten' fullname='T. Narten'>
3198      <organization>IBM</organization>
3199      <address><email>narten@us.ibm.com</email></address>
3200    </author>
3201    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3202      <organization>Google</organization>
3203      <address><email>Harald@Alvestrand.no</email></address>
3204    </author>
3205    <date year='2008' month='May' />
3206  </front>
3207  <seriesInfo name='BCP' value='26' />
3208  <seriesInfo name='RFC' value='5226' />
3209</reference>
3210
3211<reference anchor="RFC5322">
3212  <front>
3213    <title>Internet Message Format</title>
3214    <author initials="P." surname="Resnick" fullname="P. Resnick">
3215      <organization>Qualcomm Incorporated</organization>
3216    </author>
3217    <date year="2008" month="October"/>
3218  </front> 
3219  <seriesInfo name="RFC" value="5322"/>
3220</reference>
3221
3222</references>
3223
3224<section title="Compatibility with Previous Versions" anchor="compatibility">
3225<section title="Changes from RFC 2068" anchor="changes.from.rfc.2068">
3226<t>
3227   Clarified which error code should be used for inbound server failures
3228   (e.g., DNS failures). (<xref target="status.504"/>).
3229</t>
3230<t>
3231   201 (Created) had a race that required an Etag be sent when a resource is
3232   first created. (<xref target="status.201"/>).
3233</t>
3234<t>
3235   303 (See Also) and 307 (Temporary Redirect) added to address user agent
3236   failure to implement status code 302 properly.
3237   (Section <xref target="status.303" format="counter"/> and <xref target="status.307" format="counter"/>)
3238</t>
3239<t>
3240   Rewrite of message transmission requirements to make it much harder
3241   for implementors to get it wrong, as the consequences of errors here
3242   can have significant impact on the Internet, and to deal with the
3243   following problems:
3244  <list style="numbers">
3245      <t>Changing "HTTP/1.1 or later" to "HTTP/1.1", in contexts where
3246         this was incorrectly placing a requirement on the behavior of
3247         an implementation of a future version of HTTP/1.x</t>
3248
3249      <t>Made it clear that user-agents should retry requests, not
3250         "clients" in general.</t>
3251
3252      <t>Converted requirements for clients to ignore unexpected 100
3253         (Continue) responses, and for proxies to forward 100 responses,
3254         into a general requirement for 1xx responses.</t>
3255
3256      <t>Modified some TCP-specific language, to make it clearer that
3257         non-TCP transports are possible for HTTP.</t>
3258
3259      <t>Require that the origin server &MUST-NOT; wait for the request
3260         body before it sends a required 100 (Continue) response.</t>
3261
3262      <t>Allow, rather than require, a server to omit 100 (Continue) if
3263         it has already seen some of the request body.</t>
3264
3265      <t>Allow servers to defend against denial-of-service attacks and
3266         broken clients.</t>
3267  </list>
3268</t>
3269<t>
3270   This change adds the Expect header and 417 status code.
3271</t>
3272<t>
3273   Clean up confusion between 403 and 404 responses. (Section <xref target="status.403" format="counter"/>,
3274   <xref target="status.404" format="counter"/>, and <xref target="status.410" format="counter"/>)
3275</t>
3276<t>
3277   The PATCH<iref item="PATCH method" primary="true"/><iref item="Methods" subitem="PATCH" primary="true"/>, LINK<iref item="LINK method" primary="true"/><iref item="Methods" subitem="LINK" primary="true"/>, UNLINK<iref item="UNLINK method" primary="true"/><iref item="Methods" subitem="UNLINK" primary="true"/> methods were defined but not commonly
3278   implemented in previous versions of this specification. See <xref target="RFC2068" x:fmt="of" x:sec="19.6.1"/>.
3279</t>
3280</section>
3281
3282<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3283<t>
3284  This document takes over the Status Code Registry, previously defined
3285  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3286  (<xref target="status.code.registry"/>)
3287</t>
3288<t>
3289  Clarify definition of POST.
3290  (<xref target="POST"/>)
3291</t>
3292<t>
3293  Failed to consider that there are
3294  many other request methods that are safe to automatically redirect,
3295  and further that the user agent is able to make that determination
3296  based on the request method semantics.
3297  (Sections <xref format="counter" target="status.301"/>,
3298  <xref format="counter" target="status.302"/> and
3299  <xref format="counter" target="status.307"/>)
3300</t>
3301<t>
3302  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3303  It used to indicate that the requested resource must be accessed through the
3304  proxy given by the Location field. The Location field gave the URI of the
3305  proxy. The recipient was expected to repeat this single request via the proxy.
3306  (<xref target="status.305"/>)
3307</t>
3308<t>
3309  Reclassify Allow header as response header, removing the option to
3310  specify it in a PUT request.
3311  Relax the server requirement on the contents of the Allow header and
3312  remove requirement on clients to always trust the header value.
3313  (<xref target="header.allow"/>)
3314</t>
3315<t>
3316  Correct syntax of Location header to allow URI references (including
3317  relative references and fragments), as referred symbol "absoluteURI" wasn't
3318  what was expected, and add some clarifications as to when use of fragments
3319  would not be appropriate.
3320  (<xref target="header.location"/>)
3321</t>
3322<t>
3323  Allow Referer value of "about:blank" as alternative to not specifying it.
3324  (<xref target="header.referer"/>)
3325</t>
3326<t>
3327  In the description of the Server header, the Via field
3328  was described as a SHOULD. The requirement was and is stated
3329  correctly in the description of the Via header in &header-via;.
3330  (<xref target="header.server"/>)
3331</t>
3332</section>
3333
3334</section>
3335
3336<?BEGININC p2-semantics.abnf-appendix ?>
3337<section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf">
3338<figure>
3339<artwork type="abnf" name="p2-semantics.parsed-abnf">
3340<x:ref>Accept</x:ref> = &lt;Accept, defined in [Part3], Section 5.1&gt;
3341<x:ref>Accept-Charset</x:ref> = &lt;Accept-Charset, defined in [Part3], Section 5.2&gt;
3342<x:ref>Accept-Encoding</x:ref> = &lt;Accept-Encoding, defined in [Part3], Section 5.3&gt;
3343<x:ref>Accept-Language</x:ref> = &lt;Accept-Language, defined in [Part3], Section 5.4&gt;
3344<x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in [Part5], Section 5.1&gt;
3345<x:ref>Age</x:ref> = &lt;Age, defined in [Part6], Section 3.1&gt;
3346<x:ref>Allow</x:ref> = "Allow:" OWS Allow-v
3347<x:ref>Allow-v</x:ref> = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
3348<x:ref>Authorization</x:ref> = &lt;Authorization, defined in [Part7], Section 3.1&gt;
3349
3350<x:ref>ETag</x:ref> = &lt;ETag, defined in [Part4], Section 6.1&gt;
3351<x:ref>Expect</x:ref> = "Expect:" OWS Expect-v
3352<x:ref>Expect-v</x:ref> = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
3353
3354<x:ref>From</x:ref> = "From:" OWS From-v
3355<x:ref>From-v</x:ref> = mailbox
3356
3357<x:ref>HTTP-date</x:ref> = &lt;HTTP-date, defined in [Part1], Section 6.1&gt;
3358<x:ref>Host</x:ref> = &lt;Host, defined in [Part1], Section 2.6&gt;
3359
3360<x:ref>If-Match</x:ref> = &lt;If-Match, defined in [Part4], Section 6.2&gt;
3361If-Modified-Since =
3362 &lt;If-Modified-Since, defined in [Part4], Section 6.3&gt;
3363<x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in [Part4], Section 6.4&gt;
3364<x:ref>If-Range</x:ref> = &lt;If-Range, defined in [Part5], Section 5.3&gt;
3365If-Unmodified-Since =
3366 &lt;If-Unmodified-Since, defined in [Part4], Section 6.5&gt;
3367
3368<x:ref>Location</x:ref> = "Location:" OWS Location-v
3369<x:ref>Location-v</x:ref> = URI-reference
3370
3371<x:ref>Max-Forwards</x:ref> = "Max-Forwards:" OWS Max-Forwards-v
3372<x:ref>Max-Forwards-v</x:ref> = 1*DIGIT
3373<x:ref>Method</x:ref> = %x4F.50.54.49.4F.4E.53 ; OPTIONS
3374 / %x47.45.54 ; GET
3375 / %x48.45.41.44 ; HEAD
3376 / %x50.4F.53.54 ; POST
3377 / %x50.55.54 ; PUT
3378 / %x44.45.4C.45.54.45 ; DELETE
3379 / %x54.52.41.43.45 ; TRACE
3380 / %x43.4F.4E.4E.45.43.54 ; CONNECT
3381 / extension-method
3382
3383<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
3384
3385Proxy-Authenticate =
3386 &lt;Proxy-Authenticate, defined in [Part7], Section 3.2&gt;
3387Proxy-Authorization =
3388 &lt;Proxy-Authorization, defined in [Part7], Section 3.3&gt;
3389
3390<x:ref>RWS</x:ref> = &lt;RWS, defined in [Part1], Section 1.2.2&gt;
3391<x:ref>Range</x:ref> = &lt;Range, defined in [Part5], Section 5.4&gt;
3392<x:ref>Reason-Phrase</x:ref> = *( WSP / VCHAR / obs-text )
3393<x:ref>Referer</x:ref> = "Referer:" OWS Referer-v
3394<x:ref>Referer-v</x:ref> = absolute-URI / partial-URI
3395<x:ref>Retry-After</x:ref> = "Retry-After:" OWS Retry-After-v
3396<x:ref>Retry-After-v</x:ref> = HTTP-date / delta-seconds
3397
3398<x:ref>Server</x:ref> = "Server:" OWS Server-v
3399<x:ref>Server-v</x:ref> = product *( RWS ( product / comment ) )
3400<x:ref>Status-Code</x:ref> = "100" / "101" / "200" / "201" / "202" / "203" / "204" /
3401 "205" / "206" / "300" / "301" / "302" / "303" / "304" / "305" /
3402 "307" / "400" / "401" / "402" / "403" / "404" / "405" / "406" /
3403 "407" / "408" / "409" / "410" / "411" / "412" / "413" / "414" /
3404 "415" / "416" / "417" / "500" / "501" / "502" / "503" / "504" /
3405 "505" / extension-code
3406
3407<x:ref>TE</x:ref> = &lt;TE, defined in [Part1], Section 9.8&gt;
3408
3409<x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in [Part1], Section 2.6&gt;
3410<x:ref>User-Agent</x:ref> = "User-Agent:" OWS User-Agent-v
3411<x:ref>User-Agent-v</x:ref> = product *( RWS ( product / comment ) )
3412
3413<x:ref>Vary</x:ref> = &lt;Vary, defined in [Part6], Section 3.5&gt;
3414
3415WWW-Authenticate =
3416 &lt;WWW-Authenticate, defined in [Part7], Section 3.4&gt;
3417
3418<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.6&gt;
3419
3420<x:ref>comment</x:ref> = &lt;comment, defined in [Part1], Section 3.2&gt;
3421
3422<x:ref>delta-seconds</x:ref> = 1*DIGIT
3423
3424<x:ref>expect-params</x:ref> = ";" token [ "=" ( token / quoted-string ) ]
3425<x:ref>expectation</x:ref> = "100-continue" / expectation-extension
3426<x:ref>expectation-extension</x:ref> = token [ "=" ( token / quoted-string )
3427 *expect-params ]
3428<x:ref>extension-code</x:ref> = 3DIGIT
3429<x:ref>extension-method</x:ref> = token
3430
3431<x:ref>mailbox</x:ref> = &lt;mailbox, defined in [RFC5322], Section 3.4&gt;
3432
3433<x:ref>obs-text</x:ref> = &lt;obs-text, defined in [Part1], Section 1.2.2&gt;
3434
3435<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.6&gt;
3436<x:ref>product</x:ref> = &lt;product, defined in [Part1], Section 6.3&gt;
3437
3438<x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in [Part1], Section 1.2.2&gt;
3439
3440<x:ref>request-header</x:ref> = Accept / Accept-Charset / Accept-Encoding /
3441 Accept-Language / Authorization / Expect / From / Host / If-Match /
3442 If-Modified-Since / If-None-Match / If-Range / If-Unmodified-Since /
3443 Max-Forwards / Proxy-Authorization / Range / Referer / TE /
3444 User-Agent
3445<x:ref>response-header</x:ref> = Accept-Ranges / Age / Allow / ETag / Location /
3446 Proxy-Authenticate / Retry-After / Server / Vary / WWW-Authenticate
3447
3448<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 1.2.2&gt;
3449</artwork>
3450</figure>
3451<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
3452; Reason-Phrase defined but not used
3453; Status-Code defined but not used
3454; request-header defined but not used
3455; response-header defined but not used
3456</artwork></figure></section>
3457<?ENDINC p2-semantics.abnf-appendix ?>
3458
3459<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
3460
3461<section title="Since RFC2616">
3462<t>
3463  Extracted relevant partitions from <xref target="RFC2616"/>.
3464</t>
3465</section>
3466
3467<section title="Since draft-ietf-httpbis-p2-semantics-00">
3468<t>
3469  Closed issues:
3470  <list style="symbols"> 
3471    <t>
3472      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
3473      "Via is a MUST"
3474      (<eref target="http://purl.org/NET/http-errata#via-must"/>)
3475    </t>
3476    <t>
3477      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
3478      "Fragments allowed in Location"
3479      (<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
3480    </t>
3481    <t>
3482      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3483      "Safe Methods vs Redirection"
3484      (<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
3485    </t>
3486    <t>
3487      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
3488      "Revise description of the POST method"
3489      (<eref target="http://purl.org/NET/http-errata#post"/>)
3490    </t>
3491    <t>
3492      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
3493      "Normative and Informative references"
3494    </t>
3495    <t>
3496      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
3497      "RFC2606 Compliance"
3498    </t>
3499    <t>
3500      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
3501      "Informative references"
3502    </t>
3503    <t>
3504      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
3505      "Redundant cross-references"
3506    </t>
3507  </list>
3508</t>
3509<t>
3510  Other changes:
3511  <list style="symbols"> 
3512    <t>
3513      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
3514    </t>
3515  </list>
3516</t>
3517</section>
3518
3519<section title="Since draft-ietf-httpbis-p2-semantics-01">
3520<t>
3521  Closed issues:
3522  <list style="symbols"> 
3523    <t>
3524      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
3525      "PUT side effects"
3526    </t>
3527    <t>
3528      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
3529      "Duplicate Host header requirements"
3530    </t>
3531  </list>
3532</t>
3533<t>
3534  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3535  <list style="symbols"> 
3536    <t>
3537      Move "Product Tokens" section (back) into Part 1, as "token" is used
3538      in the definition of the Upgrade header.
3539    </t>
3540    <t>
3541      Add explicit references to BNF syntax and rules imported from other parts of the specification.
3542    </t>
3543    <t>
3544      Copy definition of delta-seconds from Part6 instead of referencing it.
3545    </t>
3546  </list>
3547</t>
3548</section>
3549
3550<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
3551<t>
3552  Closed issues:
3553  <list style="symbols"> 
3554    <t>
3555      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/24"/>:
3556      "Requiring Allow in 405 responses"
3557    </t>
3558    <t>
3559      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/59"/>:
3560      "Status Code Registry"
3561    </t>
3562    <t>
3563      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/61"/>:
3564      "Redirection vs. Location"
3565    </t>
3566    <t>
3567      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/70"/>:
3568      "Cacheability of 303 response"
3569    </t>
3570    <t>
3571      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/76"/>:
3572      "305 Use Proxy"
3573    </t>
3574    <t>
3575      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
3576      "Classification for Allow header"
3577    </t>
3578    <t>
3579      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
3580      "PUT - 'store under' vs 'store at'"
3581    </t>
3582  </list>
3583</t>
3584<t>
3585  Ongoing work on IANA Message Header Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
3586  <list style="symbols"> 
3587    <t>
3588      Reference RFC 3984, and update header registrations for headers defined
3589      in this document.
3590    </t>
3591  </list>
3592</t>
3593<t>
3594  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3595  <list style="symbols"> 
3596    <t>
3597      Replace string literals when the string really is case-sensitive (method).
3598    </t>
3599  </list>
3600</t>
3601</section>
3602
3603<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
3604<t>
3605  Closed issues:
3606  <list style="symbols"> 
3607    <t>
3608      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/98"/>:
3609      "OPTIONS request bodies"
3610    </t>
3611    <t>
3612      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/119"/>:
3613      "Description of CONNECT should refer to RFC2817"
3614    </t>
3615    <t>
3616      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/125"/>:
3617      "Location Content-Location reference request/response mixup"
3618    </t>
3619  </list>
3620</t>
3621<t>
3622  Ongoing work on Method Registry (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/72"/>):
3623  <list style="symbols"> 
3624    <t>
3625      Added initial proposal for registration process, plus initial
3626      content (non-HTTP/1.1 methods to be added by a separate specification).
3627    </t>
3628  </list>
3629</t>
3630</section>
3631
3632<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
3633<t>
3634  Closed issues:
3635  <list style="symbols"> 
3636    <t>
3637      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
3638      "Content-*"
3639    </t>
3640    <t>
3641      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
3642      "RFC 2822 is updated by RFC 5322"
3643    </t>
3644  </list>
3645</t>
3646<t>
3647  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3648  <list style="symbols"> 
3649    <t>
3650      Use "/" instead of "|" for alternatives.
3651    </t>
3652    <t>
3653      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
3654      whitespace ("OWS") and required whitespace ("RWS").
3655    </t>
3656    <t>
3657      Rewrite ABNFs to spell out whitespace rules, factor out
3658      header value format definitions.
3659    </t>
3660  </list>
3661</t>
3662</section>
3663
3664<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
3665<t>
3666  Closed issues:
3667  <list style="symbols"> 
3668    <t>
3669      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/94"/>:
3670      "Reason-Phrase BNF"
3671    </t>
3672  </list>
3673</t>
3674<t>
3675  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3676  <list style="symbols"> 
3677    <t>
3678      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
3679    </t>
3680  </list>
3681</t>
3682</section>
3683
3684<section title="Since draft-ietf-httpbis-p2-semantics-06" anchor="changes.since.06">
3685<t>
3686  Closed issues:
3687  <list style="symbols"> 
3688    <t>
3689      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/144"/>:
3690      "Clarify when Referer is sent"
3691    </t>
3692    <t>
3693      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/164"/>:
3694      "status codes vs methods"
3695    </t>
3696    <t>
3697      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/170"/>:
3698      "Do not require "updates" relation for specs that register status codes or method names"
3699    </t>
3700  </list>
3701</t>
3702</section>
3703
3704<section title="Since draft-ietf-httpbis-p2-semantics-07" anchor="changes.since.07">
3705<t>
3706  Closed issues:
3707  <list style="symbols"> 
3708    <t>
3709      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/27"/>:
3710      "Idempotency"
3711    </t>
3712    <t>
3713      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/33"/>:
3714      "TRACE security considerations"
3715    </t>
3716    <t>
3717      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
3718      "Clarify rules for determining what entities a response carries"
3719    </t>
3720    <t>
3721      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/140"/>:
3722      "update note citing RFC 1945 and 2068"
3723    </t>
3724    <t>
3725      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/182"/>:
3726      "update note about redirect limit"
3727    </t>
3728    <t>
3729      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/191"/>:
3730      "Location header ABNF should use 'URI'"
3731    </t>
3732    <t>
3733      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/192"/>:
3734      "fragments in Location vs status 303"
3735    </t>
3736    <t>
3737      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/198"/>:
3738      "move IANA registrations for optional status codes"
3739    </t>
3740  </list>
3741</t>
3742<t>
3743  Partly resolved issues:
3744  <list style="symbols"> 
3745    <t>
3746      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/171"/>:
3747      "Are OPTIONS and TRACE safe?"
3748    </t>
3749  </list>
3750</t>
3751</section>
3752
3753<section title="Since draft-ietf-httpbis-p2-semantics-08" anchor="changes.since.08">
3754<t>
3755  Closed issues:
3756  <list style="symbols"> 
3757    <t>
3758      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3759      "Safe Methods vs Redirection" (we missed the introduction to the 3xx
3760      status codes when fixing this previously)
3761    </t>
3762  </list>
3763</t>
3764</section>
3765
3766<section title="Since draft-ietf-httpbis-p2-semantics-09" anchor="changes.since.09">
3767<t>
3768  Closed issues:
3769  <list style="symbols"> 
3770    <t>
3771      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
3772      "Fragment combination / precedence during redirects"
3773    </t>
3774  </list>
3775</t>
3776<t>
3777  Partly resolved issues:
3778  <list style="symbols"> 
3779    <t>
3780      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/185"/>:
3781      "Location header payload handling"
3782    </t>
3783  </list>
3784</t>
3785</section>
3786
3787</section>
3788
3789</back>
3790</rfc>
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