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1<?xml version="1.0" encoding="utf-8"?>
2<?xml-stylesheet type='text/xsl' href='../myxml2rfc.xslt'?>
3<!DOCTYPE rfc [
4  <!ENTITY MAY "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MAY</bcp14>">
5  <!ENTITY MUST "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST</bcp14>">
6  <!ENTITY MUST-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST NOT</bcp14>">
7  <!ENTITY OPTIONAL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>OPTIONAL</bcp14>">
8  <!ENTITY RECOMMENDED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>RECOMMENDED</bcp14>">
9  <!ENTITY REQUIRED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>REQUIRED</bcp14>">
10  <!ENTITY SHALL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL</bcp14>">
11  <!ENTITY SHALL-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL NOT</bcp14>">
12  <!ENTITY SHOULD "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD</bcp14>">
13  <!ENTITY SHOULD-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD NOT</bcp14>">
14  <!ENTITY ID-VERSION "latest">
15  <!ENTITY ID-MONTH "March">
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 abnf-extension           "<xref target='Part1' x:rel='#abnf.extension' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
21  <!ENTITY acks                     "<xref target='Part1' x:rel='#acks' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
22  <!ENTITY whitespace               "<xref target='Part1' x:rel='#whitespace' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
23  <!ENTITY field-components         "<xref target='Part1' x:rel='#field.components' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
24  <!ENTITY caching-neg-resp         "<xref target='Part6' x:rel='#caching.negotiated.responses' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
25  <!ENTITY header-transfer-encoding "<xref target='Part1' x:rel='#header.transfer-encoding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
26  <!ENTITY header-content-length    "<xref target='Part1' x:rel='#header.content-length' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
27  <!ENTITY header-content-range     "<xref target='Part5' x:rel='#header.content-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
28  <!ENTITY header-etag              "<xref target='Part4' x:rel='#header.etag' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
29  <!ENTITY header-expires           "<xref target='Part6' x:rel='#header.expires' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
30  <!ENTITY header-last-modified     "<xref target='Part4' x:rel='#header.last-modified' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
31  <!ENTITY header-user-agent        "<xref target='Part2' x:rel='#header.user-agent' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
32  <!ENTITY header-vary              "<xref target='Part6' x:rel='#header.vary' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
33  <!ENTITY message-body             "<xref target='Part1' x:rel='#message.body' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
34  <!ENTITY multipart-byteranges     "<xref target='Part5' x:rel='#internet.media.type.multipart.byteranges' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
35  <!ENTITY http-date                "<xref target='Part2' x:rel='#http.date' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
36  <!ENTITY qvalue                   "<xref target='Part1' x:rel='#quality.values' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
37  <!ENTITY uri                      "<xref target='Part1' x:rel='#uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
38  <!ENTITY effective-request-uri    "<xref target='Part1' x:rel='#effective.request.uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
39  <!ENTITY compression-codings      "<xref target='Part1' x:rel='#compression.codings' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
40  <!ENTITY transfer-codings         "<xref target='Part1' x:rel='#transfer.codings' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
41  <!ENTITY compress-coding          "<xref target='Part1' x:rel='#compress.coding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
42  <!ENTITY deflate-coding           "<xref target='Part1' x:rel='#deflate.coding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
43  <!ENTITY gzip-coding              "<xref target='Part1' x:rel='#gzip.coding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
44  <!ENTITY response-representation  "<xref target='Part2' x:rel='#identifying.response.associated.with.representation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
45]>
46<?rfc toc="yes" ?>
47<?rfc symrefs="yes" ?>
48<?rfc sortrefs="yes" ?>
49<?rfc compact="yes"?>
50<?rfc subcompact="no" ?>
51<?rfc linkmailto="no" ?>
52<?rfc editing="no" ?>
53<?rfc comments="yes"?>
54<?rfc inline="yes"?>
55<?rfc rfcedstyle="yes"?>
56<?rfc-ext allow-markup-in-artwork="yes" ?>
57<?rfc-ext include-references-in-index="yes" ?>
58<rfc obsoletes="2616" category="std" x:maturity-level="proposed"
59     ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p3-payload-&ID-VERSION;"
60     xmlns:x='http://purl.org/net/xml2rfc/ext'>
61<x:link rel="prev" basename="p2-semantics"/>
62<x:link rel="next" basename="p4-conditional"/>
63<x:feedback template="mailto:ietf-http-wg@w3.org?subject={docname},%20%22{section}%22&amp;body=&lt;{ref}&gt;:"/>
64<front>
65
66  <title abbrev="HTTP/1.1, Part 3">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
67
68  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
69    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
70    <address>
71      <postal>
72        <street>345 Park Ave</street>
73        <city>San Jose</city>
74        <region>CA</region>
75        <code>95110</code>
76        <country>USA</country>
77      </postal>
78      <email>fielding@gbiv.com</email>
79      <uri>http://roy.gbiv.com/</uri>
80    </address>
81  </author>
82
83  <author initials="J." surname="Gettys" fullname="Jim Gettys">
84    <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
85    <address>
86      <postal>
87        <street>21 Oak Knoll Road</street>
88        <city>Carlisle</city>
89        <region>MA</region>
90        <code>01741</code>
91        <country>USA</country>
92      </postal>
93      <email>jg@freedesktop.org</email>
94      <uri>http://gettys.wordpress.com/</uri>
95    </address>
96  </author>
97 
98  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
99    <organization abbrev="HP">Hewlett-Packard Company</organization>
100    <address>
101      <postal>
102        <street>HP Labs, Large Scale Systems Group</street>
103        <street>1501 Page Mill Road, MS 1177</street>
104        <city>Palo Alto</city>
105        <region>CA</region>
106        <code>94304</code>
107        <country>USA</country>
108      </postal>
109      <email>JeffMogul@acm.org</email>
110    </address>
111  </author>
112
113  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
114    <organization abbrev="Microsoft">Microsoft Corporation</organization>
115    <address>
116      <postal>
117        <street>1 Microsoft Way</street>
118        <city>Redmond</city>
119        <region>WA</region>
120        <code>98052</code>
121        <country>USA</country>
122      </postal>
123      <email>henrikn@microsoft.com</email>
124    </address>
125  </author>
126
127  <author initials="L." surname="Masinter" fullname="Larry Masinter">
128    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
129    <address>
130      <postal>
131        <street>345 Park Ave</street>
132        <city>San Jose</city>
133        <region>CA</region>
134        <code>95110</code>
135        <country>USA</country>
136      </postal>
137      <email>LMM@acm.org</email>
138      <uri>http://larry.masinter.net/</uri>
139    </address>
140  </author>
141 
142  <author initials="P." surname="Leach" fullname="Paul J. Leach">
143    <organization abbrev="Microsoft">Microsoft Corporation</organization>
144    <address>
145      <postal>
146        <street>1 Microsoft Way</street>
147        <city>Redmond</city>
148        <region>WA</region>
149        <code>98052</code>
150      </postal>
151      <email>paulle@microsoft.com</email>
152    </address>
153  </author>
154   
155  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
156    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
157    <address>
158      <postal>
159        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
160        <street>The Stata Center, Building 32</street>
161        <street>32 Vassar Street</street>
162        <city>Cambridge</city>
163        <region>MA</region>
164        <code>02139</code>
165        <country>USA</country>
166      </postal>
167      <email>timbl@w3.org</email>
168      <uri>http://www.w3.org/People/Berners-Lee/</uri>
169    </address>
170  </author>
171
172  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
173    <organization abbrev="W3C">World Wide Web Consortium</organization>
174    <address>
175      <postal>
176        <street>W3C / ERCIM</street>
177        <street>2004, rte des Lucioles</street>
178        <city>Sophia-Antipolis</city>
179        <region>AM</region>
180        <code>06902</code>
181        <country>France</country>
182      </postal>
183      <email>ylafon@w3.org</email>
184      <uri>http://www.raubacapeu.net/people/yves/</uri>
185    </address>
186  </author>
187
188  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
189    <organization abbrev="greenbytes">greenbytes GmbH</organization>
190    <address>
191      <postal>
192        <street>Hafenweg 16</street>
193        <city>Muenster</city><region>NW</region><code>48155</code>
194        <country>Germany</country>
195      </postal>
196      <phone>+49 251 2807760</phone>
197      <facsimile>+49 251 2807761</facsimile>
198      <email>julian.reschke@greenbytes.de</email>
199      <uri>http://greenbytes.de/tech/webdav/</uri>
200    </address>
201  </author>
202
203  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
204  <workgroup>HTTPbis Working Group</workgroup>
205
206<abstract>
207<t>
208   The Hypertext Transfer Protocol (HTTP) is an application-level protocol for
209   distributed, collaborative, hypertext information systems. HTTP has been in
210   use by the World Wide Web global information initiative since 1990. This
211   document is Part 3 of the seven-part specification that defines the protocol
212   referred to as "HTTP/1.1" and, taken together, obsoletes RFC 2616.
213</t>
214<t>
215   Part 3 defines HTTP message content, metadata, and content negotiation.
216</t>
217</abstract>
218
219<note title="Editorial Note (To be removed by RFC Editor)">
220  <t>
221    Discussion of this draft should take place on the HTTPBIS working group
222    mailing list (ietf-http-wg@w3.org), which is archived at
223    <eref target="http://lists.w3.org/Archives/Public/ietf-http-wg/"/>.
224  </t>
225  <t>
226    The current issues list is at
227    <eref target="http://tools.ietf.org/wg/httpbis/trac/report/3"/> and related
228    documents (including fancy diffs) can be found at
229    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
230  </t>
231  <t>
232    The changes in this draft are summarized in <xref target="changes.since.18"/>.
233  </t>
234</note>
235</front>
236<middle>
237<section title="Introduction" anchor="introduction">
238<t>
239   This document defines HTTP/1.1 message payloads (a.k.a., content), the
240   associated metadata header fields that define how the payload is intended
241   to be interpreted by a recipient, the request header fields that
242   might influence content selection, and the various selection algorithms
243   that are collectively referred to as HTTP content negotiation.
244</t>
245<t>
246   This document is currently disorganized in order to minimize the changes
247   between drafts and enable reviewers to see the smaller errata changes.
248   A future draft will reorganize the sections to better reflect the content.
249   In particular, the sections on entities will be renamed payload and moved
250   to the first half of the document, while the sections on content negotiation
251   and associated request header fields will be moved to the second half.  The
252   current mess reflects how widely dispersed these topics and associated
253   requirements had become in <xref target="RFC2616"/>.
254</t>
255
256<section title="Terminology" anchor="terminology">
257<t>
258   This specification uses a number of terms to refer to the roles
259   played by participants in, and objects of, the HTTP communication.
260</t>
261<t>
262  <iref item="content negotiation"/>
263  <x:dfn>content negotiation</x:dfn>
264  <list>
265    <t>
266      The mechanism for selecting the appropriate representation when
267      servicing a request. The representation in any response
268      can be negotiated (including error responses).
269    </t>
270  </list>
271</t>
272<t>
273  <iref primary="true" item="selected representation"/>
274  <x:dfn>selected representation</x:dfn>
275  <list>
276    <t>
277      The current representation of the target resource that would have been
278      selected in a successful response if the same request had used the
279      method GET and excluded any conditional request header fields.
280    </t>
281  </list>
282</t>
283</section>
284
285<section title="Conformance and Error Handling" anchor="intro.conformance.and.error.handling">
286<t>
287   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
288   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
289   document are to be interpreted as described in <xref target="RFC2119"/>.
290</t>
291<t>
292   This document defines conformance criteria for several roles in HTTP
293   communication, including Senders, Recipients, Clients, Servers, User-Agents,
294   Origin Servers, Intermediaries, Proxies and Gateways. See &architecture;
295   for definitions of these terms.
296</t>
297<t>
298   An implementation is considered conformant if it complies with all of the
299   requirements associated with its role(s). Note that SHOULD-level requirements
300   are relevant here, unless one of the documented exceptions is applicable.
301</t>
302<t>
303   This document also uses ABNF to define valid protocol elements
304   (<xref target="notation"/>). In addition to the prose requirements placed
305   upon them, Senders &MUST-NOT; generate protocol elements that are invalid.
306</t>
307<t>
308   Unless noted otherwise, Recipients &MAY; take steps to recover a usable
309   protocol element from an invalid construct. However, HTTP does not define
310   specific error handling mechanisms, except in cases where it has direct
311   impact on security. This is because different uses of the protocol require
312   different error handling strategies; for example, a Web browser may wish to
313   transparently recover from a response where the Location header field
314   doesn't parse according to the ABNF, whereby in a systems control protocol
315   using HTTP, this type of error recovery could lead to dangerous consequences.
316</t>
317</section>
318
319<section title="Syntax Notation" anchor="notation">
320  <x:anchor-alias value="ALPHA"/>
321  <x:anchor-alias value="CR"/>
322  <x:anchor-alias value="DIGIT"/>
323  <x:anchor-alias value="LF"/>
324  <x:anchor-alias value="OCTET"/>
325  <x:anchor-alias value="VCHAR"/>
326<t>
327   This specification uses the Augmented Backus-Naur Form (ABNF) notation
328   of <xref target="RFC5234"/> with the list rule extension defined in
329   &notation;<xref target="collected.abnf"/> shows the collected ABNF
330   with the list rule expanded.
331</t>
332<t>
333  The following core rules are included by
334  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
335  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
336  DIGIT (decimal 0-9), DQUOTE (double quote),
337  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
338  OCTET (any 8-bit sequence of data), SP (space), and
339  VCHAR (any visible US-ASCII character).
340</t>
341
342<section title="Core Rules" anchor="core.rules">
343  <x:anchor-alias value="token"/>
344  <x:anchor-alias value="word"/>
345  <x:anchor-alias value="OWS"/>
346<t>
347  The core rules below are defined in <xref target="Part1"/>:
348</t>
349<figure><artwork type="abnf2616">
350  <x:ref>OWS</x:ref>            = &lt;OWS, defined in &whitespace;&gt;
351  <x:ref>token</x:ref>          = &lt;token, defined in &field-components;&gt;
352  <x:ref>word</x:ref>           = &lt;word, defined in &field-components;&gt;
353</artwork></figure>
354</section>
355
356<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
357  <x:anchor-alias value="absolute-URI"/>
358  <x:anchor-alias value="partial-URI"/>
359  <x:anchor-alias value="qvalue"/>
360<t>
361  The ABNF rules below are defined in other parts:
362</t>
363<figure><!--Part1--><artwork type="abnf2616">
364  <x:ref>absolute-URI</x:ref>   = &lt;absolute-URI, defined in &uri;&gt;
365  <x:ref>partial-URI</x:ref>    = &lt;partial-URI, defined in &uri;&gt;
366  <x:ref>qvalue</x:ref>         = &lt;qvalue, defined in &qvalue;&gt;
367</artwork></figure>
368</section>
369
370</section>
371
372</section>
373
374<section title="Protocol Parameters" anchor="protocol.parameters">
375
376<section title="Character Encodings (charset)" anchor="character.sets">
377<t>
378   HTTP uses charset names to indicate the character encoding of a
379   textual representation.
380</t>
381<t anchor="rule.charset">
382  <x:anchor-alias value="charset"/>
383   A character encoding is identified by a case-insensitive token. The
384   complete set of tokens is defined by the IANA Character Set registry
385   (<eref target="http://www.iana.org/assignments/character-sets"/>).
386</t>
387<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="charset"/>
388  <x:ref>charset</x:ref> = <x:ref>token</x:ref>
389</artwork></figure>
390<t>
391   Although HTTP allows an arbitrary token to be used as a charset
392   value, any token that has a predefined value within the IANA
393   Character Set registry &MUST; represent the character encoding defined
394   by that registry. Applications &SHOULD; limit their use of character
395   encodings to those defined within the IANA registry.
396</t>
397<t>
398   HTTP uses charset in two contexts: within an Accept-Charset request
399   header field (in which the charset value is an unquoted token) and as the
400   value of a parameter in a Content-Type header field (within a request or
401   response), in which case the parameter value of the charset parameter
402   can be quoted.
403</t>
404<t>
405   Implementors need to be aware of IETF character set requirements <xref target="RFC3629"/>
406   <xref target="RFC2277"/>.
407</t>
408</section>
409
410<section title="Content Codings" anchor="content.codings">
411  <x:anchor-alias value="content-coding"/>
412<t>
413   Content coding values indicate an encoding transformation that has
414   been or can be applied to a representation. Content codings are primarily
415   used to allow a representation to be compressed or otherwise usefully
416   transformed without losing the identity of its underlying media type
417   and without loss of information. Frequently, the representation is stored in
418   coded form, transmitted directly, and only decoded by the recipient.
419</t>
420<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="content-coding"/>
421  <x:ref>content-coding</x:ref>   = <x:ref>token</x:ref>
422</artwork></figure>
423<t>
424   All content-coding values are case-insensitive. HTTP/1.1 uses
425   content-coding values in the Accept-Encoding (<xref target="header.accept-encoding"/>) and
426   Content-Encoding (<xref target="header.content-encoding"/>) header fields. Although the value
427   describes the content-coding, what is more important is that it
428   indicates what decoding mechanism will be required to remove the
429   encoding.
430</t>
431<t>
432   compress<iref item="compress (Coding Format)"/><iref item="Coding Format" subitem="compress"/>
433  <list>
434    <t>
435      See &compress-coding;.
436    </t>
437  </list>
438</t>
439<t>
440   deflate<iref item="deflate (Coding Format)"/><iref item="Coding Format" subitem="deflate"/>
441  <list>
442    <t>
443      See &deflate-coding;.
444    </t>
445  </list>
446</t>
447<t>
448   gzip<iref item="gzip (Coding Format)"/><iref item="Coding Format" subitem="gzip"/>
449  <list>
450    <t>
451      See &gzip-coding;.
452    </t>
453  </list>
454</t>
455
456<section title="Content Coding Registry" anchor="content.coding.registry">
457<t>
458   The HTTP Content Coding Registry defines the name space for the content
459   coding names.
460</t>
461<t>
462   Registrations &MUST; include the following fields:
463   <list style="symbols">
464     <t>Name</t>
465     <t>Description</t>
466     <t>Pointer to specification text</t>
467   </list>
468</t>
469<t>
470   Names of content codings &MUST-NOT; overlap with names of transfer codings
471   (&transfer-codings;), unless the encoding transformation is identical (as
472   is the case for the compression codings defined in
473   &compression-codings;).
474</t>
475<t>
476   Values to be added to this name space require IETF Review
477   (see <xref target="RFC5226" x:fmt="of" x:sec="4.1"/>), and &MUST;
478   conform to the purpose of content coding defined in this section.
479</t>
480<t>
481   The registry itself is maintained at
482   <eref target="http://www.iana.org/assignments/http-parameters"/>.
483</t>
484</section>
485
486</section>
487
488<section title="Media Types" anchor="media.types">
489  <x:anchor-alias value="media-type"/>
490  <x:anchor-alias value="type"/>
491  <x:anchor-alias value="subtype"/>
492<t>
493   HTTP uses Internet Media Types <xref target="RFC2046"/> in the Content-Type (<xref target="header.content-type"/>)
494   and Accept (<xref target="header.accept"/>) header fields in order to provide
495   open and extensible data typing and type negotiation.
496</t>
497<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="media-type"/><iref primary="true" item="Grammar" subitem="type"/><iref primary="true" item="Grammar" subitem="subtype"/>
498  <x:ref>media-type</x:ref> = <x:ref>type</x:ref> "/" <x:ref>subtype</x:ref> *( <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> <x:ref>parameter</x:ref> )
499  <x:ref>type</x:ref>       = <x:ref>token</x:ref>
500  <x:ref>subtype</x:ref>    = <x:ref>token</x:ref>
501</artwork></figure>
502<t anchor="rule.parameter">
503  <x:anchor-alias value="attribute"/>
504  <x:anchor-alias value="parameter"/>
505  <x:anchor-alias value="value"/>
506   The type/subtype &MAY; be followed by parameters in the form of
507   attribute/value pairs.
508</t>
509<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="parameter"/><iref primary="true" item="Grammar" subitem="attribute"/><iref primary="true" item="Grammar" subitem="value"/>
510  <x:ref>parameter</x:ref>      = <x:ref>attribute</x:ref> "=" <x:ref>value</x:ref>
511  <x:ref>attribute</x:ref>      = <x:ref>token</x:ref>
512  <x:ref>value</x:ref>          = <x:ref>word</x:ref>
513</artwork></figure>
514<t>
515   The type, subtype, and parameter attribute names are case-insensitive.
516   Parameter values might or might not be case-sensitive, depending on the
517   semantics of the parameter name.  The presence or absence of a parameter might
518   be significant to the processing of a media-type, depending on its
519   definition within the media type registry.
520</t>
521<t>
522   A parameter value that matches the <x:ref>token</x:ref> production can be
523   transmitted as either a token or within a quoted-string. The quoted and
524   unquoted values are equivalent.
525</t>
526<t>
527   Note that some older HTTP applications do not recognize media type
528   parameters. When sending data to older HTTP applications,
529   implementations &SHOULD; only use media type parameters when they are
530   required by that type/subtype definition.
531</t>
532<t>
533   Media-type values are registered with the Internet Assigned Number
534   Authority (IANA). The media type registration process is
535   outlined in <xref target="RFC4288"/>. Use of non-registered media types is
536   discouraged.
537</t>
538
539<section title="Canonicalization and Text Defaults" anchor="canonicalization.and.text.defaults">
540<t>
541   Internet media types are registered with a canonical form. A
542   representation transferred via HTTP messages &MUST; be in the
543   appropriate canonical form prior to its transmission except for
544   "text" types, as defined in the next paragraph.
545</t>
546<t>
547   When in canonical form, media subtypes of the "text" type use CRLF as
548   the text line break. HTTP relaxes this requirement and allows the
549   transport of text media with plain CR or LF alone representing a line
550   break when it is done consistently for an entire representation. HTTP
551   applications &MUST; accept CRLF, bare CR, and bare LF as indicating
552   a line break in text media received via HTTP. In
553   addition, if the text is in a character encoding that does not
554   use octets 13 and 10 for CR and LF respectively, as is the case for
555   some multi-byte character encodings, HTTP allows the use of whatever octet
556   sequences are defined by that character encoding to represent the
557   equivalent of CR and LF for line breaks. This flexibility regarding
558   line breaks applies only to text media in the payload body; a bare CR
559   or LF &MUST-NOT; be substituted for CRLF within any of the HTTP control
560   structures (such as header fields and multipart boundaries).
561</t>
562<t>
563   If a representation is encoded with a content-coding, the underlying
564   data &MUST; be in a form defined above prior to being encoded.
565</t>
566</section>
567
568<section title="Multipart Types" anchor="multipart.types">
569<t>
570   MIME provides for a number of "multipart" types &mdash; encapsulations of
571   one or more representations within a single message body. All multipart
572   types share a common syntax, as defined in <xref target="RFC2046" x:sec="5.1.1" x:fmt="of"/>,
573   and &MUST; include a boundary parameter as part of the media type
574   value. The message body is itself a protocol element and &MUST;
575   therefore use only CRLF to represent line breaks between body-parts.
576</t>
577<t>
578   In general, HTTP treats a multipart message body no differently than
579   any other media type: strictly as payload.  HTTP does not use the
580   multipart boundary as an indicator of message body length.
581   <!-- jre: re-insert removed text pointing to caching? -->
582   In all other respects, an HTTP user agent &SHOULD; follow the same or similar
583   behavior as a MIME user agent would upon receipt of a multipart type.
584   The MIME header fields within each body-part of a multipart message body
585   do not have any significance to HTTP beyond that defined by
586   their MIME semantics.
587</t>
588<t>
589   If an application receives an unrecognized multipart subtype, the
590   application &MUST; treat it as being equivalent to "multipart/mixed".
591</t>
592<x:note>
593  <t>
594    <x:h>Note:</x:h> The "multipart/form-data" type has been specifically defined
595    for carrying form data suitable for processing via the POST
596    request method, as described in <xref target="RFC2388"/>.
597  </t>
598</x:note>
599</section>
600</section>
601
602<section title="Language Tags" anchor="language.tags">
603  <x:anchor-alias value="language-tag"/>
604<t>
605   A language tag, as defined in <xref target="RFC5646"/>, identifies a
606   natural language spoken, written, or otherwise conveyed by human beings for
607   communication of information to other human beings. Computer languages are
608   explicitly excluded. HTTP uses language tags within the Accept-Language and
609   Content-Language fields.
610</t>
611<t>
612   In summary, a language tag is composed of one or more parts: A primary
613   language subtag followed by a possibly empty series of subtags:
614</t>
615<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="language-tag"/>
616  <x:ref>language-tag</x:ref> = &lt;Language-Tag, defined in <xref target="RFC5646" x:sec="2.1"/>&gt;
617</artwork></figure>
618<t>
619   White space is not allowed within the tag and all tags are case-insensitive.
620   The name space of language subtags is administered by the IANA (see
621   <eref target="http://www.iana.org/assignments/language-subtag-registry"/>).
622</t>
623<figure>
624  <preamble>Example tags include:</preamble>
625<artwork type="example">
626  en, en-US, es-419, az-Arab, x-pig-latin, man-Nkoo-GN
627</artwork>
628</figure>
629<t>
630   See <xref target="RFC5646"/> for further information.
631</t>
632</section>
633</section>
634
635<section title="Payload" anchor="payload">
636<t>
637   HTTP messages &MAY; transfer a payload if not otherwise restricted by
638   the request method or response status code.  The payload consists of
639   metadata, in the form of header fields, and data, in the form of the
640   sequence of octets in the message body after any transfer-coding has
641   been decoded.
642</t>
643<iref item="payload"/>
644<t>   
645   A "<x:dfn>payload</x:dfn>" in HTTP is always a partial or complete
646   representation of some resource.  We use separate terms for payload
647   and representation because some messages contain only the associated
648   representation's header fields (e.g., responses to HEAD) or only some
649   part(s) of the representation (e.g., the 206 status code).
650</t>
651<section title="Payload Header Fields" anchor="payload.header.fields">
652  <x:anchor-alias value="payload-header"/>
653<t>
654   HTTP header fields that specifically define the payload, rather than the
655   associated representation, are referred to as "payload header fields".
656   The following payload header fields are defined by HTTP/1.1:
657</t>
658<texttable align="left">
659  <ttcol>Header Field Name</ttcol>
660  <ttcol>Defined in...</ttcol>
661
662  <c>Content-Length</c> <c>&header-content-length;</c>
663  <c>Content-Range</c> <c>&header-content-range;</c>
664</texttable>
665</section>
666
667<section title="Payload Body" anchor="payload.body">
668  <x:anchor-alias value="payload-body"/>
669<t>
670   A payload body is only present in a message when a message body is
671   present, as described in &message-body;. The payload body is obtained
672   from the message body by decoding any Transfer-Encoding that might
673   have been applied to ensure safe and proper transfer of the message.
674</t>
675</section>
676</section>
677
678<section title="Representation" anchor="representation">
679<iref item="representation"/>
680<t>
681   A "<x:dfn>representation</x:dfn>" is information in a format that can be readily
682   communicated from one party to another.  A resource representation
683   is information that reflects the state of that resource, as observed
684   at some point in the past (e.g., in a response to GET) or to be
685   desired at some point in the future (e.g., in a PUT request).
686</t>
687<t>
688   Most, but not all, representations transferred via HTTP are intended
689   to be a representation of the target resource (the resource identified
690   by the effective request URI).  The precise semantics of a representation
691   are determined by the type of message (request or response), the request
692   method, the response status code, and the representation metadata.
693   For example, the above semantic is true for the representation in any
694   200 (OK) response to GET and for the representation in any PUT request.
695   A 200 response to PUT, in contrast, contains either a representation
696   that describes the successful action or a representation of the target
697   resource, with the latter indicated by a Content-Location header field
698   with the same value as the effective request URI.  Likewise, response
699   messages with an error status code usually contain a representation that
700   describes the error and what next steps are suggested for resolving it.
701</t>
702
703<section title="Representation Header Fields" anchor="representation.header.fields">
704  <x:anchor-alias value="representation-header"/>
705<t>
706   Representation header fields define metadata about the representation data
707   enclosed in the message body or, if no message body is present, about
708   the representation that would have been transferred in a 200 response
709   to a simultaneous GET request with the same effective request URI.
710</t>
711<t>
712   The following header fields are defined as representation metadata:
713</t>
714<texttable align="left">
715  <ttcol>Header Field Name</ttcol>
716  <ttcol>Defined in...</ttcol>
717
718  <c>Content-Encoding</c> <c><xref target="header.content-encoding"/></c>
719  <c>Content-Language</c> <c><xref target="header.content-language"/></c>
720  <c>Content-Location</c> <c><xref target="header.content-location"/></c>
721  <c>Content-Type</c> <c><xref target="header.content-type"/></c>
722  <c>Expires</c> <c>&header-expires;</c>
723</texttable>
724<t>
725   Additional header fields define metadata about the selected
726   representation, which might differ from the representation included
727   in the message for responses to some state-changing methods.
728   The following header fields are defined as selected representation
729   metadata:
730</t>
731<texttable align="left">
732  <ttcol>Header Field Name</ttcol>
733  <ttcol>Defined in...</ttcol>
734
735  <c>ETag</c> <c>&header-etag;</c>
736  <c>Last-Modified</c> <c>&header-last-modified;</c>
737</texttable>
738</section>
739
740<section title="Representation Data" anchor="representation.data">
741  <x:anchor-alias value="representation-data"/>
742<t>
743   The representation body associated with an HTTP message is
744   either provided as the payload body of the message or
745   referred to by the message semantics and the effective request
746   URI.  The representation data is in a format and encoding defined by
747   the representation metadata header fields.
748</t>
749<t>
750   The data type of the representation data
751   is determined via the header fields Content-Type and Content-Encoding.
752   These define a two-layer, ordered encoding model:
753</t>
754<figure><artwork type="example">
755  representation-data := Content-Encoding( Content-Type( bits ) )
756</artwork></figure>
757<t>
758   Content-Type specifies the media type of the underlying data, which
759   defines both the data format and how that data &SHOULD; be processed
760   by the recipient (within the scope of the request method semantics).
761   Any HTTP/1.1 message containing a payload body &SHOULD; include a
762   Content-Type header field defining the media type of the associated
763   representation unless that metadata is unknown to the sender.
764   If the Content-Type header field is not present, it indicates that
765   the sender does not know the media type of the representation;
766   recipients &MAY; either assume that the media type is
767   "application/octet-stream" (<xref target="RFC2046" x:fmt="," x:sec="4.5.1"/>)
768   or examine the content to determine its type.
769</t>
770<t>
771   In practice, resource owners do not always properly configure their origin
772   server to provide the correct Content-Type for a given representation,
773   with the result that some clients will examine a response body's content
774   and override the specified type.
775   Clients that do so risk drawing incorrect conclusions, which might expose
776   additional security risks (e.g., "privilege escalation").  Furthermore,
777   it is impossible to determine the sender's intent by examining the data
778   format: many data formats match multiple media types that differ only in
779   processing semantics.  Implementers are encouraged to provide a means of
780   disabling such "content sniffing" when it is used.
781</t>
782<t>
783   Content-Encoding is used to indicate any additional content
784   codings applied to the data, usually for the purpose of data
785   compression, that are a property of the representation.  If
786   Content-Encoding is not present, then there is no additional
787   encoding beyond that defined by the Content-Type.
788</t>
789</section>
790</section>
791
792<section title="Content Negotiation" anchor="content.negotiation">
793<t>
794   HTTP responses include a representation which contains information for
795   interpretation, whether by a human user or for further processing.
796   Often, the server has different ways of representing the
797   same information; for example, in different formats, languages,
798   or using different character encodings.
799</t>
800<t>
801   HTTP clients and their users might have different or variable
802   capabilities, characteristics or preferences which would influence
803   which representation, among those available from the server,
804   would be best for the server to deliver. For this reason, HTTP
805   provides mechanisms for "content negotiation" &mdash; a process of
806   allowing selection of a representation of a given resource,
807   when more than one is available.
808</t>
809<t>
810   This specification defines two patterns of content negotiation;
811   "server-driven", where the server selects the representation based
812   upon the client's stated preferences, and "agent-driven" negotiation,
813   where the server provides a list of representations for the client to
814   choose from, based upon their metadata. In addition,  there are
815   other patterns: some applications use an "active content" pattern,
816   where the server returns active content which runs on the client
817   and, based on client available parameters, selects additional
818   resources to invoke. "Transparent Content Negotiation" (<xref target="RFC2295"/>)
819   has also been proposed.
820</t>
821<t>
822   These patterns are all widely used, and have trade-offs in applicability
823   and practicality. In particular, when the number of preferences or
824   capabilities to be expressed by a client are large (such as when many
825   different formats are supported by a user-agent), server-driven
826   negotiation becomes unwieldy, and might not be appropriate. Conversely,
827   when the number of representations to choose from is very large,
828   agent-driven negotiation might not be appropriate.
829</t>
830<t>
831   Note that in all cases, the supplier of representations has the
832   responsibility for determining which representations might be
833   considered to be the "same information".
834</t>
835
836<section title="Server-driven Negotiation" anchor="server-driven.negotiation">
837<t>
838   If the selection of the best representation for a response is made by
839   an algorithm located at the server, it is called server-driven
840   negotiation. Selection is based on the available representations of
841   the response (the dimensions over which it can vary; e.g., language,
842   content-coding, etc.) and the contents of particular header fields in
843   the request message or on other information pertaining to the request
844   (such as the network address of the client).
845</t>
846<t>
847   Server-driven negotiation is advantageous when the algorithm for
848   selecting from among the available representations is difficult to
849   describe to the user agent, or when the server desires to send its
850   "best guess" to the client along with the first response (hoping to
851   avoid the round-trip delay of a subsequent request if the "best
852   guess" is good enough for the user). In order to improve the server's
853   guess, the user agent &MAY; include request header fields (Accept,
854   Accept-Language, Accept-Encoding, etc.) which describe its
855   preferences for such a response.
856</t>
857<t>
858   Server-driven negotiation has disadvantages:
859  <list style="numbers">
860    <t>
861         It is impossible for the server to accurately determine what
862         might be "best" for any given user, since that would require
863         complete knowledge of both the capabilities of the user agent
864         and the intended use for the response (e.g., does the user want
865         to view it on screen or print it on paper?).
866    </t>
867    <t>
868         Having the user agent describe its capabilities in every
869         request can be both very inefficient (given that only a small
870         percentage of responses have multiple representations) and a
871         potential violation of the user's privacy.
872    </t>
873    <t>
874         It complicates the implementation of an origin server and the
875         algorithms for generating responses to a request.
876    </t>
877    <t>
878         It might limit a public cache's ability to use the same response
879         for multiple user's requests.
880    </t>
881  </list>
882</t>
883<t>
884   Server-driven negotiation allows the user agent to specify its preferences,
885   but it cannot expect responses to always honor them. For example, the origin
886   server might not implement server-driven negotiation, or it might decide that
887   sending a response that doesn't conform to them is better than sending a 406
888   (Not Acceptable) response.
889</t>
890<t>
891   Many of the mechanisms for expressing preferences use quality values to
892   declare relative preference. See &qvalue; for more information.
893</t>
894<t>
895   HTTP/1.1 includes the following header fields for enabling
896   server-driven negotiation through description of user agent
897   capabilities and user preferences: Accept (<xref target="header.accept"/>), Accept-Charset
898   (<xref target="header.accept-charset"/>), Accept-Encoding (<xref target="header.accept-encoding"/>), Accept-Language
899   (<xref target="header.accept-language"/>), and User-Agent (&header-user-agent;).
900   However, an origin server is not limited to these dimensions and &MAY; vary
901   the response based on any aspect of the request, including aspects
902   of the connection (e.g., IP address) or information within extension
903   header fields not defined by this specification.
904</t>
905<x:note>
906  <t>
907    <x:h>Note:</x:h> In practice, User-Agent based negotiation is fragile,
908    because new clients might not be recognized.
909  </t>
910</x:note>
911<t>
912   The Vary header field (&header-vary;) can be used to express the parameters the
913   server uses to select a representation that is subject to server-driven
914   negotiation.
915</t>
916</section>
917
918<section title="Agent-driven Negotiation" anchor="agent-driven.negotiation">
919<t>
920   With agent-driven negotiation, selection of the best representation
921   for a response is performed by the user agent after receiving an
922   initial response from the origin server. Selection is based on a list
923   of the available representations of the response included within the
924   header fields or body of the initial response, with each
925   representation identified by its own URI. Selection from among the
926   representations can be performed automatically (if the user agent is
927   capable of doing so) or manually by the user selecting from a
928   generated (possibly hypertext) menu.
929</t>
930<t>
931   Agent-driven negotiation is advantageous when the response would vary
932   over commonly-used dimensions (such as type, language, or encoding),
933   when the origin server is unable to determine a user agent's
934   capabilities from examining the request, and generally when public
935   caches are used to distribute server load and reduce network usage.
936</t>
937<t>
938   Agent-driven negotiation suffers from the disadvantage of needing a
939   second request to obtain the best alternate representation. This
940   second request is only efficient when caching is used. In addition,
941   this specification does not define any mechanism for supporting
942   automatic selection, though it also does not prevent any such
943   mechanism from being developed as an extension and used within
944   HTTP/1.1.
945</t>
946<t>
947   This specification defines the 300 (Multiple Choices) and 406 (Not Acceptable)
948   status codes for enabling agent-driven negotiation when the server is
949   unwilling or unable to provide a varying response using server-driven
950   negotiation.
951</t>
952</section>
953</section>
954
955<section title="Header Field Definitions" anchor="header.field.definitions">
956<t>
957   This section defines the syntax and semantics of HTTP/1.1 header fields
958   related to the payload of messages.
959</t>
960
961<section title="Accept" anchor="header.accept">
962  <iref primary="true" item="Accept header field" x:for-anchor=""/>
963  <iref primary="true" item="Header Fields" subitem="Accept" x:for-anchor=""/>
964  <x:anchor-alias value="Accept"/>
965  <x:anchor-alias value="accept-ext"/>
966  <x:anchor-alias value="accept-params"/>
967  <x:anchor-alias value="media-range"/>
968<t>
969   The "Accept" header field can be used by user agents to specify
970   response media types that are acceptable. Accept header fields can be used to
971   indicate that the request is specifically limited to a small set of desired
972   types, as in the case of a request for an in-line image.
973</t>
974<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Accept"/><iref primary="true" item="Grammar" subitem="media-range"/><iref primary="true" item="Grammar" subitem="accept-params"/><iref primary="true" item="Grammar" subitem="accept-ext"/>
975  <x:ref>Accept</x:ref> = #( <x:ref>media-range</x:ref> [ <x:ref>accept-params</x:ref> ] )
976 
977  <x:ref>media-range</x:ref>    = ( "*/*"
978                   / ( <x:ref>type</x:ref> "/" "*" )
979                   / ( <x:ref>type</x:ref> "/" <x:ref>subtype</x:ref> )
980                   ) *( <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> <x:ref>parameter</x:ref> )
981  <x:ref>accept-params</x:ref>  = <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> "q=" <x:ref>qvalue</x:ref> *( <x:ref>accept-ext</x:ref> )
982  <x:ref>accept-ext</x:ref>     = <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> <x:ref>token</x:ref> [ "=" <x:ref>word</x:ref> ]
983</artwork></figure>
984<t>
985   The asterisk "*" character is used to group media types into ranges,
986   with "*/*" indicating all media types and "type/*" indicating all
987   subtypes of that type. The media-range &MAY; include media type
988   parameters that are applicable to that range.
989</t>
990<t>
991   Each media-range &MAY; be followed by one or more accept-params,
992   beginning with the "q" parameter for indicating a relative quality
993   factor. The first "q" parameter (if any) separates the media-range
994   parameter(s) from the accept-params. Quality factors allow the user
995   or user agent to indicate the relative degree of preference for that
996   media-range, using the qvalue scale from 0 to 1 (&qvalue;). The
997   default value is q=1.
998</t>
999<x:note>
1000  <t>
1001    <x:h>Note:</x:h> Use of the "q" parameter name to separate media type
1002    parameters from Accept extension parameters is due to historical
1003    practice. Although this prevents any media type parameter named
1004    "q" from being used with a media range, such an event is believed
1005    to be unlikely given the lack of any "q" parameters in the IANA
1006    media type registry and the rare usage of any media type
1007    parameters in Accept. Future media types are discouraged from
1008    registering any parameter named "q".
1009  </t>
1010</x:note>
1011<t>
1012   The example
1013</t>
1014<figure><artwork type="example">
1015  Accept: audio/*; q=0.2, audio/basic
1016</artwork></figure>
1017<t>
1018   &SHOULD; be interpreted as "I prefer audio/basic, but send me any audio
1019   type if it is the best available after an 80% mark-down in quality".
1020</t>
1021<t>
1022   A request without any Accept header field implies that the user agent
1023   will accept any media type in response.
1024   If an Accept header field is present in a request and none of the
1025   available representations for the response have a media type that is
1026   listed as acceptable, the origin server &MAY; either
1027   honor the Accept header field by sending a 406 (Not Acceptable) response
1028   or disregard the Accept header field by treating the response as if
1029   it is not subject to content negotiation.
1030</t>
1031<t>
1032   A more elaborate example is
1033</t>
1034<figure><artwork type="example">
1035  Accept: text/plain; q=0.5, text/html,
1036          text/x-dvi; q=0.8, text/x-c
1037</artwork></figure>
1038<t>
1039   Verbally, this would be interpreted as "text/html and text/x-c are
1040   the preferred media types, but if they do not exist, then send the
1041   text/x-dvi representation, and if that does not exist, send the text/plain
1042   representation".
1043</t>
1044<t>
1045   Media ranges can be overridden by more specific media ranges or
1046   specific media types. If more than one media range applies to a given
1047   type, the most specific reference has precedence. For example,
1048</t>
1049<figure><artwork type="example">
1050  Accept: text/*, text/plain, text/plain;format=flowed, */*
1051</artwork></figure>
1052<t>
1053   have the following precedence:
1054   <list style="numbers">
1055    <t>text/plain;format=flowed</t>
1056    <t>text/plain</t>
1057    <t>text/*</t>
1058    <t>*/*</t>
1059   </list>
1060</t>
1061<t>
1062   The media type quality factor associated with a given type is
1063   determined by finding the media range with the highest precedence
1064   which matches that type. For example,
1065</t>
1066<figure><artwork type="example">
1067  Accept: text/*;q=0.3, text/html;q=0.7, text/html;level=1,
1068          text/html;level=2;q=0.4, */*;q=0.5
1069</artwork></figure>
1070<t>
1071   would cause the following values to be associated:
1072</t>
1073<texttable align="left">
1074  <ttcol>Media Type</ttcol><ttcol>Quality Value</ttcol>
1075  <c>text/html;level=1</c>    <c>1</c>
1076  <c>text/html</c>            <c>0.7</c>
1077  <c>text/plain</c>           <c>0.3</c>
1078  <c>image/jpeg</c>           <c>0.5</c>
1079  <c>text/html;level=2</c>    <c>0.4</c>
1080  <c>text/html;level=3</c>    <c>0.7</c>
1081</texttable>
1082<t>
1083      <x:h>Note:</x:h> A user agent might be provided with a default set of quality
1084      values for certain media ranges. However, unless the user agent is
1085      a closed system which cannot interact with other rendering agents,
1086      this default set ought to be configurable by the user.
1087</t>
1088</section>
1089
1090<section title="Accept-Charset" anchor="header.accept-charset">
1091  <iref primary="true" item="Accept-Charset header field" x:for-anchor=""/>
1092  <iref primary="true" item="Header Fields" subitem="Accept-Charset" x:for-anchor=""/>
1093  <x:anchor-alias value="Accept-Charset"/>
1094<t>
1095   The "Accept-Charset" header field can be used by user agents to
1096   indicate what character encodings are acceptable in a response
1097   payload. This field allows
1098   clients capable of understanding more comprehensive or special-purpose
1099   character encodings to signal that capability to a server which is capable of
1100   representing documents in those character encodings.
1101</t>
1102<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Accept-Charset"/>
1103  <x:ref>Accept-Charset</x:ref> = 1#( ( <x:ref>charset</x:ref> / "*" )
1104                         [ <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> "q=" <x:ref>qvalue</x:ref> ] )
1105</artwork></figure>
1106<t>
1107   Character encoding values (a.k.a., charsets) are described in
1108   <xref target="character.sets"/>. Each charset &MAY; be given an
1109   associated quality value which represents the user's preference
1110   for that charset. The default value is q=1. An example is
1111</t>
1112<figure><artwork type="example">
1113  Accept-Charset: iso-8859-5, unicode-1-1;q=0.8
1114</artwork></figure>
1115<t>
1116   The special value "*", if present in the Accept-Charset field,
1117   matches every character encoding which is not mentioned elsewhere in the
1118   Accept-Charset field. If no "*" is present in an Accept-Charset field, then
1119   all character encodings not explicitly mentioned get a quality value of 0.
1120</t>
1121<t>
1122   A request without any Accept-Charset header field implies that the user
1123   agent will accept any character encoding in response.
1124   If an Accept-Charset header field is present in a request and none of the
1125   available representations for the response have a character encoding that
1126   is listed as acceptable, the origin server &MAY; either honor the
1127   Accept-Charset header field by sending a 406 (Not Acceptable) response or
1128   disregard the Accept-Charset header field by treating the response as if
1129   it is not subject to content negotiation.
1130</t>
1131</section>
1132
1133<section title="Accept-Encoding" anchor="header.accept-encoding">
1134  <iref primary="true" item="Accept-Encoding header field" x:for-anchor=""/>
1135  <iref primary="true" item="Header Fields" subitem="Accept-Encoding" x:for-anchor=""/>
1136  <x:anchor-alias value="Accept-Encoding"/>
1137  <x:anchor-alias value="codings"/>
1138<t>
1139   The "Accept-Encoding" header field can be used by user agents to
1140   indicate what response content-codings (<xref target="content.codings"/>)
1141   are acceptable in the response.  An "identity" token is used as a synonym
1142   for "no encoding" in order to communicate when no encoding is preferred.
1143</t>
1144<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Accept-Encoding"/><iref primary="true" item="Grammar" subitem="codings"/>
1145  <x:ref>Accept-Encoding</x:ref>  = #( <x:ref>codings</x:ref> [ <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> "q=" <x:ref>qvalue</x:ref> ] )
1146  <x:ref>codings</x:ref>          = <x:ref>content-coding</x:ref> / "identity" / "*"
1147</artwork></figure>
1148<t>
1149   Each codings value &MAY; be given an associated quality value which
1150   represents the preference for that encoding. The default value is q=1.
1151</t>
1152<t>
1153   For example,
1154</t>
1155<figure><artwork type="example">
1156  Accept-Encoding: compress, gzip
1157  Accept-Encoding:
1158  Accept-Encoding: *
1159  Accept-Encoding: compress;q=0.5, gzip;q=1.0
1160  Accept-Encoding: gzip;q=1.0, identity; q=0.5, *;q=0
1161</artwork></figure>
1162<t>
1163   A server tests whether a content-coding for a given representation is
1164   acceptable, according to an Accept-Encoding field, using these rules:
1165  <list style="numbers">
1166      <t>The special "*" symbol in an Accept-Encoding field matches any
1167         available content-coding not explicitly listed in the header
1168         field.</t>
1169
1170      <t>If the representation has no content-coding, then it is acceptable
1171         by default unless specifically excluded by the Accept-Encoding field
1172         stating either "identity;q=0" or "*;q=0" without a more specific
1173         entry for "identity".</t>
1174
1175      <t>If the representation's content-coding is one of the content-codings
1176         listed in the Accept-Encoding field, then it is acceptable unless
1177         it is accompanied by a qvalue of 0. (As defined in &qvalue;, a
1178         qvalue of 0 means "not acceptable".)</t>
1179
1180      <t>If multiple content-codings are acceptable, then the acceptable
1181         content-coding with the highest non-zero qvalue is preferred.</t>
1182  </list>
1183</t>
1184<t>
1185   An Accept-Encoding header field with a combined field-value that is empty
1186   implies that the user agent does not want any content-coding in response.
1187   If an Accept-Encoding header field is present in a request and none of the
1188   available representations for the response have a content-coding that
1189   is listed as acceptable, the origin server &SHOULD; send a response
1190   without any content-coding.
1191</t>
1192<t>
1193   A request without an Accept-Encoding header field implies that the user
1194   agent will accept any content-coding in response, but a representation
1195   without content-coding is preferred for compatibility with the widest
1196   variety of user agents.
1197</t>
1198<x:note>
1199  <t>
1200    <x:h>Note:</x:h> Most HTTP/1.0 applications do not recognize or obey qvalues
1201    associated with content-codings. This means that qvalues will not
1202    work and are not permitted with x-gzip or x-compress.
1203  </t>
1204</x:note>
1205</section>
1206
1207<section title="Accept-Language" anchor="header.accept-language">
1208  <iref primary="true" item="Accept-Language header field" x:for-anchor=""/>
1209  <iref primary="true" item="Header Fields" subitem="Accept-Language" x:for-anchor=""/>
1210  <x:anchor-alias value="Accept-Language"/>
1211  <x:anchor-alias value="language-range"/>
1212<t>
1213   The "Accept-Language" header field can be used by user agents to
1214   indicate the set of natural languages that are preferred in the response.
1215   Language tags are defined in <xref target="language.tags"/>.
1216</t>
1217<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Accept-Language"/><iref primary="true" item="Grammar" subitem="language-range"/>
1218  <x:ref>Accept-Language</x:ref> =
1219                    1#( <x:ref>language-range</x:ref> [ <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> "q=" <x:ref>qvalue</x:ref> ] )
1220  <x:ref>language-range</x:ref>  =
1221            &lt;language-range, defined in <xref target="RFC4647" x:fmt="," x:sec="2.1"/>&gt;
1222</artwork></figure>
1223<t>
1224   Each language-range can be given an associated quality value which
1225   represents an estimate of the user's preference for the languages
1226   specified by that range. The quality value defaults to "q=1". For
1227   example,
1228</t>
1229<figure><artwork type="example">
1230  Accept-Language: da, en-gb;q=0.8, en;q=0.7
1231</artwork></figure>
1232<t>
1233   would mean: "I prefer Danish, but will accept British English and
1234   other types of English".
1235   (see also <xref target="RFC4647" x:sec="2.3" x:fmt="of"/>)
1236</t>
1237<t>
1238   For matching, <xref target="RFC4647" x:sec="3" x:fmt="of"/> defines
1239   several matching schemes. Implementations can offer the most appropriate
1240   matching scheme for their requirements.
1241</t>
1242<x:note>
1243  <t>
1244    <x:h>Note:</x:h> The "Basic Filtering" scheme (<xref target="RFC4647"
1245    x:fmt="," x:sec="3.3.1"/>) is identical to the matching scheme that was
1246    previously defined in <xref target="RFC2616" x:fmt="of" x:sec="14.4"/>.
1247  </t>
1248</x:note>
1249<t>
1250   It might be contrary to the privacy expectations of the user to send
1251   an Accept-Language header field with the complete linguistic preferences of
1252   the user in every request. For a discussion of this issue, see
1253   <xref target="privacy.issues.connected.to.accept.header.fields"/>.
1254</t>
1255<t>
1256   As intelligibility is highly dependent on the individual user, it is
1257   recommended that client applications make the choice of linguistic
1258   preference available to the user. If the choice is not made
1259   available, then the Accept-Language header field &MUST-NOT; be given in
1260   the request.
1261</t>
1262<x:note>
1263  <t>
1264    <x:h>Note:</x:h> When making the choice of linguistic preference available to
1265    the user, we remind implementors of  the fact that users are not
1266    familiar with the details of language matching as described above,
1267    and ought to be provided appropriate guidance. As an example, users
1268    might assume that on selecting "en-gb", they will be served any
1269    kind of English document if British English is not available. A
1270    user agent might suggest in such a case to add "en" to get the
1271    best matching behavior.
1272  </t>
1273</x:note>
1274</section>
1275
1276<section title="Content-Encoding" anchor="header.content-encoding">
1277  <iref primary="true" item="Content-Encoding header field" x:for-anchor=""/>
1278  <iref primary="true" item="Header Fields" subitem="Content-Encoding" x:for-anchor=""/>
1279  <x:anchor-alias value="Content-Encoding"/>
1280<t>
1281   The "Content-Encoding" header field indicates what content-codings
1282   have been applied to the representation beyond those inherent in the media
1283   type, and thus what decoding mechanisms must be applied in order to obtain
1284   the media-type referenced by the Content-Type header field.
1285   Content-Encoding is primarily used to allow a representation to be
1286   compressed without losing the identity of its underlying media type.
1287</t>
1288<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Encoding"/>
1289  <x:ref>Content-Encoding</x:ref> = 1#<x:ref>content-coding</x:ref>
1290</artwork></figure>
1291<t>
1292   Content codings are defined in <xref target="content.codings"/>. An example of its use is
1293</t>
1294<figure><artwork type="example">
1295  Content-Encoding: gzip
1296</artwork></figure>
1297<t>
1298   The content-coding is a characteristic of the representation.
1299   Typically, the representation body is stored with this
1300   encoding and is only decoded before rendering or analogous usage.
1301   However, a transforming proxy &MAY; modify the content-coding if the
1302   new coding is known to be acceptable to the recipient, unless the
1303   "no-transform" cache-control directive is present in the message.
1304</t>
1305<t>
1306   If the media type includes an inherent encoding, such as a data format
1307   that is always compressed, then that encoding would not be restated as
1308   a Content-Encoding even if it happens to be the same algorithm as one
1309   of the content-codings.  Such a content-coding would only be listed if,
1310   for some bizarre reason, it is applied a second time to form the
1311   representation.  Likewise, an origin server might choose to publish the
1312   same payload data as multiple representations that differ only in whether
1313   the coding is defined as part of Content-Type or Content-Encoding, since
1314   some user agents will behave differently in their handling of each
1315   response (e.g., open a "Save as ..." dialog instead of automatic
1316   decompression and rendering of content).
1317</t>
1318<t>
1319   A representation that has a content-coding applied to it &MUST; include
1320   a Content-Encoding header field (<xref target="header.content-encoding"/>)
1321   that lists the content-coding(s) applied.
1322</t>
1323<t>
1324   If multiple encodings have been applied to a representation, the content
1325   codings &MUST; be listed in the order in which they were applied.
1326   Additional information about the encoding parameters &MAY; be provided
1327   by other header fields not defined by this specification.
1328</t>
1329<t>
1330   If the content-coding of a representation in a request message is not
1331   acceptable to the origin server, the server &SHOULD; respond with a
1332   status code of 415 (Unsupported Media Type).
1333</t>
1334</section>
1335
1336<section title="Content-Language" anchor="header.content-language">
1337  <iref primary="true" item="Content-Language header field" x:for-anchor=""/>
1338  <iref primary="true" item="Header Fields" subitem="Content-Language" x:for-anchor=""/>
1339  <x:anchor-alias value="Content-Language"/>
1340<t>
1341   The "Content-Language" header field describes the natural
1342   language(s) of the intended audience for the representation. Note that this might
1343   not be equivalent to all the languages used within the representation.
1344</t>
1345<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Language"/>
1346  <x:ref>Content-Language</x:ref> = 1#<x:ref>language-tag</x:ref>
1347</artwork></figure>
1348<t>
1349   Language tags are defined in <xref target="language.tags"/>. The primary purpose of
1350   Content-Language is to allow a user to identify and differentiate
1351   representations according to the user's own preferred language. Thus, if the
1352   body content is intended only for a Danish-literate audience, the
1353   appropriate field is
1354</t>
1355<figure><artwork type="example">
1356  Content-Language: da
1357</artwork></figure>
1358<t>
1359   If no Content-Language is specified, the default is that the content
1360   is intended for all language audiences. This might mean that the
1361   sender does not consider it to be specific to any natural language,
1362   or that the sender does not know for which language it is intended.
1363</t>
1364<t>
1365   Multiple languages &MAY; be listed for content that is intended for
1366   multiple audiences. For example, a rendition of the "Treaty of
1367   Waitangi", presented simultaneously in the original Maori and English
1368   versions, would call for
1369</t>
1370<figure><artwork type="example">
1371  Content-Language: mi, en
1372</artwork></figure>
1373<t>
1374   However, just because multiple languages are present within a representation
1375   does not mean that it is intended for multiple linguistic audiences.
1376   An example would be a beginner's language primer, such as "A First
1377   Lesson in Latin", which is clearly intended to be used by an
1378   English-literate audience. In this case, the Content-Language would
1379   properly only include "en".
1380</t>
1381<t>
1382   Content-Language &MAY; be applied to any media type &mdash; it is not
1383   limited to textual documents.
1384</t>
1385</section>
1386
1387<section title="Content-Location" anchor="header.content-location">
1388  <iref primary="true" item="Content-Location header field" x:for-anchor=""/>
1389  <iref primary="true" item="Header Fields" subitem="Content-Location" x:for-anchor=""/>
1390  <x:anchor-alias value="Content-Location"/>
1391<t>
1392   The "Content-Location" header field supplies a URI that can be used
1393   as a specific identifier for the representation in this message.
1394   In other words, if one were to perform a GET on this URI at the time
1395   of this message's generation, then a 200 response would contain the
1396   same representation that is enclosed as payload in this message.
1397</t>
1398<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Location"/>
1399  <x:ref>Content-Location</x:ref> = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
1400</artwork></figure>
1401<t>
1402   The Content-Location value is not a replacement for the effective
1403   Request URI (&effective-request-uri;).  It is representation metadata.
1404   It has the same syntax and semantics as the header field of the same name
1405   defined for MIME body parts in <xref target="RFC2557" x:fmt="of" x:sec="4"/>.
1406   However, its appearance in an HTTP message has some special implications
1407   for HTTP recipients.
1408</t>
1409<t>
1410   If Content-Location is included in a response message and its value
1411   is the same as the effective request URI, then the response payload
1412   &SHOULD; be considered the current representation of that resource.
1413   For a GET or HEAD request, this is the same as the default semantics
1414   when no Content-Location is provided by the server.  For a state-changing
1415   request like PUT or POST, it implies that the server's response contains
1416   the new representation of that resource, thereby distinguishing it from
1417   representations that might only report about the action (e.g., "It worked!").
1418   This allows authoring applications to update their local copies without
1419   the need for a subsequent GET request.
1420</t>
1421<t>
1422   If Content-Location is included in a response message and its value
1423   differs from the effective request URI, then the origin server is
1424   informing recipients that this representation has its own, presumably
1425   more specific, identifier.  For a GET or HEAD request, this is an
1426   indication that the effective request URI identifies a resource that
1427   is subject to content negotiation and the selected representation for
1428   this response can also be found at the identified URI.  For other
1429   methods, such a Content-Location indicates that this representation
1430   contains a report on the action's status and the same report is
1431   available (for future access with GET) at the given URI.  For
1432   example, a purchase transaction made via a POST request might
1433   include a receipt document as the payload of the 200 response;
1434   the Content-Location value provides an identifier for retrieving
1435   a copy of that same receipt in the future.
1436</t>
1437<t>
1438   If Content-Location is included in a request message, then it &MAY;
1439   be interpreted by the origin server as an indication of where the
1440   user agent originally obtained the content of the enclosed
1441   representation (prior to any subsequent modification of the content
1442   by that user agent).  In other words, the user agent is providing
1443   the same representation metadata that it received with the original
1444   representation.  However, such interpretation &MUST-NOT; be used to
1445   alter the semantics of the method requested by the client.  For
1446   example, if a client makes a PUT request on a negotiated resource
1447   and the origin server accepts that PUT (without redirection), then the
1448   new set of values for that resource is expected to be consistent with
1449   the one representation supplied in that PUT; the Content-Location
1450   cannot be used as a form of reverse content selection that
1451   identifies only one of the negotiated representations to be updated.
1452   If the user agent had wanted the latter semantics, it would have applied
1453   the PUT directly to the Content-Location URI.
1454</t>
1455<t>
1456   A Content-Location field received in a request message is transitory
1457   information that &SHOULD-NOT; be saved with other representation
1458   metadata for use in later responses.  The Content-Location's value
1459   might be saved for use in other contexts, such as within source links
1460   or other metadata.
1461</t>
1462<t>
1463   A cache cannot assume that a representation with a Content-Location
1464   different from the URI used to retrieve it can be used to respond to
1465   later requests on that Content-Location URI.
1466</t>
1467<t>
1468   If the Content-Location value is a partial URI, the partial URI is
1469   interpreted relative to the effective request URI.
1470</t>
1471</section>
1472
1473<section title="Content-Type" anchor="header.content-type">
1474  <iref primary="true" item="Content-Type header field" x:for-anchor=""/>
1475  <iref primary="true" item="Header Fields" subitem="Content-Type" x:for-anchor=""/>
1476  <x:anchor-alias value="Content-Type"/>
1477<t>
1478   The "Content-Type" header field indicates the media type of the
1479   representation. In the case of responses to the HEAD method, the media type is
1480   that which would have been sent had the request been a GET.
1481</t>
1482<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Type"/>
1483  <x:ref>Content-Type</x:ref> = <x:ref>media-type</x:ref>
1484</artwork></figure>
1485<t>
1486   Media types are defined in <xref target="media.types"/>. An example of the field is
1487</t>
1488<figure><artwork type="example">
1489  Content-Type: text/html; charset=ISO-8859-4
1490</artwork></figure>
1491<t>
1492   Further discussion of Content-Type is provided in <xref target="representation.data"/>.
1493</t>
1494</section>
1495
1496</section>
1497
1498<section title="IANA Considerations" anchor="IANA.considerations">
1499<section title="Header Field Registration" anchor="header.field.registration">
1500<t>
1501   The Message Header Field Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> shall be updated
1502   with the permanent registrations below (see <xref target="RFC3864"/>):
1503</t>
1504<?BEGININC p3-payload.iana-headers ?>
1505<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
1506<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
1507   <ttcol>Header Field Name</ttcol>
1508   <ttcol>Protocol</ttcol>
1509   <ttcol>Status</ttcol>
1510   <ttcol>Reference</ttcol>
1511
1512   <c>Accept</c>
1513   <c>http</c>
1514   <c>standard</c>
1515   <c>
1516      <xref target="header.accept"/>
1517   </c>
1518   <c>Accept-Charset</c>
1519   <c>http</c>
1520   <c>standard</c>
1521   <c>
1522      <xref target="header.accept-charset"/>
1523   </c>
1524   <c>Accept-Encoding</c>
1525   <c>http</c>
1526   <c>standard</c>
1527   <c>
1528      <xref target="header.accept-encoding"/>
1529   </c>
1530   <c>Accept-Language</c>
1531   <c>http</c>
1532   <c>standard</c>
1533   <c>
1534      <xref target="header.accept-language"/>
1535   </c>
1536   <c>Content-Encoding</c>
1537   <c>http</c>
1538   <c>standard</c>
1539   <c>
1540      <xref target="header.content-encoding"/>
1541   </c>
1542   <c>Content-Language</c>
1543   <c>http</c>
1544   <c>standard</c>
1545   <c>
1546      <xref target="header.content-language"/>
1547   </c>
1548   <c>Content-Location</c>
1549   <c>http</c>
1550   <c>standard</c>
1551   <c>
1552      <xref target="header.content-location"/>
1553   </c>
1554   <c>Content-Type</c>
1555   <c>http</c>
1556   <c>standard</c>
1557   <c>
1558      <xref target="header.content-type"/>
1559   </c>
1560   <c>MIME-Version</c>
1561   <c>http</c>
1562   <c>standard</c>
1563   <c>
1564      <xref target="mime-version"/>
1565   </c>
1566</texttable>
1567<!--(END)-->
1568<?ENDINC p3-payload.iana-headers ?>
1569<t>
1570   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
1571</t>
1572</section>
1573
1574<section title="Content Coding Registry" anchor="content.coding.registration">
1575<t>
1576   The registration procedure for HTTP Content Codings is now defined
1577   by <xref target="content.coding.registry"/> of this document.
1578</t>
1579<t>
1580   The HTTP Content Codings Registry located at <eref target="http://www.iana.org/assignments/http-parameters"/>
1581   shall be updated with the registration below:
1582</t>
1583<texttable align="left" suppress-title="true" anchor="iana.content.coding.registration.table">
1584   <ttcol>Name</ttcol>
1585   <ttcol>Description</ttcol>
1586   <ttcol>Reference</ttcol>
1587   <c>compress</c>
1588   <c>UNIX "compress" program method</c>
1589   <c>
1590      &compress-coding;
1591   </c>
1592   <c>deflate</c>
1593   <c>"deflate" compression mechanism (<xref target="RFC1951"/>) used inside
1594   the "zlib" data format (<xref target="RFC1950"/>)
1595   </c>
1596   <c>
1597      &deflate-coding;
1598   </c>
1599   <c>gzip</c>
1600   <c>Same as GNU zip <xref target="RFC1952"/></c>
1601   <c>
1602      &gzip-coding;
1603   </c>
1604   <c>identity</c>
1605   <c>reserved (synonym for "no encoding" in Accept-Encoding header field)</c>
1606   <c>
1607      <xref target="header.accept-encoding"/>
1608   </c>
1609</texttable>
1610</section>
1611
1612</section>
1613
1614<section title="Security Considerations" anchor="security.considerations">
1615<t>
1616   This section is meant to inform application developers, information
1617   providers, and users of the security limitations in HTTP/1.1 as
1618   described by this document. The discussion does not include
1619   definitive solutions to the problems revealed, though it does make
1620   some suggestions for reducing security risks.
1621</t>
1622
1623<section title="Privacy Issues Connected to Accept Header Fields" anchor="privacy.issues.connected.to.accept.header.fields">
1624<t>
1625   Accept header fields can reveal information about the user to all
1626   servers which are accessed. The Accept-Language header field in particular
1627   can reveal information the user would consider to be of a private
1628   nature, because the understanding of particular languages is often
1629   strongly correlated to the membership of a particular ethnic group.
1630   User agents which offer the option to configure the contents of an
1631   Accept-Language header field to be sent in every request are strongly
1632   encouraged to let the configuration process include a message which
1633   makes the user aware of the loss of privacy involved.
1634</t>
1635<t>
1636   An approach that limits the loss of privacy would be for a user agent
1637   to omit the sending of Accept-Language header fields by default, and to ask
1638   the user whether or not to start sending Accept-Language header fields to a
1639   server if it detects, by looking for any Vary header fields
1640   generated by the server, that such sending could improve the quality
1641   of service.
1642</t>
1643<t>
1644   Elaborate user-customized accept header fields sent in every request,
1645   in particular if these include quality values, can be used by servers
1646   as relatively reliable and long-lived user identifiers. Such user
1647   identifiers would allow content providers to do click-trail tracking,
1648   and would allow collaborating content providers to match cross-server
1649   click-trails or form submissions of individual users. Note that for
1650   many users not behind a proxy, the network address of the host
1651   running the user agent will also serve as a long-lived user
1652   identifier. In environments where proxies are used to enhance
1653   privacy, user agents ought to be conservative in offering accept
1654   header configuration options to end users. As an extreme privacy
1655   measure, proxies could filter the accept header fields in relayed requests.
1656   General purpose user agents which provide a high degree of header
1657   configurability &SHOULD; warn users about the loss of privacy which can
1658   be involved.
1659</t>
1660</section>
1661
1662</section>
1663
1664<section title="Acknowledgments" anchor="acks">
1665<t>
1666  See &acks;.
1667</t>
1668</section>
1669</middle>
1670<back>
1671
1672<references title="Normative References">
1673
1674<reference anchor="Part1">
1675  <front>
1676    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
1677    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1678      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
1679      <address><email>fielding@gbiv.com</email></address>
1680    </author>
1681    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1682      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1683      <address><email>jg@freedesktop.org</email></address>
1684    </author>
1685    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1686      <organization abbrev="HP">Hewlett-Packard Company</organization>
1687      <address><email>JeffMogul@acm.org</email></address>
1688    </author>
1689    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1690      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1691      <address><email>henrikn@microsoft.com</email></address>
1692    </author>
1693    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1694      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
1695      <address><email>LMM@acm.org</email></address>
1696    </author>
1697    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1698      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1699      <address><email>paulle@microsoft.com</email></address>
1700    </author>
1701    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1702      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1703      <address><email>timbl@w3.org</email></address>
1704    </author>
1705    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1706      <organization abbrev="W3C">World Wide Web Consortium</organization>
1707      <address><email>ylafon@w3.org</email></address>
1708    </author>
1709    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1710      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1711      <address><email>julian.reschke@greenbytes.de</email></address>
1712    </author>
1713    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1714  </front>
1715  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
1716  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
1717</reference>
1718
1719<reference anchor="Part2">
1720  <front>
1721    <title abbrev="HTTP/1.1">HTTP/1.1, part 2: Message Semantics</title>
1722    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1723      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
1724      <address><email>fielding@gbiv.com</email></address>
1725    </author>
1726    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1727      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1728      <address><email>jg@freedesktop.org</email></address>
1729    </author>
1730    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1731      <organization abbrev="HP">Hewlett-Packard Company</organization>
1732      <address><email>JeffMogul@acm.org</email></address>
1733    </author>
1734    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1735      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1736      <address><email>henrikn@microsoft.com</email></address>
1737    </author>
1738    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1739      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
1740      <address><email>LMM@acm.org</email></address>
1741    </author>
1742    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1743      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1744      <address><email>paulle@microsoft.com</email></address>
1745    </author>
1746    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1747      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1748      <address><email>timbl@w3.org</email></address>
1749    </author>
1750    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1751      <organization abbrev="W3C">World Wide Web Consortium</organization>
1752      <address><email>ylafon@w3.org</email></address>
1753    </author>
1754    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1755      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1756      <address><email>julian.reschke@greenbytes.de</email></address>
1757    </author>
1758    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1759  </front>
1760  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"/>
1761  <x:source href="p2-semantics.xml" basename="p2-semantics"/>
1762</reference>
1763
1764<reference anchor="Part4">
1765  <front>
1766    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
1767    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1768      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
1769      <address><email>fielding@gbiv.com</email></address>
1770    </author>
1771    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1772      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1773      <address><email>jg@freedesktop.org</email></address>
1774    </author>
1775    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1776      <organization abbrev="HP">Hewlett-Packard Company</organization>
1777      <address><email>JeffMogul@acm.org</email></address>
1778    </author>
1779    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1780      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1781      <address><email>henrikn@microsoft.com</email></address>
1782    </author>
1783    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1784      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
1785      <address><email>LMM@acm.org</email></address>
1786    </author>
1787    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1788      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1789      <address><email>paulle@microsoft.com</email></address>
1790    </author>
1791    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1792      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1793      <address><email>timbl@w3.org</email></address>
1794    </author>
1795    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1796      <organization abbrev="W3C">World Wide Web Consortium</organization>
1797      <address><email>ylafon@w3.org</email></address>
1798    </author>
1799    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1800      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1801      <address><email>julian.reschke@greenbytes.de</email></address>
1802    </author>
1803    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1804  </front>
1805  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
1806  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
1807</reference>
1808
1809<reference anchor="Part5">
1810  <front>
1811    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
1812    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1813      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
1814      <address><email>fielding@gbiv.com</email></address>
1815    </author>
1816    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1817      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1818      <address><email>jg@freedesktop.org</email></address>
1819    </author>
1820    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1821      <organization abbrev="HP">Hewlett-Packard Company</organization>
1822      <address><email>JeffMogul@acm.org</email></address>
1823    </author>
1824    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1825      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1826      <address><email>henrikn@microsoft.com</email></address>
1827    </author>
1828    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1829      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
1830      <address><email>LMM@acm.org</email></address>
1831    </author>
1832    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1833      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1834      <address><email>paulle@microsoft.com</email></address>
1835    </author>
1836    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1837      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1838      <address><email>timbl@w3.org</email></address>
1839    </author>
1840    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1841      <organization abbrev="W3C">World Wide Web Consortium</organization>
1842      <address><email>ylafon@w3.org</email></address>
1843    </author>
1844    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1845      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1846      <address><email>julian.reschke@greenbytes.de</email></address>
1847    </author>
1848    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1849  </front>
1850  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
1851  <x:source href="p5-range.xml" basename="p5-range"/>
1852</reference>
1853
1854<reference anchor="Part6">
1855  <front>
1856    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
1857    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1858      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
1859      <address><email>fielding@gbiv.com</email></address>
1860    </author>
1861    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1862      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1863      <address><email>jg@freedesktop.org</email></address>
1864    </author>
1865    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1866      <organization abbrev="HP">Hewlett-Packard Company</organization>
1867      <address><email>JeffMogul@acm.org</email></address>
1868    </author>
1869    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1870      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1871      <address><email>henrikn@microsoft.com</email></address>
1872    </author>
1873    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1874      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
1875      <address><email>LMM@acm.org</email></address>
1876    </author>
1877    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1878      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1879      <address><email>paulle@microsoft.com</email></address>
1880    </author>
1881    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1882      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1883      <address><email>timbl@w3.org</email></address>
1884    </author>
1885    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1886      <organization abbrev="W3C">World Wide Web Consortium</organization>
1887      <address><email>ylafon@w3.org</email></address>
1888    </author>
1889    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
1890      <organization>Rackspace</organization>
1891      <address><email>mnot@mnot.net</email></address>
1892    </author>
1893    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1894      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1895      <address><email>julian.reschke@greenbytes.de</email></address>
1896    </author>
1897    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1898  </front>
1899  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
1900  <x:source href="p6-cache.xml" basename="p6-cache"/>
1901</reference>
1902
1903<reference anchor="RFC1950">
1904  <front>
1905    <title>ZLIB Compressed Data Format Specification version 3.3</title>
1906    <author initials="L.P." surname="Deutsch" fullname="L. Peter Deutsch">
1907      <organization>Aladdin Enterprises</organization>
1908      <address><email>ghost@aladdin.com</email></address>
1909    </author>
1910    <author initials="J-L." surname="Gailly" fullname="Jean-Loup Gailly"/>
1911    <date month="May" year="1996"/>
1912  </front>
1913  <seriesInfo name="RFC" value="1950"/>
1914  <!--<annotation>
1915    RFC 1950 is an Informational RFC, thus it might be less stable than
1916    this specification. On the other hand, this downward reference was
1917    present since the publication of <xref target="RFC2068" x:fmt="none">RFC 2068</xref> in 1997,
1918    therefore it is unlikely to cause problems in practice. See also
1919    <xref target="BCP97"/>.
1920  </annotation>-->
1921</reference>
1922
1923<reference anchor="RFC1951">
1924  <front>
1925    <title>DEFLATE Compressed Data Format Specification version 1.3</title>
1926    <author initials="P." surname="Deutsch" fullname="L. Peter Deutsch">
1927      <organization>Aladdin Enterprises</organization>
1928      <address><email>ghost@aladdin.com</email></address>
1929    </author>
1930    <date month="May" year="1996"/>
1931  </front>
1932  <seriesInfo name="RFC" value="1951"/>
1933  <!--<annotation>
1934    RFC 1951 is an Informational RFC, thus it might be less stable than
1935    this specification. On the other hand, this downward reference was
1936    present since the publication of <xref target="RFC2068" x:fmt="none">RFC 2068</xref> in 1997,
1937    therefore it is unlikely to cause problems in practice. See also
1938    <xref target="BCP97"/>.
1939  </annotation>-->
1940</reference>
1941
1942<reference anchor="RFC1952">
1943  <front>
1944    <title>GZIP file format specification version 4.3</title>
1945    <author initials="P." surname="Deutsch" fullname="L. Peter Deutsch">
1946      <organization>Aladdin Enterprises</organization>
1947      <address><email>ghost@aladdin.com</email></address>
1948    </author>
1949    <author initials="J-L." surname="Gailly" fullname="Jean-Loup Gailly">
1950      <address><email>gzip@prep.ai.mit.edu</email></address>
1951    </author>
1952    <author initials="M." surname="Adler" fullname="Mark Adler">
1953      <address><email>madler@alumni.caltech.edu</email></address>
1954    </author>
1955    <author initials="L.P." surname="Deutsch" fullname="L. Peter Deutsch">
1956      <address><email>ghost@aladdin.com</email></address>
1957    </author>
1958    <author initials="G." surname="Randers-Pehrson" fullname="Glenn Randers-Pehrson">
1959      <address><email>randeg@alumni.rpi.edu</email></address>
1960    </author>
1961    <date month="May" year="1996"/>
1962  </front>
1963  <seriesInfo name="RFC" value="1952"/>
1964  <!--<annotation>
1965    RFC 1952 is an Informational RFC, thus it might be less stable than
1966    this specification. On the other hand, this downward reference was
1967    present since the publication of <xref target="RFC2068" x:fmt="none">RFC 2068</xref> in 1997,
1968    therefore it is unlikely to cause problems in practice. See also
1969    <xref target="BCP97"/>.
1970  </annotation>-->
1971</reference>
1972
1973<reference anchor="RFC2045">
1974  <front>
1975    <title abbrev="Internet Message Bodies">Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies</title>
1976    <author initials="N." surname="Freed" fullname="Ned Freed">
1977      <organization>Innosoft International, Inc.</organization>
1978      <address><email>ned@innosoft.com</email></address>
1979    </author>
1980    <author initials="N.S." surname="Borenstein" fullname="Nathaniel S. Borenstein">
1981      <organization>First Virtual Holdings</organization>
1982      <address><email>nsb@nsb.fv.com</email></address>
1983    </author>
1984    <date month="November" year="1996"/>
1985  </front>
1986  <seriesInfo name="RFC" value="2045"/>
1987</reference>
1988
1989<reference anchor="RFC2046">
1990  <front>
1991    <title abbrev="Media Types">Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types</title>
1992    <author initials="N." surname="Freed" fullname="Ned Freed">
1993      <organization>Innosoft International, Inc.</organization>
1994      <address><email>ned@innosoft.com</email></address>
1995    </author>
1996    <author initials="N." surname="Borenstein" fullname="Nathaniel S. Borenstein">
1997      <organization>First Virtual Holdings</organization>
1998      <address><email>nsb@nsb.fv.com</email></address>
1999    </author>
2000    <date month="November" year="1996"/>
2001  </front>
2002  <seriesInfo name="RFC" value="2046"/>
2003</reference>
2004
2005<reference anchor="RFC2119">
2006  <front>
2007    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
2008    <author initials="S." surname="Bradner" fullname="Scott Bradner">
2009      <organization>Harvard University</organization>
2010      <address><email>sob@harvard.edu</email></address>
2011    </author>
2012    <date month="March" year="1997"/>
2013  </front>
2014  <seriesInfo name="BCP" value="14"/>
2015  <seriesInfo name="RFC" value="2119"/>
2016</reference>
2017
2018<reference anchor='RFC4647'>
2019  <front>
2020    <title>Matching of Language Tags</title>
2021    <author initials='A.' surname='Phillips' fullname='Addison Phillips' role="editor">
2022      <organization>Yahoo! Inc.</organization>
2023      <address><email>addison@inter-locale.com</email></address>
2024    </author>
2025    <author initials='M.' surname='Davis' fullname='Mark Davis' role="editor">
2026      <organization>Google</organization>
2027      <address><email>mark.davis@macchiato.com</email></address>
2028    </author>
2029    <date year='2006' month='September' />
2030  </front>
2031  <seriesInfo name='BCP' value='47' />
2032  <seriesInfo name='RFC' value='4647' />
2033</reference>
2034
2035<reference anchor="RFC5234">
2036  <front>
2037    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
2038    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
2039      <organization>Brandenburg InternetWorking</organization>
2040      <address>
2041        <email>dcrocker@bbiw.net</email>
2042      </address> 
2043    </author>
2044    <author initials="P." surname="Overell" fullname="Paul Overell">
2045      <organization>THUS plc.</organization>
2046      <address>
2047        <email>paul.overell@thus.net</email>
2048      </address>
2049    </author>
2050    <date month="January" year="2008"/>
2051  </front>
2052  <seriesInfo name="STD" value="68"/>
2053  <seriesInfo name="RFC" value="5234"/>
2054</reference>
2055
2056<reference anchor='RFC5646'>
2057  <front>
2058    <title>Tags for Identifying Languages</title>
2059    <author initials='A.' surname='Phillips' fullname='Addison Phillips' role='editor'>
2060      <organization>Lab126</organization>
2061      <address><email>addison@inter-locale.com</email></address>
2062    </author>
2063    <author initials='M.' surname='Davis' fullname='Mark Davis' role='editor'>
2064      <organization>Google</organization>
2065      <address><email>mark.davis@google.com</email></address>
2066    </author>
2067    <date month='September' year='2009' />
2068  </front>
2069  <seriesInfo name='BCP' value='47' />
2070  <seriesInfo name='RFC' value='5646' />
2071</reference>
2072
2073</references>
2074
2075<references title="Informative References">
2076
2077<reference anchor="RFC1945">
2078  <front>
2079    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
2080    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2081      <organization>MIT, Laboratory for Computer Science</organization>
2082      <address><email>timbl@w3.org</email></address>
2083    </author>
2084    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
2085      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2086      <address><email>fielding@ics.uci.edu</email></address>
2087    </author>
2088    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2089      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
2090      <address><email>frystyk@w3.org</email></address>
2091    </author>
2092    <date month="May" year="1996"/>
2093  </front>
2094  <seriesInfo name="RFC" value="1945"/>
2095</reference>
2096
2097<reference anchor="RFC2049">
2098  <front>
2099    <title abbrev="MIME Conformance">Multipurpose Internet Mail Extensions (MIME) Part Five: Conformance Criteria and Examples</title>
2100    <author initials="N." surname="Freed" fullname="Ned Freed">
2101      <organization>Innosoft International, Inc.</organization>
2102      <address><email>ned@innosoft.com</email></address>
2103    </author>
2104    <author initials="N.S." surname="Borenstein" fullname="Nathaniel S. Borenstein">
2105      <organization>First Virtual Holdings</organization>
2106      <address><email>nsb@nsb.fv.com</email></address>
2107    </author>
2108    <date month="November" year="1996"/>
2109  </front>
2110  <seriesInfo name="RFC" value="2049"/>
2111</reference>
2112
2113<reference anchor="RFC2068">
2114  <front>
2115    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
2116    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
2117      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2118      <address><email>fielding@ics.uci.edu</email></address>
2119    </author>
2120    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2121      <organization>MIT Laboratory for Computer Science</organization>
2122      <address><email>jg@w3.org</email></address>
2123    </author>
2124    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2125      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
2126      <address><email>mogul@wrl.dec.com</email></address>
2127    </author>
2128    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2129      <organization>MIT Laboratory for Computer Science</organization>
2130      <address><email>frystyk@w3.org</email></address>
2131    </author>
2132    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2133      <organization>MIT Laboratory for Computer Science</organization>
2134      <address><email>timbl@w3.org</email></address>
2135    </author>
2136    <date month="January" year="1997"/>
2137  </front>
2138  <seriesInfo name="RFC" value="2068"/>
2139</reference>
2140
2141<reference anchor="RFC2076">
2142  <front>
2143    <title abbrev="Internet Message Headers">Common Internet Message Headers</title>
2144    <author initials="J." surname="Palme" fullname="Jacob Palme">
2145      <organization>Stockholm University/KTH</organization>
2146      <address><email>jpalme@dsv.su.se</email></address>
2147    </author>
2148    <date month="February" year="1997"/>
2149  </front>
2150  <seriesInfo name="RFC" value="2076"/>
2151</reference>
2152
2153<reference anchor="RFC2277">
2154  <front>
2155    <title abbrev="Charset Policy">IETF Policy on Character Sets and Languages</title>
2156    <author initials="H.T." surname="Alvestrand" fullname="Harald Tveit Alvestrand">
2157      <organization>UNINETT</organization>
2158      <address><email>Harald.T.Alvestrand@uninett.no</email></address>
2159    </author>
2160    <date month="January" year="1998"/>
2161  </front>
2162  <seriesInfo name="BCP" value="18"/>
2163  <seriesInfo name="RFC" value="2277"/>
2164</reference>
2165
2166<reference anchor='RFC2295'>
2167  <front>
2168    <title abbrev='HTTP Content Negotiation'>Transparent Content Negotiation in HTTP</title>
2169    <author initials='K.' surname='Holtman' fullname='Koen Holtman'>
2170      <organization>Technische Universiteit Eindhoven</organization>
2171      <address>
2172        <email>koen@win.tue.nl</email>
2173      </address>
2174    </author>
2175    <author initials='A.H.' surname='Mutz' fullname='Andrew H. Mutz'>
2176      <organization>Hewlett-Packard Company</organization>
2177      <address>
2178        <email>mutz@hpl.hp.com</email>
2179      </address>
2180    </author>
2181    <date year='1998' month='March'/>
2182  </front>
2183  <seriesInfo name='RFC' value='2295'/>
2184</reference>
2185
2186<reference anchor="RFC2388">
2187  <front>
2188    <title abbrev="multipart/form-data">Returning Values from Forms:  multipart/form-data</title>
2189    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2190      <organization>Xerox Palo Alto Research Center</organization>
2191      <address><email>masinter@parc.xerox.com</email></address>
2192    </author>
2193    <date year="1998" month="August"/>
2194  </front>
2195  <seriesInfo name="RFC" value="2388"/>
2196</reference>
2197
2198<reference anchor="RFC2557">
2199  <front>
2200    <title abbrev="MIME Encapsulation of Aggregate Documents">MIME Encapsulation of Aggregate Documents, such as HTML (MHTML)</title>
2201    <author initials="F." surname="Palme" fullname="Jacob Palme">
2202      <organization>Stockholm University and KTH</organization>
2203      <address><email>jpalme@dsv.su.se</email></address>
2204    </author>
2205    <author initials="A." surname="Hopmann" fullname="Alex Hopmann">
2206      <organization>Microsoft Corporation</organization>
2207      <address><email>alexhop@microsoft.com</email></address>
2208    </author>
2209    <author initials="N." surname="Shelness" fullname="Nick Shelness">
2210      <organization>Lotus Development Corporation</organization>
2211      <address><email>Shelness@lotus.com</email></address>
2212    </author>
2213    <author initials="E." surname="Stefferud" fullname="Einar Stefferud">
2214      <address><email>stef@nma.com</email></address>
2215    </author>
2216    <date year="1999" month="March"/>
2217  </front>
2218  <seriesInfo name="RFC" value="2557"/>
2219</reference>
2220
2221<reference anchor="RFC2616">
2222  <front>
2223    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
2224    <author initials="R." surname="Fielding" fullname="R. Fielding">
2225      <organization>University of California, Irvine</organization>
2226      <address><email>fielding@ics.uci.edu</email></address>
2227    </author>
2228    <author initials="J." surname="Gettys" fullname="J. Gettys">
2229      <organization>W3C</organization>
2230      <address><email>jg@w3.org</email></address>
2231    </author>
2232    <author initials="J." surname="Mogul" fullname="J. Mogul">
2233      <organization>Compaq Computer Corporation</organization>
2234      <address><email>mogul@wrl.dec.com</email></address>
2235    </author>
2236    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
2237      <organization>MIT Laboratory for Computer Science</organization>
2238      <address><email>frystyk@w3.org</email></address>
2239    </author>
2240    <author initials="L." surname="Masinter" fullname="L. Masinter">
2241      <organization>Xerox Corporation</organization>
2242      <address><email>masinter@parc.xerox.com</email></address>
2243    </author>
2244    <author initials="P." surname="Leach" fullname="P. Leach">
2245      <organization>Microsoft Corporation</organization>
2246      <address><email>paulle@microsoft.com</email></address>
2247    </author>
2248    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
2249      <organization>W3C</organization>
2250      <address><email>timbl@w3.org</email></address>
2251    </author>
2252    <date month="June" year="1999"/>
2253  </front>
2254  <seriesInfo name="RFC" value="2616"/>
2255</reference>
2256
2257<reference anchor="RFC3629">
2258  <front>
2259    <title>UTF-8, a transformation format of ISO 10646</title>
2260    <author initials="F." surname="Yergeau" fullname="F. Yergeau">
2261      <organization>Alis Technologies</organization>
2262      <address><email>fyergeau@alis.com</email></address>
2263    </author>
2264    <date month="November" year="2003"/>
2265  </front>
2266  <seriesInfo name="STD" value="63"/>
2267  <seriesInfo name="RFC" value="3629"/>
2268</reference>
2269
2270<reference anchor='RFC3864'>
2271  <front>
2272    <title>Registration Procedures for Message Header Fields</title>
2273    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
2274      <organization>Nine by Nine</organization>
2275      <address><email>GK-IETF@ninebynine.org</email></address>
2276    </author>
2277    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
2278      <organization>BEA Systems</organization>
2279      <address><email>mnot@pobox.com</email></address>
2280    </author>
2281    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
2282      <organization>HP Labs</organization>
2283      <address><email>JeffMogul@acm.org</email></address>
2284    </author>
2285    <date year='2004' month='September' />
2286  </front>
2287  <seriesInfo name='BCP' value='90' />
2288  <seriesInfo name='RFC' value='3864' />
2289</reference>
2290
2291<reference anchor="RFC4288">
2292  <front>
2293    <title>Media Type Specifications and Registration Procedures</title>
2294    <author initials="N." surname="Freed" fullname="N. Freed">
2295      <organization>Sun Microsystems</organization>
2296      <address>
2297        <email>ned.freed@mrochek.com</email>
2298      </address>
2299    </author>
2300    <author initials="J." surname="Klensin" fullname="J. Klensin">
2301      <address>
2302        <email>klensin+ietf@jck.com</email>
2303      </address>
2304    </author>
2305    <date year="2005" month="December"/>
2306  </front>
2307  <seriesInfo name="BCP" value="13"/>
2308  <seriesInfo name="RFC" value="4288"/>
2309</reference>
2310
2311<reference anchor='RFC5226'>
2312  <front>
2313    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
2314    <author initials='T.' surname='Narten' fullname='T. Narten'>
2315      <organization>IBM</organization>
2316      <address><email>narten@us.ibm.com</email></address>
2317    </author>
2318    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
2319      <organization>Google</organization>
2320      <address><email>Harald@Alvestrand.no</email></address>
2321    </author>
2322    <date year='2008' month='May' />
2323  </front>
2324  <seriesInfo name='BCP' value='26' />
2325  <seriesInfo name='RFC' value='5226' />
2326</reference>
2327
2328<reference anchor="RFC5322">
2329  <front>
2330    <title>Internet Message Format</title>
2331    <author initials="P." surname="Resnick" fullname="P. Resnick">
2332      <organization>Qualcomm Incorporated</organization>
2333    </author>
2334    <date year="2008" month="October"/>
2335  </front> 
2336  <seriesInfo name="RFC" value="5322"/>
2337</reference>
2338
2339<reference anchor="RFC6151">
2340  <front>
2341    <title>Updated Security Considerations for the MD5 Message-Digest and the HMAC-MD5 Algorithms</title>
2342    <author initials="S." surname="Turner" fullname="S. Turner"/>
2343    <author initials="L." surname="Chen" fullname="L. Chen"/>
2344    <date year="2011" month="March" />
2345  </front>
2346  <seriesInfo name="RFC" value="6151" />
2347</reference>
2348
2349<!--<reference anchor='BCP97'>
2350  <front>
2351    <title>Handling Normative References to Standards-Track Documents</title>
2352    <author initials='J.' surname='Klensin' fullname='J. Klensin'>
2353      <address>
2354        <email>klensin+ietf@jck.com</email>
2355      </address>
2356    </author>
2357    <author initials='S.' surname='Hartman' fullname='S. Hartman'>
2358      <organization>MIT</organization>
2359      <address>
2360        <email>hartmans-ietf@mit.edu</email>
2361      </address>
2362    </author>
2363    <date year='2007' month='June' />
2364  </front>
2365  <seriesInfo name='BCP' value='97' />
2366  <seriesInfo name='RFC' value='4897' />
2367</reference>-->
2368
2369<reference anchor="RFC6266">
2370  <front>
2371    <title abbrev="Content-Disposition in HTTP">Use of the Content-Disposition Header Field
2372    in the Hypertext Transfer Protocol (HTTP)</title>
2373    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke">
2374      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2375      <address>
2376        <email>julian.reschke@greenbytes.de</email>
2377      </address>
2378    </author>
2379    <date month="June" year="2011"/>
2380  </front>
2381  <seriesInfo name='RFC' value='6266' />
2382</reference>
2383
2384</references>
2385
2386<section title="Differences between HTTP and MIME" anchor="differences.between.http.and.mime">
2387<t>
2388   HTTP/1.1 uses many of the constructs defined for Internet Mail (<xref target="RFC5322"/>) and the Multipurpose Internet Mail Extensions (MIME <xref target="RFC2045"/>) to
2389   allow a message body to be transmitted in an open variety of
2390   representations and with extensible mechanisms. However, RFC 2045
2391   discusses mail, and HTTP has a few features that are different from
2392   those described in MIME. These differences were carefully chosen
2393   to optimize performance over binary connections, to allow greater
2394   freedom in the use of new media types, to make date comparisons
2395   easier, and to acknowledge the practice of some early HTTP servers
2396   and clients.
2397</t>
2398<t>
2399   This appendix describes specific areas where HTTP differs from MIME.
2400   Proxies and gateways to strict MIME environments &SHOULD; be
2401   aware of these differences and provide the appropriate conversions
2402   where necessary. Proxies and gateways from MIME environments to HTTP
2403   also need to be aware of the differences because some conversions
2404   might be required.
2405</t>
2406
2407<section title="MIME-Version" anchor="mime-version">
2408  <iref primary="true" item="MIME-Version header field" x:for-anchor=""/>
2409  <iref primary="true" item="Header Fields" subitem="MIME-Version" x:for-anchor=""/>
2410  <x:anchor-alias value="MIME-Version"/>
2411<t>
2412   HTTP is not a MIME-compliant protocol. However, HTTP/1.1 messages &MAY;
2413   include a single MIME-Version header field to indicate what
2414   version of the MIME protocol was used to construct the message. Use
2415   of the MIME-Version header field indicates that the message is in
2416   full conformance with the MIME protocol (as defined in <xref target="RFC2045"/>).
2417   Proxies/gateways are responsible for ensuring full conformance (where
2418   possible) when exporting HTTP messages to strict MIME environments.
2419</t>
2420<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="MIME-Version"/>
2421  <x:ref>MIME-Version</x:ref> = 1*<x:ref>DIGIT</x:ref> "." 1*<x:ref>DIGIT</x:ref>
2422</artwork></figure>
2423<t>
2424   MIME version "1.0" is the default for use in HTTP/1.1. However,
2425   HTTP/1.1 message parsing and semantics are defined by this document
2426   and not the MIME specification.
2427</t>
2428</section>
2429
2430<section title="Conversion to Canonical Form" anchor="conversion.to.canonical.form">
2431<t>
2432   MIME requires that an Internet mail body-part be converted to
2433   canonical form prior to being transferred, as described in <xref target="RFC2049" x:fmt="of" x:sec="4"/>.
2434   <xref target="canonicalization.and.text.defaults"/> of this document describes the forms
2435   allowed for subtypes of the "text" media type when transmitted over
2436   HTTP. <xref target="RFC2046"/> requires that content with a type of "text" represent
2437   line breaks as CRLF and forbids the use of CR or LF outside of line
2438   break sequences. HTTP allows CRLF, bare CR, and bare LF to indicate a
2439   line break within text content when a message is transmitted over
2440   HTTP.
2441</t>
2442<t>
2443   Where it is possible, a proxy or gateway from HTTP to a strict MIME
2444   environment &SHOULD; translate all line breaks within the text media
2445   types described in <xref target="canonicalization.and.text.defaults"/>
2446   of this document to the RFC 2049
2447   canonical form of CRLF. Note, however, that this might be complicated
2448   by the presence of a Content-Encoding and by the fact that HTTP
2449   allows the use of some character encodings which do not use octets 13 and
2450   10 to represent CR and LF, respectively, as is the case for some multi-byte
2451   character encodings.
2452</t>
2453<t>
2454   Conversion will break any cryptographic
2455   checksums applied to the original content unless the original content
2456   is already in canonical form. Therefore, the canonical form is
2457   recommended for any content that uses such checksums in HTTP.
2458</t>
2459</section>
2460
2461
2462<section title="Conversion of Date Formats" anchor="conversion.of.date.formats">
2463<t>
2464   HTTP/1.1 uses a restricted set of date formats (&http-date;) to
2465   simplify the process of date comparison. Proxies and gateways from
2466   other protocols &SHOULD; ensure that any Date header field present in a
2467   message conforms to one of the HTTP/1.1 formats and rewrite the date
2468   if necessary.
2469</t>
2470</section>
2471
2472<section title="Introduction of Content-Encoding" anchor="introduction.of.content-encoding">
2473<t>
2474   MIME does not include any concept equivalent to HTTP/1.1's
2475   Content-Encoding header field. Since this acts as a modifier on the
2476   media type, proxies and gateways from HTTP to MIME-compliant
2477   protocols &MUST; either change the value of the Content-Type header
2478   field or decode the representation before forwarding the message. (Some
2479   experimental applications of Content-Type for Internet mail have used
2480   a media-type parameter of ";conversions=&lt;content-coding&gt;" to perform
2481   a function equivalent to Content-Encoding. However, this parameter is
2482   not part of the MIME standards).
2483</t>
2484</section>
2485
2486<section title="No Content-Transfer-Encoding" anchor="no.content-transfer-encoding">
2487  <iref item="Content-Transfer-Encoding header field" x:for-anchor=""/>
2488  <iref item="Header Fields" subitem="Content-Transfer-Encoding" x:for-anchor=""/>
2489<t>
2490   HTTP does not use the Content-Transfer-Encoding field of MIME.
2491   Proxies and gateways from MIME-compliant protocols to HTTP &MUST;
2492   remove any Content-Transfer-Encoding
2493   prior to delivering the response message to an HTTP client.
2494</t>
2495<t>
2496   Proxies and gateways from HTTP to MIME-compliant protocols are
2497   responsible for ensuring that the message is in the correct format
2498   and encoding for safe transport on that protocol, where "safe
2499   transport" is defined by the limitations of the protocol being used.
2500   Such a proxy or gateway &SHOULD; label the data with an appropriate
2501   Content-Transfer-Encoding if doing so will improve the likelihood of
2502   safe transport over the destination protocol.
2503</t>
2504</section>
2505
2506<section title="Introduction of Transfer-Encoding" anchor="introduction.of.transfer-encoding">
2507<t>
2508   HTTP/1.1 introduces the Transfer-Encoding header field (&header-transfer-encoding;).
2509   Proxies/gateways &MUST; remove any transfer-coding prior to
2510   forwarding a message via a MIME-compliant protocol.
2511</t>
2512</section>
2513
2514<section title="MHTML and Line Length Limitations" anchor="mhtml.line.length">
2515<t>
2516   HTTP implementations which share code with MHTML <xref target="RFC2557"/> implementations
2517   need to be aware of MIME line length limitations. Since HTTP does not
2518   have this limitation, HTTP does not fold long lines. MHTML messages
2519   being transported by HTTP follow all conventions of MHTML, including
2520   line length limitations and folding, canonicalization, etc., since
2521   HTTP transports all message-bodies as payload (see <xref target="multipart.types"/>) and
2522   does not interpret the content or any MIME header lines that might be
2523   contained therein.
2524</t>
2525</section>
2526</section>
2527
2528<section title="Additional Features" anchor="additional.features">
2529<t>
2530   <xref target="RFC1945"/> and <xref target="RFC2068"/> document protocol elements used by some
2531   existing HTTP implementations, but not consistently and correctly
2532   across most HTTP/1.1 applications. Implementors are advised to be
2533   aware of these features, but cannot rely upon their presence in, or
2534   interoperability with, other HTTP/1.1 applications. Some of these
2535   describe proposed experimental features, and some describe features
2536   that experimental deployment found lacking that are now addressed in
2537   the base HTTP/1.1 specification.
2538</t>
2539<t>
2540   A number of other header fields, such as Content-Disposition and Title,
2541   from SMTP and MIME are also often implemented (see <xref target="RFC6266"/>
2542   and <xref target="RFC2076"/>).
2543</t>
2544</section>
2545
2546<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
2547<t>
2548  Clarify contexts that charset is used in.
2549  (<xref target="character.sets"/>)
2550</t>
2551<t>
2552  Registration of Content Codings now requires IETF Review
2553  (<xref target="content.coding.registry"/>)
2554</t>
2555<t>
2556  Remove the default character encoding for text media types; the default
2557  now is whatever the media type definition says.
2558  (<xref target="canonicalization.and.text.defaults"/>)
2559</t>
2560<t>
2561  Change ABNF productions for header fields to only define the field value.
2562  (<xref target="header.field.definitions"/>)
2563</t>
2564<t>
2565  Remove definition of Content-MD5 header field because it was inconsistently
2566  implemented with respect to partial responses, and also because of known
2567  deficiencies in the hash algorithm itself (see <xref target="RFC6151"/> for details).
2568  (<xref target="header.field.definitions"/>)
2569</t>
2570<t>
2571  Remove ISO-8859-1 special-casing in Accept-Charset.
2572  (<xref target="header.accept-charset"/>)
2573</t>
2574<t>
2575  Remove base URI setting semantics for Content-Location due to poor
2576  implementation support, which was caused by too many broken servers emitting
2577  bogus Content-Location header fields, and also the potentially undesirable effect
2578  of potentially breaking relative links in content-negotiated resources.
2579  (<xref target="header.content-location"/>)
2580</t>
2581<t>
2582  Remove reference to non-existant identity transfer-coding value tokens.
2583  (<xref target="no.content-transfer-encoding"/>)
2584</t>
2585<t>
2586  Remove discussion of Content-Disposition header field, it is now defined
2587  by <xref target="RFC6266"/>.
2588  (<xref target="additional.features"/>)
2589</t>
2590</section>
2591
2592<?BEGININC p3-payload.abnf-appendix ?>
2593<section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf">
2594<figure>
2595<artwork type="abnf" name="p3-payload.parsed-abnf">
2596<x:ref>Accept</x:ref> = [ ( "," / ( media-range [ accept-params ] ) ) *( OWS "," [
2597 OWS media-range [ accept-params ] ] ) ]
2598<x:ref>Accept-Charset</x:ref> = *( "," OWS ) ( charset / "*" ) [ OWS ";" OWS "q="
2599 qvalue ] *( OWS "," [ OWS ( charset / "*" ) [ OWS ";" OWS "q="
2600 qvalue ] ] )
2601<x:ref>Accept-Encoding</x:ref> = [ ( "," / ( codings [ OWS ";" OWS "q=" qvalue ] ) )
2602 *( OWS "," [ OWS codings [ OWS ";" OWS "q=" qvalue ] ] ) ]
2603<x:ref>Accept-Language</x:ref> = *( "," OWS ) language-range [ OWS ";" OWS "q="
2604 qvalue ] *( OWS "," [ OWS language-range [ OWS ";" OWS "q=" qvalue ]
2605 ] )
2606
2607<x:ref>Content-Encoding</x:ref> = *( "," OWS ) content-coding *( OWS "," [ OWS
2608 content-coding ] )
2609<x:ref>Content-Language</x:ref> = *( "," OWS ) language-tag *( OWS "," [ OWS
2610 language-tag ] )
2611<x:ref>Content-Location</x:ref> = absolute-URI / partial-URI
2612<x:ref>Content-Type</x:ref> = media-type
2613
2614<x:ref>MIME-Version</x:ref> = 1*DIGIT "." 1*DIGIT
2615
2616<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 3.2.1&gt;
2617
2618<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.7&gt;
2619<x:ref>accept-ext</x:ref> = OWS ";" OWS token [ "=" word ]
2620<x:ref>accept-params</x:ref> = OWS ";" OWS "q=" qvalue *accept-ext
2621<x:ref>attribute</x:ref> = token
2622
2623<x:ref>charset</x:ref> = token
2624<x:ref>codings</x:ref> = content-coding / "identity" / "*"
2625<x:ref>content-coding</x:ref> = token
2626
2627<x:ref>language-range</x:ref> = &lt;language-range, defined in [RFC4647], Section 2.1&gt;
2628<x:ref>language-tag</x:ref> = &lt;Language-Tag, defined in [RFC5646], Section 2.1&gt;
2629
2630<x:ref>media-range</x:ref> = ( "*/*" / ( type "/*" ) / ( type "/" subtype ) ) *( OWS
2631 ";" OWS parameter )
2632<x:ref>media-type</x:ref> = type "/" subtype *( OWS ";" OWS parameter )
2633
2634<x:ref>parameter</x:ref> = attribute "=" value
2635<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.7&gt;
2636
2637<x:ref>qvalue</x:ref> = &lt;qvalue, defined in [Part1], Section 4.4.1&gt;
2638
2639<x:ref>subtype</x:ref> = token
2640
2641<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 3.2.4&gt;
2642<x:ref>type</x:ref> = token
2643
2644<x:ref>value</x:ref> = word
2645
2646<x:ref>word</x:ref> = &lt;word, defined in [Part1], Section 3.2.4&gt;
2647</artwork>
2648</figure>
2649<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
2650; Accept defined but not used
2651; Accept-Charset defined but not used
2652; Accept-Encoding defined but not used
2653; Accept-Language defined but not used
2654; Content-Encoding defined but not used
2655; Content-Language defined but not used
2656; Content-Location defined but not used
2657; Content-Type defined but not used
2658; MIME-Version defined but not used
2659</artwork></figure></section>
2660<?ENDINC p3-payload.abnf-appendix ?>
2661
2662<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
2663
2664<section title="Since RFC 2616">
2665<t>
2666  Extracted relevant partitions from <xref target="RFC2616"/>.
2667</t>
2668</section>
2669
2670<section title="Since draft-ietf-httpbis-p3-payload-00">
2671<t>
2672  Closed issues:
2673  <list style="symbols"> 
2674    <t>
2675      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/8"/>:
2676      "Media Type Registrations"
2677      (<eref target="http://purl.org/NET/http-errata#media-reg"/>)
2678    </t>
2679    <t>
2680      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/14"/>:
2681      "Clarification regarding quoting of charset values"
2682      (<eref target="http://purl.org/NET/http-errata#charactersets"/>)
2683    </t>
2684    <t>
2685      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/16"/>:
2686      "Remove 'identity' token references"
2687      (<eref target="http://purl.org/NET/http-errata#identity"/>)
2688    </t>
2689    <t>
2690      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/25"/>:
2691      "Accept-Encoding BNF"
2692    </t>
2693    <t>
2694      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
2695      "Normative and Informative references"
2696    </t>
2697    <t>
2698      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/46"/>:
2699      "RFC1700 references"
2700    </t>
2701    <t>
2702      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/55"/>:
2703      "Updating to RFC4288"
2704    </t>
2705    <t>
2706      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
2707      "Informative references"
2708    </t>
2709    <t>
2710      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/66"/>:
2711      "ISO-8859-1 Reference"
2712    </t>
2713    <t>
2714      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/68"/>:
2715      "Encoding References Normative"
2716    </t>
2717    <t>
2718      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/86"/>:
2719      "Normative up-to-date references"
2720    </t>
2721  </list>
2722</t>
2723</section>
2724
2725<section title="Since draft-ietf-httpbis-p3-payload-01">
2726<t>
2727  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
2728  <list style="symbols"> 
2729    <t>
2730      Add explicit references to BNF syntax and rules imported from other parts of the specification.
2731    </t>
2732  </list>
2733</t>
2734</section>
2735
2736<section title="Since draft-ietf-httpbis-p3-payload-02" anchor="changes.since.02">
2737<t>
2738  Closed issues:
2739  <list style="symbols"> 
2740    <t>
2741      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/67"/>:
2742      "Quoting Charsets"
2743    </t>
2744    <t>
2745      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
2746      "Classification for Allow header"
2747    </t>
2748    <t>
2749      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/115"/>:
2750      "missing default for qvalue in description of Accept-Encoding"
2751    </t>
2752  </list>
2753</t>
2754<t>
2755  Ongoing work on IANA Message Header Field Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
2756  <list style="symbols"> 
2757    <t>
2758      Reference RFC 3984, and update header field registrations for headers defined
2759      in this document.
2760    </t>
2761  </list>
2762</t>
2763</section>
2764
2765<section title="Since draft-ietf-httpbis-p3-payload-03" anchor="changes.since.03">
2766<t>
2767  Closed issues:
2768  <list style="symbols"> 
2769    <t>
2770      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/67"/>:
2771      "Quoting Charsets"
2772    </t>
2773    <t>
2774      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/113"/>:
2775      "language tag matching (Accept-Language) vs RFC4647"
2776    </t>
2777    <t>
2778      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/121"/>:
2779      "RFC 1806 has been replaced by RFC2183"
2780    </t>
2781  </list>
2782</t>
2783<t>
2784  Other changes:
2785  <list style="symbols"> 
2786    <t>
2787      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/68"/>:
2788      "Encoding References Normative" &mdash; rephrase the annotation and reference
2789      BCP97.
2790    </t>
2791  </list>
2792</t>
2793 </section>
2794
2795<section title="Since draft-ietf-httpbis-p3-payload-04" anchor="changes.since.04">
2796<t>
2797  Closed issues:
2798  <list style="symbols"> 
2799    <t>
2800      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
2801      "RFC 2822 is updated by RFC 5322"
2802    </t>
2803  </list>
2804</t>
2805<t>
2806  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
2807  <list style="symbols"> 
2808    <t>
2809      Use "/" instead of "|" for alternatives.
2810    </t>
2811    <t>
2812      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
2813      whitespace ("OWS") and required whitespace ("RWS").
2814    </t>
2815    <t>
2816      Rewrite ABNFs to spell out whitespace rules, factor out
2817      header field value format definitions.
2818    </t>
2819  </list>
2820</t>
2821</section>
2822
2823<section title="Since draft-ietf-httpbis-p3-payload-05" anchor="changes.since.05">
2824<t>
2825  Closed issues:
2826  <list style="symbols"> 
2827    <t>
2828      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/118"/>:
2829      "Join "Differences Between HTTP Entities and RFC 2045 Entities"?"
2830    </t>
2831  </list>
2832</t>
2833<t>
2834  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
2835  <list style="symbols"> 
2836    <t>
2837      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
2838    </t>
2839  </list>
2840</t>
2841<t>
2842  Other changes:
2843  <list style="symbols"> 
2844    <t>
2845      Move definition of quality values into Part 1.
2846    </t>
2847  </list>
2848</t>
2849</section>
2850
2851<section title="Since draft-ietf-httpbis-p3-payload-06" anchor="changes.since.06">
2852<t>
2853  Closed issues:
2854  <list style="symbols"> 
2855    <t>
2856      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/80"/>:
2857      "Content-Location isn't special"
2858    </t>
2859    <t>
2860      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/155"/>:
2861      "Content Sniffing"
2862    </t>
2863  </list>
2864</t>
2865</section>
2866
2867<section title="Since draft-ietf-httpbis-p3-payload-07" anchor="changes.since.07">
2868<t>
2869  Closed issues:
2870  <list style="symbols"> 
2871    <t>
2872      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/13"/>:
2873      "Updated reference for language tags"
2874    </t>
2875    <t>
2876      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
2877      "Clarify rules for determining what entities a response carries"
2878    </t>
2879    <t>
2880      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/154"/>:
2881      "Content-Location base-setting problems"
2882    </t>
2883    <t>
2884      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/155"/>:
2885      "Content Sniffing"
2886    </t>
2887    <t>
2888      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/188"/>:
2889      "pick IANA policy (RFC5226) for Transfer Coding / Content Coding"
2890    </t>
2891    <t>
2892      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/189"/>:
2893      "move definitions of gzip/deflate/compress to part 1"
2894    </t>
2895  </list>
2896</t>
2897<t>
2898  Partly resolved issues:
2899  <list style="symbols"> 
2900    <t>
2901      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/148"/>:
2902      "update IANA requirements wrt Transfer-Coding values" (add the
2903      IANA Considerations subsection)
2904    </t>
2905    <t>
2906      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/149"/>:
2907      "update IANA requirements wrt Content-Coding values" (add the
2908      IANA Considerations subsection)
2909    </t>
2910  </list>
2911</t>
2912</section>
2913
2914<section title="Since draft-ietf-httpbis-p3-payload-08" anchor="changes.since.08">
2915<t>
2916  Closed issues:
2917  <list style="symbols"> 
2918    <t>
2919      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/81"/>:
2920      "Content Negotiation for media types"
2921    </t>
2922    <t>
2923      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/181"/>:
2924      "Accept-Language: which RFC4647 filtering?"
2925    </t>
2926  </list>
2927</t>
2928</section>
2929
2930<section title="Since draft-ietf-httpbis-p3-payload-09" anchor="changes.since.09">
2931<t>
2932  Closed issues:
2933  <list style="symbols"> 
2934    <t>
2935      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/122"/>:
2936      "MIME-Version not listed in P1, general header fields"
2937    </t>
2938    <t>
2939      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/143"/>:
2940      "IANA registry for content/transfer encodings"
2941    </t>
2942    <t>
2943      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/155"/>:
2944      "Content Sniffing"
2945    </t>
2946    <t>
2947      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/200"/>:
2948      "use of term "word" when talking about header structure"
2949    </t>
2950  </list>
2951</t>
2952<t>
2953  Partly resolved issues:
2954  <list style="symbols"> 
2955    <t>
2956      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196"/>:
2957      "Term for the requested resource's URI"
2958    </t>
2959  </list>
2960</t>
2961</section>
2962
2963<section title="Since draft-ietf-httpbis-p3-payload-10" anchor="changes.since.10">
2964<t>
2965  Closed issues:
2966  <list style="symbols"> 
2967    <t>
2968      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/69"/>:
2969      "Clarify 'Requested Variant'"
2970    </t>
2971    <t>
2972      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/80"/>:
2973      "Content-Location isn't special"
2974    </t>
2975    <t>
2976      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/90"/>:
2977      "Delimiting messages with multipart/byteranges"
2978    </t>
2979    <t>
2980      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/109"/>:
2981      "Clarify entity / representation / variant terminology"
2982    </t>
2983    <t>
2984      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/136"/>:
2985      "confusing req. language for Content-Location"
2986    </t>
2987    <t>
2988      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/167"/>:
2989      "Content-Location on 304 responses"
2990    </t>
2991    <t>
2992      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/183"/>:
2993      "'requested resource' in content-encoding definition"
2994    </t>
2995    <t>
2996      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/220"/>:
2997      "consider removing the 'changes from 2068' sections"
2998    </t>
2999  </list>
3000</t>
3001<t>
3002  Partly resolved issues:
3003  <list style="symbols"> 
3004    <t>
3005      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/178"/>:
3006      "Content-MD5 and partial responses"
3007    </t>
3008  </list>
3009</t>
3010</section>
3011
3012<section title="Since draft-ietf-httpbis-p3-payload-11" anchor="changes.since.11">
3013<t>
3014  Closed issues:
3015  <list style="symbols"> 
3016    <t>
3017      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/123"/>:
3018      "Factor out Content-Disposition"
3019    </t>
3020  </list>
3021</t>
3022</section>
3023
3024<section title="Since draft-ietf-httpbis-p3-payload-12" anchor="changes.since.12">
3025<t>
3026  Closed issues:
3027  <list style="symbols"> 
3028    <t>
3029      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/224"/>:
3030      "Header Classification"
3031    </t>
3032    <t>
3033      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
3034      "untangle ABNFs for header fields"
3035    </t>
3036    <t>
3037      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/277"/>:
3038      "potentially misleading MAY in media-type def"
3039    </t>
3040  </list>
3041</t>
3042</section>
3043
3044<section title="Since draft-ietf-httpbis-p3-payload-13" anchor="changes.since.13">
3045<t>
3046  Closed issues:
3047  <list style="symbols"> 
3048    <t>
3049      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/20"/>:
3050      "Default charsets for text media types"
3051    </t>
3052    <t>
3053      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/178"/>:
3054      "Content-MD5 and partial responses"
3055    </t>
3056    <t>
3057      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
3058      "untangle ABNFs for header fields"
3059    </t>
3060    <t>
3061      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/281"/>:
3062      "confusing undefined parameter in media range example"
3063    </t>
3064  </list>
3065</t>
3066</section>
3067
3068<section title="Since draft-ietf-httpbis-p3-payload-14" anchor="changes.since.14">
3069<t>
3070  None.
3071</t>
3072</section>
3073
3074<section title="Since draft-ietf-httpbis-p3-payload-15" anchor="changes.since.15">
3075<t>
3076  Closed issues:
3077  <list style="symbols"> 
3078    <t>
3079      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/285"/>:
3080      "Strength of requirements on Accept re: 406"
3081    </t>
3082  </list>
3083</t>
3084</section>
3085
3086<section title="Since draft-ietf-httpbis-p3-payload-16" anchor="changes.since.16">
3087<t>
3088  Closed issues:
3089  <list style="symbols"> 
3090    <t>
3091      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/186"/>:
3092      "Document HTTP's error-handling philosophy"
3093    </t>
3094  </list>
3095</t>
3096</section>
3097
3098<section title="Since draft-ietf-httpbis-p3-payload-17" anchor="changes.since.17">
3099<t>
3100  Closed issues:
3101  <list style="symbols"> 
3102    <t>
3103      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/323"/>:
3104      "intended maturity level vs normative references"
3105    </t>
3106  </list>
3107</t>
3108</section>
3109
3110<section title="Since draft-ietf-httpbis-p3-payload-18" anchor="changes.since.18">
3111<t>
3112  Closed issues:
3113  <list style="symbols">
3114    <t>
3115      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/330"/>:
3116      "is ETag a representation header field?"
3117    </t>
3118    <t>
3119      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/346"/>:
3120      "make IANA policy definitions consistent"
3121    </t>
3122  </list>
3123</t>
3124</section>
3125
3126</section>
3127
3128</back>
3129</rfc>
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