source: draft-ietf-httpbis/latest/p2-semantics.xml @ 1537

Last change on this file since 1537 was 1536, checked in by julian.reschke@…, 8 years ago

Location header field: define header field recombination in presence of fragment identifiers, mention security impact, rephrase main definition (see #295)

  • Property svn:eol-style set to native
  • Property svn:mime-type set to text/xml
File size: 192.4 KB
Line 
1<?xml version="1.0" encoding="utf-8"?>
2<?xml-stylesheet type='text/xsl' href='../myxml2rfc.xslt'?>
3<!DOCTYPE rfc [
4  <!ENTITY MAY "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MAY</bcp14>">
5  <!ENTITY MUST "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST</bcp14>">
6  <!ENTITY MUST-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST NOT</bcp14>">
7  <!ENTITY OPTIONAL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>OPTIONAL</bcp14>">
8  <!ENTITY RECOMMENDED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>RECOMMENDED</bcp14>">
9  <!ENTITY REQUIRED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>REQUIRED</bcp14>">
10  <!ENTITY SHALL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL</bcp14>">
11  <!ENTITY SHALL-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL NOT</bcp14>">
12  <!ENTITY SHOULD "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD</bcp14>">
13  <!ENTITY SHOULD-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD NOT</bcp14>">
14  <!ENTITY ID-VERSION "latest">
15  <!ENTITY ID-MONTH "February">
16  <!ENTITY ID-YEAR "2012">
17  <!ENTITY mdash "&#8212;">
18  <!ENTITY architecture               "<xref target='Part1' x:rel='#architecture' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
19  <!ENTITY notation                   "<xref target='Part1' x:rel='#notation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
20  <!ENTITY acks                       "<xref target='Part1' x:rel='#acks' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
21  <!ENTITY messaging                  "<xref target='Part1' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
22  <!ENTITY payload                    "<xref target='Part3' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
23  <!ENTITY conditional                "<xref target='Part4' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
24  <!ENTITY range                      "<xref target='Part5' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
25  <!ENTITY caching                    "<xref target='Part6' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
26  <!ENTITY auth                       "<xref target='Part7' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
27  <!ENTITY content-negotiation        "<xref target='Part3' x:rel='#content.negotiation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
28  <!ENTITY agent-driven-negotiation   "<xref target='Part3' x:rel='#agent-driven.negotiation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
29  <!ENTITY abnf-extension             "<xref target='Part1' x:rel='#abnf.extension' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
30  <!ENTITY whitespace                 "<xref target='Part1' x:rel='#whitespace' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
31  <!ENTITY field-components           "<xref target='Part1' x:rel='#field.components' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
32  <!ENTITY uri                        "<xref target='Part1' x:rel='#uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
33  <!ENTITY effective-request-uri      "<xref target='Part1' x:rel='#effective.request.uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
34  <!ENTITY intermediaries             "<xref target='Part1' x:rel='#intermediaries' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
35  <!ENTITY chunked-encoding           "<xref target='Part1' x:rel='#chunked.encoding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
36  <!ENTITY http-url                   "<xref target='Part1' x:rel='#http-url' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
37  <!ENTITY http-version               "<xref target='Part1' x:rel='#http.version' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
38  <!ENTITY use100                     "<xref target='Part1' x:rel='#use.of.the.100.status' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
39  <!ENTITY qvalue                     "<xref target='Part3' x:rel='#quality.values' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
40  <!ENTITY request-target             "<xref target='Part1' x:rel='#request-target' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
41  <!ENTITY header-accept              "<xref target='Part3' x:rel='#header.accept' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
42  <!ENTITY header-accept-charset      "<xref target='Part3' x:rel='#header.accept-charset' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
43  <!ENTITY header-accept-encoding     "<xref target='Part3' x:rel='#header.accept-encoding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
44  <!ENTITY header-accept-language     "<xref target='Part3' x:rel='#header.accept-language' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
45  <!ENTITY header-accept-ranges       "<xref target='Part5' x:rel='#header.accept-ranges' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
46  <!ENTITY header-age                 "<xref target='Part6' x:rel='#header.age' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
47  <!ENTITY header-authorization       "<xref target='Part7' x:rel='#header.authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
48  <!ENTITY header-cache-control       "<xref target='Part6' x:rel='#header.cache-control' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
49  <!ENTITY header-connection          "<xref target='Part1' x:rel='#header.connection' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
50  <!ENTITY header-content-location    "<xref target='Part3' x:rel='#header.content-location' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
51  <!ENTITY header-content-range       "<xref target='Part5' x:rel='#header.content-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
52  <!ENTITY header-content-type        "<xref target='Part3' x:rel='#header.content-type' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
53  <!ENTITY header-etag                "<xref target='Part4' x:rel='#header.etag' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
54  <!ENTITY header-expires             "<xref target='Part6' x:rel='#header.expires' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
55  <!ENTITY header-fields              "<xref target='Part1' x:rel='#header.fields' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
56  <!ENTITY header-host                "<xref target='Part1' x:rel='#header.host' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
57  <!ENTITY header-if-match            "<xref target='Part4' x:rel='#header.if-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
58  <!ENTITY header-if-modified-since   "<xref target='Part4' x:rel='#header.if-modified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
59  <!ENTITY header-if-none-match       "<xref target='Part4' x:rel='#header.if-none-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
60  <!ENTITY header-if-range            "<xref target='Part5' x:rel='#header.if-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
61  <!ENTITY header-if-unmodified-since "<xref target='Part4' x:rel='#header.if-unmodified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
62  <!ENTITY header-pragma              "<xref target='Part6' x:rel='#header.pragma' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
63  <!ENTITY header-proxy-authenticate  "<xref target='Part7' x:rel='#header.proxy-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
64  <!ENTITY header-proxy-authorization "<xref target='Part7' x:rel='#header.proxy-authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
65  <!ENTITY header-range               "<xref target='Part5' x:rel='#header.range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
66  <!ENTITY header-upgrade             "<xref target='Part1' x:rel='#header.upgrade' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
67  <!ENTITY header-te                  "<xref target='Part1' x:rel='#header.te' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
68  <!ENTITY header-vary                "<xref target='Part6' x:rel='#header.vary' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
69  <!ENTITY header-via                 "<xref target='Part1' x:rel='#header.via' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
70  <!ENTITY header-warning             "<xref target='Part6' x:rel='#header.warning' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
71  <!ENTITY header-www-authenticate    "<xref target='Part7' x:rel='#header.www-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
72  <!ENTITY media-types                "<xref target='Part3' x:rel='#media.types' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
73  <!ENTITY message-body               "<xref target='Part1' x:rel='#message.body' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
74  <!ENTITY product-tokens             "<xref target='Part1' x:rel='#product.tokens' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
75  <!ENTITY media-type-message-http    "<xref target='Part1' x:rel='#internet.media.type.message.http' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
76  <!ENTITY status-206                 "<xref target='Part5' x:rel='#status.206' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
77  <!ENTITY status-304                 "<xref target='Part4' x:rel='#status.304' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
78  <!ENTITY status-401                 "<xref target='Part7' x:rel='#status.401' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
79  <!ENTITY status-407                 "<xref target='Part7' x:rel='#status.407' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
80  <!ENTITY status-412                 "<xref target='Part4' x:rel='#status.412' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
81  <!ENTITY status-416                 "<xref target='Part5' x:rel='#status.416' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
82  <!ENTITY p3-header-fields           "<xref target='Part3' x:rel='#header.field.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
83  <!ENTITY p4-status-codes            "<xref target='Part4' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
84  <!ENTITY p5-status-codes            "<xref target='Part5' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
85  <!ENTITY p7-status-codes            "<xref target='Part7' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
86  <!ENTITY p6-heuristic               "<xref target='Part6' x:rel='#heuristic.freshness' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
87  <!ENTITY p6-explicit                "<xref target='Part6' x:rel='#calculating.freshness.lifetime' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
88  <!ENTITY p6-invalid                 "<xref target='Part6' x:rel='#invalidation.after.updates.or.deletions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
89]>
90<?rfc toc="yes" ?>
91<?rfc symrefs="yes" ?>
92<?rfc sortrefs="yes" ?>
93<?rfc compact="yes"?>
94<?rfc subcompact="no" ?>
95<?rfc linkmailto="no" ?>
96<?rfc editing="no" ?>
97<?rfc comments="yes"?>
98<?rfc inline="yes"?>
99<?rfc rfcedstyle="yes"?>
100<?rfc-ext allow-markup-in-artwork="yes" ?>
101<?rfc-ext include-references-in-index="yes" ?>
102<rfc obsoletes="2616" updates="2817" category="std" x:maturity-level="proposed"
103     ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"
104     xmlns:x='http://purl.org/net/xml2rfc/ext'
105     xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#'>
106<x:link rel="prev" basename="p1-messaging"/>
107<x:link rel="next" basename="p3-payload"/>
108<x:feedback template="mailto:ietf-http-wg@w3.org?subject={docname},%20%22{section}%22&amp;body=&lt;{ref}&gt;:"/>
109<front>
110
111  <title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
112
113  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
114    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
115    <address>
116      <postal>
117        <street>345 Park Ave</street>
118        <city>San Jose</city>
119        <region>CA</region>
120        <code>95110</code>
121        <country>USA</country>
122      </postal>
123      <email>fielding@gbiv.com</email>
124      <uri>http://roy.gbiv.com/</uri>
125    </address>
126  </author>
127
128  <author initials="J." surname="Gettys" fullname="Jim Gettys">
129    <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
130    <address>
131      <postal>
132        <street>21 Oak Knoll Road</street>
133        <city>Carlisle</city>
134        <region>MA</region>
135        <code>01741</code>
136        <country>USA</country>
137      </postal>
138      <email>jg@freedesktop.org</email>
139      <uri>http://gettys.wordpress.com/</uri>
140    </address>
141  </author>
142 
143  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
144    <organization abbrev="HP">Hewlett-Packard Company</organization>
145    <address>
146      <postal>
147        <street>HP Labs, Large Scale Systems Group</street>
148        <street>1501 Page Mill Road, MS 1177</street>
149        <city>Palo Alto</city>
150        <region>CA</region>
151        <code>94304</code>
152        <country>USA</country>
153      </postal>
154      <email>JeffMogul@acm.org</email>
155    </address>
156  </author>
157
158  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
159    <organization abbrev="Microsoft">Microsoft Corporation</organization>
160    <address>
161      <postal>
162        <street>1 Microsoft Way</street>
163        <city>Redmond</city>
164        <region>WA</region>
165        <code>98052</code>
166        <country>USA</country>
167      </postal>
168      <email>henrikn@microsoft.com</email>
169    </address>
170  </author>
171
172  <author initials="L." surname="Masinter" fullname="Larry Masinter">
173    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
174    <address>
175      <postal>
176        <street>345 Park Ave</street>
177        <city>San Jose</city>
178        <region>CA</region>
179        <code>95110</code>
180        <country>USA</country>
181      </postal>
182      <email>LMM@acm.org</email>
183      <uri>http://larry.masinter.net/</uri>
184    </address>
185  </author>
186 
187  <author initials="P." surname="Leach" fullname="Paul J. Leach">
188    <organization abbrev="Microsoft">Microsoft Corporation</organization>
189    <address>
190      <postal>
191        <street>1 Microsoft Way</street>
192        <city>Redmond</city>
193        <region>WA</region>
194        <code>98052</code>
195      </postal>
196      <email>paulle@microsoft.com</email>
197    </address>
198  </author>
199   
200  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
201    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
202    <address>
203      <postal>
204        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
205        <street>The Stata Center, Building 32</street>
206        <street>32 Vassar Street</street>
207        <city>Cambridge</city>
208        <region>MA</region>
209        <code>02139</code>
210        <country>USA</country>
211      </postal>
212      <email>timbl@w3.org</email>
213      <uri>http://www.w3.org/People/Berners-Lee/</uri>
214    </address>
215  </author>
216
217  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
218    <organization abbrev="W3C">World Wide Web Consortium</organization>
219    <address>
220      <postal>
221        <street>W3C / ERCIM</street>
222        <street>2004, rte des Lucioles</street>
223        <city>Sophia-Antipolis</city>
224        <region>AM</region>
225        <code>06902</code>
226        <country>France</country>
227      </postal>
228      <email>ylafon@w3.org</email>
229      <uri>http://www.raubacapeu.net/people/yves/</uri>
230    </address>
231  </author>
232
233  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
234    <organization abbrev="greenbytes">greenbytes GmbH</organization>
235    <address>
236      <postal>
237        <street>Hafenweg 16</street>
238        <city>Muenster</city><region>NW</region><code>48155</code>
239        <country>Germany</country>
240      </postal>
241      <phone>+49 251 2807760</phone>
242      <facsimile>+49 251 2807761</facsimile>
243      <email>julian.reschke@greenbytes.de</email>
244      <uri>http://greenbytes.de/tech/webdav/</uri>
245    </address>
246  </author>
247
248  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
249  <workgroup>HTTPbis Working Group</workgroup>
250
251<abstract>
252<t>
253   The Hypertext Transfer Protocol (HTTP) is an application-level protocol for
254   distributed, collaborative, hypertext information systems. HTTP has been in
255   use by the World Wide Web global information initiative since 1990. This
256   document is Part 2 of the seven-part specification that defines the protocol
257   referred to as "HTTP/1.1" and, taken together, obsoletes RFC 2616.
258</t>
259<t>
260   Part 2 defines the semantics of HTTP messages as expressed by request
261   methods, request header fields, response status codes, and response header
262   fields.
263</t>
264</abstract>
265
266<note title="Editorial Note (To be removed by RFC Editor)">
267  <t>
268    Discussion of this draft should take place on the HTTPBIS working group
269    mailing list (ietf-http-wg@w3.org), which is archived at
270    <eref target="http://lists.w3.org/Archives/Public/ietf-http-wg/"/>.
271  </t>
272  <t>
273    The current issues list is at
274    <eref target="http://tools.ietf.org/wg/httpbis/trac/report/3"/> and related
275    documents (including fancy diffs) can be found at
276    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
277  </t>
278  <t>
279    The changes in this draft are summarized in <xref target="changes.since.18"/>.
280  </t>
281</note>
282</front>
283<middle>
284<section title="Introduction" anchor="introduction">
285<t>
286   This document defines HTTP/1.1 request and response semantics.  Each HTTP
287   message, as defined in &messaging;, is in the form of either a request or
288   a response.  An HTTP server listens on a connection for HTTP requests and
289   responds to each request, in the order received on that connection, with
290   one or more HTTP response messages.  This document defines the commonly
291   agreed upon semantics of the HTTP uniform interface, the intentions defined
292   by each request method, and the various response messages that might be
293   expected as a result of applying that method to the target resource.
294</t>
295<t>
296   This document is currently disorganized in order to minimize the changes
297   between drafts and enable reviewers to see the smaller errata changes.
298   A future draft will reorganize the sections to better reflect the content.
299   In particular, the sections will be ordered according to the typical
300   processing of an HTTP request message (after message parsing): resource
301   mapping, methods, request modifying header fields, response status,
302   status modifying header fields, and resource metadata.  The current mess
303   reflects how widely dispersed these topics and associated requirements
304   had become in <xref target="RFC2616"/>.
305</t>
306
307<section title="Conformance and Error Handling" anchor="intro.conformance.and.error.handling">
308<t>
309   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
310   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
311   document are to be interpreted as described in <xref target="RFC2119"/>.
312</t>
313<t>
314   This document defines conformance criteria for several roles in HTTP
315   communication, including Senders, Recipients, Clients, Servers, User-Agents,
316   Origin Servers, Intermediaries, Proxies and Gateways. See &architecture;
317   for definitions of these terms.
318</t>
319<t>
320   An implementation is considered conformant if it complies with all of the
321   requirements associated with its role(s). Note that SHOULD-level requirements
322   are relevant here, unless one of the documented exceptions is applicable.
323</t>
324<t>
325   This document also uses ABNF to define valid protocol elements
326   (<xref target="notation"/>). In addition to the prose requirements placed
327   upon them, Senders &MUST-NOT; generate protocol elements that are invalid.
328</t>
329<t>
330   Unless noted otherwise, Recipients &MAY; take steps to recover a usable
331   protocol element from an invalid construct. However, HTTP does not define
332   specific error handling mechanisms, except in cases where it has direct
333   impact on security. This is because different uses of the protocol require
334   different error handling strategies; for example, a Web browser may wish to
335   transparently recover from a response where the Location header field
336   doesn't parse according to the ABNF, whereby in a systems control protocol
337   using HTTP, this type of error recovery could lead to dangerous consequences.
338</t>
339</section>
340
341<section title="Syntax Notation" anchor="notation">
342  <x:anchor-alias value="CR"/>
343  <x:anchor-alias value="DIGIT"/>
344  <x:anchor-alias value="LF"/>
345  <x:anchor-alias value="HTAB"/>
346  <x:anchor-alias value="VCHAR"/>
347  <x:anchor-alias value="SP"/>
348<t>
349   This specification uses the Augmented Backus-Naur Form (ABNF) notation
350   of <xref target="RFC5234"/> with the list rule extension defined in
351   &notation;<xref target="collected.abnf"/> shows the collected ABNF
352   with the list rule expanded.
353</t>
354<t>
355  The following core rules are included by
356  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
357  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
358  DIGIT (decimal 0-9), DQUOTE (double quote),
359  HEXDIG (hexadecimal 0-9/A-F/a-f), HTAB (horizontal tab), LF (line feed),
360  OCTET (any 8-bit sequence of data), SP (space), and
361  VCHAR (any visible US-ASCII character).
362</t>
363
364<section title="Core Rules" anchor="core.rules">
365  <x:anchor-alias value="obs-text"/>
366  <x:anchor-alias value="quoted-string"/>
367  <x:anchor-alias value="token"/>
368  <x:anchor-alias value="BWS"/>
369  <x:anchor-alias value="OWS"/>
370  <x:anchor-alias value="RWS"/>
371<t>
372  The core rules below are defined in <xref target="Part1"/>:
373</t>
374<figure><artwork type="abnf2616">
375  <x:ref>BWS</x:ref>           = &lt;BWS, defined in &whitespace;&gt;
376  <x:ref>OWS</x:ref>           = &lt;OWS, defined in &whitespace;&gt;
377  <x:ref>RWS</x:ref>           = &lt;RWS, defined in &whitespace;&gt;
378  <x:ref>obs-text</x:ref>      = &lt;obs-text, defined in &field-components;&gt;
379  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &field-components;&gt;
380  <x:ref>token</x:ref>         = &lt;token, defined in &field-components;&gt;
381</artwork></figure>
382</section>
383
384<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
385  <x:anchor-alias value="absolute-URI"/>
386  <x:anchor-alias value="comment"/>
387  <x:anchor-alias value="partial-URI"/>
388  <x:anchor-alias value="product"/>
389  <x:anchor-alias value="URI-reference"/>
390<t>
391  The ABNF rules below are defined in other parts:
392</t>
393<figure><!--Part1--><artwork type="abnf2616">
394  <x:ref>absolute-URI</x:ref>  = &lt;absolute-URI, defined in &uri;&gt;
395  <x:ref>comment</x:ref>       = &lt;comment, defined in &field-components;&gt;
396  <x:ref>partial-URI</x:ref>   = &lt;partial-URI, defined in &uri;&gt;
397  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
398  <x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in &uri;&gt;
399</artwork></figure>
400</section>
401</section>
402</section>
403
404<section title="Method" anchor="method">
405  <x:anchor-alias value="Method"/>
406  <x:anchor-alias value="extension-method"/>
407<t>
408   The Method token indicates the request method to be performed on the target
409   resource (&effective-request-uri;). The method is case-sensitive.
410</t>
411<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/>
412  <x:ref>Method</x:ref>         = <x:ref>token</x:ref>
413</artwork></figure>
414<t>
415   The list of methods allowed by a resource can be specified in an
416   Allow header field (<xref target="header.allow"/>). The status code of the response
417   always notifies the client whether a method is currently allowed on a
418   resource, since the set of allowed methods can change dynamically. An
419   origin server &SHOULD; respond with the status code 405 (Method Not Allowed)
420   if the method is known by the origin server but not allowed for the
421   resource, and 501 (Not Implemented) if the method is
422   unrecognized or not implemented by the origin server. The methods GET
423   and HEAD &MUST; be supported by all general-purpose servers. All other
424   methods are &OPTIONAL;; however, if the above methods are implemented,
425   they &MUST; be implemented with the same semantics as those specified
426   in <xref target="method.definitions"/>.
427</t>
428
429<section title="Overview of Methods" anchor="overview.of.methods">
430<t>
431  The methods listed below are defined in <xref target="method.definitions"/>.
432</t>
433<texttable align="left">
434  <ttcol>Method Name</ttcol><ttcol>Defined in...</ttcol>
435 
436  <c>OPTIONS</c> <c><xref target="OPTIONS"/></c>
437  <c>GET</c> <c><xref target="GET"/></c>
438  <c>HEAD</c> <c><xref target="HEAD"/></c>
439  <c>POST</c> <c><xref target="POST"/></c>
440  <c>PUT</c> <c><xref target="PUT"/></c>
441  <c>DELETE</c> <c><xref target="DELETE"/></c>
442  <c>TRACE</c> <c><xref target="TRACE"/></c>
443  <c>CONNECT</c> <c><xref target="CONNECT"/></c>
444</texttable>
445<t>
446  Note that this list is not exhaustive &mdash; it does not include request methods defined
447  in other specifications.
448</t>
449</section>
450
451<section title="Method Registry" anchor="method.registry">
452<t>
453  The HTTP Method Registry defines the name space for the Method token in the
454  Request line of an HTTP request.
455</t>
456<t>
457  Registrations &MUST; include the following fields:
458  <list style="symbols">
459    <t>Method Name (see <xref target="method"/>)</t>
460    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
461    <t>Pointer to specification text</t>
462  </list>
463</t>
464<t>
465  Values to be added to this name space are subject to IETF review
466  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
467</t>
468<t>
469  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-methods"/>.
470</t>
471
472<section title="Considerations for New Methods" anchor="considerations.for.new.methods">
473<t>
474   When it is necessary to express new semantics for a HTTP request that
475   aren't specific to a single application or media type, and currently defined
476   methods are inadequate, it may be appropriate to register a new method.
477</t>
478<t>
479   HTTP methods are generic; that is, they are potentially applicable to any
480   resource, not just one particular media type, "type" of resource, or
481   application. As such, it is preferred that new HTTP methods be registered
482   in a document that isn't specific to a single application, so that this is
483   clear.
484</t>
485<t>
486   Due to the parsing rules defined in &message-body;, definitions of HTTP
487   methods cannot prohibit the presence of a message-body on either the request
488   or the response message (with responses to HEAD requests being the single
489   exception). Definitions of new methods cannot change this rule, but they can
490   specify that only zero-length bodies (as opposed to absent bodies) are allowed.
491</t>
492<t>
493   New method definitions need to indicate whether they are safe (<xref
494   target="safe.methods"/>), what semantics (if any) the request body has,
495   and whether they are idempotent (<xref target="idempotent.methods"/>).
496   They also need to state whether they can be cached (&caching;); in
497   particular what conditions a cache may store the response, and under what
498   conditions such a stored response may be used to satisfy a subsequent
499   request.
500</t>
501</section>
502
503</section>
504</section>
505
506<section title="Header Fields" anchor="header.fields">
507<t>
508   Header fields are key value pairs that can be used to communicate data about
509   the message, its payload, the target resource, or about the connection
510   itself (i.e., control data).  See &header-fields; for a general definition
511   of their syntax.
512</t>
513
514<section title="Considerations for Creating Header Fields" anchor="considerations.for.creating.header.fields">
515<t>
516   New header fields are registered using the procedures described in
517   <xref target="RFC3864"/>.
518</t>
519<t>
520   The requirements for header field names are defined in
521   <xref target="RFC3864" x:fmt="of" x:sec="4.1"/>.  Authors of specifications
522   defining new fields are advised to keep the name as short as practical, and
523   not to prefix them with "X-" if they are to be registered (either
524   immediately or in the future).
525</t>
526<t>
527   New header field values typically have their syntax defined using ABNF
528   (<xref target="RFC5234"/>), using the extension defined in &abnf-extension;
529   as necessary, and are usually constrained to the range of ASCII characters.
530   Header fields needing a greater range of characters can use an encoding
531   such as the one defined in <xref target="RFC5987"/>.
532</t>
533<t>
534   Because commas (",") are used as a generic delimiter between field-values,
535   they need to be treated with care if they are allowed in the field-value's
536   payload. Typically, components that might contain a comma are protected with
537   double-quotes using the quoted-string ABNF production (&field-components;).
538</t>
539<t>
540   For example, a textual date and a URI (either of which might contain a comma)
541   could be safely carried in field-values like these:
542</t>
543<figure><artwork type="example">
544  Example-URI-Field: "http://example.com/a.html,foo",
545                     "http://without-a-comma.example.com/"
546  Example-Date-Field: "Sat, 04 May 1996", "Wed, 14 Sep 2005"
547</artwork></figure>
548<t>
549   Note that double quote delimiters almost always are used with the
550   quoted-string production; using a different syntax inside double quotes
551   will likely cause unnecessary confusion.
552</t>
553<t>
554   Many header fields use a format including (case-insensitively) named
555   parameters (for instance, Content-Type, defined in &header-content-type;).
556   Allowing both unquoted (token) and quoted (quoted-string) syntax for the
557   parameter value enables recipients to use existing parser components. When
558   allowing both forms, the meaning of a parameter value ought to be
559   independent of the syntax used for it (for an example, see the notes on
560   parameter handling for media types in &media-types;).
561</t>
562<t>
563   Authors of specifications defining new header fields are advised to consider
564   documenting:
565  <list style="symbols">
566    <x:lt>
567      <t>Whether the field is a single value, or whether it can be a list
568      (delimited by commas; see &header-fields;).</t>
569      <t>If it does not use the list syntax, document how to treat messages
570      where the header field occurs multiple times (a sensible default would
571      be to ignore the header field, but this might not always be the right
572      choice).</t>
573      <t>Note that intermediaries and software libraries might combine
574      multiple header field instances into a single one, despite the header
575      field not allowing this. A robust format enables recipients to discover
576      these situations (good example: "Content-Type", as the comma can only
577      appear inside quoted strings; bad example: "Location", as a comma can
578      occur inside a URI).</t>
579    </x:lt>
580    <x:lt><t>Under what conditions the header field can be used; e.g., only in
581    responses or requests, in all messages, only on responses to a particular
582    request method.</t></x:lt>
583    <x:lt><t>Whether it is appropriate to list the field-name in the Connection header
584    (i.e., if the header is to be hop-by-hop, see &header-connection;).</t></x:lt>
585    <x:lt><t>Under what conditions intermediaries are allowed to modify the header
586    field's value, insert or delete it.</t></x:lt>
587    <x:lt><t>How the header might interact with caching (see <xref target="Part6"/>).</t></x:lt>
588    <x:lt><t>Whether the header field is useful or allowable in trailers (see
589    &chunked-encoding;).</t></x:lt>
590    <x:lt><t>Whether the header field should be preserved across redirects.</t></x:lt>
591  </list>
592</t>
593</section>
594
595<section title="Request Header Fields" anchor="request.header.fields">
596  <x:anchor-alias value="request-header"/>
597<t>
598   The request header fields allow the client to pass additional
599   information about the request, and about the client itself, to the
600   server. These fields act as request modifiers, with semantics
601   equivalent to the parameters on a programming language method
602   invocation.
603</t>
604<texttable align="left">
605  <ttcol>Header Field Name</ttcol>
606  <ttcol>Defined in...</ttcol>
607
608  <c>Accept</c> <c>&header-accept;</c>
609  <c>Accept-Charset</c> <c>&header-accept-charset;</c>
610  <c>Accept-Encoding</c> <c>&header-accept-encoding;</c>
611  <c>Accept-Language</c> <c>&header-accept-language;</c>
612  <c>Authorization</c> <c>&header-authorization;</c>
613  <c>Expect</c> <c><xref target="header.expect"/></c>
614  <c>From</c> <c><xref target="header.from"/></c>
615  <c>Host</c> <c>&header-host;</c>
616  <c>If-Match</c> <c>&header-if-match;</c>
617  <c>If-Modified-Since</c> <c>&header-if-modified-since;</c>
618  <c>If-None-Match</c> <c>&header-if-none-match;</c>
619  <c>If-Range</c> <c>&header-if-range;</c>
620  <c>If-Unmodified-Since</c> <c>&header-if-unmodified-since;</c>
621  <c>Max-Forwards</c> <c><xref target="header.max-forwards"/></c>
622  <c>Proxy-Authorization</c> <c>&header-proxy-authorization;</c>
623  <c>Range</c> <c>&header-range;</c>
624  <c>Referer</c> <c><xref target="header.referer"/></c>
625  <c>TE</c> <c>&header-te;</c>
626  <c>User-Agent</c> <c><xref target="header.user-agent"/></c>
627</texttable>
628</section>
629
630<section title="Response Header Fields" anchor="response.header.fields">
631  <x:anchor-alias value="response-header"/>
632<t>
633   The response header fields allow the server to pass additional
634   information about the response which cannot be placed in the Status-Line.
635   These header fields give information about the server and about
636   further access to the target resource (&effective-request-uri;).
637</t>
638<texttable align="left">
639  <ttcol>Header Field Name</ttcol><ttcol>Defined in...</ttcol>
640
641  <c>Accept-Ranges</c> <c>&header-accept-ranges;</c>
642  <c>Age</c> <c>&header-age;</c>
643  <c>Allow</c> <c><xref target="header.allow"/></c>
644  <c>Date</c> <c><xref target="header.date"/></c>
645  <c>ETag</c> <c>&header-etag;</c>
646  <c>Location</c> <c><xref target="header.location"/></c>
647  <c>Proxy-Authenticate</c> <c>&header-proxy-authenticate;</c>
648  <c>Retry-After</c> <c><xref target="header.retry-after"/></c>
649  <c>Server</c> <c><xref target="header.server"/></c>
650  <c>Vary</c> <c>&header-vary;</c>
651  <c>WWW-Authenticate</c> <c>&header-www-authenticate;</c>
652</texttable>
653</section>
654
655</section>
656
657<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
658  <x:anchor-alias value="Reason-Phrase"/>
659  <x:anchor-alias value="Status-Code"/>
660  <x:anchor-alias value="extension-code"/>
661<t>
662   The Status-Code element is a 3-digit integer result code of the attempt to
663   understand and satisfy the request.
664</t>
665<t>
666   The Reason-Phrase is intended to give a short textual description of the
667   Status-Code and is intended for a human user. The client does not need
668   to examine or display the Reason-Phrase.
669</t>
670<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"/>
671  <x:ref>Status-Code</x:ref>    = 3<x:ref>DIGIT</x:ref>
672  <x:ref>Reason-Phrase</x:ref>  = *( <x:ref>HTAB</x:ref> / <x:ref>SP</x:ref> / <x:ref>VCHAR</x:ref> / <x:ref>obs-text</x:ref> )
673</artwork></figure>
674<t>
675   HTTP status codes are extensible. HTTP applications are not required
676   to understand the meaning of all registered status codes, though such
677   understanding is obviously desirable. However, applications &MUST;
678   understand the class of any status code, as indicated by the first
679   digit, and treat any unrecognized response as being equivalent to the
680   x00 status code of that class, with the exception that an
681   unrecognized response &MUST-NOT; be cached. For example, if an
682   unrecognized status code of 431 is received by the client, it can
683   safely assume that there was something wrong with its request and
684   treat the response as if it had received a 400 status code. In such
685   cases, user agents &SHOULD; present to the user the representation enclosed
686   with the response, since that representation is likely to include human-readable
687   information which will explain the unusual status.
688</t>
689
690<section title="Overview of Status Codes" anchor="overview.of.status.codes">
691<t> 
692   The status codes listed below are defined in <xref target="status.codes"/>
693   of this specification, &p4-status-codes;, &p5-status-codes;, and &p7-status-codes;.
694   The reason phrases listed here are only recommendations &mdash; they can be
695   replaced by local equivalents without affecting the protocol.
696</t>
697<texttable align="left">
698  <ttcol>Status-Code</ttcol>
699  <ttcol>Reason-Phrase</ttcol>
700  <ttcol>Defined in...</ttcol>
701 
702  <c>100</c> <c>Continue</c> <c><xref target="status.100"/></c>
703  <c>101</c> <c>Switching Protocols</c> <c><xref target="status.101"/></c>
704
705  <c>200</c> <c>OK</c> <c><xref target="status.200"/></c>
706  <c>201</c> <c>Created</c> <c><xref target="status.201"/></c>
707  <c>202</c> <c>Accepted</c> <c><xref target="status.202"/></c>
708  <c>203</c> <c>Non-Authoritative Information</c> <c><xref target="status.203"/></c>
709  <c>204</c> <c>No Content</c> <c><xref target="status.204"/></c>
710  <c>205</c> <c>Reset Content</c> <c><xref target="status.205"/></c>
711  <c>206</c> <c>Partial Content</c> <c anchor="status.206">&status-206;</c>
712
713  <c>300</c> <c>Multiple Choices</c> <c><xref target="status.300"/></c>
714  <c>301</c> <c>Moved Permanently</c> <c><xref target="status.301"/></c>
715  <c>302</c> <c>Found</c> <c><xref target="status.302"/></c>
716  <c>303</c> <c>See Other</c> <c><xref target="status.303"/></c>
717  <c>304</c> <c>Not Modified</c> <c anchor="status.304">&status-304;</c>
718  <c>305</c> <c>Use Proxy</c> <c><xref target="status.305"/></c>
719  <c>307</c> <c>Temporary Redirect</c> <c><xref target="status.307"/></c>
720
721  <c>400</c> <c>Bad Request</c> <c><xref target="status.400"/></c>
722  <c>401</c> <c>Unauthorized</c> <c anchor="status.401">&status-401;</c>
723  <c>402</c> <c>Payment Required</c> <c><xref target="status.402"/></c>
724  <c>403</c> <c>Forbidden</c> <c><xref target="status.403"/></c>
725  <c>404</c> <c>Not Found</c> <c><xref target="status.404"/></c>
726  <c>405</c> <c>Method Not Allowed</c> <c><xref target="status.405"/></c>
727  <c>406</c> <c>Not Acceptable</c> <c><xref target="status.406"/></c>
728  <c>407</c> <c>Proxy Authentication Required</c> <c anchor="status.407">&status-407;</c>
729  <c>408</c> <c>Request Time-out</c> <c><xref target="status.408"/></c>
730  <c>409</c> <c>Conflict</c> <c><xref target="status.409"/></c>
731  <c>410</c> <c>Gone</c> <c><xref target="status.410"/></c>
732  <c>411</c> <c>Length Required</c> <c><xref target="status.411"/></c>
733  <c>412</c> <c>Precondition Failed</c> <c anchor="status.412">&status-412;</c>
734  <c>413</c> <c>Request Representation Too Large</c> <c><xref target="status.413"/></c>
735  <c>414</c> <c>URI Too Long</c> <c><xref target="status.414"/></c>
736  <c>415</c> <c>Unsupported Media Type</c> <c><xref target="status.415"/></c>
737  <c>416</c> <c>Requested range not satisfiable</c> <c anchor="status.416">&status-416;</c>
738  <c>417</c> <c>Expectation Failed</c> <c><xref target="status.417"/></c>
739  <c>426</c> <c>Upgrade Required</c> <c><xref target="status.426"/></c>
740
741  <c>500</c> <c>Internal Server Error</c> <c><xref target="status.500"/></c>
742  <c>501</c> <c>Not Implemented</c> <c><xref target="status.501"/></c>
743  <c>502</c> <c>Bad Gateway</c> <c><xref target="status.502"/></c>
744  <c>503</c> <c>Service Unavailable</c> <c><xref target="status.503"/></c>
745  <c>504</c> <c>Gateway Time-out</c> <c><xref target="status.504"/></c>
746  <c>505</c> <c>HTTP Version not supported</c> <c><xref target="status.505"/></c>
747</texttable>
748<t>
749   Note that this list is not exhaustive &mdash; it does not include
750   extension status codes defined in other specifications.
751</t>
752</section>
753
754<section title="Status Code Registry" anchor="status.code.registry">
755<t>
756  The HTTP Status Code Registry defines the name space for the Status-Code
757  token in the Status-Line of an HTTP response.
758</t>
759<t>
760  Values to be added to this name space are subject to IETF review
761  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
762</t>
763<t>
764  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
765</t>
766
767<section title="Considerations for New Status Codes" anchor="considerations.for.new.status.codes">
768<t>
769   When it is necessary to express new semantics for a HTTP response that
770   aren't specific to a single application or media type, and currently defined
771   status codes are inadequate, a new status code can be registered.
772</t>
773<t>
774   HTTP status codes are generic; that is, they are potentially applicable to
775   any resource, not just one particular media type, "type" of resource, or
776   application. As such, it is preferred that new HTTP status codes be
777   registered in a document that isn't specific to a single application, so
778   that this is clear.
779</t>
780<t>
781   Definitions of new HTTP status codes typically explain the request
782   conditions that produce a response containing the status code (e.g.,
783   combinations of request headers and/or method(s)), along with any
784   interactions with response headers (e.g., those that are required, those
785   that modify the semantics of the response).
786</t>
787<t>
788   New HTTP status codes are required to fall under one of the categories
789   defined in <xref target="status.codes"/>. To allow existing parsers to
790   properly handle them, new status codes cannot disallow a response body,
791   although they can mandate a zero-length response body. They can require the
792   presence of one or more particular HTTP response header(s).
793</t>
794<t>
795   Likewise, their definitions can specify that caches are allowed to use
796   heuristics to determine their freshness (see &caching;; by default, it is
797   not allowed), and can define how to determine the resource which they
798   carry a representation for (see <xref
799   target="identifying.response.associated.with.representation"/>; by default,
800   it is anonymous).
801</t>
802</section>
803
804</section>
805
806</section>
807
808<section title="Representation" anchor="representation">
809<t>
810   Request and Response messages &MAY; transfer a representation if not otherwise
811   restricted by the request method or response status code. A representation
812   consists of metadata (representation header fields) and data (representation
813   body).  When a complete or partial representation is enclosed in an HTTP message,
814   it is referred to as the payload of the message. HTTP representations
815   are defined in &payload;.
816</t>
817<t>
818   A representation body is only present in a message when a message-body is
819   present, as described in &message-body;. The representation body is obtained
820   from the message-body by decoding any Transfer-Encoding that might
821   have been applied to ensure safe and proper transfer of the message.
822</t>
823
824<section title="Identifying the Resource Associated with a Representation" anchor="identifying.response.associated.with.representation">
825<t>
826   It is sometimes necessary to determine an identifier for the resource
827   associated with a representation.
828</t>
829<t>
830   An HTTP request representation, when present, is always associated with an
831   anonymous (i.e., unidentified) resource.
832</t>
833<t>
834   In the common case, an HTTP response is a representation of the target
835   resource (see &effective-request-uri;). However, this is not always the
836   case. To determine the URI of the resource a response is associated with,
837   the following rules are used (with the first applicable one being selected):
838</t>
839<t><list style="numbers">
840   <t>If the response status code is 200 or 203 and the request method was GET,
841   the response payload is a representation of the target resource.</t>
842   <t>If the response status code is 204, 206, or 304 and the request method was GET
843   or HEAD, the response payload is a partial representation of the target
844   resource.</t>
845   <t>If the response has a Content-Location header field, and that URI is the same
846   as the effective request URI, the response payload is a representation of the
847   target resource.</t>
848   <t>If the response has a Content-Location header field, and that URI is not the
849   same as the effective request URI, then the response asserts that its
850   payload is a representation of the resource identified by the
851   Content-Location URI. However, such an assertion cannot be trusted unless
852   it can be verified by other means (not defined by HTTP).</t>
853   <t>Otherwise, the response is a representation of an anonymous (i.e.,
854   unidentified) resource.</t>
855</list></t>
856<t>
857  <cref anchor="TODO-req-uri">
858   The comparison function is going to have to be defined somewhere,
859   because we already need to compare URIs for things like cache invalidation.</cref>
860</t>
861</section>
862
863</section>
864
865
866<section title="Method Definitions" anchor="method.definitions">
867<t>
868   The set of common request methods for HTTP/1.1 is defined below. Although
869   this set can be expanded, additional methods cannot be assumed to
870   share the same semantics for separately extended clients and servers.
871</t>
872
873<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
874
875<section title="Safe Methods" anchor="safe.methods">
876<iref item="Safe Methods" primary="true"/>
877<t>
878   Implementors need to be aware that the software represents the user in
879   their interactions over the Internet, and need to allow
880   the user to be aware of any actions they take which might have an
881   unexpected significance to themselves or others.
882</t>
883<t>
884   In particular, the convention has been established that the GET, HEAD,
885   OPTIONS, and TRACE request methods &SHOULD-NOT; have the significance
886   of taking an action other than retrieval. These request methods ought
887   to be considered "<x:dfn anchor="safe">safe</x:dfn>".
888   This allows user agents to represent other methods, such as POST, PUT
889   and DELETE, in a special way, so that the user is made aware of the
890   fact that a possibly unsafe action is being requested.
891</t>
892<t>
893   Naturally, it is not possible to ensure that the server does not
894   generate side-effects as a result of performing a GET request; in
895   fact, some dynamic resources consider that a feature. The important
896   distinction here is that the user did not request the side-effects,
897   so therefore cannot be held accountable for them.
898</t>
899</section>
900
901<section title="Idempotent Methods" anchor="idempotent.methods">
902<iref item="Idempotent Methods" primary="true"/>
903<t>
904   Request methods can also have the property of "idempotence" in that,
905   aside from error or expiration issues, the intended effect of multiple
906   identical requests is the same as for a single request.
907   PUT, DELETE, and all safe request methods are idempotent.
908   It is important to note that idempotence refers only to changes
909   requested by the client: a server is free to change its state due
910   to multiple requests for the purpose of tracking those requests,
911   versioning of results, etc.
912</t>
913</section>
914</section>
915
916<section title="OPTIONS" anchor="OPTIONS">
917  <rdf:Description>
918    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
919  </rdf:Description>
920  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
921  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
922<t>
923   The OPTIONS method requests information about the
924   communication options available on the request/response chain
925   identified by the effective request URI. This method allows a client to
926   determine the options and/or requirements associated with a resource,
927   or the capabilities of a server, without implying a resource action
928   or initiating a resource retrieval.
929</t>
930<t>
931   Responses to the OPTIONS method are not cacheable.
932</t>
933<t>
934   If the OPTIONS request includes a message-body (as indicated by the
935   presence of Content-Length or Transfer-Encoding), then the media type
936   &MUST; be indicated by a Content-Type field. Although this
937   specification does not define any use for such a body, future
938   extensions to HTTP might use the OPTIONS body to make more detailed
939   queries on the server.
940</t>
941<t>
942   If the request-target is an asterisk ("*"), the OPTIONS request is
943   intended to apply to the server in general rather than to a specific
944   resource. Since a server's communication options typically depend on
945   the resource, the "*" request is only useful as a "ping" or "no-op"
946   type of method; it does nothing beyond allowing the client to test
947   the capabilities of the server. For example, this can be used to test
948   a proxy for HTTP/1.1 conformance (or lack thereof).
949</t>
950<t>
951   If the request-target is not an asterisk, the OPTIONS request applies
952   only to the options that are available when communicating with that
953   resource.
954</t>
955<t>
956   A 200 response &SHOULD; include any header fields that indicate
957   optional features implemented by the server and applicable to that
958   resource (e.g., Allow), possibly including extensions not defined by
959   this specification. The response body, if any, &SHOULD; also include
960   information about the communication options. The format for such a
961   body is not defined by this specification, but might be defined by
962   future extensions to HTTP. Content negotiation &MAY; be used to select
963   the appropriate response format. If no response body is included, the
964   response &MUST; include a Content-Length field with a field-value of
965   "0".
966</t>
967<t>
968   The Max-Forwards header field &MAY; be used to target a
969   specific proxy in the request chain (see <xref target="header.max-forwards"/>).
970   If no Max-Forwards field is present in the request, then the forwarded
971   request &MUST-NOT; include a Max-Forwards field.
972</t>
973</section>
974
975<section title="GET" anchor="GET">
976  <rdf:Description>
977    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
978  </rdf:Description>
979  <iref primary="true" item="GET method" x:for-anchor=""/>
980  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
981<t>
982   The GET method requests transfer of a current representation of
983   the target resource.
984</t>
985<t>   
986   If the target resource is a data-producing process, it is the
987   produced data which shall be returned as the representation in the response and not
988   the source text of the process, unless that text happens to be the output of
989   the process.
990</t>
991<t>
992   The semantics of the GET method change to a "conditional GET" if the
993   request message includes an If-Modified-Since, If-Unmodified-Since,
994   If-Match, If-None-Match, or If-Range header field. A conditional GET
995   requests that the representation be transferred only under the
996   circumstances described by the conditional header field(s). The
997   conditional GET request is intended to reduce unnecessary network
998   usage by allowing cached representations to be refreshed without requiring
999   multiple requests or transferring data already held by the client.
1000</t>
1001<t>
1002   The semantics of the GET method change to a "partial GET" if the
1003   request message includes a Range header field. A partial GET requests
1004   that only part of the representation be transferred, as described in &header-range;.
1005   The partial GET request is intended to reduce unnecessary
1006   network usage by allowing partially-retrieved representations to be
1007   completed without transferring data already held by the client.
1008</t>
1009<t>
1010   Bodies on GET requests have no defined semantics. Note that sending a body
1011   on a GET request might cause some existing implementations to reject the
1012   request.
1013</t>
1014<t>
1015   The response to a GET request is cacheable and &MAY; be used to satisfy
1016   subsequent GET and HEAD requests (see &caching;).
1017</t>
1018<t>
1019   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
1020</t>
1021</section>
1022
1023<section title="HEAD" anchor="HEAD">
1024  <rdf:Description>
1025    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
1026  </rdf:Description>
1027  <iref primary="true" item="HEAD method" x:for-anchor=""/>
1028  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
1029<t>
1030   The HEAD method is identical to GET except that the server &MUST-NOT;
1031   return a message-body in the response. The metadata contained
1032   in the HTTP header fields in response to a HEAD request &SHOULD; be identical
1033   to the information sent in response to a GET request. This method can
1034   be used for obtaining metadata about the representation implied by the
1035   request without transferring the representation body. This method is
1036   often used for testing hypertext links for validity, accessibility,
1037   and recent modification.
1038</t>
1039<t>
1040   The response to a HEAD request is cacheable and &MAY; be used to satisfy
1041   a subsequent HEAD request; see &caching;. It also &MAY; be used to update a previously cached
1042   representation from that resource; if the new field values
1043   indicate that the cached representation differs from the current representation (as
1044   would be indicated by a change in Content-Length, ETag
1045   or Last-Modified), then the cache &MUST; treat the cache entry as
1046   stale.
1047</t>
1048<t>
1049   Bodies on HEAD requests have no defined semantics. Note that sending a body
1050   on a HEAD request might cause some existing implementations to reject the
1051   request.
1052</t>
1053</section>
1054
1055<section title="POST" anchor="POST">
1056  <iref primary="true" item="POST method" x:for-anchor=""/>
1057  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
1058<t>
1059   The POST method requests that the origin server accept the
1060   representation enclosed in the request as data to be processed by the
1061   target resource. POST is designed to allow a uniform method to cover the
1062   following functions:
1063  <list style="symbols">
1064    <t>
1065      Annotation of existing resources;
1066    </t>
1067    <t>
1068        Posting a message to a bulletin board, newsgroup, mailing list,
1069        or similar group of articles;
1070    </t>
1071    <t>
1072        Providing a block of data, such as the result of submitting a
1073        form, to a data-handling process;
1074    </t>
1075    <t>
1076        Extending a database through an append operation.
1077    </t>
1078  </list>
1079</t>
1080<t>
1081   The actual function performed by the POST method is determined by the
1082   server and is usually dependent on the effective request URI.
1083</t>
1084<t>
1085   The action performed by the POST method might not result in a
1086   resource that can be identified by a URI. In this case, either 200
1087   (OK) or 204 (No Content) is the appropriate response status code,
1088   depending on whether or not the response includes a representation that
1089   describes the result.
1090</t>
1091<t>
1092   If a resource has been created on the origin server, the response
1093   &SHOULD; be 201 (Created) and contain a representation which describes the
1094   status of the request and refers to the new resource, and a Location
1095   header field (see <xref target="header.location"/>).
1096</t>
1097<t>
1098   Responses to POST requests are only cacheable when they
1099   include explicit freshness information (see &p6-explicit;). A
1100   cached POST response with a Content-Location header field
1101   (see &header-content-location;) whose value is the effective
1102   Request URI &MAY; be used to satisfy subsequent GET and HEAD requests.
1103</t>
1104<t>
1105   Note that POST caching is not widely implemented.
1106   However, the 303 (See Other) response can be used to direct the
1107   user agent to retrieve a cacheable resource.
1108</t>
1109</section>
1110
1111<section title="PUT" anchor="PUT">
1112  <iref primary="true" item="PUT method" x:for-anchor=""/>
1113  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
1114<t>
1115   The PUT method requests that the state of the target resource
1116   be created or replaced with the state defined by the representation
1117   enclosed in the request message payload.  A successful PUT of a given
1118   representation would suggest that a subsequent GET on that same target
1119   resource will result in an equivalent representation being returned in
1120   a 200 (OK) response.  However, there is no guarantee that such a state
1121   change will be observable, since the target resource might be acted
1122   upon by other user agents in parallel, or might be subject to dynamic
1123   processing by the origin server, before any subsequent GET is received.
1124   A successful response only implies that the user agent's intent was
1125   achieved at the time of its processing by the origin server.
1126</t>
1127<t>   
1128   If the target resource does not have a current representation and
1129   the PUT successfully creates one, then the origin server &MUST; inform
1130   the user agent by sending a 201 (Created) response.  If the target
1131   resource does have a current representation and that representation is
1132   successfully modified in accordance with the state of the enclosed
1133   representation, then either a 200 (OK) or 204 (No Content) response
1134   &SHOULD; be sent to indicate successful completion of the request.
1135</t>
1136<t>
1137   Unrecognized header fields &SHOULD; be ignored (i.e., not saved
1138   as part of the resource state).
1139</t>
1140<t>
1141   An origin server &SHOULD; verify that the PUT representation is
1142   consistent with any constraints which the server has for the target
1143   resource that cannot or will not be changed by the PUT.  This is
1144   particularly important when the origin server uses internal
1145   configuration information related to the URI in order to set the
1146   values for representation metadata on GET responses.  When a PUT
1147   representation is inconsistent with the target resource, the origin
1148   server &SHOULD; either make them consistent, by transforming the
1149   representation or changing the resource configuration, or respond
1150   with an appropriate error message containing sufficient information
1151   to explain why the representation is unsuitable.  The 409 (Conflict)
1152   or 415 (Unsupported Media Type) status codes are suggested, with the
1153   latter being specific to constraints on Content-Type values.
1154</t>
1155<t>
1156   For example, if the target resource is configured to always have a
1157   Content-Type of "text/html" and the representation being PUT has a
1158   Content-Type of "image/jpeg", then the origin server &SHOULD; do one of:
1159   (a) reconfigure the target resource to reflect the new media type;
1160   (b) transform the PUT representation to a format consistent with that
1161   of the resource before saving it as the new resource state; or,
1162   (c) reject the request with a 415 response indicating that the target
1163   resource is limited to "text/html", perhaps including a link to a
1164   different resource that would be a suitable target for the new
1165   representation.
1166</t>
1167<t>
1168   HTTP does not define exactly how a PUT method affects the state
1169   of an origin server beyond what can be expressed by the intent of
1170   the user agent request and the semantics of the origin server response.
1171   It does not define what a resource might be, in any sense of that
1172   word, beyond the interface provided via HTTP.  It does not define
1173   how resource state is "stored", nor how such storage might change
1174   as a result of a change in resource state, nor how the origin server
1175   translates resource state into representations.  Generally speaking,
1176   all implementation details behind the resource interface are
1177   intentionally hidden by the server.
1178</t>
1179<t>
1180   The fundamental difference between the POST and PUT methods is
1181   highlighted by the different intent for the target resource.
1182   The target resource in a POST request is intended to handle the
1183   enclosed representation as a data-accepting process, such as for
1184   a gateway to some other protocol or a document that accepts annotations.
1185   In contrast, the target resource in a PUT request is intended to
1186   take the enclosed representation as a new or replacement value.
1187   Hence, the intent of PUT is idempotent and visible to intermediaries,
1188   even though the exact effect is only known by the origin server.
1189</t>
1190<t>
1191   Proper interpretation of a PUT request presumes that the user agent
1192   knows what target resource is desired.  A service that is intended
1193   to select a proper URI on behalf of the client, after receiving
1194   a state-changing request, &SHOULD; be implemented using the POST
1195   method rather than PUT.  If the origin server will not make the
1196   requested PUT state change to the target resource and instead
1197   wishes to have it applied to a different resource, such as when the
1198   resource has been moved to a different URI, then the origin server
1199   &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
1200   then make its own decision regarding whether or not to redirect the
1201   request.
1202</t>
1203<t>
1204   A PUT request applied to the target resource &MAY; have side-effects
1205   on other resources.  For example, an article might have a URI for
1206   identifying "the current version" (a resource) which is separate
1207   from the URIs identifying each particular version (different
1208   resources that at one point shared the same state as the current version
1209   resource).  A successful PUT request on "the current version" URI might
1210   therefore create a new version resource in addition to changing the
1211   state of the target resource, and might also cause links to be added
1212   between the related resources.
1213</t>
1214<t>
1215   An origin server &SHOULD; reject any PUT request that contains a
1216   Content-Range header field, since it might be misinterpreted as
1217   partial content (or might be partial content that is being mistakenly
1218   PUT as a full representation).  Partial content updates are
1219   possible by targeting a separately identified resource with state
1220   that overlaps a portion of the larger resource, or by using a
1221   different method that has been specifically defined for partial
1222   updates (for example, the PATCH method defined in
1223   <xref target="RFC5789"/>).
1224</t>
1225<t>
1226   Responses to the PUT method are not cacheable. If a PUT request passes
1227   through a cache that has one or more stored responses for the effective
1228   request URI, those stored responses will be invalidated (see
1229   &p6-invalid;).
1230</t>
1231</section>
1232
1233<section title="DELETE" anchor="DELETE">
1234  <iref primary="true" item="DELETE method" x:for-anchor=""/>
1235  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
1236<t>
1237   The DELETE method requests that the origin server delete the target
1238   resource. This method &MAY; be overridden by
1239   human intervention (or other means) on the origin server. The client cannot
1240   be guaranteed that the operation has been carried out, even if the
1241   status code returned from the origin server indicates that the action
1242   has been completed successfully. However, the server &SHOULD-NOT; 
1243   indicate success unless, at the time the response is given, it
1244   intends to delete the resource or move it to an inaccessible
1245   location.
1246</t>
1247<t>
1248   A successful response &SHOULD; be 200 (OK) if the response includes an
1249   representation describing the status, 202 (Accepted) if the action has not
1250   yet been enacted, or 204 (No Content) if the action has been enacted
1251   but the response does not include a representation.
1252</t>
1253<t>
1254   Bodies on DELETE requests have no defined semantics. Note that sending a body
1255   on a DELETE request might cause some existing implementations to reject the
1256   request.
1257</t>
1258<t>
1259   Responses to the DELETE method are not cacheable. If a DELETE request
1260   passes through a cache that has one or more stored responses for the
1261   effective request URI, those stored responses will be invalidated (see
1262   &p6-invalid;).
1263</t>
1264</section>
1265
1266<section title="TRACE" anchor="TRACE">
1267  <rdf:Description>
1268    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
1269  </rdf:Description>
1270  <iref primary="true" item="TRACE method" x:for-anchor=""/>
1271  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
1272<t>
1273   The TRACE method requests a remote, application-layer loop-back
1274   of the request message. The final recipient of the request
1275   &SHOULD; reflect the message received back to the client as the
1276   message-body of a 200 (OK) response. The final recipient is either the
1277   origin server or the first proxy to receive a Max-Forwards
1278   value of zero (0) in the request (see <xref target="header.max-forwards"/>).
1279   A TRACE request &MUST-NOT; include a message-body.
1280</t>
1281<t>
1282   TRACE allows the client to see what is being received at the other
1283   end of the request chain and use that data for testing or diagnostic
1284   information. The value of the Via header field (&header-via;) is of
1285   particular interest, since it acts as a trace of the request chain.
1286   Use of the Max-Forwards header field allows the client to limit the
1287   length of the request chain, which is useful for testing a chain of
1288   proxies forwarding messages in an infinite loop.
1289</t>
1290<t>
1291   If the request is valid, the response &SHOULD; have a Content-Type of
1292   "message/http" (see &media-type-message-http;) and contain a message-body
1293   that encloses a copy of the entire request message.
1294   Responses to the TRACE method are not cacheable.
1295</t>
1296</section>
1297
1298<section title="CONNECT" anchor="CONNECT">
1299  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
1300  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1301<t>
1302   The CONNECT method requests that the proxy establish a tunnel
1303   to the request-target and then restrict its behavior to blind
1304   forwarding of packets until the connection is closed.
1305</t>
1306<t>
1307   When using CONNECT, the request-target &MUST; use the authority form
1308   (&request-target;); i.e., the request-target consists of only the
1309   host name and port number of the tunnel destination, separated by a colon.
1310   For example,
1311</t>
1312<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1313CONNECT server.example.com:80 HTTP/1.1
1314Host: server.example.com:80
1315
1316</artwork></figure>
1317<t>
1318   Other HTTP mechanisms can be used normally with the CONNECT method &mdash;
1319   except end-to-end protocol Upgrade requests, since the
1320   tunnel must be established first.
1321</t>
1322<t>
1323   For example, proxy authentication might be used to establish the
1324   authority to create a tunnel:
1325</t>
1326<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1327CONNECT server.example.com:80 HTTP/1.1
1328Host: server.example.com:80
1329Proxy-Authorization: basic aGVsbG86d29ybGQ=
1330
1331</artwork></figure>
1332<t>
1333   Bodies on CONNECT requests have no defined semantics. Note that sending a body
1334   on a CONNECT request might cause some existing implementations to reject the
1335   request.
1336</t>
1337<t>
1338   Like any other pipelined HTTP/1.1 request, data to be tunnel may be
1339   sent immediately after the blank line. The usual caveats also apply:
1340   data may be discarded if the eventual response is negative, and the
1341   connection may be reset with no response if more than one TCP segment
1342   is outstanding.
1343</t>
1344
1345<section title="Establishing a Tunnel with CONNECT">
1346<t>
1347   Any successful (2xx) response to a CONNECT request indicates that the
1348   proxy has established a connection to the requested host and port,
1349   and has switched to tunneling the current connection to that server
1350   connection.
1351</t>
1352<t>
1353   It may be the case that the proxy itself can only reach the requested
1354   origin server through another proxy.  In this case, the first proxy
1355   &SHOULD; make a CONNECT request of that next proxy, requesting a tunnel
1356   to the authority.  A proxy &MUST-NOT; respond with any 2xx status code
1357   unless it has either a direct or tunnel connection established to the
1358   authority.
1359</t>
1360<t>
1361   An origin server which receives a CONNECT request for itself &MAY;
1362   respond with a 2xx status code to indicate that a connection is
1363   established.
1364</t>
1365<t>
1366   If at any point either one of the peers gets disconnected, any
1367   outstanding data that came from that peer will be passed to the other
1368   one, and after that also the other connection will be terminated by
1369   the proxy. If there is outstanding data to that peer undelivered,
1370   that data will be discarded.
1371</t>
1372
1373</section>
1374</section>
1375</section>
1376
1377
1378<section title="Status Code Definitions" anchor="status.codes">
1379<t>
1380   The first digit of the Status-Code defines the class of response. The
1381   last two digits do not have any categorization role. There are 5
1382   values for the first digit:
1383  <list style="symbols">
1384    <t>
1385      1xx: Informational - Request received, continuing process
1386    </t>
1387    <t>
1388      2xx: Success - The action was successfully received,
1389        understood, and accepted
1390    </t>
1391    <t>
1392      3xx: Redirection - Further action must be taken in order to
1393        complete the request
1394    </t>
1395    <t>
1396      4xx: Client Error - The request contains bad syntax or cannot
1397        be fulfilled
1398    </t>
1399    <t>
1400      5xx: Server Error - The server failed to fulfill an apparently
1401        valid request
1402    </t>
1403  </list>
1404</t>
1405<t>
1406   Each Status-Code is described below, including any metadata required
1407   in the response.
1408</t>
1409<t>
1410   For most status codes the response can carry a payload, in which case a
1411   Content-Type header field indicates the payload's media type
1412   (&header-content-type;).
1413</t>
1414
1415<section title="Informational 1xx" anchor="status.1xx">
1416<t>
1417   This class of status code indicates a provisional response,
1418   consisting only of the Status-Line and optional header fields, and is
1419   terminated by an empty line. There are no required header fields for this
1420   class of status code. Since HTTP/1.0 did not define any 1xx status
1421   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1422   except under experimental conditions.
1423</t>
1424<t>
1425   A client &MUST; be prepared to accept one or more 1xx status responses
1426   prior to a regular response, even if the client does not expect a 100
1427   (Continue) status message. Unexpected 1xx status responses &MAY; be
1428   ignored by a user agent.
1429</t>
1430<t>
1431   Proxies &MUST; forward 1xx responses, unless the connection between the
1432   proxy and its client has been closed, or unless the proxy itself
1433   requested the generation of the 1xx response. (For example, if a
1434   proxy adds a "Expect: 100-continue" field when it forwards a request,
1435   then it need not forward the corresponding 100 (Continue)
1436   response(s).)
1437</t>
1438
1439<section title="100 Continue" anchor="status.100">
1440  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1441  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1442<t>
1443   The client &SHOULD; continue with its request. This interim response is
1444   used to inform the client that the initial part of the request has
1445   been received and has not yet been rejected by the server. The client
1446   &SHOULD; continue by sending the remainder of the request or, if the
1447   request has already been completed, ignore this response. The server
1448   &MUST; send a final response after the request has been completed. See
1449   &use100; for detailed discussion of the use and handling of this
1450   status code.
1451</t>
1452</section>
1453
1454<section title="101 Switching Protocols" anchor="status.101">
1455  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1456  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1457<t>
1458   The server understands and is willing to comply with the client's
1459   request, via the Upgrade message header field (&header-upgrade;), for a
1460   change in the application protocol being used on this connection. The
1461   server will switch protocols to those defined by the response's
1462   Upgrade header field immediately after the empty line which
1463   terminates the 101 response.
1464</t>
1465<t>
1466   The protocol &SHOULD; be switched only when it is advantageous to do
1467   so. For example, switching to a newer version of HTTP is advantageous
1468   over older versions, and switching to a real-time, synchronous
1469   protocol might be advantageous when delivering resources that use
1470   such features.
1471</t>
1472</section>
1473</section>
1474
1475<section title="Successful 2xx" anchor="status.2xx">
1476<t>
1477   This class of status code indicates that the client's request was
1478   successfully received, understood, and accepted.
1479</t>
1480
1481<section title="200 OK" anchor="status.200">
1482  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1483  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1484<t>
1485   The request has succeeded. The payload returned with the response
1486   is dependent on the method used in the request, for example:
1487  <list style="hanging">
1488    <t hangText="GET">
1489      a representation of the target resource is sent in the response;
1490    </t>
1491    <t hangText="HEAD">
1492      the same representation as GET, except without the message-body;
1493    </t>
1494    <t hangText="POST">
1495      a representation describing or containing the result of the action;
1496    </t>
1497    <t hangText="TRACE">
1498      a representation containing the request message as received by the
1499      end server.
1500    </t>
1501  </list>
1502</t>
1503<t>
1504   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1505   freshness for 200 responses.
1506</t>
1507</section>
1508
1509<section title="201 Created" anchor="status.201">
1510  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1511  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1512<t>
1513   The request has been fulfilled and has resulted in a new resource being
1514   created. The newly created resource can be referenced by the URI(s)
1515   returned in the payload of the response, with the most specific URI
1516   for the resource given by a Location header field. The response
1517   can include a payload containing a list of resource
1518   characteristics and location(s) from which the user or user agent can
1519   choose the one most appropriate.
1520</t>
1521<t>
1522   The origin server &MUST; create the resource before returning the 201 status
1523   code. If the action cannot be carried out immediately, the server &SHOULD;
1524   respond with 202 (Accepted) response instead.
1525</t>
1526<t>
1527   A 201 response &MAY; contain an ETag response header field indicating
1528   the current value of the entity-tag for the representation of the resource
1529   just created (see &header-etag;).
1530</t>
1531</section>
1532
1533<section title="202 Accepted" anchor="status.202">
1534  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1535  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1536<t>
1537   The request has been accepted for processing, but the processing has
1538   not been completed.  The request might or might not eventually be
1539   acted upon, as it might be disallowed when processing actually takes
1540   place. There is no facility for re-sending a status code from an
1541   asynchronous operation such as this.
1542</t>
1543<t>
1544   The 202 response is intentionally non-committal. Its purpose is to
1545   allow a server to accept a request for some other process (perhaps a
1546   batch-oriented process that is only run once per day) without
1547   requiring that the user agent's connection to the server persist
1548   until the process is completed. The representation returned with this
1549   response &SHOULD; include an indication of the request's current status
1550   and either a pointer to a status monitor or some estimate of when the
1551   user can expect the request to be fulfilled.
1552</t>
1553</section>
1554
1555<section title="203 Non-Authoritative Information" anchor="status.203">
1556  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1557  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1558<t>
1559   The representation in the response has been transformed or otherwise
1560   modified by a transforming proxy (&intermediaries;).  Note that the
1561   behavior of transforming intermediaries is controlled by the no-transform
1562   Cache-Control directive (&header-cache-control;).
1563</t>
1564<t>
1565   This status code is only appropriate when the response status code would
1566   have been 200 (OK) otherwise. When the status code before transformation
1567   would have been different, the 214 Transformation Applied warn-code
1568   (&header-warning;) is appropriate.
1569</t>
1570<t>
1571   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1572   freshness for 203 responses.
1573</t>
1574</section>
1575
1576<section title="204 No Content" anchor="status.204">
1577  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1578  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1579<t>
1580   The 204 (No Content) status code indicates that the server has
1581   successfully fulfilled the request and that there is no additional
1582   content to return in the response payload body.  Metadata in the
1583   response header fields refer to the target resource and its current
1584   representation after the requested action.
1585</t>
1586<t>
1587   For example, if a 204 status code is received in response to a PUT
1588   request and the response contains an ETag header field, then the PUT
1589   was successful and the ETag field-value contains the entity-tag for
1590   the new representation of that target resource.
1591</t>
1592<t>
1593   The 204 response allows a server to indicate that the action has been
1594   successfully applied to the target resource while implying that the
1595   user agent &SHOULD-NOT; traverse away from its current "document view"
1596   (if any).  The server assumes that the user agent will provide some
1597   indication of the success to its user, in accord with its own interface,
1598   and apply any new or updated metadata in the response to the active
1599   representation.
1600</t>
1601<t>
1602   For example, a 204 status code is commonly used with document editing
1603   interfaces corresponding to a "save" action, such that the document
1604   being saved remains available to the user for editing. It is also
1605   frequently used with interfaces that expect automated data transfers
1606   to be prevalent, such as within distributed version control systems.
1607</t>
1608<t>
1609   The 204 response &MUST-NOT; include a message-body, and thus is always
1610   terminated by the first empty line after the header fields.
1611</t>
1612</section>
1613
1614<section title="205 Reset Content" anchor="status.205">
1615  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1616  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1617<t>
1618   The server has fulfilled the request and the user agent &SHOULD; reset
1619   the document view which caused the request to be sent. This response
1620   is primarily intended to allow input for actions to take place via
1621   user input, followed by a clearing of the form in which the input is
1622   given so that the user can easily initiate another input action.
1623</t>
1624<t>   
1625   The message-body included with the response &MUST; be empty. Note that
1626   receivers still need to parse the response according to the algorithm defined
1627   in &message-body;.
1628</t>
1629</section>
1630</section>
1631
1632<section title="Redirection 3xx" anchor="status.3xx">
1633<t>
1634   This class of status code indicates that further action needs to be
1635   taken by the user agent in order to fulfill the request.  If the required
1636   action involves a subsequent HTTP request, it &MAY; be carried out by the
1637   user agent without interaction with the user if and only if the method used
1638   in the second request is known to be "safe", as defined in
1639   <xref target="safe.methods"/>.
1640</t>
1641<t>
1642   There are several types of redirects:
1643   <list style="numbers">
1644      <x:lt>
1645        <t>
1646          Redirects of the request to another URI, either temporarily or
1647          permanently. The new URI is specified in the Location header field.
1648          In this specification, the status codes 301 (Moved Permanently),
1649          302 (Found), and 307 (Temporary Redirect) fall under this category.
1650        </t>
1651      </x:lt>
1652      <x:lt>
1653        <t>
1654          Redirection to a new location that represents an indirect response to
1655          the request, such as the result of a POST operation to be retrieved
1656          with a subsequent GET request. This is status code 303 (See Other).
1657        </t>
1658      </x:lt>
1659      <x:lt>
1660        <t>
1661          Redirection offering a choice of matching resources for use by
1662          agent-driven content negotiation (&agent-driven-negotiation;). This
1663          is status code 300 (Multiple Choices).
1664        </t>
1665      </x:lt>
1666      <x:lt>
1667        <t>
1668          Other kinds of redirection, such as to a cached result (status code 304
1669          (Not Modified), see &status-304;).
1670        </t>
1671      </x:lt>
1672   </list>
1673</t>
1674<x:note>
1675  <t>
1676    <x:h>Note:</x:h> In HTTP/1.0, only the status codes 301 (Moved Permanently)
1677    and 302 (Found) were defined for the first type of redirect, and the second
1678    type did not exist at all (<xref target="RFC1945" x:fmt="," x:sec="9.3"/>).
1679    However it turned out that web forms using POST expected redirects to change
1680    the operation for the subsequent request to retrieval (GET). To address this
1681    use case, HTTP/1.1 introduced the second type of redirect with the status
1682    code 303 (See Other) (<xref target="RFC2068" x:fmt="," x:sec="10.3.4"/>).
1683    As user agents did not change their behavior to maintain backwards
1684    compatibility, the first revision of HTTP/1.1 added yet another status code,
1685    307 (Temporary Redirect), for which the backwards compatibility problems did
1686    not apply (<xref target="RFC2616" x:fmt="," x:sec="10.3.8"/>).
1687    Over 10 years later, most user agents still do method rewriting for
1688    status codes 301 and 302, therefore this specification makes that behavior
1689    conformant in case the original request was POST.
1690  </t>
1691</x:note>
1692<t>
1693   A Location header field on a 3xx response indicates that a client &MAY;
1694   automatically redirect to the URI provided; see <xref target="header.location"/>.
1695</t>
1696<t>
1697   Note that for methods not known to be "safe", as defined in <xref target="safe.methods"/>,
1698   automatic redirection needs to done with care, since the redirect might
1699   change the conditions under which the request was issued.
1700</t>
1701<t>
1702   Clients &SHOULD; detect and intervene in cyclical redirections (i.e.,
1703   "infinite" redirection loops).
1704</t>
1705<x:note>
1706  <t>
1707    <x:h>Note:</x:h> An earlier version of this specification recommended a
1708    maximum of five redirections (<xref target="RFC2068" x:fmt="," x:sec="10.3"/>).
1709    Content developers need to be aware that some clients might
1710    implement such a fixed limitation.
1711  </t>
1712</x:note>
1713
1714<section title="300 Multiple Choices" anchor="status.300">
1715  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1716  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1717<t>
1718   The target resource has more than one
1719   representation, each with its own specific location, and agent-driven
1720   negotiation information (&content-negotiation;) is being provided so that
1721   the user (or user agent) can select a preferred representation by
1722   redirecting its request to that location.
1723</t>
1724<t>
1725   Unless it was a HEAD request, the response &SHOULD; include a representation
1726   containing a list of representation metadata and location(s) from
1727   which the user or user agent can choose the one most appropriate. Depending
1728   upon the format and the capabilities of
1729   the user agent, selection of the most appropriate choice &MAY; be
1730   performed automatically. However, this specification does not define
1731   any standard for such automatic selection.
1732</t>
1733<t>
1734   If the server has a preferred choice of representation, it &SHOULD;
1735   include the specific URI for that representation in the Location
1736   field; user agents &MAY; use the Location field value for automatic
1737   redirection.
1738</t>
1739<t>
1740   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1741   freshness for 300 responses.
1742</t>
1743
1744</section>
1745
1746<section title="301 Moved Permanently" anchor="status.301">
1747  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1748  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1749<t>
1750   The target resource has been assigned a new permanent URI and any
1751   future references to this resource &SHOULD; use one of the returned
1752   URIs.  Clients with link editing capabilities ought to automatically
1753   re-link references to the effective request URI to one or more of the new
1754   references returned by the server, where possible.
1755</t>
1756<t>
1757   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1758   freshness for 301 responses.
1759</t>
1760<t>
1761   The new permanent URI &SHOULD; be given by the Location field in the
1762   response. A response payload can contain a short hypertext note with a
1763   hyperlink to the new URI(s).
1764</t>
1765<x:note>
1766  <t>
1767    <x:h>Note:</x:h> For historic reasons, user agents &MAY; change the
1768    request method from POST to GET for the subsequent request. If this
1769    behavior is undesired, status code 307 (Temporary Redirect) can be used
1770    instead.
1771  </t>
1772</x:note>
1773</section>
1774
1775<section title="302 Found" anchor="status.302">
1776  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1777  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1778<t>
1779   The target resource resides temporarily under a different URI.
1780   Since the redirection might be altered on occasion, the client &SHOULD;
1781   continue to use the effective request URI for future requests.
1782</t>
1783<t>
1784   The temporary URI &SHOULD; be given by the Location field in the
1785   response. A response payload can contain a short hypertext note with a
1786   hyperlink to the new URI(s).
1787</t>
1788<x:note>
1789  <t>
1790    <x:h>Note:</x:h> For historic reasons, user agents &MAY; change the
1791    request method from POST to GET for the subsequent request. If this
1792    behavior is undesired, status code 307 (Temporary Redirect) can be used
1793    instead.
1794  </t>
1795</x:note>
1796</section>
1797
1798<section title="303 See Other" anchor="status.303">
1799  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1800  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1801<t>
1802   The 303 status code indicates that the server is redirecting the
1803   user agent to a different resource, as indicated by a URI in the
1804   Location header field, that is intended to provide an indirect
1805   response to the original request.  In order to satisfy the original
1806   request, a user agent &SHOULD; perform a retrieval request using the
1807   Location URI (a GET or HEAD request if using HTTP), which
1808   may itself be redirected further, and present the eventual result as an
1809   answer to the original request.
1810   Note that the new URI in the Location header field is not considered
1811   equivalent to the effective request URI.
1812</t>
1813<t>
1814   This status code is generally applicable to any HTTP method.  It is
1815   primarily used to allow the output of a POST action to redirect
1816   the user agent to a selected resource, since doing so provides the
1817   information corresponding to the POST response in a form that
1818   can be separately identified, bookmarked, and cached independent
1819   of the original request.
1820</t>
1821<t>
1822   A 303 response to a GET request indicates that the requested
1823   resource does not have a representation of its own that can be
1824   transferred by the server over HTTP.  The Location URI indicates a
1825   resource that is descriptive of the target resource, such that the
1826   follow-on representation might be useful to recipients without
1827   implying that it adequately represents the target resource.
1828   Note that answers to the questions of what can be represented, what
1829   representations are adequate, and what might be a useful description
1830   are outside the scope of HTTP and thus entirely determined by the
1831   URI owner(s).
1832</t>
1833<t>
1834   Except for responses to a HEAD request, the representation of a 303
1835   response &SHOULD; contain a short hypertext note with a hyperlink
1836   to the Location URI.
1837</t>
1838</section>
1839
1840<section title="305 Use Proxy" anchor="status.305">
1841  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1842  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1843<t>
1844   The 305 status code was defined in a previous version of this specification
1845   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1846</t>
1847</section>
1848
1849<section title="306 (Unused)" anchor="status.306">
1850  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1851  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1852<t>
1853   The 306 status code was used in a previous version of the
1854   specification, is no longer used, and the code is reserved.
1855</t>
1856</section>
1857
1858<section title="307 Temporary Redirect" anchor="status.307">
1859  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1860  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1861<t>
1862   The target resource resides temporarily under a different URI.
1863   Since the redirection can change over time, the client &SHOULD;
1864   continue to use the effective request URI for future requests.
1865</t>
1866<t>
1867   The temporary URI &SHOULD; be given by the Location field in the
1868   response. A response payload can contain a short hypertext note with a
1869   hyperlink to the new URI(s).
1870</t>
1871<x:note>
1872  <t>
1873    <x:h>Note:</x:h> This status code is similar to 302 Found, except that
1874    it does not allow rewriting the request method from POST to GET. This
1875    specification defines no equivalent counterpart for 301 Moved Permanently.
1876  </t>
1877</x:note>
1878</section>
1879</section>
1880
1881<section title="Client Error 4xx" anchor="status.4xx">
1882<t>
1883   The 4xx class of status code is intended for cases in which the
1884   client seems to have erred. Except when responding to a HEAD request,
1885   the server &SHOULD; include a representation containing an explanation of the
1886   error situation, and whether it is a temporary or permanent
1887   condition. These status codes are applicable to any request method.
1888   User agents &SHOULD; display any included representation to the user.
1889</t>
1890
1891<section title="400 Bad Request" anchor="status.400">
1892  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1893  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1894<t>
1895   The server cannot or will not process the request, due to a client error (e.g.,
1896   malformed syntax).
1897</t>
1898</section>
1899
1900<section title="402 Payment Required" anchor="status.402">
1901  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1902  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1903<t>
1904   This code is reserved for future use.
1905</t>
1906</section>
1907
1908<section title="403 Forbidden" anchor="status.403">
1909  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1910  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1911<t>
1912   The server understood the request, but refuses to authorize it. Providing
1913   different user authentication credentials might be successful, but any
1914   credentials that were provided in the request are insufficient. The request
1915   &SHOULD-NOT; be repeated with the same credentials.
1916</t>
1917<t>
1918   If the request method was not HEAD and the server wishes to make
1919   public why the request has not been fulfilled, it &SHOULD; describe the
1920   reason for the refusal in the representation.  If the server does not wish to
1921   make this information available to the client, the status code 404
1922   (Not Found) &MAY; be used instead.
1923</t>
1924</section>
1925
1926<section title="404 Not Found" anchor="status.404">
1927  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1928  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1929<t>
1930   The server has not found anything matching the effective request URI. No
1931   indication is given of whether the condition is temporary or
1932   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1933   knows, through some internally configurable mechanism, that an old
1934   resource is permanently unavailable and has no forwarding address.
1935   This status code is commonly used when the server does not wish to
1936   reveal exactly why the request has been refused, or when no other
1937   response is applicable.
1938</t>
1939</section>
1940
1941<section title="405 Method Not Allowed" anchor="status.405">
1942  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1943  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1944<t>
1945   The method specified in the Request-Line is not allowed for the target
1946   resource. The response &MUST; include an Allow header field containing a
1947   list of valid methods for the requested resource.
1948</t>
1949</section>
1950
1951<section title="406 Not Acceptable" anchor="status.406">
1952  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1953  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1954<t>
1955   The resource identified by the request is only capable of generating
1956   response representations which have content characteristics not acceptable
1957   according to the Accept and Accept-* header fields sent in the request
1958   (see &p3-header-fields;).
1959</t>
1960<t>
1961   Unless it was a HEAD request, the response &SHOULD; include a representation
1962   containing a list of available representation characteristics and location(s)
1963   from which the user or user agent can choose the one most
1964   appropriate. Depending upon the format and the
1965   capabilities of the user agent, selection of the most appropriate
1966   choice &MAY; be performed automatically. However, this specification
1967   does not define any standard for such automatic selection.
1968</t>
1969<x:note>
1970  <t>
1971    <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1972    not acceptable according to the accept header fields sent in the
1973    request. In some cases, this might even be preferable to sending a
1974    406 response. User agents are encouraged to inspect the header fields of
1975    an incoming response to determine if it is acceptable.
1976  </t>
1977</x:note>
1978<t>
1979   If the response could be unacceptable, a user agent &SHOULD;
1980   temporarily stop receipt of more data and query the user for a
1981   decision on further actions.
1982</t>
1983</section>
1984
1985<section title="408 Request Timeout" anchor="status.408">
1986  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1987  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1988<t>
1989   The client did not produce a request within the time that the server
1990   was prepared to wait. The client &MAY; repeat the request without
1991   modifications at any later time.
1992</t>
1993</section>
1994
1995<section title="409 Conflict" anchor="status.409">
1996  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1997  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1998<t>
1999   The request could not be completed due to a conflict with the current
2000   state of the resource. This code is only allowed in situations where
2001   it is expected that the user might be able to resolve the conflict
2002   and resubmit the request. The response body &SHOULD; include enough
2003   information for the user to recognize the source of the conflict.
2004   Ideally, the response representation would include enough information for the
2005   user or user agent to fix the problem; however, that might not be
2006   possible and is not required.
2007</t>
2008<t>
2009   Conflicts are most likely to occur in response to a PUT request. For
2010   example, if versioning were being used and the representation being PUT
2011   included changes to a resource which conflict with those made by an
2012   earlier (third-party) request, the server might use the 409 response
2013   to indicate that it can't complete the request. In this case, the
2014   response representation would likely contain a list of the differences
2015   between the two versions.
2016</t>
2017</section>
2018
2019<section title="410 Gone" anchor="status.410">
2020  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
2021  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
2022<t>
2023   The target resource is no longer available at the server and no
2024   forwarding address is known. This condition is expected to be
2025   considered permanent. Clients with link editing capabilities &SHOULD;
2026   delete references to the effective request URI after user approval. If the
2027   server does not know, or has no facility to determine, whether or not
2028   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
2029   used instead.
2030</t>
2031<t>
2032   The 410 response is primarily intended to assist the task of web
2033   maintenance by notifying the recipient that the resource is
2034   intentionally unavailable and that the server owners desire that
2035   remote links to that resource be removed. Such an event is common for
2036   limited-time, promotional services and for resources belonging to
2037   individuals no longer working at the server's site. It is not
2038   necessary to mark all permanently unavailable resources as "gone" or
2039   to keep the mark for any length of time &mdash; that is left to the
2040   discretion of the server owner.
2041</t>
2042<t>
2043   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine freshness
2044   for 410 responses.
2045</t>
2046</section>
2047
2048<section title="411 Length Required" anchor="status.411">
2049  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
2050  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
2051<t>
2052   The server refuses to accept the request without a defined Content-Length.
2053   The client &MAY; repeat the request if it adds a valid
2054   Content-Length header field containing the length of the message-body
2055   in the request message.
2056</t>
2057</section>
2058
2059<section title="413 Request Representation Too Large" anchor="status.413">
2060  <iref primary="true" item="413 Request Representation Too Large (status code)" x:for-anchor=""/>
2061  <iref primary="true" item="Status Codes" subitem="413 Request Representation Too Large" x:for-anchor=""/>
2062<t>
2063   The server is refusing to process a request because the request
2064   representation is larger than the server is willing or able to process. The
2065   server &MAY; close the connection to prevent the client from continuing
2066   the request.
2067</t>
2068<t>
2069   If the condition is temporary, the server &SHOULD; include a Retry-After
2070   header field to indicate that it is temporary and after what
2071   time the client &MAY; try again.
2072</t>
2073</section>
2074
2075<section title="414 URI Too Long" anchor="status.414">
2076  <iref primary="true" item="414 URI Too Long (status code)" x:for-anchor=""/>
2077  <iref primary="true" item="Status Codes" subitem="414 URI Too Long" x:for-anchor=""/>
2078<t>
2079   The server is refusing to service the request because the effective request URI
2080   is longer than the server is willing to interpret. This rare
2081   condition is only likely to occur when a client has improperly
2082   converted a POST request to a GET request with long query
2083   information, when the client has descended into a URI "black hole" of
2084   redirection (e.g., a redirected URI prefix that points to a suffix of
2085   itself), or when the server is under attack by a client attempting to
2086   exploit security holes present in some servers using fixed-length
2087   buffers for reading or manipulating the effective request URI.
2088</t>
2089</section>
2090
2091<section title="415 Unsupported Media Type" anchor="status.415">
2092  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
2093  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
2094<t>
2095   The server is refusing to service the request because the request
2096   payload is in a format not supported by this request method on the
2097   target resource.
2098</t>
2099</section>
2100
2101<section title="417 Expectation Failed" anchor="status.417">
2102  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
2103  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
2104<t>
2105   The expectation given in an Expect header field (see <xref target="header.expect"/>)
2106   could not be met by this server, or, if the server is a proxy,
2107   the server has unambiguous evidence that the request could not be met
2108   by the next-hop server.
2109</t>
2110</section>
2111
2112<section title="426 Upgrade Required" anchor="status.426">
2113  <iref primary="true" item="426 Upgrade Required (status code)" x:for-anchor=""/>
2114  <iref primary="true" item="Status Codes" subitem="426 Upgrade Required" x:for-anchor=""/>
2115<t>
2116   The request can not be completed without a prior protocol upgrade. This
2117   response &MUST; include an Upgrade header field (&header-upgrade;)
2118   specifying the required protocols.
2119</t>
2120<figure>
2121<preamble>Example:</preamble>
2122<artwork type="message/http; msgtype=&#34;response&#34;" x:indent-with="  ">
2123HTTP/1.1 426 Upgrade Required
2124Upgrade: HTTP/3.0
2125Connection: Upgrade
2126Content-Length: <x:length-of target="s426body"/>
2127Content-Type: text/plain
2128
2129<x:span anchor="s426body">This service requires use of the HTTP/3.0 protocol.
2130</x:span></artwork></figure>
2131<t>
2132   The server &SHOULD; include a message body in the 426 response which
2133   indicates in human readable form the reason for the error and describes any
2134   alternative courses which may be available to the user.
2135</t>
2136</section>
2137</section>
2138
2139<section title="Server Error 5xx" anchor="status.5xx">
2140<t>
2141   Response status codes beginning with the digit "5" indicate cases in
2142   which the server is aware that it has erred or is incapable of
2143   performing the request. Except when responding to a HEAD request, the
2144   server &SHOULD; include a representation containing an explanation of the
2145   error situation, and whether it is a temporary or permanent
2146   condition. User agents &SHOULD; display any included representation to the
2147   user. These response codes are applicable to any request method.
2148</t>
2149
2150<section title="500 Internal Server Error" anchor="status.500">
2151  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
2152  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
2153<t>
2154   The server encountered an unexpected condition which prevented it
2155   from fulfilling the request.
2156</t>
2157</section>
2158
2159<section title="501 Not Implemented" anchor="status.501">
2160  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
2161  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
2162<t>
2163   The server does not support the functionality required to fulfill the
2164   request. This is the appropriate response when the server does not
2165   recognize the request method and is not capable of supporting it for
2166   any resource.
2167</t>
2168</section>
2169
2170<section title="502 Bad Gateway" anchor="status.502">
2171  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
2172  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
2173<t>
2174   The server, while acting as a gateway or proxy, received an invalid
2175   response from the upstream server it accessed in attempting to
2176   fulfill the request.
2177</t>
2178</section>
2179
2180<section title="503 Service Unavailable" anchor="status.503">
2181  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
2182  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
2183<t>
2184   The server is currently unable to handle the request due to a
2185   temporary overloading or maintenance of the server.
2186</t>
2187<t>
2188   The implication is that this is a temporary condition which will be
2189   alleviated after some delay. If known, the length of the delay &MAY; be
2190   indicated in a Retry-After header field (<xref target="header.retry-after"/>).
2191   If no Retry-After is given, the client &SHOULD; handle the response as it
2192   would for a 500 response.
2193</t>
2194<x:note>
2195  <t>
2196    <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
2197    server must use it when becoming overloaded. Some servers might wish
2198    to simply refuse the connection.
2199  </t>
2200</x:note>
2201</section>
2202
2203<section title="504 Gateway Timeout" anchor="status.504">
2204  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
2205  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
2206<t>
2207   The server, while acting as a gateway or proxy, did not receive a
2208   timely response from the upstream server specified by the URI (e.g.,
2209   HTTP, FTP, LDAP) or some other auxiliary server (e.g., DNS) it needed
2210   to access in attempting to complete the request.
2211</t>
2212<x:note>
2213  <t>
2214    <x:h>Note</x:h> to implementors: some deployed proxies are known to
2215    return 400 or 500 when DNS lookups time out.
2216  </t>
2217</x:note>
2218</section>
2219
2220<section title="505 HTTP Version Not Supported" anchor="status.505">
2221  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
2222  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
2223<t>
2224   The server does not support, or refuses to support, the protocol
2225   version that was used in the request message. The server is
2226   indicating that it is unable or unwilling to complete the request
2227   using the same major version as the client, as described in &http-version;,
2228   other than with this error message. The response &SHOULD; contain
2229   a representation describing why that version is not supported and what other
2230   protocols are supported by that server.
2231</t>
2232
2233</section>
2234</section>
2235</section>
2236
2237
2238<section title="Date/Time Formats" anchor="http.date">
2239  <x:anchor-alias value="HTTP-date"/>
2240<t>
2241   HTTP applications have historically allowed three different formats
2242   for date/time stamps. However, the preferred format is a fixed-length subset
2243   of that defined by <xref target="RFC1123"/>:
2244</t>
2245<figure><artwork type="example" x:indent-with="  ">
2246Sun, 06 Nov 1994 08:49:37 GMT  ; RFC 1123
2247</artwork></figure>
2248<t>
2249   The other formats are described here only for compatibility with obsolete
2250   implementations.
2251</t>
2252<figure><artwork type="example" x:indent-with="  ">
2253Sunday, 06-Nov-94 08:49:37 GMT ; obsolete RFC 850 format
2254Sun Nov  6 08:49:37 1994       ; ANSI C's asctime() format
2255</artwork></figure>
2256<t>
2257   HTTP/1.1 clients and servers that parse a date value &MUST; accept
2258   all three formats (for compatibility with HTTP/1.0), though they &MUST;
2259   only generate the RFC 1123 format for representing HTTP-date values
2260   in header fields.
2261</t>
2262<t>
2263   All HTTP date/time stamps &MUST; be represented in Greenwich Mean Time
2264   (GMT), without exception. For the purposes of HTTP, GMT is exactly
2265   equal to UTC (Coordinated Universal Time). This is indicated in the
2266   first two formats by the inclusion of "GMT" as the three-letter
2267   abbreviation for time zone, and &MUST; be assumed when reading the
2268   asctime format. HTTP-date is case sensitive and &MUST-NOT; include
2269   additional whitespace beyond that specifically included as SP in the
2270   grammar.
2271</t>
2272<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="HTTP-date"/>
2273  <x:ref>HTTP-date</x:ref>    = <x:ref>rfc1123-date</x:ref> / <x:ref>obs-date</x:ref>
2274</artwork></figure>
2275<t anchor="preferred.date.format">
2276  <x:anchor-alias value="rfc1123-date"/>
2277  <x:anchor-alias value="time-of-day"/>
2278  <x:anchor-alias value="hour"/>
2279  <x:anchor-alias value="minute"/>
2280  <x:anchor-alias value="second"/>
2281  <x:anchor-alias value="day-name"/>
2282  <x:anchor-alias value="day"/>
2283  <x:anchor-alias value="month"/>
2284  <x:anchor-alias value="year"/>
2285  <x:anchor-alias value="GMT"/>
2286  Preferred format:
2287</t>
2288<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="rfc1123-date"/><iref primary="true" item="Grammar" subitem="date1"/><iref primary="true" item="Grammar" subitem="time-of-day"/><iref primary="true" item="Grammar" subitem="hour"/><iref primary="true" item="Grammar" subitem="minute"/><iref primary="true" item="Grammar" subitem="second"/><iref primary="true" item="Grammar" subitem="day-name"/><iref primary="true" item="Grammar" subitem="day-name-l"/><iref primary="true" item="Grammar" subitem="day"/><iref primary="true" item="Grammar" subitem="month"/><iref primary="true" item="Grammar" subitem="year"/><iref primary="true" item="Grammar" subitem="GMT"/>
2289  <x:ref>rfc1123-date</x:ref> = <x:ref>day-name</x:ref> "," <x:ref>SP</x:ref> date1 <x:ref>SP</x:ref> <x:ref>time-of-day</x:ref> <x:ref>SP</x:ref> <x:ref>GMT</x:ref>
2290  ; fixed length subset of the format defined in
2291  ; <xref target="RFC1123" x:fmt="of" x:sec="5.2.14"/>
2292 
2293  <x:ref>day-name</x:ref>     = <x:abnf-char-sequence>"Mon"</x:abnf-char-sequence> ; "Mon", case-sensitive
2294               / <x:abnf-char-sequence>"Tue"</x:abnf-char-sequence> ; "Tue", case-sensitive
2295               / <x:abnf-char-sequence>"Wed"</x:abnf-char-sequence> ; "Wed", case-sensitive
2296               / <x:abnf-char-sequence>"Thu"</x:abnf-char-sequence> ; "Thu", case-sensitive
2297               / <x:abnf-char-sequence>"Fri"</x:abnf-char-sequence> ; "Fri", case-sensitive
2298               / <x:abnf-char-sequence>"Sat"</x:abnf-char-sequence> ; "Sat", case-sensitive
2299               / <x:abnf-char-sequence>"Sun"</x:abnf-char-sequence> ; "Sun", case-sensitive
2300               
2301  <x:ref>date1</x:ref>        = <x:ref>day</x:ref> <x:ref>SP</x:ref> <x:ref>month</x:ref> <x:ref>SP</x:ref> <x:ref>year</x:ref>
2302               ; e.g., 02 Jun 1982
2303
2304  <x:ref>day</x:ref>          = 2<x:ref>DIGIT</x:ref>
2305  <x:ref>month</x:ref>        = <x:abnf-char-sequence>"Jan"</x:abnf-char-sequence> ; "Jan", case-sensitive
2306               / <x:abnf-char-sequence>"Feb"</x:abnf-char-sequence> ; "Feb", case-sensitive
2307               / <x:abnf-char-sequence>"Mar"</x:abnf-char-sequence> ; "Mar", case-sensitive
2308               / <x:abnf-char-sequence>"Apr"</x:abnf-char-sequence> ; "Apr", case-sensitive
2309               / <x:abnf-char-sequence>"May"</x:abnf-char-sequence> ; "May", case-sensitive
2310               / <x:abnf-char-sequence>"Jun"</x:abnf-char-sequence> ; "Jun", case-sensitive
2311               / <x:abnf-char-sequence>"Jul"</x:abnf-char-sequence> ; "Jul", case-sensitive
2312               / <x:abnf-char-sequence>"Aug"</x:abnf-char-sequence> ; "Aug", case-sensitive
2313               / <x:abnf-char-sequence>"Sep"</x:abnf-char-sequence> ; "Sep", case-sensitive
2314               / <x:abnf-char-sequence>"Oct"</x:abnf-char-sequence> ; "Oct", case-sensitive
2315               / <x:abnf-char-sequence>"Nov"</x:abnf-char-sequence> ; "Nov", case-sensitive
2316               / <x:abnf-char-sequence>"Dec"</x:abnf-char-sequence> ; "Dec", case-sensitive
2317  <x:ref>year</x:ref>         = 4<x:ref>DIGIT</x:ref>
2318
2319  <x:ref>GMT</x:ref>   = <x:abnf-char-sequence>"GMT"</x:abnf-char-sequence> ; "GMT", case-sensitive
2320
2321  <x:ref>time-of-day</x:ref>  = <x:ref>hour</x:ref> ":" <x:ref>minute</x:ref> ":" <x:ref>second</x:ref>
2322                 ; 00:00:00 - 23:59:59
2323                 
2324  <x:ref>hour</x:ref>         = 2<x:ref>DIGIT</x:ref>               
2325  <x:ref>minute</x:ref>       = 2<x:ref>DIGIT</x:ref>               
2326  <x:ref>second</x:ref>       = 2<x:ref>DIGIT</x:ref>               
2327</artwork></figure>
2328<t>
2329  The semantics of <x:ref>day-name</x:ref>, <x:ref>day</x:ref>,
2330  <x:ref>month</x:ref>, <x:ref>year</x:ref>, and <x:ref>time-of-day</x:ref> are the
2331  same as those defined for the RFC 5322 constructs
2332  with the corresponding name (<xref target="RFC5322" x:fmt="," x:sec="3.3"/>).
2333</t>
2334<t anchor="obsolete.date.formats">
2335  <x:anchor-alias value="obs-date"/>
2336  <x:anchor-alias value="rfc850-date"/>
2337  <x:anchor-alias value="asctime-date"/>
2338  <x:anchor-alias value="date1"/>
2339  <x:anchor-alias value="date2"/>
2340  <x:anchor-alias value="date3"/>
2341  <x:anchor-alias value="rfc1123-date"/>
2342  <x:anchor-alias value="day-name-l"/>
2343  Obsolete formats:
2344</t>
2345<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="obs-date"/>
2346  <x:ref>obs-date</x:ref>     = <x:ref>rfc850-date</x:ref> / <x:ref>asctime-date</x:ref> 
2347</artwork></figure>
2348<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="rfc850-date"/>
2349  <x:ref>rfc850-date</x:ref>  = <x:ref>day-name-l</x:ref> "," <x:ref>SP</x:ref> <x:ref>date2</x:ref> <x:ref>SP</x:ref> <x:ref>time-of-day</x:ref> <x:ref>SP</x:ref> <x:ref>GMT</x:ref>
2350  <x:ref>date2</x:ref>        = <x:ref>day</x:ref> "-" <x:ref>month</x:ref> "-" 2<x:ref>DIGIT</x:ref>
2351                 ; day-month-year (e.g., 02-Jun-82)
2352
2353  <x:ref>day-name-l</x:ref>   = <x:abnf-char-sequence>"Monday"</x:abnf-char-sequence> ; "Monday", case-sensitive
2354         / <x:abnf-char-sequence>"Tuesday"</x:abnf-char-sequence> ; "Tuesday", case-sensitive
2355         / <x:abnf-char-sequence>"Wednesday"</x:abnf-char-sequence> ; "Wednesday", case-sensitive
2356         / <x:abnf-char-sequence>"Thursday"</x:abnf-char-sequence> ; "Thursday", case-sensitive
2357         / <x:abnf-char-sequence>"Friday"</x:abnf-char-sequence> ; "Friday", case-sensitive
2358         / <x:abnf-char-sequence>"Saturday"</x:abnf-char-sequence> ; "Saturday", case-sensitive
2359         / <x:abnf-char-sequence>"Sunday"</x:abnf-char-sequence> ; "Sunday", case-sensitive
2360</artwork></figure>
2361<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="asctime-date"/>
2362  <x:ref>asctime-date</x:ref> = <x:ref>day-name</x:ref> <x:ref>SP</x:ref> <x:ref>date3</x:ref> <x:ref>SP</x:ref> <x:ref>time-of-day</x:ref> <x:ref>SP</x:ref> <x:ref>year</x:ref>
2363  <x:ref>date3</x:ref>        = <x:ref>month</x:ref> <x:ref>SP</x:ref> ( 2<x:ref>DIGIT</x:ref> / ( <x:ref>SP</x:ref> 1<x:ref>DIGIT</x:ref> ))
2364                 ; month day (e.g., Jun  2)
2365</artwork></figure>
2366<x:note>
2367  <t>
2368    <x:h>Note:</x:h> Recipients of date values are encouraged to be robust in
2369    accepting date values that might have been sent by non-HTTP
2370    applications, as is sometimes the case when retrieving or posting
2371    messages via proxies/gateways to SMTP or NNTP.
2372  </t>
2373</x:note>
2374<x:note>
2375  <t>
2376    <x:h>Note:</x:h> HTTP requirements for the date/time stamp format apply only
2377    to their usage within the protocol stream. Clients and servers are
2378    not required to use these formats for user presentation, request
2379    logging, etc.
2380  </t>
2381</x:note>
2382</section>
2383
2384
2385<section title="Header Field Definitions" anchor="header.field.definitions">
2386<t>
2387   This section defines the syntax and semantics of HTTP/1.1 header fields
2388   related to request and response semantics.
2389</t>
2390
2391<section title="Allow" anchor="header.allow">
2392  <iref primary="true" item="Allow header field" x:for-anchor=""/>
2393  <iref primary="true" item="Header Fields" subitem="Allow" x:for-anchor=""/>
2394  <x:anchor-alias value="Allow"/>
2395<t>
2396   The "Allow" header field lists the set of methods advertised as
2397   supported by the target resource. The purpose of this field is strictly to
2398   inform the recipient of valid request methods associated with the resource.
2399</t>
2400<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/>
2401  <x:ref>Allow</x:ref> = #<x:ref>Method</x:ref>
2402</artwork></figure>
2403<t>
2404   Example of use:
2405</t>
2406<figure><artwork type="example">
2407  Allow: GET, HEAD, PUT
2408</artwork></figure>
2409<t>
2410   The actual set of allowed methods is defined by the origin server at the
2411   time of each request.
2412</t>
2413<t>
2414   A proxy &MUST-NOT; modify the Allow header field &mdash; it does not need to
2415   understand all the methods specified in order to handle them according to
2416   the generic message handling rules.
2417</t>
2418</section>
2419
2420<section title="Date" anchor="header.date">
2421  <iref primary="true" item="Date header field" x:for-anchor=""/>
2422  <iref primary="true" item="Header Fields" subitem="Date" x:for-anchor=""/>
2423  <x:anchor-alias value="Date"/>
2424<t>
2425   The "Date" header field represents the date and time at which
2426   the message was originated, having the same semantics as the Origination
2427   Date Field (orig-date) defined in <xref target="RFC5322" x:fmt="of" x:sec="3.6.1"/>.
2428   The field value is an HTTP-date, as defined in <xref target="http.date"/>;
2429   it &MUST; be sent in rfc1123-date format.
2430</t>
2431<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Date"/>
2432  <x:ref>Date</x:ref> = <x:ref>HTTP-date</x:ref>
2433</artwork></figure>
2434<t>
2435   An example is
2436</t>
2437<figure><artwork type="example">
2438  Date: Tue, 15 Nov 1994 08:12:31 GMT
2439</artwork></figure>
2440<t>
2441   Origin servers &MUST; include a Date header field in all responses,
2442   except in these cases:
2443  <list style="numbers">
2444      <t>If the response status code is 100 (Continue) or 101 (Switching
2445         Protocols), the response &MAY; include a Date header field, at
2446         the server's option.</t>
2447
2448      <t>If the response status code conveys a server error, e.g., 500
2449         (Internal Server Error) or 503 (Service Unavailable), and it is
2450         inconvenient or impossible to generate a valid Date.</t>
2451
2452      <t>If the server does not have a clock that can provide a
2453         reasonable approximation of the current time, its responses
2454         &MUST-NOT; include a Date header field.</t>
2455  </list>
2456</t>
2457<t>
2458   A received message that does not have a Date header field &MUST; be
2459   assigned one by the recipient if the message will be cached by that
2460   recipient.
2461</t>
2462<t>
2463   Clients can use the Date header field as well; in order to keep request
2464   messages small, they are advised not to include it when it doesn't convey
2465   any useful information (as is usually the case for requests that do not
2466   contain a payload).
2467</t>
2468<t>
2469   The HTTP-date sent in a Date header field &SHOULD-NOT; represent a date and
2470   time subsequent to the generation of the message. It &SHOULD; represent
2471   the best available approximation of the date and time of message
2472   generation, unless the implementation has no means of generating a
2473   reasonably accurate date and time. In theory, the date ought to
2474   represent the moment just before the payload is generated. In
2475   practice, the date can be generated at any time during the message
2476   origination without affecting its semantic value.
2477</t>
2478</section>
2479
2480<section title="Expect" anchor="header.expect">
2481  <iref primary="true" item="Expect header field" x:for-anchor=""/>
2482  <iref primary="true" item="Header Fields" subitem="Expect" x:for-anchor=""/>
2483  <x:anchor-alias value="Expect"/>
2484  <x:anchor-alias value="expectation"/>
2485  <x:anchor-alias value="expect-param"/>
2486  <x:anchor-alias value="expect-name"/>
2487  <x:anchor-alias value="expect-value"/>
2488<t>
2489   The "Expect" header field is used to indicate that particular
2490   server behaviors are required by the client.
2491</t>
2492<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Expect"/><iref primary="true" item="Grammar" subitem="expectation"/><iref primary="true" item="Grammar" subitem="expect-param"/><iref primary="true" item="Grammar" subitem="expect-value"/><iref primary="true" item="Grammar" subitem="expect-name"/>
2493  <x:ref>Expect</x:ref>       = 1#<x:ref>expectation</x:ref>
2494 
2495  <x:ref>expectation</x:ref>  = <x:ref>expect-name</x:ref> [ <x:ref>BWS</x:ref> "=" <x:ref>BWS</x:ref> <x:ref>expect-value</x:ref> ]
2496                             *( <x:ref>OWS</x:ref> ";" [ <x:ref>OWS</x:ref> <x:ref>expect-param</x:ref> ] )
2497  <x:ref>expect-param</x:ref> = <x:ref>expect-name</x:ref> [ <x:ref>BWS</x:ref> "=" <x:ref>BWS</x:ref> <x:ref>expect-value</x:ref> ]
2498 
2499  <x:ref>expect-name</x:ref>  = <x:ref>token</x:ref>
2500  <x:ref>expect-value</x:ref> = <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref>
2501</artwork></figure>
2502<t>
2503   If all received Expect header field(s) are syntactically valid but contain
2504   an expectation that the recipient does not understand or cannot comply with,
2505   the recipient &MUST; respond with a 417 (Expectation Failed) status code. A
2506   recipient of a syntactically invalid Expectation header field &MUST; respond
2507   with a 4xx status code other than 417.
2508</t>
2509<t>
2510   The only expectation defined by this specification is:
2511</t>
2512<t><iref primary="true" item="100-continue (expect value)"/><iref primary="true" item="Expect Values" subitem="100-continue"/>
2513  100-continue
2514   <list>
2515      <t>
2516        The "100-continue" expectation is defined &use100;. It does not support
2517        any expect-params.
2518      </t>
2519   </list>
2520</t>
2521<t>
2522   Comparison is case-insensitive for names (expect-name), and case-sensitive
2523   for values (expect-value).
2524</t>
2525<t>
2526   The Expect mechanism is hop-by-hop: the above requirements apply to any
2527   server, including proxies. However, the Expect header field itself is
2528   end-to-end; it &MUST; be forwarded if the request is forwarded.
2529</t>
2530<t>
2531   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the Expect
2532   header field.
2533</t>
2534</section>
2535
2536<section title="From" anchor="header.from">
2537  <iref primary="true" item="From header field" x:for-anchor=""/>
2538  <iref primary="true" item="Header Fields" subitem="From" x:for-anchor=""/>
2539  <x:anchor-alias value="From"/>
2540  <x:anchor-alias value="mailbox"/>
2541<t>
2542   The "From" header field, if given, &SHOULD; contain an Internet
2543   e-mail address for the human user who controls the requesting user
2544   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
2545   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
2546</t>
2547<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/>
2548  <x:ref>From</x:ref>    = <x:ref>mailbox</x:ref>
2549 
2550  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
2551</artwork></figure>
2552<t>
2553   An example is:
2554</t>
2555<figure><artwork type="example">
2556  From: webmaster@example.org
2557</artwork></figure>
2558<t>
2559   This header field &MAY; be used for logging purposes and as a means for
2560   identifying the source of invalid or unwanted requests. It &SHOULD-NOT; 
2561   be used as an insecure form of access protection. The interpretation
2562   of this field is that the request is being performed on behalf of the
2563   person given, who accepts responsibility for the method performed. In
2564   particular, robot agents &SHOULD; include this header field so that the
2565   person responsible for running the robot can be contacted if problems
2566   occur on the receiving end.
2567</t>
2568<t>
2569   The Internet e-mail address in this field &MAY; be separate from the
2570   Internet host which issued the request. For example, when a request
2571   is passed through a proxy the original issuer's address &SHOULD; be
2572   used.
2573</t>
2574<t>
2575   The client &SHOULD-NOT;  send the From header field without the user's
2576   approval, as it might conflict with the user's privacy interests or
2577   their site's security policy. It is strongly recommended that the
2578   user be able to disable, enable, and modify the value of this field
2579   at any time prior to a request.
2580</t>
2581</section>
2582
2583<section title="Location" anchor="header.location">
2584  <iref primary="true" item="Location header field" x:for-anchor=""/>
2585  <iref primary="true" item="Header Fields" subitem="Location" x:for-anchor=""/>
2586  <x:anchor-alias value="Location"/>
2587<t>
2588   The "Location" header field &MAY; be sent in responses to refer to
2589   a specific resource in accordance with the semantics of the status
2590   code.
2591</t>
2592<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/>
2593  <x:ref>Location</x:ref> = <x:ref>URI-reference</x:ref>
2594</artwork></figure>
2595<t>
2596   For 201 (Created) responses, the Location is the URI of the new resource
2597   which was created by the request. For 3xx responses, the location &SHOULD;
2598   indicate the server's preferred URI for automatic redirection to the
2599   resource.
2600</t>
2601<t>
2602   The field value consists of a single URI-reference. When it has the form
2603   of a relative reference (<xref target="RFC3986" x:fmt="," x:sec="4.2"/>),
2604   the final value is computed by resolving it against the effective request
2605   URI (<xref target="RFC3986" x:fmt="," x:sec="5"/>). If the original URI, as
2606   navigated to by the user agent, did contain a fragment identifier, and the
2607   final value does not, then the original URI's fragment identifier is added
2608   to the final value.
2609</t>
2610<figure>
2611<preamble>For example, the original URI "http://www.example.org/~tim", combined with a field value given as:</preamble><!--DO NOT DARE changing the vertical spacing below, it's necessary this way for xml2rfc-->
2612<artwork type="example">
2613  Location: /pub/WWW/People.html#tim
2614</artwork>
2615<postamble>would result in a final value of "http://www.example.org/pub/WWW/People.html#tim"</postamble>
2616</figure>
2617<figure>
2618<preamble>An original URI "http://www.example.org/index.html#larry", combined with a field value given as:</preamble><!--DO NOT DARE changing the vertical spacing below, it's necessary this way for xml2rfc-->
2619<artwork type="example">
2620  Location: http://www.example.net/index.html
2621</artwork>
2622<postamble>would result in a final value of "http://www.example.net/index.html#larry", preserving the original fragment identifier.</postamble>
2623</figure>
2624<x:note>
2625  <t>
2626    <x:h>Note:</x:h> Some recipients attempt to recover from Location fields
2627    that are not valid URI references. This specification does not mandate or
2628    define such processing, but does allow it (see <xref target="intro.conformance.and.error.handling"/>).
2629  </t>
2630</x:note>
2631<t>
2632   There are circumstances in which a fragment identifier in a Location URI
2633   would not be appropriate. For instance, when it appears in a 201 Created
2634   response, where the Location header field specifies the URI for the entire
2635   created resource.
2636</t>
2637<x:note>
2638  <t>
2639    <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
2640    from Location in that the Content-Location identifies the most specific
2641    resource corresponding to the enclosed representation.
2642    It is therefore possible for a response to contain header fields for
2643    both Location and Content-Location.
2644  </t>
2645</x:note>
2646</section>
2647
2648<section title="Max-Forwards" anchor="header.max-forwards">
2649  <iref primary="true" item="Max-Forwards header field" x:for-anchor=""/>
2650  <iref primary="true" item="Header Fields" subitem="Max-Forwards" x:for-anchor=""/>
2651  <x:anchor-alias value="Max-Forwards"/>
2652<t>
2653   The "Max-Forwards" header field provides a mechanism with the
2654   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>)
2655   methods to limit the number of times that the request is forwarded by
2656   proxies. This can be useful when the client is attempting to
2657   trace a request which appears to be failing or looping mid-chain.
2658</t>
2659<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/>
2660  <x:ref>Max-Forwards</x:ref> = 1*<x:ref>DIGIT</x:ref>
2661</artwork></figure>
2662<t>
2663   The Max-Forwards value is a decimal integer indicating the remaining
2664   number of times this request message can be forwarded.
2665</t>
2666<t>
2667   Each recipient of a TRACE or OPTIONS request
2668   containing a Max-Forwards header field &MUST; check and update its
2669   value prior to forwarding the request. If the received value is zero
2670   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2671   respond as the final recipient. If the received Max-Forwards value is
2672   greater than zero, then the forwarded message &MUST; contain an updated
2673   Max-Forwards field with a value decremented by one (1).
2674</t>
2675<t>
2676   The Max-Forwards header field &MAY; be ignored for all other request
2677   methods.
2678</t>
2679</section>
2680
2681<section title="Referer" anchor="header.referer">
2682  <iref primary="true" item="Referer header field" x:for-anchor=""/>
2683  <iref primary="true" item="Header Fields" subitem="Referer" x:for-anchor=""/>
2684  <x:anchor-alias value="Referer"/>
2685<t>
2686   The "Referer" [sic] header field allows the client to specify the
2687   URI of the resource from which the effective request URI was obtained (the
2688   "referrer", although the header field is misspelled.).
2689</t>
2690<t>
2691   The Referer header field allows servers to generate lists of back-links to
2692   resources for interest, logging, optimized caching, etc. It also allows
2693   obsolete or mistyped links to be traced for maintenance. Some servers use
2694   Referer as a means of controlling where they allow links from (so-called
2695   "deep linking"), but legitimate requests do not always
2696   contain a Referer header field.
2697</t>
2698<t>
2699   If the effective request URI was obtained from a source that does not have its own
2700   URI (e.g., input from the user keyboard), the Referer field &MUST; either be
2701   sent with the value "about:blank", or not be sent at all. Note that this
2702   requirement does not apply to sources with non-HTTP URIs (e.g., FTP).
2703</t>
2704<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/>
2705  <x:ref>Referer</x:ref> = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
2706</artwork></figure>
2707<t>
2708   Example:
2709</t>
2710<figure><artwork type="example">
2711  Referer: http://www.example.org/hypertext/Overview.html
2712</artwork></figure>
2713<t>
2714   If the field value is a relative URI, it &SHOULD; be interpreted
2715   relative to the effective request URI. The URI &MUST-NOT; include a fragment. See
2716   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
2717</t>
2718</section>
2719
2720<section title="Retry-After" anchor="header.retry-after">
2721  <iref primary="true" item="Retry-After header field" x:for-anchor=""/>
2722  <iref primary="true" item="Header Fields" subitem="Retry-After" x:for-anchor=""/>
2723  <x:anchor-alias value="Retry-After"/>
2724<t>
2725   The header "Retry-After" field can be used with a 503 (Service
2726   Unavailable) response to indicate how long the service is expected to
2727   be unavailable to the requesting client. This field &MAY; also be used
2728   with any 3xx (Redirection) response to indicate the minimum time the
2729   user-agent is asked to wait before issuing the redirected request.
2730</t>
2731<t>
2732   The value of this field can be either an HTTP-date or an integer number
2733   of seconds (in decimal) after the time of the response.
2734</t>
2735<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/>
2736  <x:ref>Retry-After</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
2737</artwork></figure>
2738<t anchor="rule.delta-seconds">
2739  <x:anchor-alias value="delta-seconds"/>
2740   Time spans are non-negative decimal integers, representing time in
2741   seconds.
2742</t>
2743<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2744  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2745</artwork></figure>
2746<t>
2747   Two examples of its use are
2748</t>
2749<figure><artwork type="example">
2750  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2751  Retry-After: 120
2752</artwork></figure>
2753<t>
2754   In the latter example, the delay is 2 minutes.
2755</t>
2756</section>
2757
2758<section title="Server" anchor="header.server">
2759  <iref primary="true" item="Server header field" x:for-anchor=""/>
2760  <iref primary="true" item="Header Fields" subitem="Server" x:for-anchor=""/>
2761  <x:anchor-alias value="Server"/>
2762<t>
2763   The "Server" header field contains information about the
2764   software used by the origin server to handle the request.
2765</t>
2766<t>
2767   The field can contain multiple product tokens (&product-tokens;) and
2768   comments (&header-fields;) identifying the server and any significant
2769   subproducts. The product tokens are listed in order of their significance
2770   for identifying the application.
2771</t>
2772<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/>
2773  <x:ref>Server</x:ref> = <x:ref>product</x:ref> *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2774</artwork></figure>
2775<t>
2776   Example:
2777</t>
2778<figure><artwork type="example">
2779  Server: CERN/3.0 libwww/2.17
2780</artwork></figure>
2781<t>
2782   If the response is being forwarded through a proxy, the proxy
2783   application &MUST-NOT; modify the Server header field. Instead, it
2784   &MUST; include a Via field (as described in &header-via;).
2785</t>
2786<x:note>
2787  <t>
2788    <x:h>Note:</x:h> Revealing the specific software version of the server might
2789    allow the server machine to become more vulnerable to attacks
2790    against software that is known to contain security holes. Server
2791    implementors are encouraged to make this field a configurable
2792    option.
2793  </t>
2794</x:note>
2795</section>
2796
2797<section title="User-Agent" anchor="header.user-agent">
2798  <iref primary="true" item="User-Agent header field" x:for-anchor=""/>
2799  <iref primary="true" item="Header Fields" subitem="User-Agent" x:for-anchor=""/>
2800  <x:anchor-alias value="User-Agent"/>
2801<t>
2802   The "User-Agent" header field contains information about the user
2803   agent originating the request. User agents &SHOULD; include this field with
2804   requests.
2805</t>
2806<t>
2807   Typically, it is used for statistical purposes, the tracing of protocol
2808   violations, and tailoring responses to avoid particular user agent
2809   limitations.
2810</t>
2811<t>
2812   The field can contain multiple product tokens (&product-tokens;)
2813   and comments (&header-fields;) identifying the agent and its
2814   significant subproducts. By convention, the product tokens are listed in
2815   order of their significance for identifying the application.
2816</t>
2817<t>
2818   Because this field is usually sent on every request a user agent makes,
2819   implementations are encouraged not to include needlessly fine-grained
2820   detail, and to limit (or even prohibit) the addition of subproducts by third
2821   parties. Overly long and detailed User-Agent field values make requests
2822   larger and can also be used to identify ("fingerprint") the user against
2823   their wishes.
2824</t>
2825<t>
2826   Likewise, implementations are encouraged not to use the product tokens of
2827   other implementations in order to declare compatibility with them, as this
2828   circumvents the purpose of the field. Finally, they are encouraged not to
2829   use comments to identify products; doing so makes the field value more
2830   difficult to parse.
2831</t>
2832<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/>
2833  <x:ref>User-Agent</x:ref> = <x:ref>product</x:ref> *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2834</artwork></figure>
2835<t>
2836   Example:
2837</t>
2838<figure><artwork type="example">
2839  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2840</artwork></figure>
2841</section>
2842
2843</section>
2844
2845<section title="IANA Considerations" anchor="IANA.considerations">
2846
2847<section title="Method Registry" anchor="method.registration">
2848<t>
2849  The registration procedure for HTTP request methods is defined by
2850  <xref target="method.registry"/> of this document.
2851</t>
2852<t>
2853   The HTTP Method Registry shall be created at <eref target="http://www.iana.org/assignments/http-methods"/>
2854   and be populated with the registrations below:
2855</t>
2856<?BEGININC p2-semantics.iana-methods ?>
2857<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2858<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2859   <ttcol>Method</ttcol>
2860   <ttcol>Safe</ttcol>
2861   <ttcol>Reference</ttcol>
2862   <c>CONNECT</c>
2863   <c>no</c>
2864   <c>
2865      <xref target="CONNECT"/>
2866   </c>
2867   <c>DELETE</c>
2868   <c>no</c>
2869   <c>
2870      <xref target="DELETE"/>
2871   </c>
2872   <c>GET</c>
2873   <c>yes</c>
2874   <c>
2875      <xref target="GET"/>
2876   </c>
2877   <c>HEAD</c>
2878   <c>yes</c>
2879   <c>
2880      <xref target="HEAD"/>
2881   </c>
2882   <c>OPTIONS</c>
2883   <c>yes</c>
2884   <c>
2885      <xref target="OPTIONS"/>
2886   </c>
2887   <c>POST</c>
2888   <c>no</c>
2889   <c>
2890      <xref target="POST"/>
2891   </c>
2892   <c>PUT</c>
2893   <c>no</c>
2894   <c>
2895      <xref target="PUT"/>
2896   </c>
2897   <c>TRACE</c>
2898   <c>yes</c>
2899   <c>
2900      <xref target="TRACE"/>
2901   </c>
2902</texttable>
2903<!--(END)-->
2904<?ENDINC p2-semantics.iana-methods ?>
2905</section>
2906
2907<section title="Status Code Registry" anchor="status.code.registration">
2908<t>
2909   The registration procedure for HTTP Status Codes &mdash; previously defined
2910   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> &mdash; is now defined
2911   by <xref target="status.code.registry"/> of this document.
2912</t>
2913<t>
2914   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
2915   shall be updated with the registrations below:
2916</t>
2917<?BEGININC p2-semantics.iana-status-codes ?>
2918<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2919<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
2920   <ttcol>Value</ttcol>
2921   <ttcol>Description</ttcol>
2922   <ttcol>Reference</ttcol>
2923   <c>100</c>
2924   <c>Continue</c>
2925   <c>
2926      <xref target="status.100"/>
2927   </c>
2928   <c>101</c>
2929   <c>Switching Protocols</c>
2930   <c>
2931      <xref target="status.101"/>
2932   </c>
2933   <c>200</c>
2934   <c>OK</c>
2935   <c>
2936      <xref target="status.200"/>
2937   </c>
2938   <c>201</c>
2939   <c>Created</c>
2940   <c>
2941      <xref target="status.201"/>
2942   </c>
2943   <c>202</c>
2944   <c>Accepted</c>
2945   <c>
2946      <xref target="status.202"/>
2947   </c>
2948   <c>203</c>
2949   <c>Non-Authoritative Information</c>
2950   <c>
2951      <xref target="status.203"/>
2952   </c>
2953   <c>204</c>
2954   <c>No Content</c>
2955   <c>
2956      <xref target="status.204"/>
2957   </c>
2958   <c>205</c>
2959   <c>Reset Content</c>
2960   <c>
2961      <xref target="status.205"/>
2962   </c>
2963   <c>300</c>
2964   <c>Multiple Choices</c>
2965   <c>
2966      <xref target="status.300"/>
2967   </c>
2968   <c>301</c>
2969   <c>Moved Permanently</c>
2970   <c>
2971      <xref target="status.301"/>
2972   </c>
2973   <c>302</c>
2974   <c>Found</c>
2975   <c>
2976      <xref target="status.302"/>
2977   </c>
2978   <c>303</c>
2979   <c>See Other</c>
2980   <c>
2981      <xref target="status.303"/>
2982   </c>
2983   <c>305</c>
2984   <c>Use Proxy</c>
2985   <c>
2986      <xref target="status.305"/>
2987   </c>
2988   <c>306</c>
2989   <c>(Unused)</c>
2990   <c>
2991      <xref target="status.306"/>
2992   </c>
2993   <c>307</c>
2994   <c>Temporary Redirect</c>
2995   <c>
2996      <xref target="status.307"/>
2997   </c>
2998   <c>400</c>
2999   <c>Bad Request</c>
3000   <c>
3001      <xref target="status.400"/>
3002   </c>
3003   <c>402</c>
3004   <c>Payment Required</c>
3005   <c>
3006      <xref target="status.402"/>
3007   </c>
3008   <c>403</c>
3009   <c>Forbidden</c>
3010   <c>
3011      <xref target="status.403"/>
3012   </c>
3013   <c>404</c>
3014   <c>Not Found</c>
3015   <c>
3016      <xref target="status.404"/>
3017   </c>
3018   <c>405</c>
3019   <c>Method Not Allowed</c>
3020   <c>
3021      <xref target="status.405"/>
3022   </c>
3023   <c>406</c>
3024   <c>Not Acceptable</c>
3025   <c>
3026      <xref target="status.406"/>
3027   </c>
3028   <c>408</c>
3029   <c>Request Timeout</c>
3030   <c>
3031      <xref target="status.408"/>
3032   </c>
3033   <c>409</c>
3034   <c>Conflict</c>
3035   <c>
3036      <xref target="status.409"/>
3037   </c>
3038   <c>410</c>
3039   <c>Gone</c>
3040   <c>
3041      <xref target="status.410"/>
3042   </c>
3043   <c>411</c>
3044   <c>Length Required</c>
3045   <c>
3046      <xref target="status.411"/>
3047   </c>
3048   <c>413</c>
3049   <c>Request Representation Too Large</c>
3050   <c>
3051      <xref target="status.413"/>
3052   </c>
3053   <c>414</c>
3054   <c>URI Too Long</c>
3055   <c>
3056      <xref target="status.414"/>
3057   </c>
3058   <c>415</c>
3059   <c>Unsupported Media Type</c>
3060   <c>
3061      <xref target="status.415"/>
3062   </c>
3063   <c>417</c>
3064   <c>Expectation Failed</c>
3065   <c>
3066      <xref target="status.417"/>
3067   </c>
3068   <c>426</c>
3069   <c>Upgrade Required</c>
3070   <c>
3071      <xref target="status.426"/>
3072   </c>
3073   <c>500</c>
3074   <c>Internal Server Error</c>
3075   <c>
3076      <xref target="status.500"/>
3077   </c>
3078   <c>501</c>
3079   <c>Not Implemented</c>
3080   <c>
3081      <xref target="status.501"/>
3082   </c>
3083   <c>502</c>
3084   <c>Bad Gateway</c>
3085   <c>
3086      <xref target="status.502"/>
3087   </c>
3088   <c>503</c>
3089   <c>Service Unavailable</c>
3090   <c>
3091      <xref target="status.503"/>
3092   </c>
3093   <c>504</c>
3094   <c>Gateway Timeout</c>
3095   <c>
3096      <xref target="status.504"/>
3097   </c>
3098   <c>505</c>
3099   <c>HTTP Version Not Supported</c>
3100   <c>
3101      <xref target="status.505"/>
3102   </c>
3103</texttable>
3104<!--(END)-->
3105<?ENDINC p2-semantics.iana-status-codes ?>
3106</section>
3107<section title="Header Field Registration" anchor="header.field.registration">
3108<t>
3109   The Message Header Field Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> shall be updated
3110   with the permanent registrations below (see <xref target="RFC3864"/>):
3111</t>
3112<?BEGININC p2-semantics.iana-headers ?>
3113<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
3114<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
3115   <ttcol>Header Field Name</ttcol>
3116   <ttcol>Protocol</ttcol>
3117   <ttcol>Status</ttcol>
3118   <ttcol>Reference</ttcol>
3119
3120   <c>Allow</c>
3121   <c>http</c>
3122   <c>standard</c>
3123   <c>
3124      <xref target="header.allow"/>
3125   </c>
3126   <c>Date</c>
3127   <c>http</c>
3128   <c>standard</c>
3129   <c>
3130      <xref target="header.date"/>
3131   </c>
3132   <c>Expect</c>
3133   <c>http</c>
3134   <c>standard</c>
3135   <c>
3136      <xref target="header.expect"/>
3137   </c>
3138   <c>From</c>
3139   <c>http</c>
3140   <c>standard</c>
3141   <c>
3142      <xref target="header.from"/>
3143   </c>
3144   <c>Location</c>
3145   <c>http</c>
3146   <c>standard</c>
3147   <c>
3148      <xref target="header.location"/>
3149   </c>
3150   <c>Max-Forwards</c>
3151   <c>http</c>
3152   <c>standard</c>
3153   <c>
3154      <xref target="header.max-forwards"/>
3155   </c>
3156   <c>Referer</c>
3157   <c>http</c>
3158   <c>standard</c>
3159   <c>
3160      <xref target="header.referer"/>
3161   </c>
3162   <c>Retry-After</c>
3163   <c>http</c>
3164   <c>standard</c>
3165   <c>
3166      <xref target="header.retry-after"/>
3167   </c>
3168   <c>Server</c>
3169   <c>http</c>
3170   <c>standard</c>
3171   <c>
3172      <xref target="header.server"/>
3173   </c>
3174   <c>User-Agent</c>
3175   <c>http</c>
3176   <c>standard</c>
3177   <c>
3178      <xref target="header.user-agent"/>
3179   </c>
3180</texttable>
3181<!--(END)-->
3182<?ENDINC p2-semantics.iana-headers ?>
3183<t>
3184   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
3185</t>
3186</section>
3187</section>
3188
3189<section title="Security Considerations" anchor="security.considerations">
3190<t>
3191   This section is meant to inform application developers, information
3192   providers, and users of the security limitations in HTTP/1.1 as
3193   described by this document. The discussion does not include
3194   definitive solutions to the problems revealed, though it does make
3195   some suggestions for reducing security risks.
3196</t>
3197
3198<section title="Transfer of Sensitive Information" anchor="security.sensitive">
3199<t>
3200   Like any generic data transfer protocol, HTTP cannot regulate the
3201   content of the data that is transferred, nor is there any a priori
3202   method of determining the sensitivity of any particular piece of
3203   information within the context of any given request. Therefore,
3204   applications &SHOULD; supply as much control over this information as
3205   possible to the provider of that information. Four header fields are
3206   worth special mention in this context: Server, Via, Referer and From.
3207</t>
3208<t>
3209   Revealing the specific software version of the server might allow the
3210   server machine to become more vulnerable to attacks against software
3211   that is known to contain security holes. Implementors &SHOULD; make the
3212   Server header field a configurable option.
3213</t>
3214<t>
3215   Proxies which serve as a portal through a network firewall &SHOULD;
3216   take special precautions regarding the transfer of header information
3217   that identifies the hosts behind the firewall. In particular, they
3218   &SHOULD; remove, or replace with sanitized versions, any Via fields
3219   generated behind the firewall.
3220</t>
3221<t>
3222   The Referer header field allows reading patterns to be studied and reverse
3223   links drawn. Although it can be very useful, its power can be abused
3224   if user details are not separated from the information contained in
3225   the Referer. Even when the personal information has been removed, the
3226   Referer header field might indicate a private document's URI whose
3227   publication would be inappropriate.
3228</t>
3229<t>
3230   The information sent in the From field might conflict with the user's
3231   privacy interests or their site's security policy, and hence it
3232   &SHOULD-NOT;  be transmitted without the user being able to disable,
3233   enable, and modify the contents of the field. The user &MUST; be able
3234   to set the contents of this field within a user preference or
3235   application defaults configuration.
3236</t>
3237<t>
3238   We suggest, though do not require, that a convenient toggle interface
3239   be provided for the user to enable or disable the sending of From and
3240   Referer information.
3241</t>
3242<t>
3243   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref
3244   target="header.server"/>) header fields can sometimes be used to determine
3245   that a specific client or server has a particular security hole which might
3246   be exploited. Unfortunately, this same information is often used for other
3247   valuable purposes for which HTTP currently has no better mechanism.
3248</t>
3249<t>
3250   Furthermore, the User-Agent header field may contain enough entropy to be
3251   used, possibly in conjunction with other material, to uniquely identify the
3252   user.
3253</t>
3254<t>
3255   Some request methods, like TRACE (<xref target="TRACE"/>), expose information
3256   that was sent in request header fields within the body of their response.
3257   Clients &SHOULD; be careful with sensitive information, like Cookies,
3258   Authorization credentials, and other header fields that might be used to
3259   collect data from the client.
3260</t> 
3261</section>
3262
3263<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
3264<t>
3265   Because the source of a link might be private information or might
3266   reveal an otherwise private information source, it is strongly
3267   recommended that the user be able to select whether or not the
3268   Referer field is sent. For example, a browser client could have a
3269   toggle switch for browsing openly/anonymously, which would
3270   respectively enable/disable the sending of Referer and From
3271   information.
3272</t>
3273<t>
3274   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
3275   HTTP request if the referring page was transferred with a secure
3276   protocol.
3277</t>
3278<t>
3279   Authors of services &SHOULD-NOT; use GET-based forms for the submission of
3280   sensitive data because that data will be placed in the request-target. Many
3281   existing servers, proxies, and user agents log or display the request-target
3282   in places where it might be visible to third parties. Such services can
3283   use POST-based form submission instead.
3284</t>
3285</section>
3286
3287<section title="Location Header Fields: Spoofing and Information Leakage" anchor="location.spoofing-leakage">
3288<t>
3289   If a single server supports multiple organizations that do not trust
3290   one another, then it &MUST; check the values of Location and Content-Location
3291   header fields in responses that are generated under control of
3292   said organizations to make sure that they do not attempt to
3293   invalidate resources over which they have no authority.
3294</t>
3295<t>
3296   Furthermore, appending the fragment identifier from one URI to another
3297   one obtained from a Location header field might leak confidential
3298   information to the target server &mdash; although the fragment identifier is
3299   not transmitted in the final request, it might be visible to the user agent
3300   through other means, such as scripting.
3301</t>
3302</section>
3303
3304<section title="Security Considerations for CONNECT">
3305<t>
3306   Since tunneled data is opaque to the proxy, there are additional
3307   risks to tunneling to other well-known or reserved ports.
3308   A HTTP client CONNECTing to port 25 could relay spam
3309   via SMTP, for example. As such, proxies &SHOULD; restrict CONNECT
3310   access to a small number of known ports.
3311</t>
3312</section>
3313
3314</section>
3315
3316<section title="Acknowledgments" anchor="acks">
3317<t>
3318  See &acks;.
3319</t>
3320</section>
3321</middle>
3322<back>
3323
3324<references title="Normative References">
3325
3326<reference anchor="Part1">
3327  <front>
3328    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
3329    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3330      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3331      <address><email>fielding@gbiv.com</email></address>
3332    </author>
3333    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3334      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3335      <address><email>jg@freedesktop.org</email></address>
3336    </author>
3337    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3338      <organization abbrev="HP">Hewlett-Packard Company</organization>
3339      <address><email>JeffMogul@acm.org</email></address>
3340    </author>
3341    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3342      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3343      <address><email>henrikn@microsoft.com</email></address>
3344    </author>
3345    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3346      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3347      <address><email>LMM@acm.org</email></address>
3348    </author>
3349    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3350      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3351      <address><email>paulle@microsoft.com</email></address>
3352    </author>
3353    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3354      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3355      <address><email>timbl@w3.org</email></address>
3356    </author>
3357    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3358      <organization abbrev="W3C">World Wide Web Consortium</organization>
3359      <address><email>ylafon@w3.org</email></address>
3360    </author>
3361    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3362      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3363      <address><email>julian.reschke@greenbytes.de</email></address>
3364    </author>
3365    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3366  </front>
3367  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
3368  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
3369</reference>
3370
3371<reference anchor="Part3">
3372  <front>
3373    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
3374    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3375      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3376      <address><email>fielding@gbiv.com</email></address>
3377    </author>
3378    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3379      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3380      <address><email>jg@freedesktop.org</email></address>
3381    </author>
3382    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3383      <organization abbrev="HP">Hewlett-Packard Company</organization>
3384      <address><email>JeffMogul@acm.org</email></address>
3385    </author>
3386    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3387      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3388      <address><email>henrikn@microsoft.com</email></address>
3389    </author>
3390    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3391      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3392      <address><email>LMM@acm.org</email></address>
3393    </author>
3394    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3395      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3396      <address><email>paulle@microsoft.com</email></address>
3397    </author>
3398    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3399      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3400      <address><email>timbl@w3.org</email></address>
3401    </author>
3402    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3403      <organization abbrev="W3C">World Wide Web Consortium</organization>
3404      <address><email>ylafon@w3.org</email></address>
3405    </author>
3406    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3407      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3408      <address><email>julian.reschke@greenbytes.de</email></address>
3409    </author>
3410    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3411  </front>
3412  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
3413  <x:source href="p3-payload.xml" basename="p3-payload"/>
3414</reference>
3415
3416<reference anchor="Part4">
3417  <front>
3418    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
3419    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3420      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3421      <address><email>fielding@gbiv.com</email></address>
3422    </author>
3423    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3424      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3425      <address><email>jg@freedesktop.org</email></address>
3426    </author>
3427    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3428      <organization abbrev="HP">Hewlett-Packard Company</organization>
3429      <address><email>JeffMogul@acm.org</email></address>
3430    </author>
3431    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3432      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3433      <address><email>henrikn@microsoft.com</email></address>
3434    </author>
3435    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3436      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3437      <address><email>LMM@acm.org</email></address>
3438    </author>
3439    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3440      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3441      <address><email>paulle@microsoft.com</email></address>
3442    </author>
3443    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3444      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3445      <address><email>timbl@w3.org</email></address>
3446    </author>
3447    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3448      <organization abbrev="W3C">World Wide Web Consortium</organization>
3449      <address><email>ylafon@w3.org</email></address>
3450    </author>
3451    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3452      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3453      <address><email>julian.reschke@greenbytes.de</email></address>
3454    </author>
3455    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3456  </front>
3457  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
3458  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
3459</reference>
3460
3461<reference anchor="Part5">
3462  <front>
3463    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
3464    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3465      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3466      <address><email>fielding@gbiv.com</email></address>
3467    </author>
3468    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3469      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3470      <address><email>jg@freedesktop.org</email></address>
3471    </author>
3472    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3473      <organization abbrev="HP">Hewlett-Packard Company</organization>
3474      <address><email>JeffMogul@acm.org</email></address>
3475    </author>
3476    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3477      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3478      <address><email>henrikn@microsoft.com</email></address>
3479    </author>
3480    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3481      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3482      <address><email>LMM@acm.org</email></address>
3483    </author>
3484    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3485      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3486      <address><email>paulle@microsoft.com</email></address>
3487    </author>
3488    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3489      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3490      <address><email>timbl@w3.org</email></address>
3491    </author>
3492    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3493      <organization abbrev="W3C">World Wide Web Consortium</organization>
3494      <address><email>ylafon@w3.org</email></address>
3495    </author>
3496    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3497      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3498      <address><email>julian.reschke@greenbytes.de</email></address>
3499    </author>
3500    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3501  </front>
3502  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
3503  <x:source href="p5-range.xml" basename="p5-range"/>
3504</reference>
3505
3506<reference anchor="Part6">
3507  <front>
3508    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
3509    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3510      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3511      <address><email>fielding@gbiv.com</email></address>
3512    </author>
3513    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3514      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3515      <address><email>jg@freedesktop.org</email></address>
3516    </author>
3517    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3518      <organization abbrev="HP">Hewlett-Packard Company</organization>
3519      <address><email>JeffMogul@acm.org</email></address>
3520    </author>
3521    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3522      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3523      <address><email>henrikn@microsoft.com</email></address>
3524    </author>
3525    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3526      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3527      <address><email>LMM@acm.org</email></address>
3528    </author>
3529    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3530      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3531      <address><email>paulle@microsoft.com</email></address>
3532    </author>
3533    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3534      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3535      <address><email>timbl@w3.org</email></address>
3536    </author>
3537    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3538      <organization abbrev="W3C">World Wide Web Consortium</organization>
3539      <address><email>ylafon@w3.org</email></address>
3540    </author>
3541    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
3542      <organization>Rackspace</organization>
3543      <address><email>mnot@mnot.net</email></address>
3544    </author>
3545    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3546      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3547      <address><email>julian.reschke@greenbytes.de</email></address>
3548    </author>
3549    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3550  </front>
3551  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
3552  <x:source href="p6-cache.xml" basename="p6-cache"/>
3553</reference>
3554
3555<reference anchor="Part7">
3556  <front>
3557    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
3558    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3559      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3560      <address><email>fielding@gbiv.com</email></address>
3561    </author>
3562    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3563      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3564      <address><email>jg@freedesktop.org</email></address>
3565    </author>
3566    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3567      <organization abbrev="HP">Hewlett-Packard Company</organization>
3568      <address><email>JeffMogul@acm.org</email></address>
3569    </author>
3570    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3571      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3572      <address><email>henrikn@microsoft.com</email></address>
3573    </author>
3574    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3575      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3576      <address><email>LMM@acm.org</email></address>
3577    </author>
3578    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3579      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3580      <address><email>paulle@microsoft.com</email></address>
3581    </author>
3582    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3583      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3584      <address><email>timbl@w3.org</email></address>
3585    </author>
3586    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3587      <organization abbrev="W3C">World Wide Web Consortium</organization>
3588      <address><email>ylafon@w3.org</email></address>
3589    </author>
3590    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3591      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3592      <address><email>julian.reschke@greenbytes.de</email></address>
3593    </author>
3594    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3595  </front>
3596  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
3597  <x:source href="p7-auth.xml" basename="p7-auth"/>
3598</reference>
3599
3600<reference anchor="RFC2119">
3601  <front>
3602    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
3603    <author initials="S." surname="Bradner" fullname="Scott Bradner">
3604      <organization>Harvard University</organization>
3605      <address><email>sob@harvard.edu</email></address>
3606    </author>
3607    <date month="March" year="1997"/>
3608  </front>
3609  <seriesInfo name="BCP" value="14"/>
3610  <seriesInfo name="RFC" value="2119"/>
3611</reference>
3612
3613<reference anchor="RFC3986">
3614 <front>
3615  <title abbrev='URI Generic Syntax'>Uniform Resource Identifier (URI): Generic Syntax</title>
3616  <author initials='T.' surname='Berners-Lee' fullname='Tim Berners-Lee'>
3617    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3618    <address>
3619       <email>timbl@w3.org</email>
3620       <uri>http://www.w3.org/People/Berners-Lee/</uri>
3621    </address>
3622  </author>
3623  <author initials='R.' surname='Fielding' fullname='Roy T. Fielding'>
3624    <organization abbrev="Day Software">Day Software</organization>
3625    <address>
3626      <email>fielding@gbiv.com</email>
3627      <uri>http://roy.gbiv.com/</uri>
3628    </address>
3629  </author>
3630  <author initials='L.' surname='Masinter' fullname='Larry Masinter'>
3631    <organization abbrev="Adobe Systems">Adobe Systems Incorporated</organization>
3632    <address>
3633      <email>LMM@acm.org</email>
3634      <uri>http://larry.masinter.net/</uri>
3635    </address>
3636  </author>
3637  <date month='January' year='2005'></date>
3638 </front>
3639 <seriesInfo name="STD" value="66"/>
3640 <seriesInfo name="RFC" value="3986"/>
3641</reference>
3642
3643<reference anchor="RFC5234">
3644  <front>
3645    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
3646    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
3647      <organization>Brandenburg InternetWorking</organization>
3648      <address>
3649        <email>dcrocker@bbiw.net</email>
3650      </address> 
3651    </author>
3652    <author initials="P." surname="Overell" fullname="Paul Overell">
3653      <organization>THUS plc.</organization>
3654      <address>
3655        <email>paul.overell@thus.net</email>
3656      </address>
3657    </author>
3658    <date month="January" year="2008"/>
3659  </front>
3660  <seriesInfo name="STD" value="68"/>
3661  <seriesInfo name="RFC" value="5234"/>
3662</reference>
3663
3664</references>
3665
3666<references title="Informative References">
3667
3668<reference anchor="RFC1123">
3669  <front>
3670    <title>Requirements for Internet Hosts - Application and Support</title>
3671    <author initials="R." surname="Braden" fullname="Robert Braden">
3672      <organization>University of Southern California (USC), Information Sciences Institute</organization>
3673      <address><email>Braden@ISI.EDU</email></address>
3674    </author>
3675    <date month="October" year="1989"/>
3676  </front>
3677  <seriesInfo name="STD" value="3"/>
3678  <seriesInfo name="RFC" value="1123"/>
3679</reference>
3680
3681<reference anchor="RFC1945">
3682  <front>
3683    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
3684    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3685      <organization>MIT, Laboratory for Computer Science</organization>
3686      <address><email>timbl@w3.org</email></address>
3687    </author>
3688    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
3689      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3690      <address><email>fielding@ics.uci.edu</email></address>
3691    </author>
3692    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3693      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
3694      <address><email>frystyk@w3.org</email></address>
3695    </author>
3696    <date month="May" year="1996"/>
3697  </front>
3698  <seriesInfo name="RFC" value="1945"/>
3699</reference>
3700
3701<reference anchor="RFC2068">
3702  <front>
3703    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
3704    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
3705      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3706      <address><email>fielding@ics.uci.edu</email></address>
3707    </author>
3708    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3709      <organization>MIT Laboratory for Computer Science</organization>
3710      <address><email>jg@w3.org</email></address>
3711    </author>
3712    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3713      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
3714      <address><email>mogul@wrl.dec.com</email></address>
3715    </author>
3716    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3717      <organization>MIT Laboratory for Computer Science</organization>
3718      <address><email>frystyk@w3.org</email></address>
3719    </author>
3720    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3721      <organization>MIT Laboratory for Computer Science</organization>
3722      <address><email>timbl@w3.org</email></address>
3723    </author>
3724    <date month="January" year="1997"/>
3725  </front>
3726  <seriesInfo name="RFC" value="2068"/>
3727</reference>
3728
3729<reference anchor="RFC2616">
3730  <front>
3731    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
3732    <author initials="R." surname="Fielding" fullname="R. Fielding">
3733      <organization>University of California, Irvine</organization>
3734      <address><email>fielding@ics.uci.edu</email></address>
3735    </author>
3736    <author initials="J." surname="Gettys" fullname="J. Gettys">
3737      <organization>W3C</organization>
3738      <address><email>jg@w3.org</email></address>
3739    </author>
3740    <author initials="J." surname="Mogul" fullname="J. Mogul">
3741      <organization>Compaq Computer Corporation</organization>
3742      <address><email>mogul@wrl.dec.com</email></address>
3743    </author>
3744    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
3745      <organization>MIT Laboratory for Computer Science</organization>
3746      <address><email>frystyk@w3.org</email></address>
3747    </author>
3748    <author initials="L." surname="Masinter" fullname="L. Masinter">
3749      <organization>Xerox Corporation</organization>
3750      <address><email>masinter@parc.xerox.com</email></address>
3751    </author>
3752    <author initials="P." surname="Leach" fullname="P. Leach">
3753      <organization>Microsoft Corporation</organization>
3754      <address><email>paulle@microsoft.com</email></address>
3755    </author>
3756    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
3757      <organization>W3C</organization>
3758      <address><email>timbl@w3.org</email></address>
3759    </author>
3760    <date month="June" year="1999"/>
3761  </front>
3762  <seriesInfo name="RFC" value="2616"/>
3763</reference>
3764
3765<reference anchor='RFC2817'>
3766  <front>
3767    <title>Upgrading to TLS Within HTTP/1.1</title>
3768    <author initials='R.' surname='Khare' fullname='R. Khare'>
3769      <organization>4K Associates / UC Irvine</organization>
3770      <address><email>rohit@4K-associates.com</email></address>
3771    </author>
3772    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
3773      <organization>Agranat Systems, Inc.</organization>
3774      <address><email>lawrence@agranat.com</email></address>
3775    </author>
3776    <date year='2000' month='May' />
3777  </front>
3778  <seriesInfo name='RFC' value='2817' />
3779</reference>
3780
3781<reference anchor='RFC3864'>
3782  <front>
3783    <title>Registration Procedures for Message Header Fields</title>
3784    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3785      <organization>Nine by Nine</organization>
3786      <address><email>GK-IETF@ninebynine.org</email></address>
3787    </author>
3788    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3789      <organization>BEA Systems</organization>
3790      <address><email>mnot@pobox.com</email></address>
3791    </author>
3792    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3793      <organization>HP Labs</organization>
3794      <address><email>JeffMogul@acm.org</email></address>
3795    </author>
3796    <date year='2004' month='September' />
3797  </front>
3798  <seriesInfo name='BCP' value='90' />
3799  <seriesInfo name='RFC' value='3864' />
3800</reference>
3801
3802<reference anchor='RFC5226'>
3803  <front>
3804    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3805    <author initials='T.' surname='Narten' fullname='T. Narten'>
3806      <organization>IBM</organization>
3807      <address><email>narten@us.ibm.com</email></address>
3808    </author>
3809    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3810      <organization>Google</organization>
3811      <address><email>Harald@Alvestrand.no</email></address>
3812    </author>
3813    <date year='2008' month='May' />
3814  </front>
3815  <seriesInfo name='BCP' value='26' />
3816  <seriesInfo name='RFC' value='5226' />
3817</reference>
3818
3819<reference anchor="RFC5322">
3820  <front>
3821    <title>Internet Message Format</title>
3822    <author initials="P." surname="Resnick" fullname="P. Resnick">
3823      <organization>Qualcomm Incorporated</organization>
3824    </author>
3825    <date year="2008" month="October"/>
3826  </front> 
3827  <seriesInfo name="RFC" value="5322"/>
3828</reference>
3829
3830<reference anchor='RFC5789'>
3831  <front>
3832    <title>PATCH Method for HTTP</title>
3833    <author initials='L.' surname='Dusseault' fullname='L. Dusseault'>
3834      <organization>Linden Lab</organization>
3835    </author>
3836    <author initials='J.' surname='Snell' fullname='J. Snell' />
3837    <date year='2010' month='March' />
3838  </front>
3839  <seriesInfo name='RFC' value='5789' />
3840</reference>
3841
3842<reference anchor="RFC5987">
3843        <front>
3844    <title>Character Set and Language Encoding for Hypertext Transfer Protocol (HTTP) Header Field Parameters</title>
3845    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke">
3846      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3847      <address>
3848        <postal>
3849          <street>Hafenweg 16</street>
3850          <city>Muenster</city><region>NW</region><code>48155</code>
3851          <country>Germany</country>
3852        </postal>
3853        <email>julian.reschke@greenbytes.de</email>     
3854        <uri>http://greenbytes.de/tech/webdav/</uri>   
3855      </address>
3856    </author>
3857    <date month="August" year="2010"/>
3858  </front>
3859  <seriesInfo name="RFC" value="5987"/>
3860</reference>
3861
3862</references>
3863
3864<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3865<t>
3866  This document takes over the Status Code Registry, previously defined
3867  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3868  (<xref target="status.code.registry"/>)
3869</t>
3870<t>
3871  Clarify definition of POST.
3872  (<xref target="POST"/>)
3873</t>
3874<t>
3875  Remove requirement to handle all Content-* header fields; ban use of
3876  Content-Range with PUT.
3877  (<xref target="PUT"/>)
3878</t>
3879<t>
3880  Take over definition of CONNECT method from <xref target="RFC2817"/>.
3881  (<xref target="CONNECT"/>)
3882</t>
3883<t>
3884  Broadened the definition of 203 (Non-Authoritative Information) to include
3885  cases of payload transformations as well.
3886  (<xref target="status.203"/>)
3887</t>
3888<t>
3889  Status codes 301, 302, and 307: removed the normative requirements on both
3890  response payloads and user interaction.
3891  (<xref target="status.3xx"/>)
3892</t>
3893<t>
3894  Failed to consider that there are many other request methods that are safe
3895  to automatically redirect, and further that the user agent is able to make
3896  that determination based on the request method semantics.
3897  Furthermore, allow user agents to rewrite the method from POST to GET
3898  for status codes 301 and 302.
3899  (Sections <xref format="counter" target="status.301"/>,
3900  <xref format="counter" target="status.302"/> and
3901  <xref format="counter" target="status.307"/>)
3902</t>
3903<t>
3904  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3905  It used to indicate that the target resource must be accessed through the
3906  proxy given by the Location field. The Location field gave the URI of the
3907  proxy. The recipient was expected to repeat this single request via the proxy.
3908  (<xref target="status.305"/>)
3909</t>
3910<t>
3911  Define status 426 (Upgrade Required) (this was incorporated from
3912  <xref target="RFC2817"/>).
3913  (<xref target="status.426"/>)
3914</t>
3915<t>
3916  Change ABNF productions for header fields to only define the field value.
3917  (<xref target="header.field.definitions"/>)
3918</t>
3919<t>
3920  Reclassify "Allow" as response header field, removing the option to
3921  specify it in a PUT request.
3922  Relax the server requirement on the contents of the Allow header field and
3923  remove requirement on clients to always trust the header field value.
3924  (<xref target="header.allow"/>)
3925</t>
3926<t>
3927  The ABNF for the Expect header field has been both fixed (allowing parameters
3928  for value-less expectations as well) and simplified (allowing trailing
3929  semicolons after "100-continue" when they were invalid before).
3930  (<xref target="header.expect"/>)
3931</t>
3932<t>
3933  Correct syntax of Location header field to allow URI references (including
3934  relative references and fragments), as referred symbol "absoluteURI" wasn't
3935  what was expected, and add some clarifications as to when use of fragments
3936  would not be appropriate.
3937  (<xref target="header.location"/>)
3938</t>
3939<t>
3940  Restrict Max-Forwards header field to OPTIONS and TRACE (previously,
3941  extension methods could have used it as well).
3942  (<xref target="header.max-forwards"/>)
3943</t>
3944<t>
3945  Allow Referer field value of "about:blank" as alternative to not specifying it.
3946  (<xref target="header.referer"/>)
3947</t>
3948<t>
3949  In the description of the Server header field, the Via field
3950  was described as a SHOULD. The requirement was and is stated
3951  correctly in the description of the Via header field in &header-via;.
3952  (<xref target="header.server"/>)
3953</t>
3954</section>
3955
3956<?BEGININC p2-semantics.abnf-appendix ?>
3957<section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf">
3958<figure>
3959<artwork type="abnf" name="p2-semantics.parsed-abnf">
3960<x:ref>Allow</x:ref> = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
3961
3962<x:ref>BWS</x:ref> = &lt;BWS, defined in [Part1], Section 3.2.1&gt;
3963
3964<x:ref>Date</x:ref> = HTTP-date
3965
3966<x:ref>Expect</x:ref> = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
3967
3968<x:ref>From</x:ref> = mailbox
3969
3970<x:ref>GMT</x:ref> = %x47.4D.54 ; GMT
3971
3972<x:ref>HTTP-date</x:ref> = rfc1123-date / obs-date
3973
3974<x:ref>Location</x:ref> = URI-reference
3975
3976<x:ref>Max-Forwards</x:ref> = 1*DIGIT
3977<x:ref>Method</x:ref> = token
3978
3979<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 3.2.1&gt;
3980
3981<x:ref>RWS</x:ref> = &lt;RWS, defined in [Part1], Section 3.2.1&gt;
3982<x:ref>Reason-Phrase</x:ref> = *( HTAB / SP / VCHAR / obs-text )
3983<x:ref>Referer</x:ref> = absolute-URI / partial-URI
3984<x:ref>Retry-After</x:ref> = HTTP-date / delta-seconds
3985
3986<x:ref>Server</x:ref> = product *( RWS ( product / comment ) )
3987<x:ref>Status-Code</x:ref> = 3DIGIT
3988
3989<x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in [Part1], Section 2.7&gt;
3990<x:ref>User-Agent</x:ref> = product *( RWS ( product / comment ) )
3991
3992<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.7&gt;
3993<x:ref>asctime-date</x:ref> = day-name SP date3 SP time-of-day SP year
3994
3995<x:ref>comment</x:ref> = &lt;comment, defined in [Part1], Section 3.2.4&gt;
3996
3997<x:ref>date1</x:ref> = day SP month SP year
3998<x:ref>date2</x:ref> = day "-" month "-" 2DIGIT
3999<x:ref>date3</x:ref> = month SP ( 2DIGIT / ( SP DIGIT ) )
4000<x:ref>day</x:ref> = 2DIGIT
4001<x:ref>day-name</x:ref> = %x4D.6F.6E ; Mon
4002 / %x54.75.65 ; Tue
4003 / %x57.65.64 ; Wed
4004 / %x54.68.75 ; Thu
4005 / %x46.72.69 ; Fri
4006 / %x53.61.74 ; Sat
4007 / %x53.75.6E ; Sun
4008<x:ref>day-name-l</x:ref> = %x4D.6F.6E.64.61.79 ; Monday
4009 / %x54.75.65.73.64.61.79 ; Tuesday
4010 / %x57.65.64.6E.65.73.64.61.79 ; Wednesday
4011 / %x54.68.75.72.73.64.61.79 ; Thursday
4012 / %x46.72.69.64.61.79 ; Friday
4013 / %x53.61.74.75.72.64.61.79 ; Saturday
4014 / %x53.75.6E.64.61.79 ; Sunday
4015<x:ref>delta-seconds</x:ref> = 1*DIGIT
4016
4017<x:ref>expect-name</x:ref> = token
4018<x:ref>expect-param</x:ref> = expect-name [ BWS "=" BWS expect-value ]
4019<x:ref>expect-value</x:ref> = token / quoted-string
4020<x:ref>expectation</x:ref> = expect-name [ BWS "=" BWS expect-value ] *( OWS ";" [
4021 OWS expect-param ] )
4022
4023<x:ref>hour</x:ref> = 2DIGIT
4024
4025<x:ref>mailbox</x:ref> = &lt;mailbox, defined in [RFC5322], Section 3.4&gt;
4026<x:ref>minute</x:ref> = 2DIGIT
4027<x:ref>month</x:ref> = %x4A.61.6E ; Jan
4028 / %x46.65.62 ; Feb
4029 / %x4D.61.72 ; Mar
4030 / %x41.70.72 ; Apr
4031 / %x4D.61.79 ; May
4032 / %x4A.75.6E ; Jun
4033 / %x4A.75.6C ; Jul
4034 / %x41.75.67 ; Aug
4035 / %x53.65.70 ; Sep
4036 / %x4F.63.74 ; Oct
4037 / %x4E.6F.76 ; Nov
4038 / %x44.65.63 ; Dec
4039
4040<x:ref>obs-date</x:ref> = rfc850-date / asctime-date
4041<x:ref>obs-text</x:ref> = &lt;obs-text, defined in [Part1], Section 3.2.4&gt;
4042
4043<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.7&gt;
4044<x:ref>product</x:ref> = &lt;product, defined in [Part1], Section 5.2&gt;
4045
4046<x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in [Part1], Section 3.2.4&gt;
4047
4048<x:ref>rfc1123-date</x:ref> = day-name "," SP date1 SP time-of-day SP GMT
4049<x:ref>rfc850-date</x:ref> = day-name-l "," SP date2 SP time-of-day SP GMT
4050
4051<x:ref>second</x:ref> = 2DIGIT
4052
4053<x:ref>time-of-day</x:ref> = hour ":" minute ":" second
4054<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 3.2.4&gt;
4055
4056<x:ref>year</x:ref> = 4DIGIT
4057</artwork>
4058</figure>
4059<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
4060; Allow defined but not used
4061; Date defined but not used
4062; Expect defined but not used
4063; From defined but not used
4064; Location defined but not used
4065; Max-Forwards defined but not used
4066; Reason-Phrase defined but not used
4067; Referer defined but not used
4068; Retry-After defined but not used
4069; Server defined but not used
4070; Status-Code defined but not used
4071; User-Agent defined but not used
4072</artwork></figure></section>
4073<?ENDINC p2-semantics.abnf-appendix ?>
4074
4075<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
4076
4077<section title="Since RFC 2616">
4078<t>
4079  Extracted relevant partitions from <xref target="RFC2616"/>.
4080</t>
4081</section>
4082
4083<section title="Since draft-ietf-httpbis-p2-semantics-00">
4084<t>
4085  Closed issues:
4086  <list style="symbols"> 
4087    <t>
4088      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
4089      "Via is a MUST"
4090      (<eref target="http://purl.org/NET/http-errata#via-must"/>)
4091    </t>
4092    <t>
4093      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
4094      "Fragments allowed in Location"
4095      (<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
4096    </t>
4097    <t>
4098      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
4099      "Safe Methods vs Redirection"
4100      (<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
4101    </t>
4102    <t>
4103      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
4104      "Revise description of the POST method"
4105      (<eref target="http://purl.org/NET/http-errata#post"/>)
4106    </t>
4107    <t>
4108      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
4109      "Normative and Informative references"
4110    </t>
4111    <t>
4112      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
4113      "RFC2606 Compliance"
4114    </t>
4115    <t>
4116      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
4117      "Informative references"
4118    </t>
4119    <t>
4120      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
4121      "Redundant cross-references"
4122    </t>
4123  </list>
4124</t>
4125<t>
4126  Other changes:
4127  <list style="symbols"> 
4128    <t>
4129      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
4130    </t>
4131  </list>
4132</t>
4133</section>
4134
4135<section title="Since draft-ietf-httpbis-p2-semantics-01">
4136<t>
4137  Closed issues:
4138  <list style="symbols"> 
4139    <t>
4140      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
4141      "PUT side effects"
4142    </t>
4143    <t>
4144      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
4145      "Duplicate Host header requirements"
4146    </t>
4147  </list>
4148</t>
4149<t>
4150  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
4151  <list style="symbols"> 
4152    <t>
4153      Move "Product Tokens" section (back) into Part 1, as "token" is used
4154      in the definition of the Upgrade header field.
4155    </t>
4156    <t>
4157      Add explicit references to BNF syntax and rules imported from other parts of the specification.
4158    </t>
4159    <t>
4160      Copy definition of delta-seconds from Part6 instead of referencing it.
4161    </t>
4162  </list>
4163</t>
4164</section>
4165
4166<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
4167<t>
4168  Closed issues:
4169  <list style="symbols"> 
4170    <t>
4171      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/24"/>:
4172      "Requiring Allow in 405 responses"
4173    </t>
4174    <t>
4175      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/59"/>:
4176      "Status Code Registry"
4177    </t>
4178    <t>
4179      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/61"/>:
4180      "Redirection vs. Location"
4181    </t>
4182    <t>
4183      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/70"/>:
4184      "Cacheability of 303 response"
4185    </t>
4186    <t>
4187      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/76"/>:
4188      "305 Use Proxy"
4189    </t>
4190    <t>
4191      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
4192      "Classification for Allow header"
4193    </t>
4194    <t>
4195      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
4196      "PUT - 'store under' vs 'store at'"
4197    </t>
4198  </list>
4199</t>
4200<t>
4201  Ongoing work on IANA Message Header Field Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
4202  <list style="symbols"> 
4203    <t>
4204      Reference RFC 3984, and update header field registrations for headers defined
4205      in this document.
4206    </t>
4207  </list>
4208</t>
4209<t>
4210  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
4211  <list style="symbols"> 
4212    <t>
4213      Replace string literals when the string really is case-sensitive (method).
4214    </t>
4215  </list>
4216</t>
4217</section>
4218
4219<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
4220<t>
4221  Closed issues:
4222  <list style="symbols"> 
4223    <t>
4224      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/98"/>:
4225      "OPTIONS request bodies"
4226    </t>
4227    <t>
4228      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/119"/>:
4229      "Description of CONNECT should refer to RFC2817"
4230    </t>
4231    <t>
4232      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/125"/>:
4233      "Location Content-Location reference request/response mixup"
4234    </t>
4235  </list>
4236</t>
4237<t>
4238  Ongoing work on Method Registry (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/72"/>):
4239  <list style="symbols"> 
4240    <t>
4241      Added initial proposal for registration process, plus initial
4242      content (non-HTTP/1.1 methods to be added by a separate specification).
4243    </t>
4244  </list>
4245</t>
4246</section>
4247
4248<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
4249<t>
4250  Closed issues:
4251  <list style="symbols"> 
4252    <t>
4253      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
4254      "Content-*"
4255    </t>
4256    <t>
4257      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
4258      "RFC 2822 is updated by RFC 5322"
4259    </t>
4260  </list>
4261</t>
4262<t>
4263  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
4264  <list style="symbols"> 
4265    <t>
4266      Use "/" instead of "|" for alternatives.
4267    </t>
4268    <t>
4269      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
4270      whitespace ("OWS") and required whitespace ("RWS").
4271    </t>
4272    <t>
4273      Rewrite ABNFs to spell out whitespace rules, factor out
4274      header field value format definitions.
4275    </t>
4276  </list>
4277</t>
4278</section>
4279
4280<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
4281<t>
4282  Closed issues:
4283  <list style="symbols"> 
4284    <t>
4285      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/94"/>:
4286      "Reason-Phrase BNF"
4287    </t>
4288  </list>
4289</t>
4290<t>
4291  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
4292  <list style="symbols"> 
4293    <t>
4294      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
4295    </t>
4296  </list>
4297</t>
4298</section>
4299
4300<section title="Since draft-ietf-httpbis-p2-semantics-06" anchor="changes.since.06">
4301<t>
4302  Closed issues:
4303  <list style="symbols"> 
4304    <t>
4305      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/144"/>:
4306      "Clarify when Referer is sent"
4307    </t>
4308    <t>
4309      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/164"/>:
4310      "status codes vs methods"
4311    </t>
4312    <t>
4313      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/170"/>:
4314      "Do not require "updates" relation for specs that register status codes or method names"
4315    </t>
4316  </list>
4317</t>
4318</section>
4319
4320<section title="Since draft-ietf-httpbis-p2-semantics-07" anchor="changes.since.07">
4321<t>
4322  Closed issues:
4323  <list style="symbols"> 
4324    <t>
4325      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/27"/>:
4326      "Idempotency"
4327    </t>
4328    <t>
4329      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/33"/>:
4330      "TRACE security considerations"
4331    </t>
4332    <t>
4333      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
4334      "Clarify rules for determining what entities a response carries"
4335    </t>
4336    <t>
4337      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/140"/>:
4338      "update note citing RFC 1945 and 2068"
4339    </t>
4340    <t>
4341      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/182"/>:
4342      "update note about redirect limit"
4343    </t>
4344    <t>
4345      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/191"/>:
4346      "Location header ABNF should use 'URI'"
4347    </t>
4348    <t>
4349      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/192"/>:
4350      "fragments in Location vs status 303"
4351    </t>
4352    <t>
4353      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/198"/>:
4354      "move IANA registrations for optional status codes"
4355    </t>
4356  </list>
4357</t>
4358<t>
4359  Partly resolved issues:
4360  <list style="symbols"> 
4361    <t>
4362      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/171"/>:
4363      "Are OPTIONS and TRACE safe?"
4364    </t>
4365  </list>
4366</t>
4367</section>
4368
4369<section title="Since draft-ietf-httpbis-p2-semantics-08" anchor="changes.since.08">
4370<t>
4371  Closed issues:
4372  <list style="symbols"> 
4373    <t>
4374      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
4375      "Safe Methods vs Redirection" (we missed the introduction to the 3xx
4376      status codes when fixing this previously)
4377    </t>
4378  </list>
4379</t>
4380</section>
4381
4382<section title="Since draft-ietf-httpbis-p2-semantics-09" anchor="changes.since.09">
4383<t>
4384  Closed issues:
4385  <list style="symbols"> 
4386    <t>
4387      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
4388      "Fragment combination / precedence during redirects"
4389    </t>
4390  </list>
4391</t>
4392<t>
4393  Partly resolved issues:
4394  <list style="symbols"> 
4395    <t>
4396      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/185"/>:
4397      "Location header payload handling"
4398    </t>
4399    <t>
4400      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196"/>:
4401      "Term for the requested resource's URI"
4402    </t>
4403  </list>
4404</t>
4405</section>
4406
4407<section title="Since draft-ietf-httpbis-p2-semantics-10" anchor="changes.since.10">
4408<t>
4409  Closed issues:
4410  <list style="symbols"> 
4411    <t>
4412      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/69"/>:
4413      "Clarify 'Requested Variant'"
4414    </t>
4415    <t>
4416      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/109"/>:
4417      "Clarify entity / representation / variant terminology"
4418    </t>
4419    <t>
4420      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/139"/>:
4421      "Methods and Caching"
4422    </t>
4423    <t>
4424      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/190"/>:
4425      "OPTIONS vs Max-Forwards"
4426    </t>
4427    <t>
4428      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/199"/>:
4429      "Status codes and caching"
4430    </t>
4431    <t>
4432      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/220"/>:
4433      "consider removing the 'changes from 2068' sections"
4434    </t>
4435  </list>
4436</t>
4437</section>
4438
4439<section title="Since draft-ietf-httpbis-p2-semantics-11" anchor="changes.since.11">
4440<t>
4441  Closed issues:
4442  <list style="symbols"> 
4443    <t>
4444      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/229"/>:
4445      "Considerations for new status codes"
4446    </t>
4447    <t>
4448      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/230"/>:
4449      "Considerations for new methods"
4450    </t>
4451    <t>
4452      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/232"/>:
4453      "User-Agent guidelines" (relating to the 'User-Agent' header field)
4454    </t>
4455  </list>
4456</t>
4457</section>
4458
4459<section title="Since draft-ietf-httpbis-p2-semantics-12" anchor="changes.since.12">
4460<t>
4461  Closed issues:
4462  <list style="symbols"> 
4463    <t>
4464      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
4465      "Fragment combination / precedence during redirects" (added warning
4466      about having a fragid on the redirect may cause inconvenience in
4467      some cases)
4468    </t>
4469    <t>
4470      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/79"/>:
4471      "Content-* vs. PUT"
4472    </t>
4473    <t>
4474      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/88"/>:
4475      "205 Bodies"
4476    </t>
4477    <t>
4478      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/102"/>:
4479      "Understanding Content-* on non-PUT requests"
4480    </t>
4481    <t>
4482      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
4483      "Content-*"
4484    </t>
4485    <t>
4486      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/104"/>:
4487      "Header type defaulting"
4488    </t>
4489    <t>
4490      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
4491      "PUT - 'store under' vs 'store at'"
4492    </t>
4493    <t>
4494      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/137"/>:
4495      "duplicate ABNF for Reason-Phrase"
4496    </t>
4497    <t>
4498      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/180"/>:
4499      "Note special status of Content-* prefix in header registration procedures"
4500    </t>
4501    <t>
4502      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/203"/>:
4503      "Max-Forwards vs extension methods"
4504    </t>
4505    <t>
4506      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/213"/>:
4507      "What is the value space of HTTP status codes?" (actually fixed in
4508      draft-ietf-httpbis-p2-semantics-11)
4509    </t>
4510    <t>
4511      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/224"/>:
4512      "Header Classification"
4513    </t>
4514    <t>
4515      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/225"/>:
4516      "PUT side effect: invalidation or just stale?"
4517    </t>
4518    <t>
4519      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/226"/>:
4520      "proxies not supporting certain methods"
4521    </t>
4522    <t>
4523      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/239"/>:
4524      "Migrate CONNECT from RFC2817 to p2"
4525    </t>
4526    <t>
4527      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/240"/>:
4528      "Migrate Upgrade details from RFC2817"
4529    </t>
4530    <t>
4531      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/267"/>:
4532      "clarify PUT semantics'"
4533    </t>
4534    <t>
4535      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/275"/>:
4536      "duplicate ABNF for 'Method'"
4537    </t>
4538    <t>
4539      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
4540      "untangle ABNFs for header fields"
4541    </t>
4542  </list>
4543</t>
4544</section>
4545
4546<section title="Since draft-ietf-httpbis-p2-semantics-13" anchor="changes.since.13">
4547<t>
4548  Closed issues:
4549  <list style="symbols"> 
4550    <t>
4551      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
4552      "untangle ABNFs for header fields"
4553    </t>
4554    <t>
4555      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/251"/>:
4556      "message-body in CONNECT request"
4557    </t>
4558  </list>
4559</t>
4560</section>
4561
4562<section title="Since draft-ietf-httpbis-p2-semantics-14" anchor="changes.since.14">
4563<t>
4564  Closed issues:
4565  <list style="symbols"> 
4566    <t>
4567      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/255"/>:
4568      "Clarify status code for rate limiting"
4569    </t>
4570    <t>
4571      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/294"/>:
4572      "clarify 403 forbidden"
4573    </t>
4574    <t>
4575      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/296"/>:
4576      "Clarify 203 Non-Authoritative Information"
4577    </t>
4578    <t>
4579      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/298"/>:
4580      "update default reason phrase for 413"
4581    </t>
4582  </list>
4583</t>
4584</section>
4585
4586<section title="Since draft-ietf-httpbis-p2-semantics-15" anchor="changes.since.15">
4587<t>
4588  Closed issues:
4589  <list style="symbols"> 
4590    <t>
4591      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/285"/>:
4592      "Strength of requirements on Accept re: 406"
4593    </t>
4594    <t>
4595      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/303"/>:
4596      "400 response isn't generic"
4597    </t>
4598  </list>
4599</t>
4600</section>
4601
4602<section title="Since draft-ietf-httpbis-p2-semantics-16" anchor="changes.since.16">
4603<t>
4604  Closed issues:
4605  <list style="symbols"> 
4606    <t>
4607      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/160"/>:
4608      "Redirects and non-GET methods"
4609    </t>
4610    <t>
4611      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/186"/>:
4612      "Document HTTP's error-handling philosophy"
4613    </t>
4614    <t>
4615      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/231"/>:
4616      "Considerations for new headers"
4617    </t>
4618    <t>
4619      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/310"/>:
4620      "clarify 303 redirect on HEAD"
4621    </t>
4622  </list>
4623</t>
4624</section>
4625
4626<section title="Since draft-ietf-httpbis-p2-semantics-17" anchor="changes.since.17">
4627<t>
4628  Closed issues:
4629  <list style="symbols"> 
4630    <t>
4631      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/185"/>:
4632      "Location header payload handling"
4633    </t>
4634    <t>
4635      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/255"/>:
4636      "Clarify status code for rate limiting" (change backed out because
4637      a new status code is being defined for this purpose)
4638    </t>
4639    <t>
4640      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/312"/>:
4641      "should there be a permanent variant of 307"
4642    </t>
4643    <t>
4644      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/325"/>:
4645      "When are Location's semantics triggered?"
4646    </t>
4647    <t>
4648      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/327"/>:
4649      "'expect' grammar missing OWS"
4650    </t>
4651    <t>
4652      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/329"/>:
4653      "header field considerations: quoted-string vs use of double quotes"
4654    </t>
4655  </list>
4656</t>
4657</section>
4658
4659<section title="Since draft-ietf-httpbis-p2-semantics-18" anchor="changes.since.18">
4660<t>
4661  Closed issues:
4662  <list style="symbols"> 
4663    <t>
4664      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/238"/>:
4665      "Requirements for user intervention during redirects"
4666    </t>
4667    <t>
4668      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/295"/>:
4669      "Applying original fragment to 'plain' redirected URI"
4670    </t>
4671    <t>
4672      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/302"/>:
4673      "Misplaced text on connection handling in p2"
4674    </t>
4675    <t>
4676      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/332"/>:
4677      "relax requirements on hypertext in 3/4/5xx error responses"
4678    </t>
4679    <t>
4680      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/333"/>:
4681      "example for 426 response should have a payload"
4682    </t>
4683    <t>
4684      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/336"/>:
4685      "drop indirection entries for status codes"
4686    </t>
4687  </list>
4688</t>
4689</section>
4690
4691</section>
4692
4693</back>
4694</rfc>
Note: See TracBrowser for help on using the repository browser.