source: draft-ietf-httpbis/latest/p2-semantics.xml @ 856

Last change on this file since 856 was 856, checked in by fielding@…, 9 years ago

Addresses #69: Clarify "Requested Variant"
Addresses #109: Clarify entity / representation / variant terminology

Replaced entity with payload and variant with representation.
Cleaned up description of 204 status code (related to ticket #22)
Rewrote section on Content-Location and refer to def in RFC2557.

Addresses #110: Clarify rules for determining what entities a response carries

Detail the rules for Content-Location and remove the cross-ref.

Addresses #167: Content-Location on 304 responses

Removed sentence in C-Loc that refers to using C-Loc to select a

variant from cache (an already removed "feature")

Addresses #136: confusing req. language for Content-Location

Removed the confusing paragraph because HTTP does not know
anything about variants behind the resource interface and
thus cannot make this an interop requirement. In any case,
it only existed to support the already removed cache feature
that nobody implemented.

Addresses #80: Content-Location isn't special

Clarifies that C-Loc is representation metadata and what
(not) to do with it if received on a request.

  • Property svn:eol-style set to native
File size: 161.5 KB
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1<?xml version="1.0" encoding="utf-8"?>
2<?xml-stylesheet type='text/xsl' href='../myxml2rfc.xslt'?>
3<!DOCTYPE rfc [
4  <!ENTITY MAY "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MAY</bcp14>">
5  <!ENTITY MUST "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST</bcp14>">
6  <!ENTITY MUST-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST NOT</bcp14>">
7  <!ENTITY OPTIONAL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>OPTIONAL</bcp14>">
8  <!ENTITY RECOMMENDED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>RECOMMENDED</bcp14>">
9  <!ENTITY REQUIRED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>REQUIRED</bcp14>">
10  <!ENTITY SHALL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL</bcp14>">
11  <!ENTITY SHALL-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL NOT</bcp14>">
12  <!ENTITY SHOULD "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD</bcp14>">
13  <!ENTITY SHOULD-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD NOT</bcp14>">
14  <!ENTITY ID-VERSION "latest">
15  <!ENTITY ID-MONTH "July">
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 effective-request-uri      "<xref target='Part1' x:rel='#effective.request.uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
30  <!ENTITY full-date                  "<xref target='Part1' x:rel='#date.time.formats.full.date' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
31  <!ENTITY http-url                   "<xref target='Part1' x:rel='#http-url' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
32  <!ENTITY http-version               "<xref target='Part1' x:rel='#http.version' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
33  <!ENTITY use100                     "<xref target='Part1' x:rel='#use.of.the.100.status' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
34  <!ENTITY qvalue                     "<xref target='Part3' x:rel='#quality.values' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
35  <!ENTITY header-accept              "<xref target='Part3' x:rel='#header.accept' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
36  <!ENTITY header-accept-charset      "<xref target='Part3' x:rel='#header.accept-charset' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
37  <!ENTITY header-accept-encoding     "<xref target='Part3' x:rel='#header.accept-encoding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
38  <!ENTITY header-accept-language     "<xref target='Part3' x:rel='#header.accept-language' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
39  <!ENTITY header-accept-ranges       "<xref target='Part5' x:rel='#header.accept-ranges' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
40  <!ENTITY header-age                 "<xref target='Part6' x:rel='#header.age' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
41  <!ENTITY header-authorization       "<xref target='Part7' x:rel='#header.authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
42  <!ENTITY header-cache-control       "<xref target='Part6' x:rel='#header.cache-control' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
43  <!ENTITY header-content-location    "<xref target='Part3' x:rel='#header.content-location' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
44  <!ENTITY header-content-range       "<xref target='Part5' x:rel='#header.content-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
45  <!ENTITY header-etag                "<xref target='Part4' x:rel='#header.etag' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
46  <!ENTITY header-expires             "<xref target='Part6' x:rel='#header.expires' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
47  <!ENTITY header-fields              "<xref target='Part1' x:rel='#header.fields' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
48  <!ENTITY header-host                "<xref target='Part1' x:rel='#header.host' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
49  <!ENTITY header-if-match            "<xref target='Part4' x:rel='#header.if-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
50  <!ENTITY header-if-modified-since   "<xref target='Part4' x:rel='#header.if-modified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
51  <!ENTITY header-if-none-match       "<xref target='Part4' x:rel='#header.if-none-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
52  <!ENTITY header-if-range            "<xref target='Part5' x:rel='#header.if-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
53  <!ENTITY header-if-unmodified-since "<xref target='Part4' x:rel='#header.if-unmodified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
54  <!ENTITY header-pragma              "<xref target='Part6' x:rel='#header.pragma' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
55  <!ENTITY header-proxy-authenticate  "<xref target='Part7' x:rel='#header.proxy-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
56  <!ENTITY header-proxy-authorization "<xref target='Part7' x:rel='#header.proxy-authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
57  <!ENTITY header-range               "<xref target='Part5' x:rel='#header.range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
58  <!ENTITY header-upgrade             "<xref target='Part1' x:rel='#header.upgrade' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
59  <!ENTITY header-te                  "<xref target='Part1' x:rel='#header.te' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
60  <!ENTITY header-vary                "<xref target='Part6' x:rel='#header.vary' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
61  <!ENTITY header-via                 "<xref target='Part1' x:rel='#header.via' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
62  <!ENTITY header-warning             "<xref target='Part6' x:rel='#header.warning' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
63  <!ENTITY header-www-authenticate    "<xref target='Part7' x:rel='#header.www-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
64  <!ENTITY message-body               "<xref target='Part1' x:rel='#message.body' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
65  <!ENTITY product-tokens             "<xref target='Part1' x:rel='#product.tokens' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
66  <!ENTITY media-type-message-http    "<xref target='Part1' x:rel='#internet.media.type.message.http' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
67  <!ENTITY status-206                 "<xref target='Part5' x:rel='#status.206' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
68  <!ENTITY status-304                 "<xref target='Part4' x:rel='#status.304' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
69  <!ENTITY status-401                 "<xref target='Part7' x:rel='#status.401' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
70  <!ENTITY status-407                 "<xref target='Part7' x:rel='#status.407' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
71  <!ENTITY status-412                 "<xref target='Part4' x:rel='#status.412' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
72  <!ENTITY status-416                 "<xref target='Part5' x:rel='#status.416' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
73  <!ENTITY p4-status-codes            "<xref target='Part4' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
74  <!ENTITY p5-status-codes            "<xref target='Part5' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
75  <!ENTITY p7-status-codes            "<xref target='Part7' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
76]>
77<?rfc toc="yes" ?>
78<?rfc symrefs="yes" ?>
79<?rfc sortrefs="yes" ?>
80<?rfc compact="yes"?>
81<?rfc subcompact="no" ?>
82<?rfc linkmailto="no" ?>
83<?rfc editing="no" ?>
84<?rfc comments="yes"?>
85<?rfc inline="yes"?>
86<?rfc rfcedstyle="yes"?>
87<?rfc-ext allow-markup-in-artwork="yes" ?>
88<?rfc-ext include-references-in-index="yes" ?>
89<rfc obsoletes="2616" updates="2817" category="std" x:maturity-level="draft"
90     ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"
91     xmlns:x='http://purl.org/net/xml2rfc/ext'
92     xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#'>
93<front>
94
95  <title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
96
97  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
98    <organization abbrev="Day Software">Day Software</organization>
99    <address>
100      <postal>
101        <street>23 Corporate Plaza DR, Suite 280</street>
102        <city>Newport Beach</city>
103        <region>CA</region>
104        <code>92660</code>
105        <country>USA</country>
106      </postal>
107      <phone>+1-949-706-5300</phone>
108      <facsimile>+1-949-706-5305</facsimile>
109      <email>fielding@gbiv.com</email>
110      <uri>http://roy.gbiv.com/</uri>
111    </address>
112  </author>
113
114  <author initials="J." surname="Gettys" fullname="Jim Gettys">
115    <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
116    <address>
117      <postal>
118        <street>21 Oak Knoll Road</street>
119        <city>Carlisle</city>
120        <region>MA</region>
121        <code>01741</code>
122        <country>USA</country>
123      </postal>
124      <email>jg@freedesktop.org</email>
125      <uri>http://gettys.wordpress.com/</uri>
126    </address>
127  </author>
128 
129  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
130    <organization abbrev="HP">Hewlett-Packard Company</organization>
131    <address>
132      <postal>
133        <street>HP Labs, Large Scale Systems Group</street>
134        <street>1501 Page Mill Road, MS 1177</street>
135        <city>Palo Alto</city>
136        <region>CA</region>
137        <code>94304</code>
138        <country>USA</country>
139      </postal>
140      <email>JeffMogul@acm.org</email>
141    </address>
142  </author>
143
144  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
145    <organization abbrev="Microsoft">Microsoft Corporation</organization>
146    <address>
147      <postal>
148        <street>1 Microsoft Way</street>
149        <city>Redmond</city>
150        <region>WA</region>
151        <code>98052</code>
152        <country>USA</country>
153      </postal>
154      <email>henrikn@microsoft.com</email>
155    </address>
156  </author>
157
158  <author initials="L." surname="Masinter" fullname="Larry Masinter">
159    <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
160    <address>
161      <postal>
162        <street>345 Park Ave</street>
163        <city>San Jose</city>
164        <region>CA</region>
165        <code>95110</code>
166        <country>USA</country>
167      </postal>
168      <email>LMM@acm.org</email>
169      <uri>http://larry.masinter.net/</uri>
170    </address>
171  </author>
172 
173  <author initials="P." surname="Leach" fullname="Paul J. Leach">
174    <organization abbrev="Microsoft">Microsoft Corporation</organization>
175    <address>
176      <postal>
177        <street>1 Microsoft Way</street>
178        <city>Redmond</city>
179        <region>WA</region>
180        <code>98052</code>
181      </postal>
182      <email>paulle@microsoft.com</email>
183    </address>
184  </author>
185   
186  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
187    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
188    <address>
189      <postal>
190        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
191        <street>The Stata Center, Building 32</street>
192        <street>32 Vassar Street</street>
193        <city>Cambridge</city>
194        <region>MA</region>
195        <code>02139</code>
196        <country>USA</country>
197      </postal>
198      <email>timbl@w3.org</email>
199      <uri>http://www.w3.org/People/Berners-Lee/</uri>
200    </address>
201  </author>
202
203  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
204    <organization abbrev="W3C">World Wide Web Consortium</organization>
205    <address>
206      <postal>
207        <street>W3C / ERCIM</street>
208        <street>2004, rte des Lucioles</street>
209        <city>Sophia-Antipolis</city>
210        <region>AM</region>
211        <code>06902</code>
212        <country>France</country>
213      </postal>
214      <email>ylafon@w3.org</email>
215      <uri>http://www.raubacapeu.net/people/yves/</uri>
216    </address>
217  </author>
218
219  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
220    <organization abbrev="greenbytes">greenbytes GmbH</organization>
221    <address>
222      <postal>
223        <street>Hafenweg 16</street>
224        <city>Muenster</city><region>NW</region><code>48155</code>
225        <country>Germany</country>
226      </postal>
227      <phone>+49 251 2807760</phone>
228      <facsimile>+49 251 2807761</facsimile>
229      <email>julian.reschke@greenbytes.de</email>
230      <uri>http://greenbytes.de/tech/webdav/</uri>
231    </address>
232  </author>
233
234  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
235  <workgroup>HTTPbis Working Group</workgroup>
236
237<abstract>
238<t>
239   The Hypertext Transfer Protocol (HTTP) is an application-level
240   protocol for distributed, collaborative, hypermedia information
241   systems. HTTP has been in use by the World Wide Web global information
242   initiative since 1990. This document is Part 2 of the seven-part specification
243   that defines the protocol referred to as "HTTP/1.1" and, taken together,
244   obsoletes RFC 2616.  Part 2 defines the semantics of HTTP messages
245   as expressed by request methods, request-header fields, response status codes,
246   and response-header fields.
247</t>
248</abstract>
249
250<note title="Editorial Note (To be removed by RFC Editor)">
251  <t>
252    Discussion of this draft should take place on the HTTPBIS working group
253    mailing list (ietf-http-wg@w3.org). The current issues list is
254    at <eref target="http://tools.ietf.org/wg/httpbis/trac/report/3"/>
255    and related documents (including fancy diffs) can be found at
256    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
257  </t>
258  <t>
259    The changes in this draft are summarized in <xref target="changes.since.10"/>.
260  </t>
261</note>
262</front>
263<middle>
264<section title="Introduction" anchor="introduction">
265<t>
266   This document defines HTTP/1.1 request and response semantics.  Each HTTP
267   message, as defined in &messaging;, is in the form of either a request or
268   a response.  An HTTP server listens on a connection for HTTP requests and
269   responds to each request, in the order received on that connection, with
270   one or more HTTP response messages.  This document defines the commonly
271   agreed upon semantics of the HTTP uniform interface, the intentions defined
272   by each request method, and the various response messages that might be
273   expected as a result of applying that method for the requested resource.
274</t>
275<t>
276   This document is currently disorganized in order to minimize the changes
277   between drafts and enable reviewers to see the smaller errata changes.
278   The next draft will reorganize the sections to better reflect the content.
279   In particular, the sections will be ordered according to the typical
280   processing of an HTTP request message (after message parsing): resource
281   mapping, general header fields, methods, request modifiers, response
282   status, and resource metadata.  The current mess reflects how widely
283   dispersed these topics and associated requirements had become in
284   <xref target="RFC2616"/>.
285</t>
286
287<section title="Requirements" anchor="intro.requirements">
288<t>
289   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
290   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
291   document are to be interpreted as described in <xref target="RFC2119"/>.
292</t>
293<t>
294   An implementation is not compliant if it fails to satisfy one or more
295   of the "MUST" or "REQUIRED" level requirements for the protocols it
296   implements. An implementation that satisfies all the "MUST" or "REQUIRED"
297   level and all the "SHOULD" level requirements for its protocols is said
298   to be "unconditionally compliant"; one that satisfies all the "MUST"
299   level requirements but not all the "SHOULD" level requirements for its
300   protocols is said to be "conditionally compliant".
301</t>
302</section>
303
304<section title="Syntax Notation" anchor="notation">
305  <x:anchor-alias value="CR"/>
306  <x:anchor-alias value="DIGIT"/>
307  <x:anchor-alias value="LF"/>
308  <x:anchor-alias value="VCHAR"/>
309  <x:anchor-alias value="WSP"/>
310<t>
311  This specification uses the ABNF syntax defined in &notation; (which
312  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
313  <xref target="collected.abnf"/> shows the collected ABNF, with the list
314  rule expanded.
315</t>
316<t>
317  The following core rules are included by
318  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
319  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
320  DIGIT (decimal 0-9), DQUOTE (double quote),
321  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
322  OCTET (any 8-bit sequence of data), SP (space),
323  VCHAR (any visible USASCII character),
324  and WSP (whitespace).
325</t>
326
327<section title="Core Rules" anchor="core.rules">
328  <x:anchor-alias value="obs-text"/>
329  <x:anchor-alias value="quoted-string"/>
330  <x:anchor-alias value="token"/>
331  <x:anchor-alias value="OWS"/>
332  <x:anchor-alias value="RWS"/>
333<t>
334  The core rules below are defined in &basic-rules;:
335</t>
336<figure><artwork type="abnf2616">
337  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &basic-rules;&gt;
338  <x:ref>token</x:ref>         = &lt;token, defined in &basic-rules;&gt;
339  <x:ref>OWS</x:ref>           = &lt;OWS, defined in &basic-rules;&gt;
340  <x:ref>RWS</x:ref>           = &lt;RWS, defined in &basic-rules;&gt;
341  <x:ref>obs-text</x:ref>      = &lt;obs-text, defined in &basic-rules;&gt;
342</artwork></figure>
343</section>
344
345<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
346  <x:anchor-alias value="absolute-URI"/>
347  <x:anchor-alias value="Accept"/>
348  <x:anchor-alias value="Accept-Charset"/>
349  <x:anchor-alias value="Accept-Encoding"/>
350  <x:anchor-alias value="Accept-Language"/>
351  <x:anchor-alias value="Accept-Ranges"/>
352  <x:anchor-alias value="Age"/>
353  <x:anchor-alias value="Authorization"/>
354  <x:anchor-alias value="comment"/>
355  <x:anchor-alias value="ETag"/>
356  <x:anchor-alias value="Host"/>
357  <x:anchor-alias value="HTTP-date"/>
358  <x:anchor-alias value="If-Match"/>
359  <x:anchor-alias value="If-Modified-Since"/>
360  <x:anchor-alias value="If-None-Match"/>
361  <x:anchor-alias value="If-Range"/>
362  <x:anchor-alias value="If-Unmodified-Since"/>
363  <x:anchor-alias value="partial-URI"/>
364  <x:anchor-alias value="product"/>
365  <x:anchor-alias value="Proxy-Authenticate"/>
366  <x:anchor-alias value="Proxy-Authorization"/>
367  <x:anchor-alias value="Range"/>
368  <x:anchor-alias value="TE"/>
369  <x:anchor-alias value="URI-reference"/>
370  <x:anchor-alias value="Vary"/>
371  <x:anchor-alias value="WWW-Authenticate"/>
372<t>
373  The ABNF rules below are defined in other parts:
374</t>
375<figure><!--Part1--><artwork type="abnf2616">
376  <x:ref>absolute-URI</x:ref>  = &lt;absolute-URI, defined in &uri;&gt;
377  <x:ref>comment</x:ref>       = &lt;comment, defined in &header-fields;&gt;
378  <x:ref>Host</x:ref>          = &lt;Host, defined in &uri;&gt;
379  <x:ref>HTTP-date</x:ref>     = &lt;HTTP-date, defined in &full-date;&gt;
380  <x:ref>partial-URI</x:ref>   = &lt;partial-URI, defined in &uri;&gt;
381  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
382  <x:ref>TE</x:ref>            = &lt;TE, defined in &header-te;&gt;
383  <x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in &uri;&gt;
384</artwork></figure>
385<figure><!--Part3--><artwork type="abnf2616">
386  <x:ref>Accept</x:ref>        = &lt;Accept, defined in &header-accept;&gt;
387  <x:ref>Accept-Charset</x:ref> =
388             &lt;Accept-Charset, defined in &header-accept-charset;&gt;
389  <x:ref>Accept-Encoding</x:ref> =
390             &lt;Accept-Encoding, defined in &header-accept-encoding;&gt;
391  <x:ref>Accept-Language</x:ref> =
392             &lt;Accept-Language, defined in &header-accept-language;&gt;
393</artwork></figure>
394<figure><!--Part4--><artwork type="abnf2616">
395  <x:ref>ETag</x:ref>          = &lt;ETag, defined in &header-etag;&gt;
396  <x:ref>If-Match</x:ref>      = &lt;If-Match, defined in &header-if-match;&gt;
397  <x:ref>If-Modified-Since</x:ref> =
398             &lt;If-Modified-Since, defined in &header-if-modified-since;&gt;
399  <x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in &header-if-none-match;&gt;
400  <x:ref>If-Unmodified-Since</x:ref> =
401             &lt;If-Unmodified-Since, defined in &header-if-unmodified-since;&gt;
402</artwork></figure>
403<figure><!--Part5--><artwork type="abnf2616">
404  <x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in &header-accept-ranges;&gt;
405  <x:ref>If-Range</x:ref>      = &lt;If-Range, defined in &header-if-range;&gt;
406  <x:ref>Range</x:ref>         = &lt;Range, defined in &header-range;&gt;
407</artwork></figure>
408<figure><!--Part6--><artwork type="abnf2616">
409  <x:ref>Age</x:ref>           = &lt;Age, defined in &header-age;&gt;
410  <x:ref>Vary</x:ref>          = &lt;Vary, defined in &header-vary;&gt;
411</artwork><!--Part7--></figure>
412<figure><artwork type="abnf2616">
413  <x:ref>Authorization</x:ref> = &lt;Authorization, defined in &header-authorization;&gt;
414  <x:ref>Proxy-Authenticate</x:ref> =
415             &lt;Proxy-Authenticate, defined in &header-proxy-authenticate;&gt;
416  <x:ref>Proxy-Authorization</x:ref> =
417             &lt;Proxy-Authorization, defined in &header-proxy-authorization;&gt;
418  <x:ref>WWW-Authenticate</x:ref> =
419             &lt;WWW-Authenticate, defined in &header-www-authenticate;&gt;
420</artwork></figure>
421</section>
422</section>
423</section>
424
425<section title="Method" anchor="method">
426  <x:anchor-alias value="Method"/>
427  <x:anchor-alias value="extension-method"/>
428<t>
429   The Method token indicates the method to be performed on the resource
430   identified by the Effective Request URI (&effective-request-uri;). The
431   method is case-sensitive.
432</t>
433<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/><iref primary="true" item="Grammar" subitem="extension-method"/>
434  <x:ref>Method</x:ref>         = <x:abnf-char-sequence>"OPTIONS"</x:abnf-char-sequence>   ; "OPTIONS", <xref target="OPTIONS"/>
435                 / <x:abnf-char-sequence>"GET"</x:abnf-char-sequence>               ; "GET", <xref target="GET"/>
436                 / <x:abnf-char-sequence>"HEAD"</x:abnf-char-sequence>            ; "HEAD", <xref target="HEAD"/>
437                 / <x:abnf-char-sequence>"POST"</x:abnf-char-sequence>            ; "POST", <xref target="POST"/>
438                 / <x:abnf-char-sequence>"PUT"</x:abnf-char-sequence>               ; "PUT", <xref target="PUT"/>
439                 / <x:abnf-char-sequence>"DELETE"</x:abnf-char-sequence>      ; "DELETE", <xref target="DELETE"/>
440                 / <x:abnf-char-sequence>"TRACE"</x:abnf-char-sequence>         ; "TRACE", <xref target="TRACE"/>
441                 / <x:abnf-char-sequence>"CONNECT"</x:abnf-char-sequence>   ; "CONNECT", <xref target="CONNECT"/>
442                 / <x:ref>extension-method</x:ref>
443  <x:ref>extension-method</x:ref> = <x:ref>token</x:ref>
444</artwork></figure>
445<t>
446   The list of methods allowed by a resource can be specified in an
447   Allow header field (<xref target="header.allow"/>). The return code of the response
448   always notifies the client whether a method is currently allowed on a
449   resource, since the set of allowed methods can change dynamically. An
450   origin server &SHOULD; return the status code 405 (Method Not Allowed)
451   if the method is known by the origin server but not allowed for the
452   requested resource, and 501 (Not Implemented) if the method is
453   unrecognized or not implemented by the origin server. The methods GET
454   and HEAD &MUST; be supported by all general-purpose servers. All other
455   methods are &OPTIONAL;; however, if the above methods are implemented,
456   they &MUST; be implemented with the same semantics as those specified
457   in <xref target="method.definitions"/>.
458</t>
459
460<section title="Method Registry" anchor="method.registry">
461<t>
462  The HTTP Method Registry defines the name space for the Method token in the
463  Request line of an HTTP request.
464</t>
465<t>
466  Registrations &MUST; include the following fields:
467  <list style="symbols">
468    <t>Method Name (see <xref target="method"/>)</t>
469    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
470    <t>Pointer to specification text</t>
471  </list>
472</t>
473<t>
474  Values to be added to this name space are subject to IETF review
475  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
476</t>
477<t>
478  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-methods"/>.
479</t>
480</section>
481</section>
482
483<section title="Request Header Fields" anchor="request.header.fields">
484  <x:anchor-alias value="request-header"/>
485<t>
486   The request-header fields allow the client to pass additional
487   information about the request, and about the client itself, to the
488   server. These fields act as request modifiers, with semantics
489   equivalent to the parameters on a programming language method
490   invocation.
491</t>
492<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="request-header"/>
493  <x:ref>request-header</x:ref> = <x:ref>Accept</x:ref>                   ; &header-accept;
494                 / <x:ref>Accept-Charset</x:ref>           ; &header-accept-charset;
495                 / <x:ref>Accept-Encoding</x:ref>          ; &header-accept-encoding;
496                 / <x:ref>Accept-Language</x:ref>          ; &header-accept-language;
497                 / <x:ref>Authorization</x:ref>            ; &header-authorization;
498                 / <x:ref>Expect</x:ref>                   ; <xref target="header.expect"/>
499                 / <x:ref>From</x:ref>                     ; <xref target="header.from"/>
500                 / <x:ref>Host</x:ref>                     ; &header-host;
501                 / <x:ref>If-Match</x:ref>                 ; &header-if-match;
502                 / <x:ref>If-Modified-Since</x:ref>        ; &header-if-modified-since;
503                 / <x:ref>If-None-Match</x:ref>            ; &header-if-none-match;
504                 / <x:ref>If-Range</x:ref>                 ; &header-if-range;
505                 / <x:ref>If-Unmodified-Since</x:ref>      ; &header-if-unmodified-since;
506                 / <x:ref>Max-Forwards</x:ref>             ; <xref target="header.max-forwards"/>
507                 / <x:ref>Proxy-Authorization</x:ref>      ; &header-proxy-authorization;
508                 / <x:ref>Range</x:ref>                    ; &header-range;
509                 / <x:ref>Referer</x:ref>                  ; <xref target="header.referer"/>
510                 / <x:ref>TE</x:ref>                       ; &header-te;
511                 / <x:ref>User-Agent</x:ref>               ; <xref target="header.user-agent"/>
512</artwork></figure>
513<t>
514   Request-header field names can be extended reliably only in
515   combination with a change in the protocol version. However, new or
516   experimental header fields &MAY; be given the semantics of request-header
517   fields if all parties in the communication recognize them to
518   be request-header fields. Unrecognized header fields are treated as
519   entity-header fields.
520</t>
521</section>
522
523<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
524  <x:anchor-alias value="Reason-Phrase"/>
525  <x:anchor-alias value="Status-Code"/>
526  <x:anchor-alias value="extension-code"/>
527<t>
528   The Status-Code element is a 3-digit integer result code of the
529   attempt to understand and satisfy the request. The status codes listed
530   below are defined in <xref target="status.codes"/>, &p4-status-codes;,
531   &p5-status-codes;, and &p7-status-codes;.
532</t>
533<t>
534   The Reason-Phrase is intended to give a short
535   textual description of the Status-Code. The Status-Code is intended
536   for use by automata and the Reason-Phrase is intended for the human
537   user. The client is not required to examine or display the Reason-Phrase.
538</t>
539<t> 
540   The individual values of the numeric status codes defined for
541   HTTP/1.1, and an example set of corresponding Reason-Phrase values, are
542   presented below. The reason phrases listed here are only
543   recommendations -- they &MAY; be replaced by local equivalents without
544   affecting the protocol.
545</t>
546<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"/>
547  <x:ref>Status-Code</x:ref> =
548       "100"  ; <xref target="status.100"/>: Continue
549     / "101"  ; <xref target="status.101"/>: Switching Protocols
550     / "200"  ; <xref target="status.200"/>: OK
551     / "201"  ; <xref target="status.201"/>: Created
552     / "202"  ; <xref target="status.202"/>: Accepted
553     / "203"  ; <xref target="status.203"/>: Non-Authoritative Information
554     / "204"  ; <xref target="status.204"/>: No Content
555     / "205"  ; <xref target="status.205"/>: Reset Content
556     / "206"  ; &status-206;: Partial Content
557     / "300"  ; <xref target="status.300"/>: Multiple Choices
558     / "301"  ; <xref target="status.301"/>: Moved Permanently
559     / "302"  ; <xref target="status.302"/>: Found
560     / "303"  ; <xref target="status.303"/>: See Other
561     / "304"  ; &status-304;: Not Modified
562     / "305"  ; <xref target="status.305"/>: Use Proxy
563     / "307"  ; <xref target="status.307"/>: Temporary Redirect
564     / "400"  ; <xref target="status.400"/>: Bad Request
565     / "401"  ; &status-401;: Unauthorized
566     / "402"  ; <xref target="status.402"/>: Payment Required
567     / "403"  ; <xref target="status.403"/>: Forbidden
568     / "404"  ; <xref target="status.404"/>: Not Found
569     / "405"  ; <xref target="status.405"/>: Method Not Allowed
570     / "406"  ; <xref target="status.406"/>: Not Acceptable
571     / "407"  ; &status-407;: Proxy Authentication Required
572     / "408"  ; <xref target="status.408"/>: Request Time-out
573     / "409"  ; <xref target="status.409"/>: Conflict
574     / "410"  ; <xref target="status.410"/>: Gone
575     / "411"  ; <xref target="status.411"/>: Length Required
576     / "412"  ; &status-412;: Precondition Failed
577     / "413"  ; <xref target="status.413"/>: Request Entity Too Large
578     / "414"  ; <xref target="status.414"/>: URI Too Long
579     / "415"  ; <xref target="status.415"/>: Unsupported Media Type
580     / "416"  ; &status-416;: Requested range not satisfiable
581     / "417"  ; <xref target="status.417"/>: Expectation Failed
582     / "500"  ; <xref target="status.500"/>: Internal Server Error
583     / "501"  ; <xref target="status.501"/>: Not Implemented
584     / "502"  ; <xref target="status.502"/>: Bad Gateway
585     / "503"  ; <xref target="status.503"/>: Service Unavailable
586     / "504"  ; <xref target="status.504"/>: Gateway Time-out
587     / "505"  ; <xref target="status.505"/>: HTTP Version not supported
588     / <x:ref>extension-code</x:ref>
589
590  <x:ref>extension-code</x:ref> = 3<x:ref>DIGIT</x:ref>
591  <x:ref>Reason-Phrase</x:ref>  = *( <x:ref>WSP</x:ref> / <x:ref>VCHAR</x:ref> / <x:ref>obs-text</x:ref> )
592</artwork></figure>
593<t>
594   HTTP status codes are extensible. HTTP applications are not required
595   to understand the meaning of all registered status codes, though such
596   understanding is obviously desirable. However, applications &MUST;
597   understand the class of any status code, as indicated by the first
598   digit, and treat any unrecognized response as being equivalent to the
599   x00 status code of that class, with the exception that an
600   unrecognized response &MUST-NOT; be cached. For example, if an
601   unrecognized status code of 431 is received by the client, it can
602   safely assume that there was something wrong with its request and
603   treat the response as if it had received a 400 status code. In such
604   cases, user agents &SHOULD; present to the user the entity returned
605   with the response, since that entity is likely to include human-readable
606   information which will explain the unusual status.
607</t>
608
609<section title="Status Code Registry" anchor="status.code.registry">
610<t>
611  The HTTP Status Code Registry defines the name space for the Status-Code
612  token in the Status line of an HTTP response.
613</t>
614<t>
615  Values to be added to this name space are subject to IETF review
616  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
617</t>
618<t>
619  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
620</t>
621</section>
622
623</section>
624
625<section title="Response Header Fields" anchor="response.header.fields">
626  <x:anchor-alias value="response-header"/>
627<t>
628   The response-header fields allow the server to pass additional
629   information about the response which cannot be placed in the Status-Line.
630   These header fields give information about the server and about
631   further access to the resource identified by the Effective Request URI
632   (&effective-request-uri;).
633</t>
634<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="response-header"/>
635  <x:ref>response-header</x:ref> = <x:ref>Accept-Ranges</x:ref>           ; &header-accept-ranges;
636                  / <x:ref>Age</x:ref>                     ; &header-age;
637                  / <x:ref>Allow</x:ref>                   ; <xref target="header.allow"/>
638                  / <x:ref>ETag</x:ref>                    ; &header-etag;
639                  / <x:ref>Location</x:ref>                ; <xref target="header.location"/>
640                  / <x:ref>Proxy-Authenticate</x:ref>      ; &header-proxy-authenticate;
641                  / <x:ref>Retry-After</x:ref>             ; <xref target="header.retry-after"/>
642                  / <x:ref>Server</x:ref>                  ; <xref target="header.server"/>
643                  / <x:ref>Vary</x:ref>                    ; &header-vary;
644                  / <x:ref>WWW-Authenticate</x:ref>        ; &header-www-authenticate;
645</artwork></figure>
646<t>
647   Response-header field names can be extended reliably only in
648   combination with a change in the protocol version. However, new or
649   experimental header fields &MAY; be given the semantics of response-header
650   fields if all parties in the communication recognize them to
651   be response-header fields. Unrecognized header fields are treated as
652   entity-header fields.
653</t>
654</section>
655
656<section title="Entity" anchor="entity">
657<t>
658   Request and Response messages &MAY; transfer an entity if not otherwise
659   restricted by the request method or response status code. An entity
660   consists of entity-header fields and an entity-body, although some
661   responses will only include the entity-headers. HTTP entity-body and
662   entity-header fields are defined in &payload;.
663</t>
664<t>
665   An entity-body is only present in a message when a message-body is
666   present, as described in &message-body;. The entity-body is obtained
667   from the message-body by decoding any Transfer-Encoding that might
668   have been applied to ensure safe and proper transfer of the message.
669</t>
670
671<section title="Identifying the Resource Associated with a Representation" anchor="identifying.response.associated.with.representation">
672<t>
673   It is sometimes necessary to determine the identity of the resource
674   associated with a representation.
675</t>
676<t>
677   An HTTP request representation, when present, is always associated with an
678   anonymous (i.e., unidentified) resource.
679</t>
680<t>
681   In the common case, an HTTP response is a representation of the resource
682   located at the Effective Request URI (see &effective-request-uri;). However,
683   this is not always the case. To determine the URI of the resource a
684   response is associated with, the following rules are used (with the first
685   applicable one being selected):
686</t>
687<t><list style="numbers">
688   <t>If the response status code is 200 or 203 and the request method was GET,
689   the response is a representation of the resource at the Effective Request URI.</t>
690   <t>If the response status is 204, 206, or 304 and the request method was GET
691   or HEAD, the response is a partial representation of the resource at the
692   Effective Request URI (see &caching-combining-headers;).</t>
693   <t>If the response has a Content-Location header, and that URI is the same
694   as the Effective Request URI, the response is a representation of the
695   resource at the Effective Request URI.</t>
696   <t>If the response has a Content-Location header, and that URI is not the
697   same as the Effective Request URI, the response asserts that it is a
698   representation of the resource at the Content-Location URI (but it may not
699   be).</t>
700   <t>Otherwise, the response is a representation of an anonymous (i.e.,
701   unidentified) resource.</t>
702</list></t>
703<t>
704  <cref anchor="TODO-req-uri">
705   The comparison function is going to have to be defined somewhere,
706   because we already need to compare URIs for things like cache invalidation.</cref>
707</t>
708</section>
709
710</section>
711
712
713<section title="Method Definitions" anchor="method.definitions">
714<t>
715   The set of common methods for HTTP/1.1 is defined below. Although
716   this set can be expanded, additional methods cannot be assumed to
717   share the same semantics for separately extended clients and servers.
718</t>
719
720<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
721
722<section title="Safe Methods" anchor="safe.methods">
723<iref item="Safe Methods" primary="true"/>
724<t>
725   Implementors should be aware that the software represents the user in
726   their interactions over the Internet, and should be careful to allow
727   the user to be aware of any actions they might take which may have an
728   unexpected significance to themselves or others.
729</t>
730<t>
731   In particular, the convention has been established that the GET, HEAD,
732   OPTIONS, and TRACE methods &SHOULD-NOT;  have the significance of taking an action
733   other than retrieval. These methods ought to be considered "<x:dfn anchor="safe">safe</x:dfn>".
734   This allows user agents to represent other methods, such as POST, PUT
735   and DELETE, in a special way, so that the user is made aware of the
736   fact that a possibly unsafe action is being requested.
737</t>
738<t>
739   Naturally, it is not possible to ensure that the server does not
740   generate side-effects as a result of performing a GET request; in
741   fact, some dynamic resources consider that a feature. The important
742   distinction here is that the user did not request the side-effects,
743   so therefore cannot be held accountable for them.
744</t>
745</section>
746
747<section title="Idempotent Methods" anchor="idempotent.methods">
748<iref item="Idempotent Methods" primary="true"/>
749<t>
750   Methods can also have the property of "idempotence" in that, aside
751   from error or expiration issues, the intended effect of multiple
752   identical requests is the same as for a single request.
753   The methods PUT, DELETE, and all safe methods are idempotent.
754   It is important to note that idempotence refers only to changes
755   requested by the client: a server is free to change its state due
756   to multiple requests for the purpose of tracking those requests,
757   versioning of results, etc.
758</t>
759</section>
760</section>
761
762<section title="OPTIONS" anchor="OPTIONS">
763  <rdf:Description>
764    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
765  </rdf:Description>
766  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
767  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
768<t>
769   The OPTIONS method represents a request for information about the
770   communication options available on the request/response chain
771   identified by the Effective Request URI. This method allows the client to
772   determine the options and/or requirements associated with a resource,
773   or the capabilities of a server, without implying a resource action
774   or initiating a resource retrieval.
775</t>
776<t>
777   Responses to this method are not cacheable.
778</t>
779<t>
780   If the OPTIONS request includes an entity-body (as indicated by the
781   presence of Content-Length or Transfer-Encoding), then the media type
782   &MUST; be indicated by a Content-Type field. Although this
783   specification does not define any use for such a body, future
784   extensions to HTTP might use the OPTIONS body to make more detailed
785   queries on the server.
786</t>
787<t>
788   If the request-target is an asterisk ("*"), the OPTIONS request is
789   intended to apply to the server in general rather than to a specific
790   resource. Since a server's communication options typically depend on
791   the resource, the "*" request is only useful as a "ping" or "no-op"
792   type of method; it does nothing beyond allowing the client to test
793   the capabilities of the server. For example, this can be used to test
794   a proxy for HTTP/1.1 compliance (or lack thereof).
795</t>
796<t>
797   If the request-target is not an asterisk, the OPTIONS request applies
798   only to the options that are available when communicating with that
799   resource.
800</t>
801<t>
802   A 200 response &SHOULD; include any header fields that indicate
803   optional features implemented by the server and applicable to that
804   resource (e.g., Allow), possibly including extensions not defined by
805   this specification. The response body, if any, &SHOULD; also include
806   information about the communication options. The format for such a
807   body is not defined by this specification, but might be defined by
808   future extensions to HTTP. Content negotiation &MAY; be used to select
809   the appropriate response format. If no response body is included, the
810   response &MUST; include a Content-Length field with a field-value of
811   "0".
812</t>
813<t>
814   The Max-Forwards request-header field &MAY; be used to target a
815   specific proxy in the request chain. When a proxy receives an OPTIONS
816   request on an absolute-URI for which request forwarding is permitted,
817   the proxy &MUST; check for a Max-Forwards field. If the Max-Forwards
818   field-value is zero ("0"), the proxy &MUST-NOT; forward the message;
819   instead, the proxy &SHOULD; respond with its own communication options.
820   If the Max-Forwards field-value is an integer greater than zero, the
821   proxy &MUST; decrement the field-value when it forwards the request. If
822   no Max-Forwards field is present in the request, then the forwarded
823   request &MUST-NOT; include a Max-Forwards field.
824</t>
825</section>
826
827<section title="GET" anchor="GET">
828  <rdf:Description>
829    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
830  </rdf:Description>
831  <iref primary="true" item="GET method" x:for-anchor=""/>
832  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
833<t>
834   The GET method means retrieve whatever information (in the form of an
835   entity) currently corresponds to the resource identified by the
836   Effective Request URI.
837</t>
838<t>   
839   If the Effective Request URI identifies a data-producing process, it is the
840   produced data which shall be returned as the entity in the response and not
841   the source text of the process, unless that text happens to be the output of
842   the process.
843</t>
844<t>
845   The semantics of the GET method change to a "conditional GET" if the
846   request message includes an If-Modified-Since, If-Unmodified-Since,
847   If-Match, If-None-Match, or If-Range header field. A conditional GET
848   method requests that the entity be transferred only under the
849   circumstances described by the conditional header field(s). The
850   conditional GET method is intended to reduce unnecessary network
851   usage by allowing cached entities to be refreshed without requiring
852   multiple requests or transferring data already held by the client.
853</t>
854<t>
855   The semantics of the GET method change to a "partial GET" if the
856   request message includes a Range header field. A partial GET requests
857   that only part of the entity be transferred, as described in &header-range;.
858   The partial GET method is intended to reduce unnecessary
859   network usage by allowing partially-retrieved entities to be
860   completed without transferring data already held by the client.
861</t>
862<t>
863   The response to a GET request is cacheable if and only if it meets
864   the requirements for HTTP caching described in &caching;.
865</t>
866<t>
867   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
868</t>
869</section>
870
871<section title="HEAD" anchor="HEAD">
872  <rdf:Description>
873    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
874  </rdf:Description>
875  <iref primary="true" item="HEAD method" x:for-anchor=""/>
876  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
877<t>
878   The HEAD method is identical to GET except that the server &MUST-NOT;
879   return a message-body in the response. The metainformation contained
880   in the HTTP headers in response to a HEAD request &SHOULD; be identical
881   to the information sent in response to a GET request. This method can
882   be used for obtaining metainformation about the entity implied by the
883   request without transferring the entity-body itself. This method is
884   often used for testing hypertext links for validity, accessibility,
885   and recent modification.
886</t>
887<t>
888   The response to a HEAD request &MAY; be cacheable in the sense that the
889   information contained in the response &MAY; be used to update a
890   previously cached entity from that resource. If the new field values
891   indicate that the cached entity differs from the current entity (as
892   would be indicated by a change in Content-Length, Content-MD5, ETag
893   or Last-Modified), then the cache &MUST; treat the cache entry as
894   stale.
895</t>
896</section>
897
898<section title="POST" anchor="POST">
899  <iref primary="true" item="POST method" x:for-anchor=""/>
900  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
901<t>
902   The POST method is used to request that the origin server accept the
903   entity enclosed in the request as data to be processed by the resource
904   identified by the Effective Request URI. POST is designed
905   to allow a uniform method to cover the following functions:
906  <list style="symbols">
907    <t>
908      Annotation of existing resources;
909    </t>
910    <t>
911        Posting a message to a bulletin board, newsgroup, mailing list,
912        or similar group of articles;
913    </t>
914    <t>
915        Providing a block of data, such as the result of submitting a
916        form, to a data-handling process;
917    </t>
918    <t>
919        Extending a database through an append operation.
920    </t>
921  </list>
922</t>
923<t>
924   The actual function performed by the POST method is determined by the
925   server and is usually dependent on the Effective Request URI.
926</t>
927<t>
928   The action performed by the POST method might not result in a
929   resource that can be identified by a URI. In this case, either 200
930   (OK) or 204 (No Content) is the appropriate response status,
931   depending on whether or not the response includes an entity that
932   describes the result.
933</t>
934<t>
935   If a resource has been created on the origin server, the response
936   &SHOULD; be 201 (Created) and contain an entity which describes the
937   status of the request and refers to the new resource, and a Location
938   header (see <xref target="header.location"/>).
939</t>
940<t>
941   Responses to this method are not cacheable, unless the response
942   includes appropriate Cache-Control or Expires header fields. However,
943   the 303 (See Other) response can be used to direct the user agent to
944   retrieve a cacheable resource.
945</t>
946</section>
947
948<section title="PUT" anchor="PUT">
949  <iref primary="true" item="PUT method" x:for-anchor=""/>
950  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
951<t>
952   The PUT method requests that the enclosed entity be stored at the
953   Effective Request URI. If the Effective Request URI refers to an already
954   existing resource, the enclosed entity &SHOULD; be considered as a
955   modified version of the one residing on the origin server. Otherwise, if the
956   Effective Request URI does not point to an existing resource, and that URI is
957   capable of being defined as a new resource by the requesting user
958   agent, the origin server can create the resource with that URI.
959</t>
960<t>   
961   If a new resource is created at the Effective Request URI, the origin
962   server &MUST; inform the user agent
963   via the 201 (Created) response. If an existing resource is modified,
964   either the 200 (OK) or 204 (No Content) response codes &SHOULD; be sent
965   to indicate successful completion of the request.
966</t>
967<t>   
968   If the resource could not be created or modified with the Effective Request
969   URI, an appropriate error response &SHOULD; be given that reflects the nature
970   of the problem. The recipient of the entity &MUST-NOT; ignore any Content-*
971   headers (headers starting with the prefix "Content-") that it does
972   not understand or implement
973   and &MUST; return a 501 (Not Implemented) response in such cases.
974</t>
975<t>
976   If the request passes through a cache and the Effective Request URI
977   identifies one or more currently cached entities, those entries &SHOULD; be
978   treated as stale. Responses to this method are not cacheable.
979</t>
980<t>
981   The fundamental difference between the POST and PUT requests is
982   reflected in the different meaning of the Effective Request URI. The URI in a
983   POST request identifies the resource that will handle the enclosed
984   entity. That resource might be a data-accepting process, a gateway to
985   some other protocol, or a separate entity that accepts annotations.
986   In contrast, the URI in a PUT request identifies the entity enclosed
987   with the request -- the user agent knows what URI is intended and the
988   server &MUST-NOT; attempt to apply the request to some other resource.
989   If the server desires that the request be applied to a different URI,
990   it &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
991   then make its own decision regarding whether or not to redirect the
992   request.
993</t>
994<t>
995   A single resource &MAY; be identified by many different URIs. For
996   example, an article might have a URI for identifying "the current
997   version" which is separate from the URI identifying each particular
998   version. In this case, a PUT request on a general URI might result in
999   several other URIs being defined by the origin server.
1000</t>
1001<t>
1002   HTTP/1.1 does not define how a PUT method affects the state of an
1003   origin server.
1004</t>
1005<t>
1006   Unless otherwise specified for a particular entity-header, the
1007   entity-headers in the PUT request &SHOULD; be applied to the resource
1008   created or modified by the PUT.
1009</t>
1010</section>
1011
1012<section title="DELETE" anchor="DELETE">
1013  <iref primary="true" item="DELETE method" x:for-anchor=""/>
1014  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
1015<t>
1016   The DELETE method requests that the origin server delete the resource
1017   identified by the Effective Request URI. This method &MAY; be overridden by
1018   human intervention (or other means) on the origin server. The client cannot
1019   be guaranteed that the operation has been carried out, even if the
1020   status code returned from the origin server indicates that the action
1021   has been completed successfully. However, the server &SHOULD-NOT; 
1022   indicate success unless, at the time the response is given, it
1023   intends to delete the resource or move it to an inaccessible
1024   location.
1025</t>
1026<t>
1027   A successful response &SHOULD; be 200 (OK) if the response includes an
1028   entity describing the status, 202 (Accepted) if the action has not
1029   yet been enacted, or 204 (No Content) if the action has been enacted
1030   but the response does not include an entity.
1031</t>
1032<t>
1033   If the request passes through a cache and the Effective Request URI
1034   identifies one or more currently cached entities, those entries &SHOULD; be
1035   treated as stale. Responses to this method are not cacheable.
1036</t>
1037</section>
1038
1039<section title="TRACE" anchor="TRACE">
1040  <rdf:Description>
1041    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
1042  </rdf:Description>
1043  <iref primary="true" item="TRACE method" x:for-anchor=""/>
1044  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
1045<t>
1046   The TRACE method is used to invoke a remote, application-layer loop-back
1047   of the request message. The final recipient of the request
1048   &SHOULD; reflect the message received back to the client as the
1049   entity-body of a 200 (OK) response. The final recipient is either the
1050   origin server or the first proxy or gateway to receive a Max-Forwards
1051   value of zero (0) in the request (see <xref target="header.max-forwards"/>). A TRACE request
1052   &MUST-NOT; include an entity.
1053</t>
1054<t>
1055   TRACE allows the client to see what is being received at the other
1056   end of the request chain and use that data for testing or diagnostic
1057   information. The value of the Via header field (&header-via;) is of
1058   particular interest, since it acts as a trace of the request chain.
1059   Use of the Max-Forwards header field allows the client to limit the
1060   length of the request chain, which is useful for testing a chain of
1061   proxies forwarding messages in an infinite loop.
1062</t>
1063<t>
1064   If the request is valid, the response &SHOULD; contain the entire
1065   request message in the entity-body, with a Content-Type of
1066   "message/http" (see &media-type-message-http;). Responses to this method
1067   &MUST-NOT; be cached.
1068</t>
1069</section>
1070
1071<section title="CONNECT" anchor="CONNECT">
1072  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
1073  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1074<t>
1075   This specification reserves the method name CONNECT for use with a
1076   proxy that can dynamically switch to being a tunnel (e.g., SSL
1077   tunneling <xref target="RFC2817"/>).
1078</t>
1079</section>
1080</section>
1081
1082
1083<section title="Status Code Definitions" anchor="status.codes">
1084<t>
1085   Each Status-Code is described below, including any metainformation required
1086   in the response.
1087</t>
1088
1089<section title="Informational 1xx" anchor="status.1xx">
1090<t>
1091   This class of status code indicates a provisional response,
1092   consisting only of the Status-Line and optional headers, and is
1093   terminated by an empty line. There are no required headers for this
1094   class of status code. Since HTTP/1.0 did not define any 1xx status
1095   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1096   except under experimental conditions.
1097</t>
1098<t>
1099   A client &MUST; be prepared to accept one or more 1xx status responses
1100   prior to a regular response, even if the client does not expect a 100
1101   (Continue) status message. Unexpected 1xx status responses &MAY; be
1102   ignored by a user agent.
1103</t>
1104<t>
1105   Proxies &MUST; forward 1xx responses, unless the connection between the
1106   proxy and its client has been closed, or unless the proxy itself
1107   requested the generation of the 1xx response. (For example, if a
1108   proxy adds a "Expect: 100-continue" field when it forwards a request,
1109   then it need not forward the corresponding 100 (Continue)
1110   response(s).)
1111</t>
1112
1113<section title="100 Continue" anchor="status.100">
1114  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1115  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1116<t>
1117   The client &SHOULD; continue with its request. This interim response is
1118   used to inform the client that the initial part of the request has
1119   been received and has not yet been rejected by the server. The client
1120   &SHOULD; continue by sending the remainder of the request or, if the
1121   request has already been completed, ignore this response. The server
1122   &MUST; send a final response after the request has been completed. See
1123   &use100; for detailed discussion of the use and handling of this
1124   status code.
1125</t>
1126</section>
1127
1128<section title="101 Switching Protocols" anchor="status.101">
1129  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1130  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1131<t>
1132   The server understands and is willing to comply with the client's
1133   request, via the Upgrade message header field (&header-upgrade;), for a
1134   change in the application protocol being used on this connection. The
1135   server will switch protocols to those defined by the response's
1136   Upgrade header field immediately after the empty line which
1137   terminates the 101 response.
1138</t>
1139<t>
1140   The protocol &SHOULD; be switched only when it is advantageous to do
1141   so. For example, switching to a newer version of HTTP is advantageous
1142   over older versions, and switching to a real-time, synchronous
1143   protocol might be advantageous when delivering resources that use
1144   such features.
1145</t>
1146</section>
1147</section>
1148
1149<section title="Successful 2xx" anchor="status.2xx">
1150<t>
1151   This class of status code indicates that the client's request was
1152   successfully received, understood, and accepted.
1153</t>
1154
1155<section title="200 OK" anchor="status.200">
1156  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1157  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1158<t>
1159   The request has succeeded. The information returned with the response
1160   is dependent on the method used in the request, for example:
1161  <list style="hanging">
1162    <t hangText="GET">
1163          an entity corresponding to the requested resource is sent in
1164          the response;
1165    </t>
1166    <t hangText="HEAD">
1167          the entity-header fields corresponding to the requested
1168          resource are sent in the response without any message-body;
1169    </t>
1170    <t hangText="POST">
1171      an entity describing or containing the result of the action;
1172    </t>
1173    <t hangText="TRACE">
1174      an entity containing the request message as received by the
1175      end server.
1176    </t>
1177  </list>
1178</t>
1179</section>
1180
1181<section title="201 Created" anchor="status.201">
1182  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1183  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1184<t>
1185   The request has been fulfilled and has resulted in a new resource being
1186   created. The newly created resource can be referenced by the URI(s)
1187   returned in the payload of the response, with the most specific URI
1188   for the resource given by a Location header field. The response
1189   &SHOULD; include a payload containing a list of resource
1190   characteristics and location(s) from which the user or user agent can
1191   choose the one most appropriate. The payload format is specified by
1192   the media type given in the Content-Type header field. The origin
1193   server &MUST; create the resource before returning the 201 status code.
1194   If the action cannot be carried out immediately, the server &SHOULD;
1195   respond with 202 (Accepted) response instead.
1196</t>
1197<t>
1198   A 201 response &MAY; contain an ETag response header field indicating
1199   the current value of the entity tag for the representation of the resource
1200   just created (see &header-etag;).
1201</t>
1202</section>
1203
1204<section title="202 Accepted" anchor="status.202">
1205  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1206  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1207<t>
1208   The request has been accepted for processing, but the processing has
1209   not been completed.  The request might or might not eventually be
1210   acted upon, as it might be disallowed when processing actually takes
1211   place. There is no facility for re-sending a status code from an
1212   asynchronous operation such as this.
1213</t>
1214<t>
1215   The 202 response is intentionally non-committal. Its purpose is to
1216   allow a server to accept a request for some other process (perhaps a
1217   batch-oriented process that is only run once per day) without
1218   requiring that the user agent's connection to the server persist
1219   until the process is completed. The entity returned with this
1220   response &SHOULD; include an indication of the request's current status
1221   and either a pointer to a status monitor or some estimate of when the
1222   user can expect the request to be fulfilled.
1223</t>
1224</section>
1225
1226<section title="203 Non-Authoritative Information" anchor="status.203">
1227  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1228  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1229<t>
1230   The returned metainformation in the entity-header is not the
1231   definitive set as available from the origin server, but is gathered
1232   from a local or a third-party copy. The set presented &MAY; be a subset
1233   or superset of the original version. For example, including local
1234   annotation information about the resource might result in a superset
1235   of the metainformation known by the origin server. Use of this
1236   response code is not required and is only appropriate when the
1237   response would otherwise be 200 (OK).
1238</t>
1239</section>
1240
1241<section title="204 No Content" anchor="status.204">
1242  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1243  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1244<t>
1245   The server has successfully fulfilled the request, but there is no
1246   additional content to return in the response payload body.  The
1247   resource metadata and representation metadata in the response message's
1248   header fields refer to the requested resource and its current
1249   representation, respectively, after the requested action.
1250   For example, if a 204 status is received in response to a PUT
1251   and the response contains an Etag header field, then the value of
1252   that field is the current entity-tag for the representation that
1253   was successfully PUT to the requested resource.
1254</t>
1255<t>
1256   If the client is a user agent, it &SHOULD-NOT; change its document view
1257   from that which caused the request to be sent. This response is
1258   primarily intended to allow input for actions to take place without
1259   causing a change to the user agent's active document view, although
1260   any new or updated metadata &SHOULD; be applied to the document
1261   currently in the user agent's active view.
1262</t>
1263<t>
1264   The 204 response &MUST-NOT; include a message-body, and thus is always
1265   terminated by the first empty line after the header fields.
1266</t>
1267</section>
1268
1269<section title="205 Reset Content" anchor="status.205">
1270  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1271  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1272<t>
1273   The server has fulfilled the request and the user agent &SHOULD; reset
1274   the document view which caused the request to be sent. This response
1275   is primarily intended to allow input for actions to take place via
1276   user input, followed by a clearing of the form in which the input is
1277   given so that the user can easily initiate another input action. The
1278   response &MUST-NOT; include an entity.
1279</t>
1280</section>
1281
1282<section title="206 Partial Content" anchor="status.206">
1283  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1284  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1285  <rdf:Description>
1286    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1287  </rdf:Description>
1288<t>
1289   The server has fulfilled the partial GET request for the resource
1290   and the enclosed entity is a partial representation as defined in &status-206;.
1291</t>
1292</section>
1293</section>
1294
1295<section title="Redirection 3xx" anchor="status.3xx">
1296<t>
1297   This class of status code indicates that further action needs to be
1298   taken by the user agent in order to fulfill the request.  The action
1299   required &MAY; be carried out by the user agent without interaction
1300   with the user if and only if the method used in the second request is
1301   known to be "safe", as defined in <xref target="safe.methods"/>.
1302   A client &SHOULD; detect infinite redirection loops, since such loops
1303   generate network traffic for each redirection.
1304</t>
1305<x:note>
1306  <t>
1307    <x:h>Note:</x:h> An earlier version of this specification recommended a
1308    maximum of five redirections (<xref target="RFC2068" x:fmt="," x:sec="10.3"/>).
1309    Content developers should be aware that there might be clients that
1310    implement such a fixed limitation.
1311  </t>
1312</x:note>
1313
1314<section title="300 Multiple Choices" anchor="status.300">
1315  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1316  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1317<t>
1318   The requested resource corresponds to any one of a set of
1319   representations, each with its own specific location, and agent-driven
1320   negotiation information (&content-negotiation;) is being provided so that
1321   the user (or user agent) can select a preferred representation and
1322   redirect its request to that location.
1323</t>
1324<t>
1325   Unless it was a HEAD request, the response &SHOULD; include an entity
1326   containing a list of resource characteristics and location(s) from
1327   which the user or user agent can choose the one most appropriate. The
1328   entity format is specified by the media type given in the Content-Type
1329   header field. Depending upon the format and the capabilities of
1330   the user agent, selection of the most appropriate choice &MAY; be
1331   performed automatically. However, this specification does not define
1332   any standard for such automatic selection.
1333</t>
1334<t>
1335   If the server has a preferred choice of representation, it &SHOULD;
1336   include the specific URI for that representation in the Location
1337   field; user agents &MAY; use the Location field value for automatic
1338   redirection. This response is cacheable unless indicated otherwise.
1339</t>
1340</section>
1341
1342<section title="301 Moved Permanently" anchor="status.301">
1343  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1344  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1345<t>
1346   The requested resource has been assigned a new permanent URI and any
1347   future references to this resource &SHOULD; use one of the returned
1348   URIs.  Clients with link editing capabilities ought to automatically
1349   re-link references to the Effective Request URI to one or more of the new
1350   references returned by the server, where possible. This response is
1351   cacheable unless indicated otherwise.
1352</t>
1353<t>
1354   The new permanent URI &SHOULD; be given by the Location field in the
1355   response. Unless the request method was HEAD, the entity of the
1356   response &SHOULD; contain a short hypertext note with a hyperlink to
1357   the new URI(s).
1358</t>
1359<t>
1360   If the 301 status code is received in response to a request method
1361   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1362   then the request &MAY; be automatically redirected by the user agent without
1363   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1364   request unless it can be confirmed by the user, since this might
1365   change the conditions under which the request was issued.
1366</t>
1367<x:note>
1368  <t>
1369    <x:h>Note:</x:h> When automatically redirecting a POST request after
1370    receiving a 301 status code, some existing HTTP/1.0 user agents
1371    will erroneously change it into a GET request.
1372  </t>
1373</x:note>
1374</section>
1375
1376<section title="302 Found" anchor="status.302">
1377  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1378  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1379<t>
1380   The requested resource resides temporarily under a different URI.
1381   Since the redirection might be altered on occasion, the client &SHOULD;
1382   continue to use the Effectice Request URI for future requests.  This response
1383   is only cacheable if indicated by a Cache-Control or Expires header
1384   field.
1385</t>
1386<t>
1387   The temporary URI &SHOULD; be given by the Location field in the
1388   response. Unless the request method was HEAD, the entity of the
1389   response &SHOULD; contain a short hypertext note with a hyperlink to
1390   the new URI(s).
1391</t>
1392<t>
1393   If the 302 status code is received in response to a request method
1394   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1395   then the request &MAY; be automatically redirected by the user agent without
1396   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1397   request unless it can be confirmed by the user, since this might
1398   change the conditions under which the request was issued.
1399</t>
1400<x:note>
1401  <t>
1402    <x:h>Note:</x:h> HTTP/1.0 (<xref target="RFC1945" x:fmt="," x:sec="9.3"/>)
1403    and the first version of HTTP/1.1 (<xref target="RFC2068" x:fmt="," x:sec ="10.3.3"/>)
1404    specify that the client is not allowed to change the method on the
1405    redirected request.  However, most existing user agent implementations
1406    treat 302 as if it were a 303 response, performing a GET on the Location
1407    field-value regardless of the original request method. Therefore, a
1408    previous version of this specification
1409    (<xref target="RFC2616" x:fmt="," x:sec="10.3.3"/>) has added the
1410    status codes
1411    <xref target="status.303" format="none">303</xref> and
1412    <xref target="status.307" format="none">307</xref> for servers that wish
1413    to make unambiguously clear which kind of reaction is expected of the
1414    client.
1415  </t>
1416</x:note>
1417</section>
1418
1419<section title="303 See Other" anchor="status.303">
1420  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1421  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1422<t>
1423   The server directs the user agent to a different resource, indicated
1424   by a URI in the Location header field, that provides an indirect
1425   response to the original request.  The user agent &MAY; perform a GET
1426   request on the URI in the Location field in order to obtain a
1427   representation corresponding to the response, be redirected again,
1428   or end with an error status.  The Location URI is not a substitute
1429   reference for the originally requested resource.
1430</t>
1431<t>
1432   The 303 status is generally applicable to any HTTP method.  It is
1433   primarily used to allow the output of a POST action to redirect
1434   the user agent to a selected resource, since doing so provides the
1435   information corresponding to the POST response in a form that
1436   can be separately identified, bookmarked, and cached independent
1437   of the original request.
1438</t>
1439<t>
1440   A 303 response to a GET request indicates that the requested
1441   resource does not have a representation of its own that can be
1442   transferred by the server over HTTP.  The Location URI indicates a
1443   resource that is descriptive of the requested resource such that
1444   the follow-on representation may be useful without implying that
1445   it adequately represents the previously requested resource.
1446   Note that answers to the questions of what can be represented, what
1447   representations are adequate, and what might be a useful description
1448   are outside the scope of HTTP and thus entirely determined by the
1449   URI owner(s).
1450</t>
1451<t>
1452   A 303 response &SHOULD-NOT; be cached unless it is indicated as
1453   cacheable by Cache-Control or Expires header fields.  Except for
1454   responses to a HEAD request, the entity of a 303 response &SHOULD;
1455   contain a short hypertext note with a hyperlink to the Location URI.
1456</t>
1457</section>
1458
1459<section title="304 Not Modified" anchor="status.304">
1460  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1461  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1462  <rdf:Description>
1463    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1464  </rdf:Description>
1465<t>
1466   The response to the request has not been modified since the conditions
1467   indicated by the client's conditional GET request, as defined in &status-304;.
1468</t>
1469</section>
1470
1471<section title="305 Use Proxy" anchor="status.305">
1472  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1473  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1474<t>
1475   The 305 status was defined in a previous version of this specification
1476   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1477</t>
1478</section>
1479
1480<section title="306 (Unused)" anchor="status.306">
1481  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1482  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1483<t>
1484   The 306 status code was used in a previous version of the
1485   specification, is no longer used, and the code is reserved.
1486</t>
1487</section>
1488
1489<section title="307 Temporary Redirect" anchor="status.307">
1490  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1491  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1492<t>
1493   The requested resource resides temporarily under a different URI.
1494   Since the redirection &MAY; be altered on occasion, the client &SHOULD;
1495   continue to use the Effective Request URI for future requests.  This response
1496   is only cacheable if indicated by a Cache-Control or Expires header
1497   field.
1498</t>
1499<t>
1500   The temporary URI &SHOULD; be given by the Location field in the
1501   response. Unless the request method was HEAD, the entity of the
1502   response &SHOULD; contain a short hypertext note with a hyperlink to
1503   the new URI(s) , since many pre-HTTP/1.1 user agents do not
1504   understand the 307 status. Therefore, the note &SHOULD; contain the
1505   information necessary for a user to repeat the original request on
1506   the new URI.
1507</t>
1508<t>
1509   If the 307 status code is received in response to a request method
1510   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1511   then the request &MAY; be automatically redirected by the user agent without
1512   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1513   request unless it can be confirmed by the user, since this might
1514   change the conditions under which the request was issued.
1515</t>
1516</section>
1517</section>
1518
1519<section title="Client Error 4xx" anchor="status.4xx">
1520<t>
1521   The 4xx class of status code is intended for cases in which the
1522   client seems to have erred. Except when responding to a HEAD request,
1523   the server &SHOULD; include an entity containing an explanation of the
1524   error situation, and whether it is a temporary or permanent
1525   condition. These status codes are applicable to any request method.
1526   User agents &SHOULD; display any included entity to the user.
1527</t>
1528<t>
1529   If the client is sending data, a server implementation using TCP
1530   &SHOULD; be careful to ensure that the client acknowledges receipt of
1531   the packet(s) containing the response, before the server closes the
1532   input connection. If the client continues sending data to the server
1533   after the close, the server's TCP stack will send a reset packet to
1534   the client, which may erase the client's unacknowledged input buffers
1535   before they can be read and interpreted by the HTTP application.
1536</t>
1537
1538<section title="400 Bad Request" anchor="status.400">
1539  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1540  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1541<t>
1542   The request could not be understood by the server due to malformed
1543   syntax. The client &SHOULD-NOT;  repeat the request without
1544   modifications.
1545</t>
1546</section>
1547
1548<section title="401 Unauthorized" anchor="status.401">
1549  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1550  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1551  <rdf:Description>
1552    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part7</redirects-to>
1553  </rdf:Description>
1554<t>
1555   The request requires user authentication (see &status-401;).
1556</t>
1557</section>
1558
1559<section title="402 Payment Required" anchor="status.402">
1560  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1561  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1562<t>
1563   This code is reserved for future use.
1564</t>
1565</section>
1566
1567<section title="403 Forbidden" anchor="status.403">
1568  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1569  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1570<t>
1571   The server understood the request, but is refusing to fulfill it.
1572   Authorization will not help and the request &SHOULD-NOT;  be repeated.
1573   If the request method was not HEAD and the server wishes to make
1574   public why the request has not been fulfilled, it &SHOULD; describe the
1575   reason for the refusal in the entity.  If the server does not wish to
1576   make this information available to the client, the status code 404
1577   (Not Found) can be used instead.
1578</t>
1579</section>
1580
1581<section title="404 Not Found" anchor="status.404">
1582  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1583  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1584<t>
1585   The server has not found anything matching the Effective Request URI. No
1586   indication is given of whether the condition is temporary or
1587   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1588   knows, through some internally configurable mechanism, that an old
1589   resource is permanently unavailable and has no forwarding address.
1590   This status code is commonly used when the server does not wish to
1591   reveal exactly why the request has been refused, or when no other
1592   response is applicable.
1593</t>
1594</section>
1595
1596<section title="405 Method Not Allowed" anchor="status.405">
1597  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1598  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1599<t>
1600   The method specified in the Request-Line is not allowed for the
1601   resource identified by the Effective Request URI. The response &MUST; include an
1602   Allow header containing a list of valid methods for the requested
1603   resource.
1604</t>
1605</section>
1606
1607<section title="406 Not Acceptable" anchor="status.406">
1608  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1609  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1610<t>
1611   The resource identified by the request is only capable of generating
1612   response entities which have content characteristics not acceptable
1613   according to the accept headers sent in the request.
1614</t>
1615<t>
1616   Unless it was a HEAD request, the response &SHOULD; include an entity
1617   containing a list of available entity characteristics and location(s)
1618   from which the user or user agent can choose the one most
1619   appropriate. The entity format is specified by the media type given
1620   in the Content-Type header field. Depending upon the format and the
1621   capabilities of the user agent, selection of the most appropriate
1622   choice &MAY; be performed automatically. However, this specification
1623   does not define any standard for such automatic selection.
1624</t>
1625<x:note>
1626  <t>
1627    <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1628    not acceptable according to the accept headers sent in the
1629    request. In some cases, this may even be preferable to sending a
1630    406 response. User agents are encouraged to inspect the headers of
1631    an incoming response to determine if it is acceptable.
1632  </t>
1633</x:note>
1634<t>
1635   If the response could be unacceptable, a user agent &SHOULD;
1636   temporarily stop receipt of more data and query the user for a
1637   decision on further actions.
1638</t>
1639</section>
1640
1641<section title="407 Proxy Authentication Required" anchor="status.407">
1642  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1643  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1644<t>
1645   This code is similar to 401 (Unauthorized), but indicates that the
1646   client must first authenticate itself with the proxy (see &status-407;).
1647</t>
1648</section>
1649
1650<section title="408 Request Timeout" anchor="status.408">
1651  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1652  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1653<t>
1654   The client did not produce a request within the time that the server
1655   was prepared to wait. The client &MAY; repeat the request without
1656   modifications at any later time.
1657</t>
1658</section>
1659
1660<section title="409 Conflict" anchor="status.409">
1661  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1662  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1663<t>
1664   The request could not be completed due to a conflict with the current
1665   state of the resource. This code is only allowed in situations where
1666   it is expected that the user might be able to resolve the conflict
1667   and resubmit the request. The response body &SHOULD; include enough
1668   information for the user to recognize the source of the conflict.
1669   Ideally, the response entity would include enough information for the
1670   user or user agent to fix the problem; however, that might not be
1671   possible and is not required.
1672</t>
1673<t>
1674   Conflicts are most likely to occur in response to a PUT request. For
1675   example, if versioning were being used and the entity being PUT
1676   included changes to a resource which conflict with those made by an
1677   earlier (third-party) request, the server might use the 409 response
1678   to indicate that it can't complete the request. In this case, the
1679   response entity would likely contain a list of the differences
1680   between the two versions in a format defined by the response
1681   Content-Type.
1682</t>
1683</section>
1684
1685<section title="410 Gone" anchor="status.410">
1686  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1687  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1688<t>
1689   The requested resource is no longer available at the server and no
1690   forwarding address is known. This condition is expected to be
1691   considered permanent. Clients with link editing capabilities &SHOULD;
1692   delete references to the Effective Request URI after user approval. If the
1693   server does not know, or has no facility to determine, whether or not
1694   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
1695   used instead. This response is cacheable unless indicated otherwise.
1696</t>
1697<t>
1698   The 410 response is primarily intended to assist the task of web
1699   maintenance by notifying the recipient that the resource is
1700   intentionally unavailable and that the server owners desire that
1701   remote links to that resource be removed. Such an event is common for
1702   limited-time, promotional services and for resources belonging to
1703   individuals no longer working at the server's site. It is not
1704   necessary to mark all permanently unavailable resources as "gone" or
1705   to keep the mark for any length of time -- that is left to the
1706   discretion of the server owner.
1707</t>
1708</section>
1709
1710<section title="411 Length Required" anchor="status.411">
1711  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1712  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1713<t>
1714   The server refuses to accept the request without a defined Content-Length.
1715   The client &MAY; repeat the request if it adds a valid
1716   Content-Length header field containing the length of the message-body
1717   in the request message.
1718</t>
1719</section>
1720
1721<section title="412 Precondition Failed" anchor="status.412">
1722  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1723  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
1724  <rdf:Description>
1725    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1726  </rdf:Description>
1727<t>
1728   The precondition given in one or more of the request-header fields
1729   evaluated to false when it was tested on the server, as defined in
1730   &status-412;.
1731</t>
1732</section>
1733
1734<section title="413 Request Entity Too Large" anchor="status.413">
1735  <iref primary="true" item="413 Request Entity Too Large (status code)" x:for-anchor=""/>
1736  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large" x:for-anchor=""/>
1737<t>
1738   The server is refusing to process a request because the request
1739   entity is larger than the server is willing or able to process. The
1740   server &MAY; close the connection to prevent the client from continuing
1741   the request.
1742</t>
1743<t>
1744   If the condition is temporary, the server &SHOULD; include a Retry-After
1745   header field to indicate that it is temporary and after what
1746   time the client &MAY; try again.
1747</t>
1748</section>
1749
1750<section title="414 URI Too Long" anchor="status.414">
1751  <iref primary="true" item="414 URI Too Long (status code)" x:for-anchor=""/>
1752  <iref primary="true" item="Status Codes" subitem="414 URI Too Long" x:for-anchor=""/>
1753<t>
1754   The server is refusing to service the request because the Effective Request URI
1755   is longer than the server is willing to interpret. This rare
1756   condition is only likely to occur when a client has improperly
1757   converted a POST request to a GET request with long query
1758   information, when the client has descended into a URI "black hole" of
1759   redirection (e.g., a redirected URI prefix that points to a suffix of
1760   itself), or when the server is under attack by a client attempting to
1761   exploit security holes present in some servers using fixed-length
1762   buffers for reading or manipulating the Effective Request URI.
1763</t>
1764</section>
1765
1766<section title="415 Unsupported Media Type" anchor="status.415">
1767  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1768  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
1769<t>
1770   The server is refusing to service the request because the entity of
1771   the request is in a format not supported by the requested resource
1772   for the requested method.
1773</t>
1774</section>
1775
1776<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1777  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
1778  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
1779  <rdf:Description>
1780    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1781  </rdf:Description>
1782<t>
1783   The request included a Range request-header field (&header-range;) and none of
1784   the range-specifier values in this field overlap the current extent
1785   of the selected resource. See &status-416;
1786</t>
1787</section>
1788
1789<section title="417 Expectation Failed" anchor="status.417">
1790  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
1791  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
1792<t>
1793   The expectation given in an Expect request-header field (see <xref target="header.expect"/>)
1794   could not be met by this server, or, if the server is a proxy,
1795   the server has unambiguous evidence that the request could not be met
1796   by the next-hop server.
1797</t>
1798</section>
1799</section>
1800
1801<section title="Server Error 5xx" anchor="status.5xx">
1802<t>
1803   Response status codes beginning with the digit "5" indicate cases in
1804   which the server is aware that it has erred or is incapable of
1805   performing the request. Except when responding to a HEAD request, the
1806   server &SHOULD; include an entity containing an explanation of the
1807   error situation, and whether it is a temporary or permanent
1808   condition. User agents &SHOULD; display any included entity to the
1809   user. These response codes are applicable to any request method.
1810</t>
1811
1812<section title="500 Internal Server Error" anchor="status.500">
1813  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
1814  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
1815<t>
1816   The server encountered an unexpected condition which prevented it
1817   from fulfilling the request.
1818</t>
1819</section>
1820
1821<section title="501 Not Implemented" anchor="status.501">
1822  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
1823  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
1824<t>
1825   The server does not support the functionality required to fulfill the
1826   request. This is the appropriate response when the server does not
1827   recognize the request method and is not capable of supporting it for
1828   any resource.
1829</t>
1830</section>
1831
1832<section title="502 Bad Gateway" anchor="status.502">
1833  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
1834  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
1835<t>
1836   The server, while acting as a gateway or proxy, received an invalid
1837   response from the upstream server it accessed in attempting to
1838   fulfill the request.
1839</t>
1840</section>
1841
1842<section title="503 Service Unavailable" anchor="status.503">
1843  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
1844  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
1845<t>
1846   The server is currently unable to handle the request due to a
1847   temporary overloading or maintenance of the server. The implication
1848   is that this is a temporary condition which will be alleviated after
1849   some delay. If known, the length of the delay &MAY; be indicated in a
1850   Retry-After header. If no Retry-After is given, the client &SHOULD;
1851   handle the response as it would for a 500 response.
1852</t>
1853<x:note>
1854  <t>
1855    <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
1856    server must use it when becoming overloaded. Some servers may wish
1857    to simply refuse the connection.
1858  </t>
1859</x:note>
1860</section>
1861
1862<section title="504 Gateway Timeout" anchor="status.504">
1863  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
1864  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
1865<t>
1866   The server, while acting as a gateway or proxy, did not receive a
1867   timely response from the upstream server specified by the URI (e.g.,
1868   HTTP, FTP, LDAP) or some other auxiliary server (e.g., DNS) it needed
1869   to access in attempting to complete the request.
1870</t>
1871<x:note>
1872  <t>
1873    <x:h>Note</x:h> to implementors: some deployed proxies are known to
1874    return 400 or 500 when DNS lookups time out.
1875  </t>
1876</x:note>
1877</section>
1878
1879<section title="505 HTTP Version Not Supported" anchor="status.505">
1880  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
1881  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
1882<t>
1883   The server does not support, or refuses to support, the protocol
1884   version that was used in the request message. The server is
1885   indicating that it is unable or unwilling to complete the request
1886   using the same major version as the client, as described in &http-version;,
1887   other than with this error message. The response &SHOULD; contain
1888   an entity describing why that version is not supported and what other
1889   protocols are supported by that server.
1890</t>
1891
1892</section>
1893</section>
1894</section>
1895
1896
1897<section title="Header Field Definitions" anchor="header.fields">
1898<t>
1899   This section defines the syntax and semantics of HTTP/1.1 header fields
1900   related to request and response semantics.
1901</t>
1902<t>
1903   For entity-header fields, both sender and recipient refer to either the
1904   client or the server, depending on who sends and who receives the entity.
1905</t>
1906
1907<section title="Allow" anchor="header.allow">
1908  <iref primary="true" item="Allow header" x:for-anchor=""/>
1909  <iref primary="true" item="Headers" subitem="Allow" x:for-anchor=""/>
1910  <x:anchor-alias value="Allow"/>
1911  <x:anchor-alias value="Allow-v"/>
1912<t>
1913   The "Allow" response-header field lists the set of methods advertised as
1914   supported by the resource identified by the Effective Request URI. The purpose of
1915   this field is strictly to inform the recipient of valid methods
1916   associated with the resource.
1917</t>
1918<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/><iref primary="true" item="Grammar" subitem="Allow-v"/>
1919  <x:ref>Allow</x:ref>   = "Allow" ":" <x:ref>OWS</x:ref> <x:ref>Allow-v</x:ref>
1920  <x:ref>Allow-v</x:ref> = #<x:ref>Method</x:ref>
1921</artwork></figure>
1922<t>
1923      Example of use:
1924</t>
1925<figure><artwork type="example">
1926  Allow: GET, HEAD, PUT
1927</artwork></figure>
1928<t>
1929      The actual set of allowed methods is defined
1930      by the origin server at the time of each request.
1931</t>
1932<t>
1933      A proxy &MUST-NOT; modify the Allow header field even if it does not
1934      understand all the methods specified, since the user agent might
1935      have other means of communicating with the origin server.
1936</t>
1937</section>
1938
1939<section title="Expect" anchor="header.expect">
1940  <iref primary="true" item="Expect header" x:for-anchor=""/>
1941  <iref primary="true" item="Headers" subitem="Expect" x:for-anchor=""/>
1942  <x:anchor-alias value="Expect"/>
1943  <x:anchor-alias value="Expect-v"/>
1944  <x:anchor-alias value="expectation"/>
1945  <x:anchor-alias value="expectation-extension"/>
1946  <x:anchor-alias value="expect-params"/>
1947<t>
1948   The "Expect" request-header field is used to indicate that particular
1949   server behaviors are required by the client.
1950</t>
1951<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"/>
1952  <x:ref>Expect</x:ref>       = "Expect" ":" <x:ref>OWS</x:ref> <x:ref>Expect-v</x:ref>
1953  <x:ref>Expect-v</x:ref>     = 1#<x:ref>expectation</x:ref>
1954 
1955  <x:ref>expectation</x:ref>  = "100-continue" / <x:ref>expectation-extension</x:ref>
1956  <x:ref>expectation-extension</x:ref> = <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> )
1957                           *<x:ref>expect-params</x:ref> ]
1958  <x:ref>expect-params</x:ref> = ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> ) ]
1959</artwork></figure>
1960<t>
1961   A server that does not understand or is unable to comply with any of
1962   the expectation values in the Expect field of a request &MUST; respond
1963   with appropriate error status. The server &MUST; respond with a 417
1964   (Expectation Failed) status if any of the expectations cannot be met
1965   or, if there are other problems with the request, some other 4xx
1966   status.
1967</t>
1968<t>
1969   This header field is defined with extensible syntax to allow for
1970   future extensions. If a server receives a request containing an
1971   Expect field that includes an expectation-extension that it does not
1972   support, it &MUST; respond with a 417 (Expectation Failed) status.
1973</t>
1974<t>
1975   Comparison of expectation values is case-insensitive for unquoted
1976   tokens (including the 100-continue token), and is case-sensitive for
1977   quoted-string expectation-extensions.
1978</t>
1979<t>
1980   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
1981   return a 417 (Expectation Failed) status if it receives a request
1982   with an expectation that it cannot meet. However, the Expect
1983   request-header itself is end-to-end; it &MUST; be forwarded if the
1984   request is forwarded.
1985</t>
1986<t>
1987   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
1988   Expect header.
1989</t>
1990<t>
1991   See &use100; for the use of the 100 (Continue) status.
1992</t>
1993</section>
1994
1995<section title="From" anchor="header.from">
1996  <iref primary="true" item="From header" x:for-anchor=""/>
1997  <iref primary="true" item="Headers" subitem="From" x:for-anchor=""/>
1998  <x:anchor-alias value="From"/>
1999  <x:anchor-alias value="From-v"/>
2000  <x:anchor-alias value="mailbox"/>
2001<t>
2002   The "From" request-header field, if given, &SHOULD; contain an Internet
2003   e-mail address for the human user who controls the requesting user
2004   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
2005   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
2006</t>
2007<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/><iref primary="true" item="Grammar" subitem="From-v"/>
2008  <x:ref>From</x:ref>    = "From" ":" <x:ref>OWS</x:ref> <x:ref>From-v</x:ref>
2009  <x:ref>From-v</x:ref>  = <x:ref>mailbox</x:ref>
2010 
2011  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
2012</artwork></figure>
2013<t>
2014   An example is:
2015</t>
2016<figure><artwork type="example">
2017  From: webmaster@example.org
2018</artwork></figure>
2019<t>
2020   This header field &MAY; be used for logging purposes and as a means for
2021   identifying the source of invalid or unwanted requests. It &SHOULD-NOT; 
2022   be used as an insecure form of access protection. The interpretation
2023   of this field is that the request is being performed on behalf of the
2024   person given, who accepts responsibility for the method performed. In
2025   particular, robot agents &SHOULD; include this header so that the
2026   person responsible for running the robot can be contacted if problems
2027   occur on the receiving end.
2028</t>
2029<t>
2030   The Internet e-mail address in this field &MAY; be separate from the
2031   Internet host which issued the request. For example, when a request
2032   is passed through a proxy the original issuer's address &SHOULD; be
2033   used.
2034</t>
2035<t>
2036   The client &SHOULD-NOT;  send the From header field without the user's
2037   approval, as it might conflict with the user's privacy interests or
2038   their site's security policy. It is strongly recommended that the
2039   user be able to disable, enable, and modify the value of this field
2040   at any time prior to a request.
2041</t>
2042</section>
2043
2044<section title="Location" anchor="header.location">
2045  <iref primary="true" item="Location header" x:for-anchor=""/>
2046  <iref primary="true" item="Headers" subitem="Location" x:for-anchor=""/>
2047  <x:anchor-alias value="Location"/>
2048  <x:anchor-alias value="Location-v"/>
2049<t>
2050   The "Location" response-header field is used to identify a newly created
2051   resource, or to redirect the recipient to a different location for
2052   completion of the request.
2053</t>
2054<t>
2055   For 201 (Created) responses, the Location is the URI of the new resource
2056   which was created by the request. For 3xx responses, the location &SHOULD;
2057   indicate the server's preferred URI for automatic redirection to the
2058   resource.
2059</t>
2060<t>
2061   The field value consists of a single URI-reference. When it has the form
2062   of a relative reference (<xref target="RFC3986" x:fmt="," x:sec="4.2"/>),
2063   the final value is computed by resolving it against the effective request
2064   URI (<xref target="RFC3986" x:fmt="," x:sec="5"/>).
2065</t>
2066<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/><iref primary="true" item="Grammar" subitem="Location-v"/>
2067  <x:ref>Location</x:ref>       = "Location" ":" <x:ref>OWS</x:ref> <x:ref>Location-v</x:ref>
2068  <x:ref>Location-v</x:ref>     = <x:ref>URI-reference</x:ref>
2069</artwork></figure>
2070<figure>
2071<preamble>Examples are:</preamble><!--DO NOT DARE changing the vertical WSP below, it's necessary this way for xml2rfc-->
2072<artwork type="example">
2073  Location: http://www.example.org/pub/WWW/People.html#tim
2074</artwork></figure><figure><artwork type="example">  Location: /index.html
2075</artwork></figure>
2076<t>
2077   There are circumstances in which a fragment identifier in a Location URI
2078   would not be appropriate:
2079   <list style="symbols">
2080      <t>With a 201 Created response, because in this usage the Location header
2081      specifies the URI for the entire created resource.</t>
2082      <t>With 305 Use Proxy.</t>
2083   </list>
2084</t>
2085<x:note>
2086  <t>
2087    <x:h>Note:</x:h> This specification does not define precedence rules
2088    for the case where the original URI, as navigated to by the user
2089    agent, and the Location header field value both contain fragment
2090    identifiers.
2091  </t>
2092</x:note>
2093<x:note>
2094  <t>
2095    <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
2096    from Location in that the Content-Location identifies the original
2097    location of the entity enclosed in the response. It is therefore
2098    possible for a response to contain header fields for both Location
2099    and Content-Location.
2100  </t>
2101</x:note>
2102</section>
2103
2104<section title="Max-Forwards" anchor="header.max-forwards">
2105  <iref primary="true" item="Max-Forwards header" x:for-anchor=""/>
2106  <iref primary="true" item="Headers" subitem="Max-Forwards" x:for-anchor=""/>
2107  <x:anchor-alias value="Max-Forwards"/>
2108  <x:anchor-alias value="Max-Forwards-v"/>
2109<t>
2110   The "Max-Forwards" request-header field provides a mechanism with the
2111   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>)
2112   methods to limit the number of times that the request is forwarded by
2113   proxies or gateways. This can be useful when the client is attempting to
2114   trace a request which appears to be failing or looping in mid-chain.
2115</t>
2116<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/><iref primary="true" item="Grammar" subitem="Max-Forwards-v"/>
2117  <x:ref>Max-Forwards</x:ref>   = "Max-Forwards" ":" <x:ref>OWS</x:ref> <x:ref>Max-Forwards-v</x:ref>
2118  <x:ref>Max-Forwards-v</x:ref> = 1*<x:ref>DIGIT</x:ref>
2119</artwork></figure>
2120<t>
2121   The Max-Forwards value is a decimal integer indicating the remaining
2122   number of times this request message may be forwarded.
2123</t>
2124<t>
2125   Each proxy or gateway recipient of a TRACE or OPTIONS request
2126   containing a Max-Forwards header field &MUST; check and update its
2127   value prior to forwarding the request. If the received value is zero
2128   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2129   respond as the final recipient. If the received Max-Forwards value is
2130   greater than zero, then the forwarded message &MUST; contain an updated
2131   Max-Forwards field with a value decremented by one (1).
2132</t>
2133<t>
2134   The Max-Forwards header field &MAY; be ignored for all other methods
2135   defined by this specification and for any extension methods for which
2136   it is not explicitly referred to as part of that method definition.
2137</t>
2138</section>
2139
2140<section title="Referer" anchor="header.referer">
2141  <iref primary="true" item="Referer header" x:for-anchor=""/>
2142  <iref primary="true" item="Headers" subitem="Referer" x:for-anchor=""/>
2143  <x:anchor-alias value="Referer"/>
2144  <x:anchor-alias value="Referer-v"/>
2145<t>
2146   The "Referer" [sic] request-header field allows the client to specify the
2147   URI of the resource from which the Effective Request URI was obtained (the
2148   "referrer", although the header field is misspelled.).
2149</t>
2150<t>
2151   The Referer header allows servers to generate lists of back-links to
2152   resources for interest, logging, optimized caching, etc. It also allows
2153   obsolete or mistyped links to be traced for maintenance. Some servers use
2154   Referer as a means of controlling where they allow links from (so-called
2155   "deep linking"), but it should be noted that legitimate requests are not
2156   required to contain a Referer header field.
2157</t>
2158<t>
2159   If the Effective Request URI was obtained from a source that does not have its own
2160   URI (e.g., input from the user keyboard), the Referer field &MUST; either be
2161   sent with the value "about:blank", or not be sent at all. Note that this
2162   requirement does not apply to sources with non-HTTP URIs (e.g., FTP).
2163</t>
2164<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/><iref primary="true" item="Grammar" subitem="Referer-v"/>
2165  <x:ref>Referer</x:ref>        = "Referer" ":" <x:ref>OWS</x:ref> <x:ref>Referer-v</x:ref>
2166  <x:ref>Referer-v</x:ref>      = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
2167</artwork></figure>
2168<t>
2169   Example:
2170</t>
2171<figure><artwork type="example">
2172  Referer: http://www.example.org/hypertext/Overview.html
2173</artwork></figure>
2174<t>
2175   If the field value is a relative URI, it &SHOULD; be interpreted
2176   relative to the Effective Request URI. The URI &MUST-NOT; include a fragment. See
2177   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
2178</t>
2179</section>
2180
2181<section title="Retry-After" anchor="header.retry-after">
2182  <iref primary="true" item="Retry-After header" x:for-anchor=""/>
2183  <iref primary="true" item="Headers" subitem="Retry-After" x:for-anchor=""/>
2184  <x:anchor-alias value="Retry-After"/>
2185  <x:anchor-alias value="Retry-After-v"/>
2186<t>
2187   The response-header "Retry-After" field can be used with a 503 (Service
2188   Unavailable) response to indicate how long the service is expected to
2189   be unavailable to the requesting client. This field &MAY; also be used
2190   with any 3xx (Redirection) response to indicate the minimum time the
2191   user-agent is asked wait before issuing the redirected request.
2192</t>
2193<t>
2194   The value of this field can be either an HTTP-date or an integer number
2195   of seconds (in decimal) after the time of the response.
2196</t>
2197<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/><iref primary="true" item="Grammar" subitem="Retry-After-v"/>
2198  <x:ref>Retry-After</x:ref>   = "Retry-After" ":" <x:ref>OWS</x:ref> <x:ref>Retry-After-v</x:ref>
2199  <x:ref>Retry-After-v</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
2200</artwork></figure>
2201<t anchor="rule.delta-seconds">
2202  <x:anchor-alias value="delta-seconds"/>
2203   Time spans are non-negative decimal integers, representing time in
2204   seconds.
2205</t>
2206<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2207  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2208</artwork></figure>
2209<t>
2210   Two examples of its use are
2211</t>
2212<figure><artwork type="example">
2213  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2214  Retry-After: 120
2215</artwork></figure>
2216<t>
2217   In the latter example, the delay is 2 minutes.
2218</t>
2219</section>
2220
2221<section title="Server" anchor="header.server">
2222  <iref primary="true" item="Server header" x:for-anchor=""/>
2223  <iref primary="true" item="Headers" subitem="Server" x:for-anchor=""/>
2224  <x:anchor-alias value="Server"/>
2225  <x:anchor-alias value="Server-v"/>
2226<t>
2227   The "Server" response-header field contains information about the
2228   software used by the origin server to handle the request.
2229</t>
2230<t>
2231   The field can contain multiple product tokens (&product-tokens;) and
2232   comments (&header-fields;) identifying the server and any significant
2233   subproducts. The product tokens are listed in order of their significance
2234   for identifying the application.
2235</t>
2236<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/><iref primary="true" item="Grammar" subitem="Server-v"/>
2237  <x:ref>Server</x:ref>         = "Server" ":" <x:ref>OWS</x:ref> <x:ref>Server-v</x:ref>
2238  <x:ref>Server-v</x:ref>       = <x:ref>product</x:ref>
2239                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2240</artwork></figure>
2241<t>
2242   Example:
2243</t>
2244<figure><artwork type="example">
2245  Server: CERN/3.0 libwww/2.17
2246</artwork></figure>
2247<t>
2248   If the response is being forwarded through a proxy, the proxy
2249   application &MUST-NOT; modify the Server response-header. Instead, it
2250   &MUST; include a Via field (as described in &header-via;).
2251</t>
2252<x:note>
2253  <t>
2254    <x:h>Note:</x:h> Revealing the specific software version of the server might
2255    allow the server machine to become more vulnerable to attacks
2256    against software that is known to contain security holes. Server
2257    implementors are encouraged to make this field a configurable
2258    option.
2259  </t>
2260</x:note>
2261</section>
2262
2263<section title="User-Agent" anchor="header.user-agent">
2264  <iref primary="true" item="User-Agent header" x:for-anchor=""/>
2265  <iref primary="true" item="Headers" subitem="User-Agent" x:for-anchor=""/>
2266  <x:anchor-alias value="User-Agent"/>
2267  <x:anchor-alias value="User-Agent-v"/>
2268<t>
2269   The "User-Agent" request-header field contains information about the
2270   user agent originating the request. This is for statistical purposes,
2271   the tracing of protocol violations, and automated recognition of user
2272   agents for the sake of tailoring responses to avoid particular user
2273   agent limitations.
2274</t>
2275<t>
2276   User agents &SHOULD; include this field with requests. The field can contain
2277   multiple product tokens (&product-tokens;) and comments (&header-fields;)
2278   identifying the agent and any subproducts which form a significant part of
2279   the user agent. By convention, the product tokens are listed in order of
2280   their significance for identifying the application.
2281</t>
2282<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/><iref primary="true" item="Grammar" subitem="User-Agent-v"/>
2283  <x:ref>User-Agent</x:ref>     = "User-Agent" ":" <x:ref>OWS</x:ref> <x:ref>User-Agent-v</x:ref>
2284  <x:ref>User-Agent-v</x:ref>   = <x:ref>product</x:ref>
2285                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2286</artwork></figure>
2287<t>
2288   Example:
2289</t>
2290<figure><artwork type="example">
2291  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2292</artwork></figure>
2293</section>
2294
2295</section>
2296
2297<section title="IANA Considerations" anchor="IANA.considerations">
2298
2299<section title="Method Registry" anchor="method.registration">
2300<t>
2301  The registration procedure for HTTP Methods is defined by
2302  <xref target="method.registry"/> of this document.
2303</t>
2304<t>
2305   The HTTP Method Registry should be created at <eref target="http://www.iana.org/assignments/http-methods"/>
2306   and be populated with the registrations below:
2307</t>
2308<?BEGININC p2-semantics.iana-methods ?>
2309<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2310<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2311   <ttcol>Method</ttcol>
2312   <ttcol>Safe</ttcol>
2313   <ttcol>Reference</ttcol>
2314   <c>CONNECT</c>
2315   <c>no</c>
2316   <c>
2317      <xref target="CONNECT"/>
2318   </c>
2319   <c>DELETE</c>
2320   <c>no</c>
2321   <c>
2322      <xref target="DELETE"/>
2323   </c>
2324   <c>GET</c>
2325   <c>yes</c>
2326   <c>
2327      <xref target="GET"/>
2328   </c>
2329   <c>HEAD</c>
2330   <c>yes</c>
2331   <c>
2332      <xref target="HEAD"/>
2333   </c>
2334   <c>OPTIONS</c>
2335   <c>yes</c>
2336   <c>
2337      <xref target="OPTIONS"/>
2338   </c>
2339   <c>POST</c>
2340   <c>no</c>
2341   <c>
2342      <xref target="POST"/>
2343   </c>
2344   <c>PUT</c>
2345   <c>no</c>
2346   <c>
2347      <xref target="PUT"/>
2348   </c>
2349   <c>TRACE</c>
2350   <c>yes</c>
2351   <c>
2352      <xref target="TRACE"/>
2353   </c>
2354</texttable>
2355<!--(END)-->
2356<?ENDINC p2-semantics.iana-methods ?>
2357</section>
2358
2359<section title="Status Code Registry" anchor="status.code.registration">
2360<t>
2361   The registration procedure for HTTP Status Codes -- previously defined
2362   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> -- is now defined
2363   by <xref target="status.code.registry"/> of this document.
2364</t>
2365<t>
2366   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
2367   should be updated with the registrations below:
2368</t>
2369<?BEGININC p2-semantics.iana-status-codes ?>
2370<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2371<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
2372   <ttcol>Value</ttcol>
2373   <ttcol>Description</ttcol>
2374   <ttcol>Reference</ttcol>
2375   <c>100</c>
2376   <c>Continue</c>
2377   <c>
2378      <xref target="status.100"/>
2379   </c>
2380   <c>101</c>
2381   <c>Switching Protocols</c>
2382   <c>
2383      <xref target="status.101"/>
2384   </c>
2385   <c>200</c>
2386   <c>OK</c>
2387   <c>
2388      <xref target="status.200"/>
2389   </c>
2390   <c>201</c>
2391   <c>Created</c>
2392   <c>
2393      <xref target="status.201"/>
2394   </c>
2395   <c>202</c>
2396   <c>Accepted</c>
2397   <c>
2398      <xref target="status.202"/>
2399   </c>
2400   <c>203</c>
2401   <c>Non-Authoritative Information</c>
2402   <c>
2403      <xref target="status.203"/>
2404   </c>
2405   <c>204</c>
2406   <c>No Content</c>
2407   <c>
2408      <xref target="status.204"/>
2409   </c>
2410   <c>205</c>
2411   <c>Reset Content</c>
2412   <c>
2413      <xref target="status.205"/>
2414   </c>
2415   <c>300</c>
2416   <c>Multiple Choices</c>
2417   <c>
2418      <xref target="status.300"/>
2419   </c>
2420   <c>301</c>
2421   <c>Moved Permanently</c>
2422   <c>
2423      <xref target="status.301"/>
2424   </c>
2425   <c>302</c>
2426   <c>Found</c>
2427   <c>
2428      <xref target="status.302"/>
2429   </c>
2430   <c>303</c>
2431   <c>See Other</c>
2432   <c>
2433      <xref target="status.303"/>
2434   </c>
2435   <c>305</c>
2436   <c>Use Proxy</c>
2437   <c>
2438      <xref target="status.305"/>
2439   </c>
2440   <c>306</c>
2441   <c>(Unused)</c>
2442   <c>
2443      <xref target="status.306"/>
2444   </c>
2445   <c>307</c>
2446   <c>Temporary Redirect</c>
2447   <c>
2448      <xref target="status.307"/>
2449   </c>
2450   <c>400</c>
2451   <c>Bad Request</c>
2452   <c>
2453      <xref target="status.400"/>
2454   </c>
2455   <c>402</c>
2456   <c>Payment Required</c>
2457   <c>
2458      <xref target="status.402"/>
2459   </c>
2460   <c>403</c>
2461   <c>Forbidden</c>
2462   <c>
2463      <xref target="status.403"/>
2464   </c>
2465   <c>404</c>
2466   <c>Not Found</c>
2467   <c>
2468      <xref target="status.404"/>
2469   </c>
2470   <c>405</c>
2471   <c>Method Not Allowed</c>
2472   <c>
2473      <xref target="status.405"/>
2474   </c>
2475   <c>406</c>
2476   <c>Not Acceptable</c>
2477   <c>
2478      <xref target="status.406"/>
2479   </c>
2480   <c>407</c>
2481   <c>Proxy Authentication Required</c>
2482   <c>
2483      <xref target="status.407"/>
2484   </c>
2485   <c>408</c>
2486   <c>Request Timeout</c>
2487   <c>
2488      <xref target="status.408"/>
2489   </c>
2490   <c>409</c>
2491   <c>Conflict</c>
2492   <c>
2493      <xref target="status.409"/>
2494   </c>
2495   <c>410</c>
2496   <c>Gone</c>
2497   <c>
2498      <xref target="status.410"/>
2499   </c>
2500   <c>411</c>
2501   <c>Length Required</c>
2502   <c>
2503      <xref target="status.411"/>
2504   </c>
2505   <c>413</c>
2506   <c>Request Entity Too Large</c>
2507   <c>
2508      <xref target="status.413"/>
2509   </c>
2510   <c>414</c>
2511   <c>URI Too Long</c>
2512   <c>
2513      <xref target="status.414"/>
2514   </c>
2515   <c>415</c>
2516   <c>Unsupported Media Type</c>
2517   <c>
2518      <xref target="status.415"/>
2519   </c>
2520   <c>417</c>
2521   <c>Expectation Failed</c>
2522   <c>
2523      <xref target="status.417"/>
2524   </c>
2525   <c>500</c>
2526   <c>Internal Server Error</c>
2527   <c>
2528      <xref target="status.500"/>
2529   </c>
2530   <c>501</c>
2531   <c>Not Implemented</c>
2532   <c>
2533      <xref target="status.501"/>
2534   </c>
2535   <c>502</c>
2536   <c>Bad Gateway</c>
2537   <c>
2538      <xref target="status.502"/>
2539   </c>
2540   <c>503</c>
2541   <c>Service Unavailable</c>
2542   <c>
2543      <xref target="status.503"/>
2544   </c>
2545   <c>504</c>
2546   <c>Gateway Timeout</c>
2547   <c>
2548      <xref target="status.504"/>
2549   </c>
2550   <c>505</c>
2551   <c>HTTP Version Not Supported</c>
2552   <c>
2553      <xref target="status.505"/>
2554   </c>
2555</texttable>
2556<!--(END)-->
2557<?ENDINC p2-semantics.iana-status-codes ?>
2558</section>
2559<section title="Message Header Registration" anchor="message.header.registration">
2560<t>
2561   The Message Header Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> should be updated
2562   with the permanent registrations below (see <xref target="RFC3864"/>):
2563</t>
2564<?BEGININC p2-semantics.iana-headers ?>
2565<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
2566<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
2567   <ttcol>Header Field Name</ttcol>
2568   <ttcol>Protocol</ttcol>
2569   <ttcol>Status</ttcol>
2570   <ttcol>Reference</ttcol>
2571
2572   <c>Allow</c>
2573   <c>http</c>
2574   <c>standard</c>
2575   <c>
2576      <xref target="header.allow"/>
2577   </c>
2578   <c>Expect</c>
2579   <c>http</c>
2580   <c>standard</c>
2581   <c>
2582      <xref target="header.expect"/>
2583   </c>
2584   <c>From</c>
2585   <c>http</c>
2586   <c>standard</c>
2587   <c>
2588      <xref target="header.from"/>
2589   </c>
2590   <c>Location</c>
2591   <c>http</c>
2592   <c>standard</c>
2593   <c>
2594      <xref target="header.location"/>
2595   </c>
2596   <c>Max-Forwards</c>
2597   <c>http</c>
2598   <c>standard</c>
2599   <c>
2600      <xref target="header.max-forwards"/>
2601   </c>
2602   <c>Referer</c>
2603   <c>http</c>
2604   <c>standard</c>
2605   <c>
2606      <xref target="header.referer"/>
2607   </c>
2608   <c>Retry-After</c>
2609   <c>http</c>
2610   <c>standard</c>
2611   <c>
2612      <xref target="header.retry-after"/>
2613   </c>
2614   <c>Server</c>
2615   <c>http</c>
2616   <c>standard</c>
2617   <c>
2618      <xref target="header.server"/>
2619   </c>
2620   <c>User-Agent</c>
2621   <c>http</c>
2622   <c>standard</c>
2623   <c>
2624      <xref target="header.user-agent"/>
2625   </c>
2626</texttable>
2627<!--(END)-->
2628<?ENDINC p2-semantics.iana-headers ?>
2629<t>
2630   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
2631</t>
2632</section>
2633</section>
2634
2635<section title="Security Considerations" anchor="security.considerations">
2636<t>
2637   This section is meant to inform application developers, information
2638   providers, and users of the security limitations in HTTP/1.1 as
2639   described by this document. The discussion does not include
2640   definitive solutions to the problems revealed, though it does make
2641   some suggestions for reducing security risks.
2642</t>
2643
2644<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2645<t>
2646   Like any generic data transfer protocol, HTTP cannot regulate the
2647   content of the data that is transferred, nor is there any a priori
2648   method of determining the sensitivity of any particular piece of
2649   information within the context of any given request. Therefore,
2650   applications &SHOULD; supply as much control over this information as
2651   possible to the provider of that information. Four header fields are
2652   worth special mention in this context: Server, Via, Referer and From.
2653</t>
2654<t>
2655   Revealing the specific software version of the server might allow the
2656   server machine to become more vulnerable to attacks against software
2657   that is known to contain security holes. Implementors &SHOULD; make the
2658   Server header field a configurable option.
2659</t>
2660<t>
2661   Proxies which serve as a portal through a network firewall &SHOULD;
2662   take special precautions regarding the transfer of header information
2663   that identifies the hosts behind the firewall. In particular, they
2664   &SHOULD; remove, or replace with sanitized versions, any Via fields
2665   generated behind the firewall.
2666</t>
2667<t>
2668   The Referer header allows reading patterns to be studied and reverse
2669   links drawn. Although it can be very useful, its power can be abused
2670   if user details are not separated from the information contained in
2671   the Referer. Even when the personal information has been removed, the
2672   Referer header might indicate a private document's URI whose
2673   publication would be inappropriate.
2674</t>
2675<t>
2676   The information sent in the From field might conflict with the user's
2677   privacy interests or their site's security policy, and hence it
2678   &SHOULD-NOT;  be transmitted without the user being able to disable,
2679   enable, and modify the contents of the field. The user &MUST; be able
2680   to set the contents of this field within a user preference or
2681   application defaults configuration.
2682</t>
2683<t>
2684   We suggest, though do not require, that a convenient toggle interface
2685   be provided for the user to enable or disable the sending of From and
2686   Referer information.
2687</t>
2688<t>
2689   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref target="header.server"/>) header
2690   fields can sometimes be used to determine that a specific client or
2691   server have a particular security hole which might be exploited.
2692   Unfortunately, this same information is often used for other valuable
2693   purposes for which HTTP currently has no better mechanism.
2694</t>
2695<t>
2696   Some methods, like TRACE (<xref target="TRACE"/>) may expose
2697   information sent in request headers in the response entity.
2698   Clients &SHOULD; be careful with sensitive information, like Cookies,
2699   Authorization credentials and other headers that might be used to
2700   collect data from the client.
2701</t> 
2702</section>
2703
2704<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
2705<t>
2706   Because the source of a link might be private information or might
2707   reveal an otherwise private information source, it is strongly
2708   recommended that the user be able to select whether or not the
2709   Referer field is sent. For example, a browser client could have a
2710   toggle switch for browsing openly/anonymously, which would
2711   respectively enable/disable the sending of Referer and From
2712   information.
2713</t>
2714<t>
2715   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
2716   HTTP request if the referring page was transferred with a secure
2717   protocol.
2718</t>
2719<t>
2720   Authors of services should not use GET-based forms for the submission of
2721   sensitive data because that data will be encoded in the request-target. Many
2722   existing servers, proxies, and user agents log or display the request-target
2723   in places where it might be visible to third parties. Such services can
2724   use POST-based form submission instead.
2725</t>
2726</section>
2727
2728<section title="Location Headers and Spoofing" anchor="location.spoofing">
2729<t>
2730   If a single server supports multiple organizations that do not trust
2731   one another, then it &MUST; check the values of Location and Content-Location
2732   headers in responses that are generated under control of
2733   said organizations to make sure that they do not attempt to
2734   invalidate resources over which they have no authority.
2735</t>
2736</section>
2737
2738</section>
2739
2740<section title="Acknowledgments" anchor="ack">
2741</section>
2742</middle>
2743<back>
2744
2745<references title="Normative References">
2746
2747<reference anchor="Part1">
2748  <front>
2749    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
2750    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2751      <organization abbrev="Day Software">Day Software</organization>
2752      <address><email>fielding@gbiv.com</email></address>
2753    </author>
2754    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2755      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2756      <address><email>jg@freedesktop.org</email></address>
2757    </author>
2758    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2759      <organization abbrev="HP">Hewlett-Packard Company</organization>
2760      <address><email>JeffMogul@acm.org</email></address>
2761    </author>
2762    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2763      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2764      <address><email>henrikn@microsoft.com</email></address>
2765    </author>
2766    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2767      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2768      <address><email>LMM@acm.org</email></address>
2769    </author>
2770    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2771      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2772      <address><email>paulle@microsoft.com</email></address>
2773    </author>
2774    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2775      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2776      <address><email>timbl@w3.org</email></address>
2777    </author>
2778    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2779      <organization abbrev="W3C">World Wide Web Consortium</organization>
2780      <address><email>ylafon@w3.org</email></address>
2781    </author>
2782    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2783      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2784      <address><email>julian.reschke@greenbytes.de</email></address>
2785    </author>
2786    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2787  </front>
2788  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
2789  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
2790</reference>
2791
2792<reference anchor="Part3">
2793  <front>
2794    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
2795    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2796      <organization abbrev="Day Software">Day Software</organization>
2797      <address><email>fielding@gbiv.com</email></address>
2798    </author>
2799    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2800      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2801      <address><email>jg@freedesktop.org</email></address>
2802    </author>
2803    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2804      <organization abbrev="HP">Hewlett-Packard Company</organization>
2805      <address><email>JeffMogul@acm.org</email></address>
2806    </author>
2807    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2808      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2809      <address><email>henrikn@microsoft.com</email></address>
2810    </author>
2811    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2812      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2813      <address><email>LMM@acm.org</email></address>
2814    </author>
2815    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2816      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2817      <address><email>paulle@microsoft.com</email></address>
2818    </author>
2819    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2820      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2821      <address><email>timbl@w3.org</email></address>
2822    </author>
2823    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2824      <organization abbrev="W3C">World Wide Web Consortium</organization>
2825      <address><email>ylafon@w3.org</email></address>
2826    </author>
2827    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2828      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2829      <address><email>julian.reschke@greenbytes.de</email></address>
2830    </author>
2831    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2832  </front>
2833  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
2834  <x:source href="p3-payload.xml" basename="p3-payload"/>
2835</reference>
2836
2837<reference anchor="Part4">
2838  <front>
2839    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
2840    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2841      <organization abbrev="Day Software">Day Software</organization>
2842      <address><email>fielding@gbiv.com</email></address>
2843    </author>
2844    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2845      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2846      <address><email>jg@freedesktop.org</email></address>
2847    </author>
2848    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2849      <organization abbrev="HP">Hewlett-Packard Company</organization>
2850      <address><email>JeffMogul@acm.org</email></address>
2851    </author>
2852    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2853      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2854      <address><email>henrikn@microsoft.com</email></address>
2855    </author>
2856    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2857      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2858      <address><email>LMM@acm.org</email></address>
2859    </author>
2860    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2861      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2862      <address><email>paulle@microsoft.com</email></address>
2863    </author>
2864    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2865      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2866      <address><email>timbl@w3.org</email></address>
2867    </author>
2868    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2869      <organization abbrev="W3C">World Wide Web Consortium</organization>
2870      <address><email>ylafon@w3.org</email></address>
2871    </author>
2872    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2873      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2874      <address><email>julian.reschke@greenbytes.de</email></address>
2875    </author>
2876    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2877  </front>
2878  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
2879  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
2880</reference>
2881
2882<reference anchor="Part5">
2883  <front>
2884    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
2885    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2886      <organization abbrev="Day Software">Day Software</organization>
2887      <address><email>fielding@gbiv.com</email></address>
2888    </author>
2889    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2890      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2891      <address><email>jg@freedesktop.org</email></address>
2892    </author>
2893    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2894      <organization abbrev="HP">Hewlett-Packard Company</organization>
2895      <address><email>JeffMogul@acm.org</email></address>
2896    </author>
2897    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2898      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2899      <address><email>henrikn@microsoft.com</email></address>
2900    </author>
2901    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2902      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2903      <address><email>LMM@acm.org</email></address>
2904    </author>
2905    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2906      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2907      <address><email>paulle@microsoft.com</email></address>
2908    </author>
2909    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2910      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2911      <address><email>timbl@w3.org</email></address>
2912    </author>
2913    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2914      <organization abbrev="W3C">World Wide Web Consortium</organization>
2915      <address><email>ylafon@w3.org</email></address>
2916    </author>
2917    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2918      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2919      <address><email>julian.reschke@greenbytes.de</email></address>
2920    </author>
2921    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2922  </front>
2923  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
2924  <x:source href="p5-range.xml" basename="p5-range"/>
2925</reference>
2926
2927<reference anchor="Part6">
2928  <front>
2929    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
2930    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2931      <organization abbrev="Day Software">Day Software</organization>
2932      <address><email>fielding@gbiv.com</email></address>
2933    </author>
2934    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2935      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2936      <address><email>jg@freedesktop.org</email></address>
2937    </author>
2938    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2939      <organization abbrev="HP">Hewlett-Packard Company</organization>
2940      <address><email>JeffMogul@acm.org</email></address>
2941    </author>
2942    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2943      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2944      <address><email>henrikn@microsoft.com</email></address>
2945    </author>
2946    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2947      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2948      <address><email>LMM@acm.org</email></address>
2949    </author>
2950    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2951      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2952      <address><email>paulle@microsoft.com</email></address>
2953    </author>
2954    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2955      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2956      <address><email>timbl@w3.org</email></address>
2957    </author>
2958    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2959      <organization abbrev="W3C">World Wide Web Consortium</organization>
2960      <address><email>ylafon@w3.org</email></address>
2961    </author>
2962    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
2963      <address><email>mnot@mnot.net</email></address>
2964    </author>
2965    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2966      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2967      <address><email>julian.reschke@greenbytes.de</email></address>
2968    </author>
2969    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2970  </front>
2971  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
2972  <x:source href="p6-cache.xml" basename="p6-cache"/>
2973</reference>
2974
2975<reference anchor="Part7">
2976  <front>
2977    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
2978    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2979      <organization abbrev="Day Software">Day Software</organization>
2980      <address><email>fielding@gbiv.com</email></address>
2981    </author>
2982    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2983      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2984      <address><email>jg@freedesktop.org</email></address>
2985    </author>
2986    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2987      <organization abbrev="HP">Hewlett-Packard Company</organization>
2988      <address><email>JeffMogul@acm.org</email></address>
2989    </author>
2990    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2991      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2992      <address><email>henrikn@microsoft.com</email></address>
2993    </author>
2994    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2995      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2996      <address><email>LMM@acm.org</email></address>
2997    </author>
2998    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2999      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3000      <address><email>paulle@microsoft.com</email></address>
3001    </author>
3002    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3003      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3004      <address><email>timbl@w3.org</email></address>
3005    </author>
3006    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3007      <organization abbrev="W3C">World Wide Web Consortium</organization>
3008      <address><email>ylafon@w3.org</email></address>
3009    </author>
3010    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3011      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3012      <address><email>julian.reschke@greenbytes.de</email></address>
3013    </author>
3014    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3015  </front>
3016  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
3017  <x:source href="p7-auth.xml" basename="p7-auth"/>
3018</reference>
3019
3020<reference anchor="RFC2119">
3021  <front>
3022    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
3023    <author initials="S." surname="Bradner" fullname="Scott Bradner">
3024      <organization>Harvard University</organization>
3025      <address><email>sob@harvard.edu</email></address>
3026    </author>
3027    <date month="March" year="1997"/>
3028  </front>
3029  <seriesInfo name="BCP" value="14"/>
3030  <seriesInfo name="RFC" value="2119"/>
3031</reference>
3032
3033<reference anchor="RFC3986">
3034 <front>
3035  <title abbrev='URI Generic Syntax'>Uniform Resource Identifier (URI): Generic Syntax</title>
3036  <author initials='T.' surname='Berners-Lee' fullname='Tim Berners-Lee'>
3037    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3038    <address>
3039       <email>timbl@w3.org</email>
3040       <uri>http://www.w3.org/People/Berners-Lee/</uri>
3041    </address>
3042  </author>
3043  <author initials='R.' surname='Fielding' fullname='Roy T. Fielding'>
3044    <organization abbrev="Day Software">Day Software</organization>
3045    <address>
3046      <email>fielding@gbiv.com</email>
3047      <uri>http://roy.gbiv.com/</uri>
3048    </address>
3049  </author>
3050  <author initials='L.' surname='Masinter' fullname='Larry Masinter'>
3051    <organization abbrev="Adobe Systems">Adobe Systems Incorporated</organization>
3052    <address>
3053      <email>LMM@acm.org</email>
3054      <uri>http://larry.masinter.net/</uri>
3055    </address>
3056  </author>
3057  <date month='January' year='2005'></date>
3058 </front>
3059 <seriesInfo name="RFC" value="3986"/>
3060 <seriesInfo name="STD" value="66"/>
3061</reference>
3062
3063<reference anchor="RFC5234">
3064  <front>
3065    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
3066    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
3067      <organization>Brandenburg InternetWorking</organization>
3068      <address>
3069        <email>dcrocker@bbiw.net</email>
3070      </address> 
3071    </author>
3072    <author initials="P." surname="Overell" fullname="Paul Overell">
3073      <organization>THUS plc.</organization>
3074      <address>
3075        <email>paul.overell@thus.net</email>
3076      </address>
3077    </author>
3078    <date month="January" year="2008"/>
3079  </front>
3080  <seriesInfo name="STD" value="68"/>
3081  <seriesInfo name="RFC" value="5234"/>
3082</reference>
3083
3084</references>
3085
3086<references title="Informative References">
3087
3088<reference anchor="RFC1945">
3089  <front>
3090    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
3091    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3092      <organization>MIT, Laboratory for Computer Science</organization>
3093      <address><email>timbl@w3.org</email></address>
3094    </author>
3095    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
3096      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3097      <address><email>fielding@ics.uci.edu</email></address>
3098    </author>
3099    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3100      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
3101      <address><email>frystyk@w3.org</email></address>
3102    </author>
3103    <date month="May" year="1996"/>
3104  </front>
3105  <seriesInfo name="RFC" value="1945"/>
3106</reference>
3107
3108<reference anchor="RFC2068">
3109  <front>
3110    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
3111    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
3112      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3113      <address><email>fielding@ics.uci.edu</email></address>
3114    </author>
3115    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3116      <organization>MIT Laboratory for Computer Science</organization>
3117      <address><email>jg@w3.org</email></address>
3118    </author>
3119    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3120      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
3121      <address><email>mogul@wrl.dec.com</email></address>
3122    </author>
3123    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3124      <organization>MIT Laboratory for Computer Science</organization>
3125      <address><email>frystyk@w3.org</email></address>
3126    </author>
3127    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3128      <organization>MIT Laboratory for Computer Science</organization>
3129      <address><email>timbl@w3.org</email></address>
3130    </author>
3131    <date month="January" year="1997"/>
3132  </front>
3133  <seriesInfo name="RFC" value="2068"/>
3134</reference>
3135
3136<reference anchor="RFC2616">
3137  <front>
3138    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
3139    <author initials="R." surname="Fielding" fullname="R. Fielding">
3140      <organization>University of California, Irvine</organization>
3141      <address><email>fielding@ics.uci.edu</email></address>
3142    </author>
3143    <author initials="J." surname="Gettys" fullname="J. Gettys">
3144      <organization>W3C</organization>
3145      <address><email>jg@w3.org</email></address>
3146    </author>
3147    <author initials="J." surname="Mogul" fullname="J. Mogul">
3148      <organization>Compaq Computer Corporation</organization>
3149      <address><email>mogul@wrl.dec.com</email></address>
3150    </author>
3151    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
3152      <organization>MIT Laboratory for Computer Science</organization>
3153      <address><email>frystyk@w3.org</email></address>
3154    </author>
3155    <author initials="L." surname="Masinter" fullname="L. Masinter">
3156      <organization>Xerox Corporation</organization>
3157      <address><email>masinter@parc.xerox.com</email></address>
3158    </author>
3159    <author initials="P." surname="Leach" fullname="P. Leach">
3160      <organization>Microsoft Corporation</organization>
3161      <address><email>paulle@microsoft.com</email></address>
3162    </author>
3163    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
3164      <organization>W3C</organization>
3165      <address><email>timbl@w3.org</email></address>
3166    </author>
3167    <date month="June" year="1999"/>
3168  </front>
3169  <seriesInfo name="RFC" value="2616"/>
3170</reference>
3171
3172<reference anchor='RFC2817'>
3173  <front>
3174    <title>Upgrading to TLS Within HTTP/1.1</title>
3175    <author initials='R.' surname='Khare' fullname='R. Khare'>
3176      <organization>4K Associates / UC Irvine</organization>
3177      <address><email>rohit@4K-associates.com</email></address>
3178    </author>
3179    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
3180      <organization>Agranat Systems, Inc.</organization>
3181      <address><email>lawrence@agranat.com</email></address>
3182    </author>
3183    <date year='2000' month='May' />
3184  </front>
3185  <seriesInfo name='RFC' value='2817' />
3186</reference>
3187
3188<reference anchor='RFC3864'>
3189  <front>
3190    <title>Registration Procedures for Message Header Fields</title>
3191    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3192      <organization>Nine by Nine</organization>
3193      <address><email>GK-IETF@ninebynine.org</email></address>
3194    </author>
3195    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3196      <organization>BEA Systems</organization>
3197      <address><email>mnot@pobox.com</email></address>
3198    </author>
3199    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3200      <organization>HP Labs</organization>
3201      <address><email>JeffMogul@acm.org</email></address>
3202    </author>
3203    <date year='2004' month='September' />
3204  </front>
3205  <seriesInfo name='BCP' value='90' />
3206  <seriesInfo name='RFC' value='3864' />
3207</reference>
3208
3209<reference anchor='RFC5226'>
3210  <front>
3211    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3212    <author initials='T.' surname='Narten' fullname='T. Narten'>
3213      <organization>IBM</organization>
3214      <address><email>narten@us.ibm.com</email></address>
3215    </author>
3216    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3217      <organization>Google</organization>
3218      <address><email>Harald@Alvestrand.no</email></address>
3219    </author>
3220    <date year='2008' month='May' />
3221  </front>
3222  <seriesInfo name='BCP' value='26' />
3223  <seriesInfo name='RFC' value='5226' />
3224</reference>
3225
3226<reference anchor="RFC5322">
3227  <front>
3228    <title>Internet Message Format</title>
3229    <author initials="P." surname="Resnick" fullname="P. Resnick">
3230      <organization>Qualcomm Incorporated</organization>
3231    </author>
3232    <date year="2008" month="October"/>
3233  </front> 
3234  <seriesInfo name="RFC" value="5322"/>
3235</reference>
3236
3237</references>
3238
3239<section title="Compatibility with Previous Versions" anchor="compatibility">
3240<section title="Changes from RFC 2068" anchor="changes.from.rfc.2068">
3241<t>
3242   Clarified which error code should be used for inbound server failures
3243   (e.g., DNS failures). (<xref target="status.504"/>).
3244</t>
3245<t>
3246   201 (Created) had a race that required an Etag be sent when a resource is
3247   first created. (<xref target="status.201"/>).
3248</t>
3249<t>
3250   303 (See Also) and 307 (Temporary Redirect) added to address user agent
3251   failure to implement status code 302 properly.
3252   (Section <xref target="status.303" format="counter"/> and <xref target="status.307" format="counter"/>)
3253</t>
3254<t>
3255   Rewrite of message transmission requirements to make it much harder
3256   for implementors to get it wrong, as the consequences of errors here
3257   can have significant impact on the Internet, and to deal with the
3258   following problems:
3259  <list style="numbers">
3260      <t>Changing "HTTP/1.1 or later" to "HTTP/1.1", in contexts where
3261         this was incorrectly placing a requirement on the behavior of
3262         an implementation of a future version of HTTP/1.x</t>
3263
3264      <t>Made it clear that user-agents should retry requests, not
3265         "clients" in general.</t>
3266
3267      <t>Converted requirements for clients to ignore unexpected 100
3268         (Continue) responses, and for proxies to forward 100 responses,
3269         into a general requirement for 1xx responses.</t>
3270
3271      <t>Modified some TCP-specific language, to make it clearer that
3272         non-TCP transports are possible for HTTP.</t>
3273
3274      <t>Require that the origin server &MUST-NOT; wait for the request
3275         body before it sends a required 100 (Continue) response.</t>
3276
3277      <t>Allow, rather than require, a server to omit 100 (Continue) if
3278         it has already seen some of the request body.</t>
3279
3280      <t>Allow servers to defend against denial-of-service attacks and
3281         broken clients.</t>
3282  </list>
3283</t>
3284<t>
3285   This change adds the Expect header and 417 status code.
3286</t>
3287<t>
3288   Clean up confusion between 403 and 404 responses. (Section <xref target="status.403" format="counter"/>,
3289   <xref target="status.404" format="counter"/>, and <xref target="status.410" format="counter"/>)
3290</t>
3291<t>
3292   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
3293   implemented in previous versions of this specification. See <xref target="RFC2068" x:fmt="of" x:sec="19.6.1"/>.
3294</t>
3295</section>
3296
3297<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3298<t>
3299  This document takes over the Status Code Registry, previously defined
3300  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3301  (<xref target="status.code.registry"/>)
3302</t>
3303<t>
3304  Clarify definition of POST.
3305  (<xref target="POST"/>)
3306</t>
3307<t>
3308  Failed to consider that there are
3309  many other request methods that are safe to automatically redirect,
3310  and further that the user agent is able to make that determination
3311  based on the request method semantics.
3312  (Sections <xref format="counter" target="status.301"/>,
3313  <xref format="counter" target="status.302"/> and
3314  <xref format="counter" target="status.307"/>)
3315</t>
3316<t>
3317  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3318  It used to indicate that the requested resource must be accessed through the
3319  proxy given by the Location field. The Location field gave the URI of the
3320  proxy. The recipient was expected to repeat this single request via the proxy.
3321  (<xref target="status.305"/>)
3322</t>
3323<t>
3324  Reclassify Allow header as response header, removing the option to
3325  specify it in a PUT request.
3326  Relax the server requirement on the contents of the Allow header and
3327  remove requirement on clients to always trust the header value.
3328  (<xref target="header.allow"/>)
3329</t>
3330<t>
3331  Correct syntax of Location header to allow URI references (including
3332  relative references and fragments), as referred symbol "absoluteURI" wasn't
3333  what was expected, and add some clarifications as to when use of fragments
3334  would not be appropriate.
3335  (<xref target="header.location"/>)
3336</t>
3337<t>
3338  Allow Referer value of "about:blank" as alternative to not specifying it.
3339  (<xref target="header.referer"/>)
3340</t>
3341<t>
3342  In the description of the Server header, the Via field
3343  was described as a SHOULD. The requirement was and is stated
3344  correctly in the description of the Via header in &header-via;.
3345  (<xref target="header.server"/>)
3346</t>
3347</section>
3348
3349</section>
3350
3351<?BEGININC p2-semantics.abnf-appendix ?>
3352<section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf">
3353<figure>
3354<artwork type="abnf" name="p2-semantics.parsed-abnf">
3355<x:ref>Accept</x:ref> = &lt;Accept, defined in [Part3], Section 5.1&gt;
3356<x:ref>Accept-Charset</x:ref> = &lt;Accept-Charset, defined in [Part3], Section 5.2&gt;
3357<x:ref>Accept-Encoding</x:ref> = &lt;Accept-Encoding, defined in [Part3], Section 5.3&gt;
3358<x:ref>Accept-Language</x:ref> = &lt;Accept-Language, defined in [Part3], Section 5.4&gt;
3359<x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in [Part5], Section 5.1&gt;
3360<x:ref>Age</x:ref> = &lt;Age, defined in [Part6], Section 3.1&gt;
3361<x:ref>Allow</x:ref> = "Allow:" OWS Allow-v
3362<x:ref>Allow-v</x:ref> = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
3363<x:ref>Authorization</x:ref> = &lt;Authorization, defined in [Part7], Section 3.1&gt;
3364
3365<x:ref>ETag</x:ref> = &lt;ETag, defined in [Part4], Section 6.1&gt;
3366<x:ref>Expect</x:ref> = "Expect:" OWS Expect-v
3367<x:ref>Expect-v</x:ref> = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
3368
3369<x:ref>From</x:ref> = "From:" OWS From-v
3370<x:ref>From-v</x:ref> = mailbox
3371
3372<x:ref>HTTP-date</x:ref> = &lt;HTTP-date, defined in [Part1], Section 6.1&gt;
3373<x:ref>Host</x:ref> = &lt;Host, defined in [Part1], Section 2.6&gt;
3374
3375<x:ref>If-Match</x:ref> = &lt;If-Match, defined in [Part4], Section 6.2&gt;
3376If-Modified-Since =
3377 &lt;If-Modified-Since, defined in [Part4], Section 6.3&gt;
3378<x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in [Part4], Section 6.4&gt;
3379<x:ref>If-Range</x:ref> = &lt;If-Range, defined in [Part5], Section 5.3&gt;
3380If-Unmodified-Since =
3381 &lt;If-Unmodified-Since, defined in [Part4], Section 6.5&gt;
3382
3383<x:ref>Location</x:ref> = "Location:" OWS Location-v
3384<x:ref>Location-v</x:ref> = URI-reference
3385
3386<x:ref>Max-Forwards</x:ref> = "Max-Forwards:" OWS Max-Forwards-v
3387<x:ref>Max-Forwards-v</x:ref> = 1*DIGIT
3388<x:ref>Method</x:ref> = %x4F.50.54.49.4F.4E.53 ; OPTIONS
3389 / %x47.45.54 ; GET
3390 / %x48.45.41.44 ; HEAD
3391 / %x50.4F.53.54 ; POST
3392 / %x50.55.54 ; PUT
3393 / %x44.45.4C.45.54.45 ; DELETE
3394 / %x54.52.41.43.45 ; TRACE
3395 / %x43.4F.4E.4E.45.43.54 ; CONNECT
3396 / extension-method
3397
3398<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
3399
3400Proxy-Authenticate =
3401 &lt;Proxy-Authenticate, defined in [Part7], Section 3.2&gt;
3402Proxy-Authorization =
3403 &lt;Proxy-Authorization, defined in [Part7], Section 3.3&gt;
3404
3405<x:ref>RWS</x:ref> = &lt;RWS, defined in [Part1], Section 1.2.2&gt;
3406<x:ref>Range</x:ref> = &lt;Range, defined in [Part5], Section 5.4&gt;
3407<x:ref>Reason-Phrase</x:ref> = *( WSP / VCHAR / obs-text )
3408<x:ref>Referer</x:ref> = "Referer:" OWS Referer-v
3409<x:ref>Referer-v</x:ref> = absolute-URI / partial-URI
3410<x:ref>Retry-After</x:ref> = "Retry-After:" OWS Retry-After-v
3411<x:ref>Retry-After-v</x:ref> = HTTP-date / delta-seconds
3412
3413<x:ref>Server</x:ref> = "Server:" OWS Server-v
3414<x:ref>Server-v</x:ref> = product *( RWS ( product / comment ) )
3415<x:ref>Status-Code</x:ref> = "100" / "101" / "200" / "201" / "202" / "203" / "204" /
3416 "205" / "206" / "300" / "301" / "302" / "303" / "304" / "305" /
3417 "307" / "400" / "401" / "402" / "403" / "404" / "405" / "406" /
3418 "407" / "408" / "409" / "410" / "411" / "412" / "413" / "414" /
3419 "415" / "416" / "417" / "500" / "501" / "502" / "503" / "504" /
3420 "505" / extension-code
3421
3422<x:ref>TE</x:ref> = &lt;TE, defined in [Part1], Section 9.5&gt;
3423
3424<x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in [Part1], Section 2.6&gt;
3425<x:ref>User-Agent</x:ref> = "User-Agent:" OWS User-Agent-v
3426<x:ref>User-Agent-v</x:ref> = product *( RWS ( product / comment ) )
3427
3428<x:ref>Vary</x:ref> = &lt;Vary, defined in [Part6], Section 3.5&gt;
3429
3430WWW-Authenticate =
3431 &lt;WWW-Authenticate, defined in [Part7], Section 3.4&gt;
3432
3433<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.6&gt;
3434
3435<x:ref>comment</x:ref> = &lt;comment, defined in [Part1], Section 3.2&gt;
3436
3437<x:ref>delta-seconds</x:ref> = 1*DIGIT
3438
3439<x:ref>expect-params</x:ref> = ";" token [ "=" ( token / quoted-string ) ]
3440<x:ref>expectation</x:ref> = "100-continue" / expectation-extension
3441<x:ref>expectation-extension</x:ref> = token [ "=" ( token / quoted-string )
3442 *expect-params ]
3443<x:ref>extension-code</x:ref> = 3DIGIT
3444<x:ref>extension-method</x:ref> = token
3445
3446<x:ref>mailbox</x:ref> = &lt;mailbox, defined in [RFC5322], Section 3.4&gt;
3447
3448<x:ref>obs-text</x:ref> = &lt;obs-text, defined in [Part1], Section 1.2.2&gt;
3449
3450<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.6&gt;
3451<x:ref>product</x:ref> = &lt;product, defined in [Part1], Section 6.3&gt;
3452
3453<x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in [Part1], Section 1.2.2&gt;
3454
3455<x:ref>request-header</x:ref> = Accept / Accept-Charset / Accept-Encoding /
3456 Accept-Language / Authorization / Expect / From / Host / If-Match /
3457 If-Modified-Since / If-None-Match / If-Range / If-Unmodified-Since /
3458 Max-Forwards / Proxy-Authorization / Range / Referer / TE /
3459 User-Agent
3460<x:ref>response-header</x:ref> = Accept-Ranges / Age / Allow / ETag / Location /
3461 Proxy-Authenticate / Retry-After / Server / Vary / WWW-Authenticate
3462
3463<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 1.2.2&gt;
3464</artwork>
3465</figure>
3466<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
3467; Reason-Phrase defined but not used
3468; Status-Code defined but not used
3469; request-header defined but not used
3470; response-header defined but not used
3471</artwork></figure></section>
3472<?ENDINC p2-semantics.abnf-appendix ?>
3473
3474<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
3475
3476<section title="Since RFC2616">
3477<t>
3478  Extracted relevant partitions from <xref target="RFC2616"/>.
3479</t>
3480</section>
3481
3482<section title="Since draft-ietf-httpbis-p2-semantics-00">
3483<t>
3484  Closed issues:
3485  <list style="symbols"> 
3486    <t>
3487      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
3488      "Via is a MUST"
3489      (<eref target="http://purl.org/NET/http-errata#via-must"/>)
3490    </t>
3491    <t>
3492      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
3493      "Fragments allowed in Location"
3494      (<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
3495    </t>
3496    <t>
3497      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3498      "Safe Methods vs Redirection"
3499      (<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
3500    </t>
3501    <t>
3502      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
3503      "Revise description of the POST method"
3504      (<eref target="http://purl.org/NET/http-errata#post"/>)
3505    </t>
3506    <t>
3507      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
3508      "Normative and Informative references"
3509    </t>
3510    <t>
3511      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
3512      "RFC2606 Compliance"
3513    </t>
3514    <t>
3515      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
3516      "Informative references"
3517    </t>
3518    <t>
3519      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
3520      "Redundant cross-references"
3521    </t>
3522  </list>
3523</t>
3524<t>
3525  Other changes:
3526  <list style="symbols"> 
3527    <t>
3528      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
3529    </t>
3530  </list>
3531</t>
3532</section>
3533
3534<section title="Since draft-ietf-httpbis-p2-semantics-01">
3535<t>
3536  Closed issues:
3537  <list style="symbols"> 
3538    <t>
3539      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
3540      "PUT side effects"
3541    </t>
3542    <t>
3543      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
3544      "Duplicate Host header requirements"
3545    </t>
3546  </list>
3547</t>
3548<t>
3549  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3550  <list style="symbols"> 
3551    <t>
3552      Move "Product Tokens" section (back) into Part 1, as "token" is used
3553      in the definition of the Upgrade header.
3554    </t>
3555    <t>
3556      Add explicit references to BNF syntax and rules imported from other parts of the specification.
3557    </t>
3558    <t>
3559      Copy definition of delta-seconds from Part6 instead of referencing it.
3560    </t>
3561  </list>
3562</t>
3563</section>
3564
3565<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
3566<t>
3567  Closed issues:
3568  <list style="symbols"> 
3569    <t>
3570      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/24"/>:
3571      "Requiring Allow in 405 responses"
3572    </t>
3573    <t>
3574      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/59"/>:
3575      "Status Code Registry"
3576    </t>
3577    <t>
3578      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/61"/>:
3579      "Redirection vs. Location"
3580    </t>
3581    <t>
3582      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/70"/>:
3583      "Cacheability of 303 response"
3584    </t>
3585    <t>
3586      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/76"/>:
3587      "305 Use Proxy"
3588    </t>
3589    <t>
3590      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
3591      "Classification for Allow header"
3592    </t>
3593    <t>
3594      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
3595      "PUT - 'store under' vs 'store at'"
3596    </t>
3597  </list>
3598</t>
3599<t>
3600  Ongoing work on IANA Message Header Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
3601  <list style="symbols"> 
3602    <t>
3603      Reference RFC 3984, and update header registrations for headers defined
3604      in this document.
3605    </t>
3606  </list>
3607</t>
3608<t>
3609  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3610  <list style="symbols"> 
3611    <t>
3612      Replace string literals when the string really is case-sensitive (method).
3613    </t>
3614  </list>
3615</t>
3616</section>
3617
3618<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
3619<t>
3620  Closed issues:
3621  <list style="symbols"> 
3622    <t>
3623      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/98"/>:
3624      "OPTIONS request bodies"
3625    </t>
3626    <t>
3627      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/119"/>:
3628      "Description of CONNECT should refer to RFC2817"
3629    </t>
3630    <t>
3631      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/125"/>:
3632      "Location Content-Location reference request/response mixup"
3633    </t>
3634  </list>
3635</t>
3636<t>
3637  Ongoing work on Method Registry (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/72"/>):
3638  <list style="symbols"> 
3639    <t>
3640      Added initial proposal for registration process, plus initial
3641      content (non-HTTP/1.1 methods to be added by a separate specification).
3642    </t>
3643  </list>
3644</t>
3645</section>
3646
3647<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
3648<t>
3649  Closed issues:
3650  <list style="symbols"> 
3651    <t>
3652      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
3653      "Content-*"
3654    </t>
3655    <t>
3656      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
3657      "RFC 2822 is updated by RFC 5322"
3658    </t>
3659  </list>
3660</t>
3661<t>
3662  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3663  <list style="symbols"> 
3664    <t>
3665      Use "/" instead of "|" for alternatives.
3666    </t>
3667    <t>
3668      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
3669      whitespace ("OWS") and required whitespace ("RWS").
3670    </t>
3671    <t>
3672      Rewrite ABNFs to spell out whitespace rules, factor out
3673      header value format definitions.
3674    </t>
3675  </list>
3676</t>
3677</section>
3678
3679<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
3680<t>
3681  Closed issues:
3682  <list style="symbols"> 
3683    <t>
3684      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/94"/>:
3685      "Reason-Phrase BNF"
3686    </t>
3687  </list>
3688</t>
3689<t>
3690  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3691  <list style="symbols"> 
3692    <t>
3693      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
3694    </t>
3695  </list>
3696</t>
3697</section>
3698
3699<section title="Since draft-ietf-httpbis-p2-semantics-06" anchor="changes.since.06">
3700<t>
3701  Closed issues:
3702  <list style="symbols"> 
3703    <t>
3704      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/144"/>:
3705      "Clarify when Referer is sent"
3706    </t>
3707    <t>
3708      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/164"/>:
3709      "status codes vs methods"
3710    </t>
3711    <t>
3712      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/170"/>:
3713      "Do not require "updates" relation for specs that register status codes or method names"
3714    </t>
3715  </list>
3716</t>
3717</section>
3718
3719<section title="Since draft-ietf-httpbis-p2-semantics-07" anchor="changes.since.07">
3720<t>
3721  Closed issues:
3722  <list style="symbols"> 
3723    <t>
3724      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/27"/>:
3725      "Idempotency"
3726    </t>
3727    <t>
3728      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/33"/>:
3729      "TRACE security considerations"
3730    </t>
3731    <t>
3732      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
3733      "Clarify rules for determining what entities a response carries"
3734    </t>
3735    <t>
3736      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/140"/>:
3737      "update note citing RFC 1945 and 2068"
3738    </t>
3739    <t>
3740      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/182"/>:
3741      "update note about redirect limit"
3742    </t>
3743    <t>
3744      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/191"/>:
3745      "Location header ABNF should use 'URI'"
3746    </t>
3747    <t>
3748      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/192"/>:
3749      "fragments in Location vs status 303"
3750    </t>
3751    <t>
3752      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/198"/>:
3753      "move IANA registrations for optional status codes"
3754    </t>
3755  </list>
3756</t>
3757<t>
3758  Partly resolved issues:
3759  <list style="symbols"> 
3760    <t>
3761      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/171"/>:
3762      "Are OPTIONS and TRACE safe?"
3763    </t>
3764  </list>
3765</t>
3766</section>
3767
3768<section title="Since draft-ietf-httpbis-p2-semantics-08" anchor="changes.since.08">
3769<t>
3770  Closed issues:
3771  <list style="symbols"> 
3772    <t>
3773      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3774      "Safe Methods vs Redirection" (we missed the introduction to the 3xx
3775      status codes when fixing this previously)
3776    </t>
3777  </list>
3778</t>
3779</section>
3780
3781<section title="Since draft-ietf-httpbis-p2-semantics-09" anchor="changes.since.09">
3782<t>
3783  Closed issues:
3784  <list style="symbols"> 
3785    <t>
3786      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
3787      "Fragment combination / precedence during redirects"
3788    </t>
3789  </list>
3790</t>
3791<t>
3792  Partly resolved issues:
3793  <list style="symbols"> 
3794    <t>
3795      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/185"/>:
3796      "Location header payload handling"
3797    </t>
3798    <t>
3799      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196"/>:
3800      "Term for the requested resource's URI"
3801    </t>
3802  </list>
3803</t>
3804</section>
3805
3806<section title="Since draft-ietf-httpbis-p2-semantics-10" anchor="changes.since.10">
3807<t>
3808  None yet.
3809</t>
3810</section>
3811
3812</section>
3813
3814</back>
3815</rfc>
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