source: draft-ietf-httpbis/latest/p3-payload.xml @ 1423

Last change on this file since 1423 was 1423, checked in by fielding@…, 8 years ago

Restore the IANA registration of "identity" under content-coding
values to ensure that the name is reserved (and properly defined).
This is an update to [1406].

  • Property svn:eol-style set to native
File size: 123.8 KB
Line 
1<?xml version="1.0" encoding="utf-8"?>
2<?xml-stylesheet type='text/xsl' href='../myxml2rfc.xslt'?>
3<!DOCTYPE rfc [
4  <!ENTITY MAY "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MAY</bcp14>">
5  <!ENTITY MUST "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST</bcp14>">
6  <!ENTITY MUST-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST NOT</bcp14>">
7  <!ENTITY OPTIONAL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>OPTIONAL</bcp14>">
8  <!ENTITY RECOMMENDED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>RECOMMENDED</bcp14>">
9  <!ENTITY REQUIRED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>REQUIRED</bcp14>">
10  <!ENTITY SHALL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL</bcp14>">
11  <!ENTITY SHALL-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL NOT</bcp14>">
12  <!ENTITY SHOULD "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD</bcp14>">
13  <!ENTITY SHOULD-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD NOT</bcp14>">
14  <!ENTITY ID-VERSION "latest">
15  <!ENTITY ID-MONTH "August">
16  <!ENTITY ID-YEAR "2011">
17  <!ENTITY mdash "&#8212;">
18  <!ENTITY notation                 "<xref target='Part1' x:rel='#notation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
19  <!ENTITY notation-abnf            "<xref target='Part1' x:rel='#notation.abnf' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
20  <!ENTITY acks                     "<xref target='Part1' x:rel='#acks' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
21  <!ENTITY basic-rules              "<xref target='Part1' x:rel='#basic.rules' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
22  <!ENTITY field-rules              "<xref target='Part1' x:rel='#field.rules' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
23  <!ENTITY caching-neg-resp         "<xref target='Part6' x:rel='#caching.negotiated.responses' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
24  <!ENTITY header-transfer-encoding "<xref target='Part1' x:rel='#header.transfer-encoding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
25  <!ENTITY header-content-length    "<xref target='Part1' x:rel='#header.content-length' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
26  <!ENTITY header-content-range     "<xref target='Part5' x:rel='#header.content-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
27  <!ENTITY header-expires           "<xref target='Part6' x:rel='#header.expires' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
28  <!ENTITY header-last-modified     "<xref target='Part4' x:rel='#header.last-modified' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
29  <!ENTITY header-user-agent        "<xref target='Part2' x:rel='#header.user-agent' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
30  <!ENTITY header-vary              "<xref target='Part6' x:rel='#header.vary' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
31  <!ENTITY message-body             "<xref target='Part1' x:rel='#message.body' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
32  <!ENTITY multipart-byteranges     "<xref target='Part5' x:rel='#internet.media.type.multipart.byteranges' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
33  <!ENTITY full-date                "<xref target='Part1' x:rel='#date.time.formats.full.date' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
34  <!ENTITY qvalue                   "<xref target='Part1' x:rel='#quality.values' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
35  <!ENTITY uri                      "<xref target='Part1' x:rel='#uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
36  <!ENTITY effective-request-uri    "<xref target='Part1' x:rel='#effective.request.uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
37  <!ENTITY compression-codings      "<xref target='Part1' x:rel='#compression.codings' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
38  <!ENTITY transfer-codings         "<xref target='Part1' x:rel='#transfer.codings' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
39  <!ENTITY compress-coding          "<xref target='Part1' x:rel='#compress.coding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
40  <!ENTITY deflate-coding           "<xref target='Part1' x:rel='#deflate.coding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
41  <!ENTITY gzip-coding              "<xref target='Part1' x:rel='#gzip.coding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
42  <!ENTITY response-representation  "<xref target='Part2' x:rel='#identifying.response.associated.with.representation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
43]>
44<?rfc toc="yes" ?>
45<?rfc symrefs="yes" ?>
46<?rfc sortrefs="yes" ?>
47<?rfc compact="yes"?>
48<?rfc subcompact="no" ?>
49<?rfc linkmailto="no" ?>
50<?rfc editing="no" ?>
51<?rfc comments="yes"?>
52<?rfc inline="yes"?>
53<?rfc rfcedstyle="yes"?>
54<?rfc-ext allow-markup-in-artwork="yes" ?>
55<?rfc-ext include-references-in-index="yes" ?>
56<rfc obsoletes="2616" category="std" x:maturity-level="draft"
57     ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p3-payload-&ID-VERSION;"
58     xmlns:x='http://purl.org/net/xml2rfc/ext'>
59<front>
60
61  <title abbrev="HTTP/1.1, Part 3">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
62
63  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
64    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
65    <address>
66      <postal>
67        <street>345 Park Ave</street>
68        <city>San Jose</city>
69        <region>CA</region>
70        <code>95110</code>
71        <country>USA</country>
72      </postal>
73      <email>fielding@gbiv.com</email>
74      <uri>http://roy.gbiv.com/</uri>
75    </address>
76  </author>
77
78  <author initials="J." surname="Gettys" fullname="Jim Gettys">
79    <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
80    <address>
81      <postal>
82        <street>21 Oak Knoll Road</street>
83        <city>Carlisle</city>
84        <region>MA</region>
85        <code>01741</code>
86        <country>USA</country>
87      </postal>
88      <email>jg@freedesktop.org</email>
89      <uri>http://gettys.wordpress.com/</uri>
90    </address>
91  </author>
92 
93  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
94    <organization abbrev="HP">Hewlett-Packard Company</organization>
95    <address>
96      <postal>
97        <street>HP Labs, Large Scale Systems Group</street>
98        <street>1501 Page Mill Road, MS 1177</street>
99        <city>Palo Alto</city>
100        <region>CA</region>
101        <code>94304</code>
102        <country>USA</country>
103      </postal>
104      <email>JeffMogul@acm.org</email>
105    </address>
106  </author>
107
108  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
109    <organization abbrev="Microsoft">Microsoft Corporation</organization>
110    <address>
111      <postal>
112        <street>1 Microsoft Way</street>
113        <city>Redmond</city>
114        <region>WA</region>
115        <code>98052</code>
116        <country>USA</country>
117      </postal>
118      <email>henrikn@microsoft.com</email>
119    </address>
120  </author>
121
122  <author initials="L." surname="Masinter" fullname="Larry Masinter">
123    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
124    <address>
125      <postal>
126        <street>345 Park Ave</street>
127        <city>San Jose</city>
128        <region>CA</region>
129        <code>95110</code>
130        <country>USA</country>
131      </postal>
132      <email>LMM@acm.org</email>
133      <uri>http://larry.masinter.net/</uri>
134    </address>
135  </author>
136 
137  <author initials="P." surname="Leach" fullname="Paul J. Leach">
138    <organization abbrev="Microsoft">Microsoft Corporation</organization>
139    <address>
140      <postal>
141        <street>1 Microsoft Way</street>
142        <city>Redmond</city>
143        <region>WA</region>
144        <code>98052</code>
145      </postal>
146      <email>paulle@microsoft.com</email>
147    </address>
148  </author>
149   
150  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
151    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
152    <address>
153      <postal>
154        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
155        <street>The Stata Center, Building 32</street>
156        <street>32 Vassar Street</street>
157        <city>Cambridge</city>
158        <region>MA</region>
159        <code>02139</code>
160        <country>USA</country>
161      </postal>
162      <email>timbl@w3.org</email>
163      <uri>http://www.w3.org/People/Berners-Lee/</uri>
164    </address>
165  </author>
166
167  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
168    <organization abbrev="W3C">World Wide Web Consortium</organization>
169    <address>
170      <postal>
171        <street>W3C / ERCIM</street>
172        <street>2004, rte des Lucioles</street>
173        <city>Sophia-Antipolis</city>
174        <region>AM</region>
175        <code>06902</code>
176        <country>France</country>
177      </postal>
178      <email>ylafon@w3.org</email>
179      <uri>http://www.raubacapeu.net/people/yves/</uri>
180    </address>
181  </author>
182
183  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
184    <organization abbrev="greenbytes">greenbytes GmbH</organization>
185    <address>
186      <postal>
187        <street>Hafenweg 16</street>
188        <city>Muenster</city><region>NW</region><code>48155</code>
189        <country>Germany</country>
190      </postal>
191      <phone>+49 251 2807760</phone>
192      <facsimile>+49 251 2807761</facsimile>
193      <email>julian.reschke@greenbytes.de</email>
194      <uri>http://greenbytes.de/tech/webdav/</uri>
195    </address>
196  </author>
197
198  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
199  <workgroup>HTTPbis Working Group</workgroup>
200
201<abstract>
202<t>
203   The Hypertext Transfer Protocol (HTTP) is an application-level protocol for
204   distributed, collaborative, hypertext information systems. HTTP has been in
205   use by the World Wide Web global information initiative since 1990. This
206   document is Part 3 of the seven-part specification that defines the protocol
207   referred to as "HTTP/1.1" and, taken together, obsoletes RFC 2616.
208</t>
209<t>
210   Part 3 defines HTTP message content, metadata, and content negotiation.
211</t>
212</abstract>
213
214<note title="Editorial Note (To be removed by RFC Editor)">
215  <t>
216    Discussion of this draft should take place on the HTTPBIS working group
217    mailing list (ietf-http-wg@w3.org), which is archived at
218    <eref target="http://lists.w3.org/Archives/Public/ietf-http-wg/"/>.
219  </t>
220  <t>
221    The current issues list is at
222    <eref target="http://tools.ietf.org/wg/httpbis/trac/report/3"/> and related
223    documents (including fancy diffs) can be found at
224    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
225  </t>
226  <t>
227    The changes in this draft are summarized in <xref target="changes.since.16"/>.
228  </t>
229</note>
230</front>
231<middle>
232<section title="Introduction" anchor="introduction">
233<t>
234   This document defines HTTP/1.1 message payloads (a.k.a., content), the
235   associated metadata header fields that define how the payload is intended
236   to be interpreted by a recipient, the request header fields that
237   might influence content selection, and the various selection algorithms
238   that are collectively referred to as HTTP content negotiation.
239</t>
240<t>
241   This document is currently disorganized in order to minimize the changes
242   between drafts and enable reviewers to see the smaller errata changes.
243   A future draft will reorganize the sections to better reflect the content.
244   In particular, the sections on entities will be renamed payload and moved
245   to the first half of the document, while the sections on content negotiation
246   and associated request header fields will be moved to the second half.  The
247   current mess reflects how widely dispersed these topics and associated
248   requirements had become in <xref target="RFC2616"/>.
249</t>
250
251<section title="Terminology" anchor="terminology">
252<t>
253   This specification uses a number of terms to refer to the roles
254   played by participants in, and objects of, the HTTP communication.
255</t>
256<t>
257  <iref item="content negotiation"/>
258  <x:dfn>content negotiation</x:dfn>
259  <list>
260    <t>
261      The mechanism for selecting the appropriate representation when
262      servicing a request. The representation in any response
263      can be negotiated (including error responses).
264    </t>
265  </list>
266</t>
267</section>
268
269<section title="Requirements" anchor="intro.requirements">
270<t>
271   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
272   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
273   document are to be interpreted as described in <xref target="RFC2119"/>.
274</t>
275<t>
276   An implementation is not compliant if it fails to satisfy one or more
277   of the "MUST" or "REQUIRED" level requirements for the protocols it
278   implements. An implementation that satisfies all the "MUST" or "REQUIRED"
279   level and all the "SHOULD" level requirements for its protocols is said
280   to be "unconditionally compliant"; one that satisfies all the "MUST"
281   level requirements but not all the "SHOULD" level requirements for its
282   protocols is said to be "conditionally compliant".
283</t>
284</section>
285
286<section title="Syntax Notation" anchor="notation">
287  <x:anchor-alias value="ALPHA"/>
288  <x:anchor-alias value="CR"/>
289  <x:anchor-alias value="DIGIT"/>
290  <x:anchor-alias value="LF"/>
291  <x:anchor-alias value="OCTET"/>
292  <x:anchor-alias value="VCHAR"/>
293  <x:anchor-alias value="WSP"/>
294<t>
295  This specification uses the ABNF syntax defined in &notation; (which
296  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
297  <xref target="collected.abnf"/> shows the collected ABNF, with the list
298  rule expanded.
299</t>
300<t>
301  The following core rules are included by
302  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
303  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
304  DIGIT (decimal 0-9), DQUOTE (double quote),
305  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
306  OCTET (any 8-bit sequence of data), SP (space),
307  VCHAR (any visible USASCII character),
308  and WSP (whitespace).
309</t>
310
311<section title="Core Rules" anchor="core.rules">
312  <x:anchor-alias value="token"/>
313  <x:anchor-alias value="word"/>
314  <x:anchor-alias value="OWS"/>
315<t>
316  The core rules below are defined in <xref target="Part1"/>:
317</t>
318<figure><artwork type="abnf2616">
319  <x:ref>OWS</x:ref>            = &lt;OWS, defined in &basic-rules;&gt;
320  <x:ref>token</x:ref>          = &lt;token, defined in &field-rules;&gt;
321  <x:ref>word</x:ref>           = &lt;word, defined in &field-rules;&gt;
322</artwork></figure>
323</section>
324
325<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
326  <x:anchor-alias value="absolute-URI"/>
327  <x:anchor-alias value="partial-URI"/>
328  <x:anchor-alias value="qvalue"/>
329<t>
330  The ABNF rules below are defined in other parts:
331</t>
332<figure><!--Part1--><artwork type="abnf2616">
333  <x:ref>absolute-URI</x:ref>   = &lt;absolute-URI, defined in &uri;&gt;
334  <x:ref>partial-URI</x:ref>    = &lt;partial-URI, defined in &uri;&gt;
335  <x:ref>qvalue</x:ref>         = &lt;qvalue, defined in &qvalue;&gt;
336</artwork></figure>
337</section>
338
339</section>
340
341</section>
342
343<section title="Protocol Parameters" anchor="protocol.parameters">
344
345<section title="Character Encodings (charset)" anchor="character.sets">
346<t>
347   HTTP uses charset names to indicate the character encoding of a
348   textual representation.
349</t>
350<t anchor="rule.charset">
351  <x:anchor-alias value="charset"/>
352   A character encoding is identified by a case-insensitive token. The
353   complete set of tokens is defined by the IANA Character Set registry
354   (<eref target="http://www.iana.org/assignments/character-sets"/>).
355</t>
356<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="charset"/>
357  <x:ref>charset</x:ref> = <x:ref>token</x:ref>
358</artwork></figure>
359<t>
360   Although HTTP allows an arbitrary token to be used as a charset
361   value, any token that has a predefined value within the IANA
362   Character Set registry &MUST; represent the character encoding defined
363   by that registry. Applications &SHOULD; limit their use of character
364   encodings to those defined within the IANA registry.
365</t>
366<t>
367   HTTP uses charset in two contexts: within an Accept-Charset request
368   header field (in which the charset value is an unquoted token) and as the
369   value of a parameter in a Content-Type header field (within a request or
370   response), in which case the parameter value of the charset parameter
371   can be quoted.
372</t>
373<t>
374   Implementors need to be aware of IETF character set requirements <xref target="RFC3629"/>
375   <xref target="RFC2277"/>.
376</t>
377</section>
378
379<section title="Content Codings" anchor="content.codings">
380  <x:anchor-alias value="content-coding"/>
381<t>
382   Content coding values indicate an encoding transformation that has
383   been or can be applied to a representation. Content codings are primarily
384   used to allow a representation to be compressed or otherwise usefully
385   transformed without losing the identity of its underlying media type
386   and without loss of information. Frequently, the representation is stored in
387   coded form, transmitted directly, and only decoded by the recipient.
388</t>
389<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="content-coding"/>
390  <x:ref>content-coding</x:ref>   = <x:ref>token</x:ref>
391</artwork></figure>
392<t>
393   All content-coding values are case-insensitive. HTTP/1.1 uses
394   content-coding values in the Accept-Encoding (<xref target="header.accept-encoding"/>) and
395   Content-Encoding (<xref target="header.content-encoding"/>) header fields. Although the value
396   describes the content-coding, what is more important is that it
397   indicates what decoding mechanism will be required to remove the
398   encoding.
399</t>
400<t>
401   compress<iref item="compress (Coding Format)"/><iref item="Coding Format" subitem="compress"/>
402  <list>
403    <t>
404      See &compress-coding;.
405    </t>
406  </list>
407</t>
408<t>
409   deflate<iref item="deflate (Coding Format)"/><iref item="Coding Format" subitem="deflate"/>
410  <list>
411    <t>
412      See &deflate-coding;.
413    </t>
414  </list>
415</t>
416<t>
417   gzip<iref item="gzip (Coding Format)"/><iref item="Coding Format" subitem="gzip"/>
418  <list>
419    <t>
420      See &gzip-coding;.
421    </t>
422  </list>
423</t>
424
425<section title="Content Coding Registry" anchor="content.coding.registry">
426<t>
427   The HTTP Content Coding Registry defines the name space for the content
428   coding names.
429</t>
430<t>
431   Registrations &MUST; include the following fields:
432   <list style="symbols">
433     <t>Name</t>
434     <t>Description</t>
435     <t>Pointer to specification text</t>
436   </list>
437</t>
438<t>
439   Names of content codings &MUST-NOT; overlap with names of transfer codings
440   (&transfer-codings;), unless the encoding transformation is identical (as it
441   is the case for the compression codings defined in
442   &compression-codings;).
443</t>
444<t>
445   Values to be added to this name space require a specification
446   (see "Specification Required" in
447   <xref target="RFC5226" x:fmt="of" x:sec="4.1"/>), and &MUST;
448   conform to the purpose of content coding defined in this section.
449</t>
450<t>
451   The registry itself is maintained at
452   <eref target="http://www.iana.org/assignments/http-parameters"/>.
453</t>
454</section>
455
456</section>
457
458<section title="Media Types" anchor="media.types">
459  <x:anchor-alias value="media-type"/>
460  <x:anchor-alias value="type"/>
461  <x:anchor-alias value="subtype"/>
462<t>
463   HTTP uses Internet Media Types <xref target="RFC2046"/> in the Content-Type (<xref target="header.content-type"/>)
464   and Accept (<xref target="header.accept"/>) header fields in order to provide
465   open and extensible data typing and type negotiation.
466</t>
467<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"/>
468  <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> )
469  <x:ref>type</x:ref>       = <x:ref>token</x:ref>
470  <x:ref>subtype</x:ref>    = <x:ref>token</x:ref>
471</artwork></figure>
472<t anchor="rule.parameter">
473  <x:anchor-alias value="attribute"/>
474  <x:anchor-alias value="parameter"/>
475  <x:anchor-alias value="value"/>
476   The type/subtype &MAY; be followed by parameters in the form of
477   attribute/value pairs.
478</t>
479<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"/>
480  <x:ref>parameter</x:ref>      = <x:ref>attribute</x:ref> "=" <x:ref>value</x:ref>
481  <x:ref>attribute</x:ref>      = <x:ref>token</x:ref>
482  <x:ref>value</x:ref>          = <x:ref>word</x:ref>
483</artwork></figure>
484<t>
485   The type, subtype, and parameter attribute names are case-insensitive.
486   Parameter values might or might not be case-sensitive, depending on the
487   semantics of the parameter name.  The presence or absence of a parameter might
488   be significant to the processing of a media-type, depending on its
489   definition within the media type registry.
490</t>
491<t>
492   A parameter value that matches the <x:ref>token</x:ref> production can be
493   transmitted as either a token or within a quoted-string. The quoted and
494   unquoted values are equivalent.
495</t>
496<t>
497   Note that some older HTTP applications do not recognize media type
498   parameters. When sending data to older HTTP applications,
499   implementations &SHOULD; only use media type parameters when they are
500   required by that type/subtype definition.
501</t>
502<t>
503   Media-type values are registered with the Internet Assigned Number
504   Authority (IANA). The media type registration process is
505   outlined in <xref target="RFC4288"/>. Use of non-registered media types is
506   discouraged.
507</t>
508
509<section title="Canonicalization and Text Defaults" anchor="canonicalization.and.text.defaults">
510<t>
511   Internet media types are registered with a canonical form. A
512   representation transferred via HTTP messages &MUST; be in the
513   appropriate canonical form prior to its transmission except for
514   "text" types, as defined in the next paragraph.
515</t>
516<t>
517   When in canonical form, media subtypes of the "text" type use CRLF as
518   the text line break. HTTP relaxes this requirement and allows the
519   transport of text media with plain CR or LF alone representing a line
520   break when it is done consistently for an entire representation. HTTP
521   applications &MUST; accept CRLF, bare CR, and bare LF as indicating
522   a line break in text media received via HTTP. In
523   addition, if the text is in a character encoding that does not
524   use octets 13 and 10 for CR and LF respectively, as is the case for
525   some multi-byte character encodings, HTTP allows the use of whatever octet
526   sequences are defined by that character encoding to represent the
527   equivalent of CR and LF for line breaks. This flexibility regarding
528   line breaks applies only to text media in the payload body; a bare CR
529   or LF &MUST-NOT; be substituted for CRLF within any of the HTTP control
530   structures (such as header fields and multipart boundaries).
531</t>
532<t>
533   If a representation is encoded with a content-coding, the underlying
534   data &MUST; be in a form defined above prior to being encoded.
535</t>
536</section>
537
538<section title="Multipart Types" anchor="multipart.types">
539<t>
540   MIME provides for a number of "multipart" types &mdash; encapsulations of
541   one or more representations within a single message-body. All multipart
542   types share a common syntax, as defined in <xref target="RFC2046" x:sec="5.1.1" x:fmt="of"/>,
543   and &MUST; include a boundary parameter as part of the media type
544   value. The message body is itself a protocol element and &MUST;
545   therefore use only CRLF to represent line breaks between body-parts.
546</t>
547<t>
548   In general, HTTP treats a multipart message-body no differently than
549   any other media type: strictly as payload.  HTTP does not use the
550   multipart boundary as an indicator of message-body length.
551   <!-- jre: re-insert removed text pointing to caching? -->
552   In all other respects, an HTTP user agent &SHOULD; follow the same or similar
553   behavior as a MIME user agent would upon receipt of a multipart type.
554   The MIME header fields within each body-part of a multipart message-body
555   do not have any significance to HTTP beyond that defined by
556   their MIME semantics.
557</t>
558<t>
559   If an application receives an unrecognized multipart subtype, the
560   application &MUST; treat it as being equivalent to "multipart/mixed".
561</t>
562<x:note>
563  <t>
564    <x:h>Note:</x:h> The "multipart/form-data" type has been specifically defined
565    for carrying form data suitable for processing via the POST
566    request method, as described in <xref target="RFC2388"/>.
567  </t>
568</x:note>
569</section>
570</section>
571
572<section title="Language Tags" anchor="language.tags">
573  <x:anchor-alias value="language-tag"/>
574<t>
575   A language tag, as defined in <xref target="RFC5646"/>, identifies a
576   natural language spoken, written, or otherwise conveyed by human beings for
577   communication of information to other human beings. Computer languages are
578   explicitly excluded. HTTP uses language tags within the Accept-Language and
579   Content-Language fields.
580</t>
581<t>
582   In summary, a language tag is composed of one or more parts: A primary
583   language subtag followed by a possibly empty series of subtags:
584</t>
585<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="language-tag"/>
586  <x:ref>language-tag</x:ref> = &lt;Language-Tag, defined in <xref target="RFC5646" x:sec="2.1"/>&gt;
587</artwork></figure>
588<t>
589   White space is not allowed within the tag and all tags are case-insensitive.
590   The name space of language subtags is administered by the IANA (see
591   <eref target="http://www.iana.org/assignments/language-subtag-registry"/>).
592</t>
593<figure>
594  <preamble>Example tags include:</preamble>
595<artwork type="example">
596  en, en-US, es-419, az-Arab, x-pig-latin, man-Nkoo-GN
597</artwork>
598</figure>
599<t>
600   See <xref target="RFC5646"/> for further information.
601</t>
602</section>
603</section>
604
605<section title="Payload" anchor="payload">
606<t>
607   HTTP messages &MAY; transfer a payload if not otherwise restricted by
608   the request method or response status code.  The payload consists of
609   metadata, in the form of header fields, and data, in the form of the
610   sequence of octets in the message-body after any transfer-coding has
611   been decoded.
612</t>
613<iref item="payload"/>
614<t>   
615   A "<x:dfn>payload</x:dfn>" in HTTP is always a partial or complete
616   representation of some resource.  We use separate terms for payload
617   and representation because some messages contain only the associated
618   representation's header fields (e.g., responses to HEAD) or only some
619   part(s) of the representation (e.g., the 206 status code).
620</t>
621<section title="Payload Header Fields" anchor="payload.header.fields">
622  <x:anchor-alias value="payload-header"/>
623<t>
624   HTTP header fields that specifically define the payload, rather than the
625   associated representation, are referred to as "payload header fields".
626   The following payload header fields are defined by HTTP/1.1:
627</t>
628<texttable align="left">
629  <ttcol>Header Field Name</ttcol>
630  <ttcol>Defined in...</ttcol>
631
632  <c>Content-Length</c> <c>&header-content-length;</c>
633  <c>Content-Range</c> <c>&header-content-range;</c>
634</texttable>
635</section>
636
637<section title="Payload Body" anchor="payload.body">
638  <x:anchor-alias value="payload-body"/>
639<t>
640   A payload body is only present in a message when a message-body is
641   present, as described in &message-body;. The payload body is obtained
642   from the message-body by decoding any Transfer-Encoding that might
643   have been applied to ensure safe and proper transfer of the message.
644</t>
645</section>
646</section>
647
648<section title="Representation" anchor="representation">
649<iref item="representation"/>
650<t>
651   A "<x:dfn>representation</x:dfn>" is information in a format that can be readily
652   communicated from one party to another.  A resource representation
653   is information that reflects the state of that resource, as observed
654   at some point in the past (e.g., in a response to GET) or to be
655   desired at some point in the future (e.g., in a PUT request).
656</t>
657<t>
658   Most, but not all, representations transferred via HTTP are intended
659   to be a representation of the target resource (the resource identified
660   by the effective request URI).  The precise semantics of a representation
661   are determined by the type of message (request or response), the request
662   method, the response status code, and the representation metadata.
663   For example, the above semantic is true for the representation in any
664   200 (OK) response to GET and for the representation in any PUT request.
665   A 200 response to PUT, in contrast, contains either a representation
666   that describes the successful action or a representation of the target
667   resource, with the latter indicated by a Content-Location header field
668   with the same value as the effective request URI.  Likewise, response
669   messages with an error status code usually contain a representation that
670   describes the error and what next steps are suggested for resolving it.
671</t>
672
673<section title="Representation Header Fields" anchor="representation.header.fields">
674  <x:anchor-alias value="representation-header"/>
675<t>
676   Representation header fields define metadata about the representation data
677   enclosed in the message-body or, if no message-body is present, about
678   the representation that would have been transferred in a 200 response
679   to a simultaneous GET request with the same effective request URI.
680</t>
681<t>
682   The following header fields are defined as representation metadata:
683</t>
684<texttable align="left">
685  <ttcol>Header Field Name</ttcol>
686  <ttcol>Defined in...</ttcol>
687
688  <c>Content-Encoding</c> <c><xref target="header.content-encoding"/></c>
689  <c>Content-Language</c> <c><xref target="header.content-language"/></c>
690  <c>Content-Location</c> <c><xref target="header.content-location"/></c>
691  <c>Content-Type</c> <c><xref target="header.content-type"/></c>
692  <c>Expires</c> <c>&header-expires;</c>
693  <c>Last-Modified</c> <c>&header-last-modified;</c>
694</texttable>
695</section>
696
697<section title="Representation Data" anchor="representation.data">
698  <x:anchor-alias value="representation-data"/>
699<t>
700   The representation body associated with an HTTP message is
701   either provided as the payload body of the message or
702   referred to by the message semantics and the effective request
703   URI.  The representation data is in a format and encoding defined by
704   the representation metadata header fields.
705</t>
706<t>
707   The data type of the representation data
708   is determined via the header fields Content-Type and Content-Encoding.
709   These define a two-layer, ordered encoding model:
710</t>
711<figure><artwork type="example">
712  representation-data := Content-Encoding( Content-Type( bits ) )
713</artwork></figure>
714<t>
715   Content-Type specifies the media type of the underlying data, which
716   defines both the data format and how that data &SHOULD; be processed
717   by the recipient (within the scope of the request method semantics).
718   Any HTTP/1.1 message containing a payload body &SHOULD; include a
719   Content-Type header field defining the media type of the associated
720   representation unless that metadata is unknown to the sender.
721   If the Content-Type header field is not present, it indicates that
722   the sender does not know the media type of the representation;
723   recipients &MAY; either assume that the media type is
724   "application/octet-stream" (<xref target="RFC2046" x:fmt="," x:sec="4.5.1"/>)
725   or examine the content to determine its type.
726</t>
727<t>
728   In practice, resource owners do not always properly configure their origin
729   server to provide the correct Content-Type for a given representation,
730   with the result that some clients will examine a response body's content
731   and override the specified type.
732   Clients that do so risk drawing incorrect conclusions, which might expose
733   additional security risks (e.g., "privilege escalation").  Furthermore,
734   it is impossible to determine the sender's intent by examining the data
735   format: many data formats match multiple media types that differ only in
736   processing semantics.  Implementers are encouraged to provide a means of
737   disabling such "content sniffing" when it is used.
738</t>
739<t>
740   Content-Encoding is used to indicate any additional content
741   codings applied to the data, usually for the purpose of data
742   compression, that are a property of the representation.  If
743   Content-Encoding is not present, then there is no additional
744   encoding beyond that defined by the Content-Type.
745</t>
746</section>
747</section>
748
749<section title="Content Negotiation" anchor="content.negotiation">
750<t>
751   HTTP responses include a representation which contains information for
752   interpretation, whether by a human user or for further processing.
753   Often, the server has different ways of representing the
754   same information; for example, in different formats, languages,
755   or using different character encodings.
756</t>
757<t>
758   HTTP clients and their users might have different or variable
759   capabilities, characteristics or preferences which would influence
760   which representation, among those available from the server,
761   would be best for the server to deliver. For this reason, HTTP
762   provides mechanisms for "content negotiation" &mdash; a process of
763   allowing selection of a representation of a given resource,
764   when more than one is available.
765</t>
766<t>
767   This specification defines two patterns of content negotiation;
768   "server-driven", where the server selects the representation based
769   upon the client's stated preferences, and "agent-driven" negotiation,
770   where the server provides a list of representations for the client to
771   choose from, based upon their metadata. In addition,  there are
772   other patterns: some applications use an "active content" pattern,
773   where the server returns active content which runs on the client
774   and, based on client available parameters, selects additional
775   resources to invoke. "Transparent Content Negotiation" (<xref target="RFC2295"/>)
776   has also been proposed.
777</t>
778<t>
779   These patterns are all widely used, and have trade-offs in applicability
780   and practicality. In particular, when the number of preferences or
781   capabilities to be expressed by a client are large (such as when many
782   different formats are supported by a user-agent), server-driven
783   negotiation becomes unwieldy, and might not be appropriate. Conversely,
784   when the number of representations to choose from is very large,
785   agent-driven negotiation might not be appropriate.
786</t>
787<t>
788   Note that in all cases, the supplier of representations has the
789   responsibility for determining which representations might be
790   considered to be the "same information".
791</t>
792
793<section title="Server-driven Negotiation" anchor="server-driven.negotiation">
794<t>
795   If the selection of the best representation for a response is made by
796   an algorithm located at the server, it is called server-driven
797   negotiation. Selection is based on the available representations of
798   the response (the dimensions over which it can vary; e.g., language,
799   content-coding, etc.) and the contents of particular header fields in
800   the request message or on other information pertaining to the request
801   (such as the network address of the client).
802</t>
803<t>
804   Server-driven negotiation is advantageous when the algorithm for
805   selecting from among the available representations is difficult to
806   describe to the user agent, or when the server desires to send its
807   "best guess" to the client along with the first response (hoping to
808   avoid the round-trip delay of a subsequent request if the "best
809   guess" is good enough for the user). In order to improve the server's
810   guess, the user agent &MAY; include request header fields (Accept,
811   Accept-Language, Accept-Encoding, etc.) which describe its
812   preferences for such a response.
813</t>
814<t>
815   Server-driven negotiation has disadvantages:
816  <list style="numbers">
817    <t>
818         It is impossible for the server to accurately determine what
819         might be "best" for any given user, since that would require
820         complete knowledge of both the capabilities of the user agent
821         and the intended use for the response (e.g., does the user want
822         to view it on screen or print it on paper?).
823    </t>
824    <t>
825         Having the user agent describe its capabilities in every
826         request can be both very inefficient (given that only a small
827         percentage of responses have multiple representations) and a
828         potential violation of the user's privacy.
829    </t>
830    <t>
831         It complicates the implementation of an origin server and the
832         algorithms for generating responses to a request.
833    </t>
834    <t>
835         It might limit a public cache's ability to use the same response
836         for multiple user's requests.
837    </t>
838  </list>
839</t>
840<t>
841   Server-driven negotiation allows the user agent to specify its preferences,
842   but it cannot expect responses to always honour them. For example, the origin
843   server might not implement server-driven negotiation, or it might decide that
844   sending a response that doesn't conform to them is better than sending a 406
845   (Not Acceptable) response.
846</t>
847<t>
848   Many of the mechanisms for expressing preferences use quality values to
849   declare relative preference. See &qvalue; for more information.
850</t>
851<t>
852   HTTP/1.1 includes the following header fields for enabling
853   server-driven negotiation through description of user agent
854   capabilities and user preferences: Accept (<xref target="header.accept"/>), Accept-Charset
855   (<xref target="header.accept-charset"/>), Accept-Encoding (<xref target="header.accept-encoding"/>), Accept-Language
856   (<xref target="header.accept-language"/>), and User-Agent (&header-user-agent;).
857   However, an origin server is not limited to these dimensions and &MAY; vary
858   the response based on any aspect of the request, including aspects
859   of the connection (e.g., IP address) or information within extension
860   header fields not defined by this specification.
861</t>
862<x:note>
863  <t>
864    <x:h>Note:</x:h> In practice, User-Agent based negotiation is fragile,
865    because new clients might not be recognized.
866  </t>
867</x:note>
868<t>
869   The Vary header field (&header-vary;) can be used to express the parameters the
870   server uses to select a representation that is subject to server-driven
871   negotiation.
872</t>
873</section>
874
875<section title="Agent-driven Negotiation" anchor="agent-driven.negotiation">
876<t>
877   With agent-driven negotiation, selection of the best representation
878   for a response is performed by the user agent after receiving an
879   initial response from the origin server. Selection is based on a list
880   of the available representations of the response included within the
881   header fields or body of the initial response, with each
882   representation identified by its own URI. Selection from among the
883   representations can be performed automatically (if the user agent is
884   capable of doing so) or manually by the user selecting from a
885   generated (possibly hypertext) menu.
886</t>
887<t>
888   Agent-driven negotiation is advantageous when the response would vary
889   over commonly-used dimensions (such as type, language, or encoding),
890   when the origin server is unable to determine a user agent's
891   capabilities from examining the request, and generally when public
892   caches are used to distribute server load and reduce network usage.
893</t>
894<t>
895   Agent-driven negotiation suffers from the disadvantage of needing a
896   second request to obtain the best alternate representation. This
897   second request is only efficient when caching is used. In addition,
898   this specification does not define any mechanism for supporting
899   automatic selection, though it also does not prevent any such
900   mechanism from being developed as an extension and used within
901   HTTP/1.1.
902</t>
903<t>
904   This specification defines the 300 (Multiple Choices) and 406 (Not Acceptable)
905   status codes for enabling agent-driven negotiation when the server is
906   unwilling or unable to provide a varying response using server-driven
907   negotiation.
908</t>
909</section>
910</section>
911
912<section title="Header Field Definitions" anchor="header.field.definitions">
913<t>
914   This section defines the syntax and semantics of HTTP/1.1 header fields
915   related to the payload of messages.
916</t>
917
918<section title="Accept" anchor="header.accept">
919  <iref primary="true" item="Accept header field" x:for-anchor=""/>
920  <iref primary="true" item="Header Fields" subitem="Accept" x:for-anchor=""/>
921  <x:anchor-alias value="Accept"/>
922  <x:anchor-alias value="accept-ext"/>
923  <x:anchor-alias value="accept-params"/>
924  <x:anchor-alias value="media-range"/>
925<t>
926   The "Accept" header field can be used by user agents to specify
927   response media types that are acceptable. Accept header fields can be used to
928   indicate that the request is specifically limited to a small set of desired
929   types, as in the case of a request for an in-line image.
930</t>
931<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"/>
932  <x:ref>Accept</x:ref> = #( <x:ref>media-range</x:ref> [ <x:ref>accept-params</x:ref> ] )
933 
934  <x:ref>media-range</x:ref>    = ( "*/*"
935                   / ( <x:ref>type</x:ref> "/" "*" )
936                   / ( <x:ref>type</x:ref> "/" <x:ref>subtype</x:ref> )
937                   ) *( <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> <x:ref>parameter</x:ref> )
938  <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> )
939  <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> ]
940</artwork></figure>
941<t>
942   The asterisk "*" character is used to group media types into ranges,
943   with "*/*" indicating all media types and "type/*" indicating all
944   subtypes of that type. The media-range &MAY; include media type
945   parameters that are applicable to that range.
946</t>
947<t>
948   Each media-range &MAY; be followed by one or more accept-params,
949   beginning with the "q" parameter for indicating a relative quality
950   factor. The first "q" parameter (if any) separates the media-range
951   parameter(s) from the accept-params. Quality factors allow the user
952   or user agent to indicate the relative degree of preference for that
953   media-range, using the qvalue scale from 0 to 1 (&qvalue;). The
954   default value is q=1.
955</t>
956<x:note>
957  <t>
958    <x:h>Note:</x:h> Use of the "q" parameter name to separate media type
959    parameters from Accept extension parameters is due to historical
960    practice. Although this prevents any media type parameter named
961    "q" from being used with a media range, such an event is believed
962    to be unlikely given the lack of any "q" parameters in the IANA
963    media type registry and the rare usage of any media type
964    parameters in Accept. Future media types are discouraged from
965    registering any parameter named "q".
966  </t>
967</x:note>
968<t>
969   The example
970</t>
971<figure><artwork type="example">
972  Accept: audio/*; q=0.2, audio/basic
973</artwork></figure>
974<t>
975   &SHOULD; be interpreted as "I prefer audio/basic, but send me any audio
976   type if it is the best available after an 80% mark-down in quality".
977</t>
978<t>
979   A request without any Accept header field implies that the user agent
980   will accept any media type in response.
981   If an Accept header field is present in a request and none of the
982   available representations for the response have a media type that is
983   listed as acceptable, the origin server &MAY; either
984   honor the Accept header field by sending a 406 (Not Acceptable) response
985   or disregard the Accept header field by treating the response as if
986   it is not subject to content negotiation.
987</t>
988<t>
989   A more elaborate example is
990</t>
991<figure><artwork type="example">
992  Accept: text/plain; q=0.5, text/html,
993          text/x-dvi; q=0.8, text/x-c
994</artwork></figure>
995<t>
996   Verbally, this would be interpreted as "text/html and text/x-c are
997   the preferred media types, but if they do not exist, then send the
998   text/x-dvi representation, and if that does not exist, send the text/plain
999   representation".
1000</t>
1001<t>
1002   Media ranges can be overridden by more specific media ranges or
1003   specific media types. If more than one media range applies to a given
1004   type, the most specific reference has precedence. For example,
1005</t>
1006<figure><artwork type="example">
1007  Accept: text/*, text/plain, text/plain;format=flowed, */*
1008</artwork></figure>
1009<t>
1010   have the following precedence:
1011   <list style="numbers">
1012    <t>text/plain;format=flowed</t>
1013    <t>text/plain</t>
1014    <t>text/*</t>
1015    <t>*/*</t>
1016   </list>
1017</t>
1018<t>
1019   The media type quality factor associated with a given type is
1020   determined by finding the media range with the highest precedence
1021   which matches that type. For example,
1022</t>
1023<figure><artwork type="example">
1024  Accept: text/*;q=0.3, text/html;q=0.7, text/html;level=1,
1025          text/html;level=2;q=0.4, */*;q=0.5
1026</artwork></figure>
1027<t>
1028   would cause the following values to be associated:
1029</t>
1030<texttable align="left">
1031  <ttcol>Media Type</ttcol><ttcol>Quality Value</ttcol>
1032  <c>text/html;level=1</c>    <c>1</c>
1033  <c>text/html</c>            <c>0.7</c>
1034  <c>text/plain</c>           <c>0.3</c>
1035  <c>image/jpeg</c>           <c>0.5</c>
1036  <c>text/html;level=2</c>    <c>0.4</c>
1037  <c>text/html;level=3</c>    <c>0.7</c>
1038</texttable>
1039<t>
1040      <x:h>Note:</x:h> A user agent might be provided with a default set of quality
1041      values for certain media ranges. However, unless the user agent is
1042      a closed system which cannot interact with other rendering agents,
1043      this default set ought to be configurable by the user.
1044</t>
1045</section>
1046
1047<section title="Accept-Charset" anchor="header.accept-charset">
1048  <iref primary="true" item="Accept-Charset header field" x:for-anchor=""/>
1049  <iref primary="true" item="Header Fields" subitem="Accept-Charset" x:for-anchor=""/>
1050  <x:anchor-alias value="Accept-Charset"/>
1051<t>
1052   The "Accept-Charset" header field can be used by user agents to
1053   indicate what character encodings are acceptable in a response
1054   payload. This field allows
1055   clients capable of understanding more comprehensive or special-purpose
1056   character encodings to signal that capability to a server which is capable of
1057   representing documents in those character encodings.
1058</t>
1059<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Accept-Charset"/>
1060  <x:ref>Accept-Charset</x:ref> = 1#( ( <x:ref>charset</x:ref> / "*" )
1061                         [ <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> "q=" <x:ref>qvalue</x:ref> ] )
1062</artwork></figure>
1063<t>
1064   Character encoding values (a.k.a., charsets) are described in
1065   <xref target="character.sets"/>. Each charset &MAY; be given an
1066   associated quality value which represents the user's preference
1067   for that charset. The default value is q=1. An example is
1068</t>
1069<figure><artwork type="example">
1070  Accept-Charset: iso-8859-5, unicode-1-1;q=0.8
1071</artwork></figure>
1072<t>
1073   The special value "*", if present in the Accept-Charset field,
1074   matches every character encoding which is not mentioned elsewhere in the
1075   Accept-Charset field. If no "*" is present in an Accept-Charset field, then
1076   all character encodings not explicitly mentioned get a quality value of 0.
1077</t>
1078<t>
1079   A request without any Accept-Charset header field implies that the user
1080   agent will accept any character encoding in response.
1081   If an Accept-Charset header field is present in a request and none of the
1082   available representations for the response have a character encoding that
1083   is listed as acceptable, the origin server &MAY; either honor the
1084   Accept-Charset header field by sending a 406 (Not Acceptable) response or
1085   disregard the Accept-Charset header field by treating the response as if
1086   it is not subject to content negotiation.
1087</t>
1088</section>
1089
1090<section title="Accept-Encoding" anchor="header.accept-encoding">
1091  <iref primary="true" item="Accept-Encoding header field" x:for-anchor=""/>
1092  <iref primary="true" item="Header Fields" subitem="Accept-Encoding" x:for-anchor=""/>
1093  <x:anchor-alias value="Accept-Encoding"/>
1094  <x:anchor-alias value="codings"/>
1095<t>
1096   The "Accept-Encoding" header field can be used by user agents to
1097   indicate what response content-codings (<xref target="content.codings"/>)
1098   are acceptable in the response.  An "identity" token is used as a synonym
1099   for "no encoding" in order to communicate when no encoding is preferred.
1100</t>
1101<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Accept-Encoding"/><iref primary="true" item="Grammar" subitem="codings"/>
1102  <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> ] )
1103  <x:ref>codings</x:ref>          = <x:ref>content-coding</x:ref> / "identity" / "*"
1104</artwork></figure>
1105<t>
1106   Each codings value &MAY; be given an associated quality value which
1107   represents the preference for that encoding. The default value is q=1.
1108</t>
1109<t>
1110   For example,
1111</t>
1112<figure><artwork type="example">
1113  Accept-Encoding: compress, gzip
1114  Accept-Encoding:
1115  Accept-Encoding: *
1116  Accept-Encoding: compress;q=0.5, gzip;q=1.0
1117  Accept-Encoding: gzip;q=1.0, identity; q=0.5, *;q=0
1118</artwork></figure>
1119<t>
1120   A server tests whether a content-coding for a given representation is
1121   acceptable, according to an Accept-Encoding field, using these rules:
1122  <list style="numbers">
1123      <t>The special "*" symbol in an Accept-Encoding field matches any
1124         available content-coding not explicitly listed in the header
1125         field.</t>
1126
1127      <t>If the representation has no content-coding, then it is acceptable
1128         by default unless specifically excluded by the Accept-Encoding field
1129         stating either "identity;q=0" or "*;q=0" without a more specific
1130         entry for "identity".</t>
1131
1132      <t>If the representation's content-coding is one of the content-codings
1133         listed in the Accept-Encoding field, then it is acceptable unless
1134         it is accompanied by a qvalue of 0. (As defined in &qvalue;, a
1135         qvalue of 0 means "not acceptable".)</t>
1136
1137      <t>If multiple content-codings are acceptable, then the acceptable
1138         content-coding with the highest non-zero qvalue is preferred.</t>
1139  </list>
1140</t>
1141<t>
1142   An Accept-Encoding header field with a combined field-value that is empty
1143   implies that the user agent does not want any content-coding in response.
1144   If an Accept-Encoding header field is present in a request and none of the
1145   available representations for the response have a content-coding that
1146   is listed as acceptable, the origin server &SHOULD; send a response
1147   without any content-coding.
1148</t>
1149<t>
1150   A request without an Accept-Encoding header field implies that the user
1151   agent will accept any content-coding in response, but a representation
1152   without content-coding is preferred for compatibility with the widest
1153   variety of user agents.
1154</t>
1155<x:note>
1156  <t>
1157    <x:h>Note:</x:h> Most HTTP/1.0 applications do not recognize or obey qvalues
1158    associated with content-codings. This means that qvalues will not
1159    work and are not permitted with x-gzip or x-compress.
1160  </t>
1161</x:note>
1162</section>
1163
1164<section title="Accept-Language" anchor="header.accept-language">
1165  <iref primary="true" item="Accept-Language header field" x:for-anchor=""/>
1166  <iref primary="true" item="Header Fields" subitem="Accept-Language" x:for-anchor=""/>
1167  <x:anchor-alias value="Accept-Language"/>
1168  <x:anchor-alias value="language-range"/>
1169<t>
1170   The "Accept-Language" header field can be used by user agents to
1171   indicate the set of natural languages that are preferred in the response.
1172   Language tags are defined in <xref target="language.tags"/>.
1173</t>
1174<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Accept-Language"/><iref primary="true" item="Grammar" subitem="language-range"/>
1175  <x:ref>Accept-Language</x:ref> =
1176                    1#( <x:ref>language-range</x:ref> [ <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> "q=" <x:ref>qvalue</x:ref> ] )
1177  <x:ref>language-range</x:ref>  =
1178            &lt;language-range, defined in <xref target="RFC4647" x:fmt="," x:sec="2.1"/>&gt;
1179</artwork></figure>
1180<t>
1181   Each language-range can be given an associated quality value which
1182   represents an estimate of the user's preference for the languages
1183   specified by that range. The quality value defaults to "q=1". For
1184   example,
1185</t>
1186<figure><artwork type="example">
1187  Accept-Language: da, en-gb;q=0.8, en;q=0.7
1188</artwork></figure>
1189<t>
1190   would mean: "I prefer Danish, but will accept British English and
1191   other types of English".
1192   (see also <xref target="RFC4647" x:sec="2.3" x:fmt="of"/>)
1193</t>
1194<t>
1195   For matching, <xref target="RFC4647" x:sec="3" x:fmt="of"/> defines
1196   several matching schemes. Implementations can offer the most appropriate
1197   matching scheme for their requirements.
1198</t>
1199<x:note>
1200  <t>
1201    <x:h>Note:</x:h> The "Basic Filtering" scheme (<xref target="RFC4647"
1202    x:fmt="," x:sec="3.3.1"/>) is identical to the matching scheme that was
1203    previously defined in <xref target="RFC2616" x:fmt="of" x:sec="14.4"/>.
1204  </t>
1205</x:note>
1206<t>
1207   It might be contrary to the privacy expectations of the user to send
1208   an Accept-Language header field with the complete linguistic preferences of
1209   the user in every request. For a discussion of this issue, see
1210   <xref target="privacy.issues.connected.to.accept.header.fields"/>.
1211</t>
1212<t>
1213   As intelligibility is highly dependent on the individual user, it is
1214   recommended that client applications make the choice of linguistic
1215   preference available to the user. If the choice is not made
1216   available, then the Accept-Language header field &MUST-NOT; be given in
1217   the request.
1218</t>
1219<x:note>
1220  <t>
1221    <x:h>Note:</x:h> When making the choice of linguistic preference available to
1222    the user, we remind implementors of  the fact that users are not
1223    familiar with the details of language matching as described above,
1224    and ought to be provided appropriate guidance. As an example, users
1225    might assume that on selecting "en-gb", they will be served any
1226    kind of English document if British English is not available. A
1227    user agent might suggest in such a case to add "en" to get the
1228    best matching behavior.
1229  </t>
1230</x:note>
1231</section>
1232
1233<section title="Content-Encoding" anchor="header.content-encoding">
1234  <iref primary="true" item="Content-Encoding header field" x:for-anchor=""/>
1235  <iref primary="true" item="Header Fields" subitem="Content-Encoding" x:for-anchor=""/>
1236  <x:anchor-alias value="Content-Encoding"/>
1237<t>
1238   The "Content-Encoding" header field indicates what content-codings
1239   have been applied to the representation beyond those inherent in the media
1240   type, and thus what decoding mechanisms must be applied in order to obtain
1241   the media-type referenced by the Content-Type header field.
1242   Content-Encoding is primarily used to allow a representation to be
1243   compressed without losing the identity of its underlying media type.
1244</t>
1245<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Encoding"/>
1246  <x:ref>Content-Encoding</x:ref> = 1#<x:ref>content-coding</x:ref>
1247</artwork></figure>
1248<t>
1249   Content codings are defined in <xref target="content.codings"/>. An example of its use is
1250</t>
1251<figure><artwork type="example">
1252  Content-Encoding: gzip
1253</artwork></figure>
1254<t>
1255   The content-coding is a characteristic of the representation.
1256   Typically, the representation body is stored with this
1257   encoding and is only decoded before rendering or analogous usage.
1258   However, a transforming proxy &MAY; modify the content-coding if the
1259   new coding is known to be acceptable to the recipient, unless the
1260   "no-transform" cache-control directive is present in the message.
1261</t>
1262<t>
1263   If the media type includes an inherent encoding, such as a data format
1264   that is always compressed, then that encoding would not be restated as
1265   a Content-Encoding even if it happens to be the same algorithm as one
1266   of the content-codings.  Such a content-coding would only be listed if,
1267   for some bizarre reason, it is applied a second time to form the
1268   representation.  Likewise, an origin server might choose to publish the
1269   same payload data as multiple representations that differ only in whether
1270   the coding is defined as part of Content-Type or Content-Encoding, since
1271   some user agents will behave differently in their handling of each
1272   response (e.g., open a "Save as ..." dialog instead of automatic
1273   decompression and rendering of content).
1274</t>
1275<t>
1276   A representation that has a content-coding applied to it &MUST; include
1277   a Content-Encoding header field (<xref target="header.content-encoding"/>)
1278   that lists the content-coding(s) applied.
1279</t>
1280<t>
1281   If multiple encodings have been applied to a representation, the content
1282   codings &MUST; be listed in the order in which they were applied.
1283   Additional information about the encoding parameters &MAY; be provided
1284   by other header fields not defined by this specification.
1285</t>
1286<t>
1287   If the content-coding of a representation in a request message is not
1288   acceptable to the origin server, the server &SHOULD; respond with a
1289   status code of 415 (Unsupported Media Type).
1290</t>
1291</section>
1292
1293<section title="Content-Language" anchor="header.content-language">
1294  <iref primary="true" item="Content-Language header field" x:for-anchor=""/>
1295  <iref primary="true" item="Header Fields" subitem="Content-Language" x:for-anchor=""/>
1296  <x:anchor-alias value="Content-Language"/>
1297<t>
1298   The "Content-Language" header field describes the natural
1299   language(s) of the intended audience for the representation. Note that this might
1300   not be equivalent to all the languages used within the representation.
1301</t>
1302<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Language"/>
1303  <x:ref>Content-Language</x:ref> = 1#<x:ref>language-tag</x:ref>
1304</artwork></figure>
1305<t>
1306   Language tags are defined in <xref target="language.tags"/>. The primary purpose of
1307   Content-Language is to allow a user to identify and differentiate
1308   representations according to the user's own preferred language. Thus, if the
1309   body content is intended only for a Danish-literate audience, the
1310   appropriate field is
1311</t>
1312<figure><artwork type="example">
1313  Content-Language: da
1314</artwork></figure>
1315<t>
1316   If no Content-Language is specified, the default is that the content
1317   is intended for all language audiences. This might mean that the
1318   sender does not consider it to be specific to any natural language,
1319   or that the sender does not know for which language it is intended.
1320</t>
1321<t>
1322   Multiple languages &MAY; be listed for content that is intended for
1323   multiple audiences. For example, a rendition of the "Treaty of
1324   Waitangi", presented simultaneously in the original Maori and English
1325   versions, would call for
1326</t>
1327<figure><artwork type="example">
1328  Content-Language: mi, en
1329</artwork></figure>
1330<t>
1331   However, just because multiple languages are present within a representation
1332   does not mean that it is intended for multiple linguistic audiences.
1333   An example would be a beginner's language primer, such as "A First
1334   Lesson in Latin", which is clearly intended to be used by an
1335   English-literate audience. In this case, the Content-Language would
1336   properly only include "en".
1337</t>
1338<t>
1339   Content-Language &MAY; be applied to any media type &mdash; it is not
1340   limited to textual documents.
1341</t>
1342</section>
1343
1344<section title="Content-Location" anchor="header.content-location">
1345  <iref primary="true" item="Content-Location header field" x:for-anchor=""/>
1346  <iref primary="true" item="Header Fields" subitem="Content-Location" x:for-anchor=""/>
1347  <x:anchor-alias value="Content-Location"/>
1348<t>
1349   The "Content-Location" header field supplies a URI that can be used
1350   as a specific identifier for the representation in this message.
1351   In other words, if one were to perform a GET on this URI at the time
1352   of this message's generation, then a 200 response would contain the
1353   same representation that is enclosed as payload in this message.
1354</t>
1355<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Location"/>
1356  <x:ref>Content-Location</x:ref> = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
1357</artwork></figure>
1358<t>
1359   The Content-Location value is not a replacement for the effective
1360   Request URI (&effective-request-uri;).  It is representation metadata.
1361   It has the same syntax and semantics as the header field of the same name
1362   defined for MIME body parts in <xref target="RFC2557" x:fmt="of" x:sec="4"/>.
1363   However, its appearance in an HTTP message has some special implications
1364   for HTTP recipients.
1365</t>
1366<t>
1367   If Content-Location is included in a response message and its value
1368   is the same as the effective request URI, then the response payload
1369   &SHOULD; be considered the current representation of that resource.
1370   For a GET or HEAD request, this is the same as the default semantics
1371   when no Content-Location is provided by the server.  For a state-changing
1372   request like PUT or POST, it implies that the server's response contains
1373   the new representation of that resource, thereby distinguishing it from
1374   representations that might only report about the action (e.g., "It worked!").
1375   This allows authoring applications to update their local copies without
1376   the need for a subsequent GET request.
1377</t>
1378<t>
1379   If Content-Location is included in a response message and its value
1380   differs from the effective request URI, then the origin server is
1381   informing recipients that this representation has its own, presumably
1382   more specific, identifier.  For a GET or HEAD request, this is an
1383   indication that the effective request URI identifies a resource that
1384   is subject to content negotiation and the representation selected for
1385   this response can also be found at the identified URI.  For other
1386   methods, such a Content-Location indicates that this representation
1387   contains a report on the action's status and the same report is
1388   available (for future access with GET) at the given URI.  For
1389   example, a purchase transaction made via a POST request might
1390   include a receipt document as the payload of the 200 response;
1391   the Content-Location value provides an identifier for retrieving
1392   a copy of that same receipt in the future.
1393</t>
1394<t>
1395   If Content-Location is included in a request message, then it &MAY;
1396   be interpreted by the origin server as an indication of where the
1397   user agent originally obtained the content of the enclosed
1398   representation (prior to any subsequent modification of the content
1399   by that user agent).  In other words, the user agent is providing
1400   the same representation metadata that it received with the original
1401   representation.  However, such interpretation &MUST-NOT; be used to
1402   alter the semantics of the method requested by the client.  For
1403   example, if a client makes a PUT request on a negotiated resource
1404   and the origin server accepts that PUT (without redirection), then the
1405   new set of values for that resource is expected to be consistent with
1406   the one representation supplied in that PUT; the Content-Location
1407   cannot be used as a form of reverse content selection that
1408   identifies only one of the negotiated representations to be updated.
1409   If the user agent had wanted the latter semantics, it would have applied
1410   the PUT directly to the Content-Location URI.
1411</t>
1412<t>
1413   A Content-Location field received in a request message is transitory
1414   information that &SHOULD-NOT; be saved with other representation
1415   metadata for use in later responses.  The Content-Location's value
1416   might be saved for use in other contexts, such as within source links
1417   or other metadata.
1418</t>
1419<t>
1420   A cache cannot assume that a representation with a Content-Location
1421   different from the URI used to retrieve it can be used to respond to
1422   later requests on that Content-Location URI.
1423</t>
1424<t>
1425   If the Content-Location value is a partial URI, the partial URI is
1426   interpreted relative to the effective request URI.
1427</t>
1428</section>
1429
1430<section title="Content-Type" anchor="header.content-type">
1431  <iref primary="true" item="Content-Type header field" x:for-anchor=""/>
1432  <iref primary="true" item="Header Fields" subitem="Content-Type" x:for-anchor=""/>
1433  <x:anchor-alias value="Content-Type"/>
1434<t>
1435   The "Content-Type" header field indicates the media type of the
1436   representation. In the case of responses to the HEAD method, the media type is
1437   that which would have been sent had the request been a GET.
1438</t>
1439<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Type"/>
1440  <x:ref>Content-Type</x:ref> = <x:ref>media-type</x:ref>
1441</artwork></figure>
1442<t>
1443   Media types are defined in <xref target="media.types"/>. An example of the field is
1444</t>
1445<figure><artwork type="example">
1446  Content-Type: text/html; charset=ISO-8859-4
1447</artwork></figure>
1448<t>
1449   Further discussion of Content-Type is provided in <xref target="representation.data"/>.
1450</t>
1451</section>
1452
1453</section>
1454
1455<section title="IANA Considerations" anchor="IANA.considerations">
1456<section title="Header Field Registration" anchor="header.field.registration">
1457<t>
1458   The Message Header Field Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> shall be updated
1459   with the permanent registrations below (see <xref target="RFC3864"/>):
1460</t>
1461<?BEGININC p3-payload.iana-headers ?>
1462<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
1463<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
1464   <ttcol>Header Field Name</ttcol>
1465   <ttcol>Protocol</ttcol>
1466   <ttcol>Status</ttcol>
1467   <ttcol>Reference</ttcol>
1468
1469   <c>Accept</c>
1470   <c>http</c>
1471   <c>standard</c>
1472   <c>
1473      <xref target="header.accept"/>
1474   </c>
1475   <c>Accept-Charset</c>
1476   <c>http</c>
1477   <c>standard</c>
1478   <c>
1479      <xref target="header.accept-charset"/>
1480   </c>
1481   <c>Accept-Encoding</c>
1482   <c>http</c>
1483   <c>standard</c>
1484   <c>
1485      <xref target="header.accept-encoding"/>
1486   </c>
1487   <c>Accept-Language</c>
1488   <c>http</c>
1489   <c>standard</c>
1490   <c>
1491      <xref target="header.accept-language"/>
1492   </c>
1493   <c>Content-Encoding</c>
1494   <c>http</c>
1495   <c>standard</c>
1496   <c>
1497      <xref target="header.content-encoding"/>
1498   </c>
1499   <c>Content-Language</c>
1500   <c>http</c>
1501   <c>standard</c>
1502   <c>
1503      <xref target="header.content-language"/>
1504   </c>
1505   <c>Content-Location</c>
1506   <c>http</c>
1507   <c>standard</c>
1508   <c>
1509      <xref target="header.content-location"/>
1510   </c>
1511   <c>Content-Type</c>
1512   <c>http</c>
1513   <c>standard</c>
1514   <c>
1515      <xref target="header.content-type"/>
1516   </c>
1517   <c>MIME-Version</c>
1518   <c>http</c>
1519   <c>standard</c>
1520   <c>
1521      <xref target="mime-version"/>
1522   </c>
1523</texttable>
1524<!--(END)-->
1525<?ENDINC p3-payload.iana-headers ?>
1526<t>
1527   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
1528</t>
1529</section>
1530
1531<section title="Content Coding Registry" anchor="content.coding.registration">
1532<t>
1533   The registration procedure for HTTP Content Codings is now defined
1534   by <xref target="content.coding.registry"/> of this document.
1535</t>
1536<t>
1537   The HTTP Content Codings Registry located at <eref target="http://www.iana.org/assignments/http-parameters"/>
1538   shall be updated with the registration below:
1539</t>
1540<texttable align="left" suppress-title="true" anchor="iana.content.coding.registration.table">
1541   <ttcol>Name</ttcol>
1542   <ttcol>Description</ttcol>
1543   <ttcol>Reference</ttcol>
1544   <c>compress</c>
1545   <c>UNIX "compress" program method</c>
1546   <c>
1547      &compress-coding;
1548   </c>
1549   <c>deflate</c>
1550   <c>"deflate" compression mechanism (<xref target="RFC1951"/>) used inside
1551   the "zlib" data format (<xref target="RFC1950"/>)
1552   </c>
1553   <c>
1554      &deflate-coding;
1555   </c>
1556   <c>gzip</c>
1557   <c>Same as GNU zip <xref target="RFC1952"/></c>
1558   <c>
1559      &gzip-coding;
1560   </c>
1561   <c>identity</c>
1562   <c>reserved (synonym for "no encoding" in Accept-Encoding header field)</c>
1563   <c>
1564      <xref target="header.accept-encoding"/>
1565   </c>
1566</texttable>
1567</section>
1568
1569</section>
1570
1571<section title="Security Considerations" anchor="security.considerations">
1572<t>
1573   This section is meant to inform application developers, information
1574   providers, and users of the security limitations in HTTP/1.1 as
1575   described by this document. The discussion does not include
1576   definitive solutions to the problems revealed, though it does make
1577   some suggestions for reducing security risks.
1578</t>
1579
1580<section title="Privacy Issues Connected to Accept Header Fields" anchor="privacy.issues.connected.to.accept.header.fields">
1581<t>
1582   Accept headers fields can reveal information about the user to all
1583   servers which are accessed. The Accept-Language header field in particular
1584   can reveal information the user would consider to be of a private
1585   nature, because the understanding of particular languages is often
1586   strongly correlated to the membership of a particular ethnic group.
1587   User agents which offer the option to configure the contents of an
1588   Accept-Language header field to be sent in every request are strongly
1589   encouraged to let the configuration process include a message which
1590   makes the user aware of the loss of privacy involved.
1591</t>
1592<t>
1593   An approach that limits the loss of privacy would be for a user agent
1594   to omit the sending of Accept-Language header fields by default, and to ask
1595   the user whether or not to start sending Accept-Language header fields to a
1596   server if it detects, by looking for any Vary header fields
1597   generated by the server, that such sending could improve the quality
1598   of service.
1599</t>
1600<t>
1601   Elaborate user-customized accept header fields sent in every request,
1602   in particular if these include quality values, can be used by servers
1603   as relatively reliable and long-lived user identifiers. Such user
1604   identifiers would allow content providers to do click-trail tracking,
1605   and would allow collaborating content providers to match cross-server
1606   click-trails or form submissions of individual users. Note that for
1607   many users not behind a proxy, the network address of the host
1608   running the user agent will also serve as a long-lived user
1609   identifier. In environments where proxies are used to enhance
1610   privacy, user agents ought to be conservative in offering accept
1611   header configuration options to end users. As an extreme privacy
1612   measure, proxies could filter the accept header fields in relayed requests.
1613   General purpose user agents which provide a high degree of header
1614   configurability &SHOULD; warn users about the loss of privacy which can
1615   be involved.
1616</t>
1617</section>
1618
1619</section>
1620
1621<section title="Acknowledgments" anchor="acks">
1622<t>
1623  See &acks;.
1624</t>
1625</section>
1626</middle>
1627<back>
1628
1629<references title="Normative References">
1630
1631<reference anchor="Part1">
1632  <front>
1633    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
1634    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1635      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
1636      <address><email>fielding@gbiv.com</email></address>
1637    </author>
1638    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1639      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1640      <address><email>jg@freedesktop.org</email></address>
1641    </author>
1642    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1643      <organization abbrev="HP">Hewlett-Packard Company</organization>
1644      <address><email>JeffMogul@acm.org</email></address>
1645    </author>
1646    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1647      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1648      <address><email>henrikn@microsoft.com</email></address>
1649    </author>
1650    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1651      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
1652      <address><email>LMM@acm.org</email></address>
1653    </author>
1654    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1655      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1656      <address><email>paulle@microsoft.com</email></address>
1657    </author>
1658    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1659      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1660      <address><email>timbl@w3.org</email></address>
1661    </author>
1662    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1663      <organization abbrev="W3C">World Wide Web Consortium</organization>
1664      <address><email>ylafon@w3.org</email></address>
1665    </author>
1666    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1667      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1668      <address><email>julian.reschke@greenbytes.de</email></address>
1669    </author>
1670    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1671  </front>
1672  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
1673  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
1674</reference>
1675
1676<reference anchor="Part2">
1677  <front>
1678    <title abbrev="HTTP/1.1">HTTP/1.1, part 2: Message Semantics</title>
1679    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1680      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
1681      <address><email>fielding@gbiv.com</email></address>
1682    </author>
1683    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1684      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1685      <address><email>jg@freedesktop.org</email></address>
1686    </author>
1687    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1688      <organization abbrev="HP">Hewlett-Packard Company</organization>
1689      <address><email>JeffMogul@acm.org</email></address>
1690    </author>
1691    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1692      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1693      <address><email>henrikn@microsoft.com</email></address>
1694    </author>
1695    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1696      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
1697      <address><email>LMM@acm.org</email></address>
1698    </author>
1699    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1700      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1701      <address><email>paulle@microsoft.com</email></address>
1702    </author>
1703    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1704      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1705      <address><email>timbl@w3.org</email></address>
1706    </author>
1707    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1708      <organization abbrev="W3C">World Wide Web Consortium</organization>
1709      <address><email>ylafon@w3.org</email></address>
1710    </author>
1711    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1712      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1713      <address><email>julian.reschke@greenbytes.de</email></address>
1714    </author>
1715    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1716  </front>
1717  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"/>
1718  <x:source href="p2-semantics.xml" basename="p2-semantics"/>
1719</reference>
1720
1721<reference anchor="Part4">
1722  <front>
1723    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
1724    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1725      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
1726      <address><email>fielding@gbiv.com</email></address>
1727    </author>
1728    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1729      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1730      <address><email>jg@freedesktop.org</email></address>
1731    </author>
1732    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1733      <organization abbrev="HP">Hewlett-Packard Company</organization>
1734      <address><email>JeffMogul@acm.org</email></address>
1735    </author>
1736    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1737      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1738      <address><email>henrikn@microsoft.com</email></address>
1739    </author>
1740    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1741      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
1742      <address><email>LMM@acm.org</email></address>
1743    </author>
1744    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1745      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1746      <address><email>paulle@microsoft.com</email></address>
1747    </author>
1748    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1749      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1750      <address><email>timbl@w3.org</email></address>
1751    </author>
1752    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1753      <organization abbrev="W3C">World Wide Web Consortium</organization>
1754      <address><email>ylafon@w3.org</email></address>
1755    </author>
1756    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1757      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1758      <address><email>julian.reschke@greenbytes.de</email></address>
1759    </author>
1760    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1761  </front>
1762  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
1763  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
1764</reference>
1765
1766<reference anchor="Part5">
1767  <front>
1768    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
1769    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1770      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
1771      <address><email>fielding@gbiv.com</email></address>
1772    </author>
1773    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1774      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1775      <address><email>jg@freedesktop.org</email></address>
1776    </author>
1777    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1778      <organization abbrev="HP">Hewlett-Packard Company</organization>
1779      <address><email>JeffMogul@acm.org</email></address>
1780    </author>
1781    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1782      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1783      <address><email>henrikn@microsoft.com</email></address>
1784    </author>
1785    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1786      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
1787      <address><email>LMM@acm.org</email></address>
1788    </author>
1789    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1790      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1791      <address><email>paulle@microsoft.com</email></address>
1792    </author>
1793    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1794      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1795      <address><email>timbl@w3.org</email></address>
1796    </author>
1797    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1798      <organization abbrev="W3C">World Wide Web Consortium</organization>
1799      <address><email>ylafon@w3.org</email></address>
1800    </author>
1801    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1802      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1803      <address><email>julian.reschke@greenbytes.de</email></address>
1804    </author>
1805    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1806  </front>
1807  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
1808  <x:source href="p5-range.xml" basename="p5-range"/>
1809</reference>
1810
1811<reference anchor="Part6">
1812  <front>
1813    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
1814    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1815      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
1816      <address><email>fielding@gbiv.com</email></address>
1817    </author>
1818    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1819      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1820      <address><email>jg@freedesktop.org</email></address>
1821    </author>
1822    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1823      <organization abbrev="HP">Hewlett-Packard Company</organization>
1824      <address><email>JeffMogul@acm.org</email></address>
1825    </author>
1826    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1827      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1828      <address><email>henrikn@microsoft.com</email></address>
1829    </author>
1830    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1831      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
1832      <address><email>LMM@acm.org</email></address>
1833    </author>
1834    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1835      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1836      <address><email>paulle@microsoft.com</email></address>
1837    </author>
1838    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1839      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1840      <address><email>timbl@w3.org</email></address>
1841    </author>
1842    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1843      <organization abbrev="W3C">World Wide Web Consortium</organization>
1844      <address><email>ylafon@w3.org</email></address>
1845    </author>
1846    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
1847      <address><email>mnot@mnot.net</email></address>
1848    </author>
1849    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1850      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1851      <address><email>julian.reschke@greenbytes.de</email></address>
1852    </author>
1853    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1854  </front>
1855  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
1856  <x:source href="p6-cache.xml" basename="p6-cache"/>
1857</reference>
1858
1859<reference anchor="RFC1950">
1860  <front>
1861    <title>ZLIB Compressed Data Format Specification version 3.3</title>
1862    <author initials="L.P." surname="Deutsch" fullname="L. Peter Deutsch">
1863      <organization>Aladdin Enterprises</organization>
1864      <address><email>ghost@aladdin.com</email></address>
1865    </author>
1866    <author initials="J-L." surname="Gailly" fullname="Jean-Loup Gailly"/>
1867    <date month="May" year="1996"/>
1868  </front>
1869  <seriesInfo name="RFC" value="1950"/>
1870  <annotation>
1871    RFC 1950 is an Informational RFC, thus it might be less stable than
1872    this specification. On the other hand, this downward reference was
1873    present since the publication of <xref target="RFC2068" x:fmt="none">RFC 2068</xref> in 1997,
1874    therefore it is unlikely to cause problems in practice. See also
1875    <xref target="BCP97"/>.
1876  </annotation>
1877</reference>
1878
1879<reference anchor="RFC1951">
1880  <front>
1881    <title>DEFLATE Compressed Data Format Specification version 1.3</title>
1882    <author initials="P." surname="Deutsch" fullname="L. Peter Deutsch">
1883      <organization>Aladdin Enterprises</organization>
1884      <address><email>ghost@aladdin.com</email></address>
1885    </author>
1886    <date month="May" year="1996"/>
1887  </front>
1888  <seriesInfo name="RFC" value="1951"/>
1889  <annotation>
1890    RFC 1951 is an Informational RFC, thus it might be less stable than
1891    this specification. On the other hand, this downward reference was
1892    present since the publication of <xref target="RFC2068" x:fmt="none">RFC 2068</xref> in 1997,
1893    therefore it is unlikely to cause problems in practice. See also
1894    <xref target="BCP97"/>.
1895  </annotation>
1896</reference>
1897
1898<reference anchor="RFC1952">
1899  <front>
1900    <title>GZIP file format specification version 4.3</title>
1901    <author initials="P." surname="Deutsch" fullname="L. Peter Deutsch">
1902      <organization>Aladdin Enterprises</organization>
1903      <address><email>ghost@aladdin.com</email></address>
1904    </author>
1905    <author initials="J-L." surname="Gailly" fullname="Jean-Loup Gailly">
1906      <address><email>gzip@prep.ai.mit.edu</email></address>
1907    </author>
1908    <author initials="M." surname="Adler" fullname="Mark Adler">
1909      <address><email>madler@alumni.caltech.edu</email></address>
1910    </author>
1911    <author initials="L.P." surname="Deutsch" fullname="L. Peter Deutsch">
1912      <address><email>ghost@aladdin.com</email></address>
1913    </author>
1914    <author initials="G." surname="Randers-Pehrson" fullname="Glenn Randers-Pehrson">
1915      <address><email>randeg@alumni.rpi.edu</email></address>
1916    </author>
1917    <date month="May" year="1996"/>
1918  </front>
1919  <seriesInfo name="RFC" value="1952"/>
1920  <annotation>
1921    RFC 1952 is an Informational RFC, thus it might be less stable than
1922    this specification. On the other hand, this downward reference was
1923    present since the publication of <xref target="RFC2068" x:fmt="none">RFC 2068</xref> in 1997,
1924    therefore it is unlikely to cause problems in practice. See also
1925    <xref target="BCP97"/>.
1926  </annotation>
1927</reference>
1928
1929<reference anchor="RFC2045">
1930  <front>
1931    <title abbrev="Internet Message Bodies">Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies</title>
1932    <author initials="N." surname="Freed" fullname="Ned Freed">
1933      <organization>Innosoft International, Inc.</organization>
1934      <address><email>ned@innosoft.com</email></address>
1935    </author>
1936    <author initials="N.S." surname="Borenstein" fullname="Nathaniel S. Borenstein">
1937      <organization>First Virtual Holdings</organization>
1938      <address><email>nsb@nsb.fv.com</email></address>
1939    </author>
1940    <date month="November" year="1996"/>
1941  </front>
1942  <seriesInfo name="RFC" value="2045"/>
1943</reference>
1944
1945<reference anchor="RFC2046">
1946  <front>
1947    <title abbrev="Media Types">Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types</title>
1948    <author initials="N." surname="Freed" fullname="Ned Freed">
1949      <organization>Innosoft International, Inc.</organization>
1950      <address><email>ned@innosoft.com</email></address>
1951    </author>
1952    <author initials="N." surname="Borenstein" fullname="Nathaniel S. Borenstein">
1953      <organization>First Virtual Holdings</organization>
1954      <address><email>nsb@nsb.fv.com</email></address>
1955    </author>
1956    <date month="November" year="1996"/>
1957  </front>
1958  <seriesInfo name="RFC" value="2046"/>
1959</reference>
1960
1961<reference anchor="RFC2119">
1962  <front>
1963    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
1964    <author initials="S." surname="Bradner" fullname="Scott Bradner">
1965      <organization>Harvard University</organization>
1966      <address><email>sob@harvard.edu</email></address>
1967    </author>
1968    <date month="March" year="1997"/>
1969  </front>
1970  <seriesInfo name="BCP" value="14"/>
1971  <seriesInfo name="RFC" value="2119"/>
1972</reference>
1973
1974<reference anchor='RFC4647'>
1975  <front>
1976    <title>Matching of Language Tags</title>
1977    <author initials='A.' surname='Phillips' fullname='Addison Phillips' role="editor">
1978      <organization>Yahoo! Inc.</organization>
1979      <address><email>addison@inter-locale.com</email></address>
1980    </author>
1981    <author initials='M.' surname='Davis' fullname='Mark Davis' role="editor">
1982      <organization>Google</organization>
1983      <address><email>mark.davis@macchiato.com</email></address>
1984    </author>
1985    <date year='2006' month='September' />
1986  </front>
1987  <seriesInfo name='BCP' value='47' />
1988  <seriesInfo name='RFC' value='4647' />
1989</reference>
1990
1991<reference anchor="RFC5234">
1992  <front>
1993    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
1994    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
1995      <organization>Brandenburg InternetWorking</organization>
1996      <address>
1997        <email>dcrocker@bbiw.net</email>
1998      </address> 
1999    </author>
2000    <author initials="P." surname="Overell" fullname="Paul Overell">
2001      <organization>THUS plc.</organization>
2002      <address>
2003        <email>paul.overell@thus.net</email>
2004      </address>
2005    </author>
2006    <date month="January" year="2008"/>
2007  </front>
2008  <seriesInfo name="STD" value="68"/>
2009  <seriesInfo name="RFC" value="5234"/>
2010</reference>
2011
2012<reference anchor='RFC5646'>
2013  <front>
2014    <title>Tags for Identifying Languages</title>
2015    <author initials='A.' surname='Phillips' fullname='Addison Phillips' role='editor'>
2016      <organization>Lab126</organization>
2017      <address><email>addison@inter-locale.com</email></address>
2018    </author>
2019    <author initials='M.' surname='Davis' fullname='Mark Davis' role='editor'>
2020      <organization>Google</organization>
2021      <address><email>mark.davis@google.com</email></address>
2022    </author>
2023    <date month='September' year='2009' />
2024  </front>
2025  <seriesInfo name='BCP' value='47' />
2026  <seriesInfo name='RFC' value='5646' />
2027</reference>
2028
2029</references>
2030
2031<references title="Informative References">
2032
2033<reference anchor="RFC1945">
2034  <front>
2035    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
2036    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2037      <organization>MIT, Laboratory for Computer Science</organization>
2038      <address><email>timbl@w3.org</email></address>
2039    </author>
2040    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
2041      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2042      <address><email>fielding@ics.uci.edu</email></address>
2043    </author>
2044    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2045      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
2046      <address><email>frystyk@w3.org</email></address>
2047    </author>
2048    <date month="May" year="1996"/>
2049  </front>
2050  <seriesInfo name="RFC" value="1945"/>
2051</reference>
2052
2053<reference anchor="RFC2049">
2054  <front>
2055    <title abbrev="MIME Conformance">Multipurpose Internet Mail Extensions (MIME) Part Five: Conformance Criteria and Examples</title>
2056    <author initials="N." surname="Freed" fullname="Ned Freed">
2057      <organization>Innosoft International, Inc.</organization>
2058      <address><email>ned@innosoft.com</email></address>
2059    </author>
2060    <author initials="N.S." surname="Borenstein" fullname="Nathaniel S. Borenstein">
2061      <organization>First Virtual Holdings</organization>
2062      <address><email>nsb@nsb.fv.com</email></address>
2063    </author>
2064    <date month="November" year="1996"/>
2065  </front>
2066  <seriesInfo name="RFC" value="2049"/>
2067</reference>
2068
2069<reference anchor="RFC2068">
2070  <front>
2071    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
2072    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
2073      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2074      <address><email>fielding@ics.uci.edu</email></address>
2075    </author>
2076    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2077      <organization>MIT Laboratory for Computer Science</organization>
2078      <address><email>jg@w3.org</email></address>
2079    </author>
2080    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2081      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
2082      <address><email>mogul@wrl.dec.com</email></address>
2083    </author>
2084    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2085      <organization>MIT Laboratory for Computer Science</organization>
2086      <address><email>frystyk@w3.org</email></address>
2087    </author>
2088    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2089      <organization>MIT Laboratory for Computer Science</organization>
2090      <address><email>timbl@w3.org</email></address>
2091    </author>
2092    <date month="January" year="1997"/>
2093  </front>
2094  <seriesInfo name="RFC" value="2068"/>
2095</reference>
2096
2097<reference anchor="RFC2076">
2098  <front>
2099    <title abbrev="Internet Message Headers">Common Internet Message Headers</title>
2100    <author initials="J." surname="Palme" fullname="Jacob Palme">
2101      <organization>Stockholm University/KTH</organization>
2102      <address><email>jpalme@dsv.su.se</email></address>
2103    </author>
2104    <date month="February" year="1997"/>
2105  </front>
2106  <seriesInfo name="RFC" value="2076"/>
2107</reference>
2108
2109<reference anchor="RFC2277">
2110  <front>
2111    <title abbrev="Charset Policy">IETF Policy on Character Sets and Languages</title>
2112    <author initials="H.T." surname="Alvestrand" fullname="Harald Tveit Alvestrand">
2113      <organization>UNINETT</organization>
2114      <address><email>Harald.T.Alvestrand@uninett.no</email></address>
2115    </author>
2116    <date month="January" year="1998"/>
2117  </front>
2118  <seriesInfo name="BCP" value="18"/>
2119  <seriesInfo name="RFC" value="2277"/>
2120</reference>
2121
2122<reference anchor='RFC2295'>
2123  <front>
2124    <title abbrev='HTTP Content Negotiation'>Transparent Content Negotiation in HTTP</title>
2125    <author initials='K.' surname='Holtman' fullname='Koen Holtman'>
2126      <organization>Technische Universiteit Eindhoven</organization>
2127      <address>
2128        <email>koen@win.tue.nl</email>
2129      </address>
2130    </author>
2131    <author initials='A.H.' surname='Mutz' fullname='Andrew H. Mutz'>
2132      <organization>Hewlett-Packard Company</organization>
2133      <address>
2134        <email>mutz@hpl.hp.com</email>
2135      </address>
2136    </author>
2137    <date year='1998' month='March'/>
2138  </front>
2139  <seriesInfo name='RFC' value='2295'/>
2140</reference>
2141
2142<reference anchor="RFC2388">
2143  <front>
2144    <title abbrev="multipart/form-data">Returning Values from Forms:  multipart/form-data</title>
2145    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2146      <organization>Xerox Palo Alto Research Center</organization>
2147      <address><email>masinter@parc.xerox.com</email></address>
2148    </author>
2149    <date year="1998" month="August"/>
2150  </front>
2151  <seriesInfo name="RFC" value="2388"/>
2152</reference>
2153
2154<reference anchor="RFC2557">
2155  <front>
2156    <title abbrev="MIME Encapsulation of Aggregate Documents">MIME Encapsulation of Aggregate Documents, such as HTML (MHTML)</title>
2157    <author initials="F." surname="Palme" fullname="Jacob Palme">
2158      <organization>Stockholm University and KTH</organization>
2159      <address><email>jpalme@dsv.su.se</email></address>
2160    </author>
2161    <author initials="A." surname="Hopmann" fullname="Alex Hopmann">
2162      <organization>Microsoft Corporation</organization>
2163      <address><email>alexhop@microsoft.com</email></address>
2164    </author>
2165    <author initials="N." surname="Shelness" fullname="Nick Shelness">
2166      <organization>Lotus Development Corporation</organization>
2167      <address><email>Shelness@lotus.com</email></address>
2168    </author>
2169    <author initials="E." surname="Stefferud" fullname="Einar Stefferud">
2170      <address><email>stef@nma.com</email></address>
2171    </author>
2172    <date year="1999" month="March"/>
2173  </front>
2174  <seriesInfo name="RFC" value="2557"/>
2175</reference>
2176
2177<reference anchor="RFC2616">
2178  <front>
2179    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
2180    <author initials="R." surname="Fielding" fullname="R. Fielding">
2181      <organization>University of California, Irvine</organization>
2182      <address><email>fielding@ics.uci.edu</email></address>
2183    </author>
2184    <author initials="J." surname="Gettys" fullname="J. Gettys">
2185      <organization>W3C</organization>
2186      <address><email>jg@w3.org</email></address>
2187    </author>
2188    <author initials="J." surname="Mogul" fullname="J. Mogul">
2189      <organization>Compaq Computer Corporation</organization>
2190      <address><email>mogul@wrl.dec.com</email></address>
2191    </author>
2192    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
2193      <organization>MIT Laboratory for Computer Science</organization>
2194      <address><email>frystyk@w3.org</email></address>
2195    </author>
2196    <author initials="L." surname="Masinter" fullname="L. Masinter">
2197      <organization>Xerox Corporation</organization>
2198      <address><email>masinter@parc.xerox.com</email></address>
2199    </author>
2200    <author initials="P." surname="Leach" fullname="P. Leach">
2201      <organization>Microsoft Corporation</organization>
2202      <address><email>paulle@microsoft.com</email></address>
2203    </author>
2204    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
2205      <organization>W3C</organization>
2206      <address><email>timbl@w3.org</email></address>
2207    </author>
2208    <date month="June" year="1999"/>
2209  </front>
2210  <seriesInfo name="RFC" value="2616"/>
2211</reference>
2212
2213<reference anchor="RFC3629">
2214  <front>
2215    <title>UTF-8, a transformation format of ISO 10646</title>
2216    <author initials="F." surname="Yergeau" fullname="F. Yergeau">
2217      <organization>Alis Technologies</organization>
2218      <address><email>fyergeau@alis.com</email></address>
2219    </author>
2220    <date month="November" year="2003"/>
2221  </front>
2222  <seriesInfo name="STD" value="63"/>
2223  <seriesInfo name="RFC" value="3629"/>
2224</reference>
2225
2226<reference anchor='RFC3864'>
2227  <front>
2228    <title>Registration Procedures for Message Header Fields</title>
2229    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
2230      <organization>Nine by Nine</organization>
2231      <address><email>GK-IETF@ninebynine.org</email></address>
2232    </author>
2233    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
2234      <organization>BEA Systems</organization>
2235      <address><email>mnot@pobox.com</email></address>
2236    </author>
2237    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
2238      <organization>HP Labs</organization>
2239      <address><email>JeffMogul@acm.org</email></address>
2240    </author>
2241    <date year='2004' month='September' />
2242  </front>
2243  <seriesInfo name='BCP' value='90' />
2244  <seriesInfo name='RFC' value='3864' />
2245</reference>
2246
2247<reference anchor="RFC4288">
2248  <front>
2249    <title>Media Type Specifications and Registration Procedures</title>
2250    <author initials="N." surname="Freed" fullname="N. Freed">
2251      <organization>Sun Microsystems</organization>
2252      <address>
2253        <email>ned.freed@mrochek.com</email>
2254      </address>
2255    </author>
2256    <author initials="J." surname="Klensin" fullname="J. Klensin">
2257      <address>
2258        <email>klensin+ietf@jck.com</email>
2259      </address>
2260    </author>
2261    <date year="2005" month="December"/>
2262  </front>
2263  <seriesInfo name="BCP" value="13"/>
2264  <seriesInfo name="RFC" value="4288"/>
2265</reference>
2266
2267<reference anchor='RFC5226'>
2268  <front>
2269    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
2270    <author initials='T.' surname='Narten' fullname='T. Narten'>
2271      <organization>IBM</organization>
2272      <address><email>narten@us.ibm.com</email></address>
2273    </author>
2274    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
2275      <organization>Google</organization>
2276      <address><email>Harald@Alvestrand.no</email></address>
2277    </author>
2278    <date year='2008' month='May' />
2279  </front>
2280  <seriesInfo name='BCP' value='26' />
2281  <seriesInfo name='RFC' value='5226' />
2282</reference>
2283
2284<reference anchor="RFC5322">
2285  <front>
2286    <title>Internet Message Format</title>
2287    <author initials="P." surname="Resnick" fullname="P. Resnick">
2288      <organization>Qualcomm Incorporated</organization>
2289    </author>
2290    <date year="2008" month="October"/>
2291  </front> 
2292  <seriesInfo name="RFC" value="5322"/>
2293</reference>
2294
2295<reference anchor="RFC6151">
2296  <front>
2297    <title>Updated Security Considerations for the MD5 Message-Digest and the HMAC-MD5 Algorithms</title>
2298    <author initials="S." surname="Turner" fullname="S. Turner"/>
2299    <author initials="L." surname="Chen" fullname="L. Chen"/>
2300    <date year="2011" month="March" />
2301  </front>
2302  <seriesInfo name="RFC" value="6151" />
2303</reference>
2304
2305<reference anchor='BCP97'>
2306  <front>
2307    <title>Handling Normative References to Standards-Track Documents</title>
2308    <author initials='J.' surname='Klensin' fullname='J. Klensin'>
2309      <address>
2310        <email>klensin+ietf@jck.com</email>
2311      </address>
2312    </author>
2313    <author initials='S.' surname='Hartman' fullname='S. Hartman'>
2314      <organization>MIT</organization>
2315      <address>
2316        <email>hartmans-ietf@mit.edu</email>
2317      </address>
2318    </author>
2319    <date year='2007' month='June' />
2320  </front>
2321  <seriesInfo name='BCP' value='97' />
2322  <seriesInfo name='RFC' value='4897' />
2323</reference>
2324
2325<reference anchor="RFC6266">
2326  <front>
2327    <title abbrev="Content-Disposition in HTTP">Use of the Content-Disposition Header Field
2328    in the Hypertext Transfer Protocol (HTTP)</title>
2329    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke">
2330      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2331      <address>
2332        <email>julian.reschke@greenbytes.de</email>
2333      </address>
2334    </author>
2335    <date month="June" year="2011"/>
2336  </front>
2337  <seriesInfo name='RFC' value='6266' />
2338</reference>
2339
2340</references>
2341
2342<section title="Differences between HTTP and MIME" anchor="differences.between.http.and.mime">
2343<t>
2344   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
2345   allow a message-body to be transmitted in an open variety of
2346   representations and with extensible mechanisms. However, RFC 2045
2347   discusses mail, and HTTP has a few features that are different from
2348   those described in MIME. These differences were carefully chosen
2349   to optimize performance over binary connections, to allow greater
2350   freedom in the use of new media types, to make date comparisons
2351   easier, and to acknowledge the practice of some early HTTP servers
2352   and clients.
2353</t>
2354<t>
2355   This appendix describes specific areas where HTTP differs from MIME.
2356   Proxies and gateways to strict MIME environments &SHOULD; be
2357   aware of these differences and provide the appropriate conversions
2358   where necessary. Proxies and gateways from MIME environments to HTTP
2359   also need to be aware of the differences because some conversions
2360   might be required.
2361</t>
2362
2363<section title="MIME-Version" anchor="mime-version">
2364  <iref primary="true" item="MIME-Version header field" x:for-anchor=""/>
2365  <iref primary="true" item="Header Fields" subitem="MIME-Version" x:for-anchor=""/>
2366  <x:anchor-alias value="MIME-Version"/>
2367<t>
2368   HTTP is not a MIME-compliant protocol. However, HTTP/1.1 messages &MAY;
2369   include a single MIME-Version header field to indicate what
2370   version of the MIME protocol was used to construct the message. Use
2371   of the MIME-Version header field indicates that the message is in
2372   full compliance with the MIME protocol (as defined in <xref target="RFC2045"/>).
2373   Proxies/gateways are responsible for ensuring full compliance (where
2374   possible) when exporting HTTP messages to strict MIME environments.
2375</t>
2376<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="MIME-Version"/>
2377  <x:ref>MIME-Version</x:ref> = 1*<x:ref>DIGIT</x:ref> "." 1*<x:ref>DIGIT</x:ref>
2378</artwork></figure>
2379<t>
2380   MIME version "1.0" is the default for use in HTTP/1.1. However,
2381   HTTP/1.1 message parsing and semantics are defined by this document
2382   and not the MIME specification.
2383</t>
2384</section>
2385
2386<section title="Conversion to Canonical Form" anchor="conversion.to.canonical.form">
2387<t>
2388   MIME requires that an Internet mail body-part be converted to
2389   canonical form prior to being transferred, as described in <xref target="RFC2049" x:fmt="of" x:sec="4"/>.
2390   <xref target="canonicalization.and.text.defaults"/> of this document describes the forms
2391   allowed for subtypes of the "text" media type when transmitted over
2392   HTTP. <xref target="RFC2046"/> requires that content with a type of "text" represent
2393   line breaks as CRLF and forbids the use of CR or LF outside of line
2394   break sequences. HTTP allows CRLF, bare CR, and bare LF to indicate a
2395   line break within text content when a message is transmitted over
2396   HTTP.
2397</t>
2398<t>
2399   Where it is possible, a proxy or gateway from HTTP to a strict MIME
2400   environment &SHOULD; translate all line breaks within the text media
2401   types described in <xref target="canonicalization.and.text.defaults"/>
2402   of this document to the RFC 2049
2403   canonical form of CRLF. Note, however, that this might be complicated
2404   by the presence of a Content-Encoding and by the fact that HTTP
2405   allows the use of some character encodings which do not use octets 13 and
2406   10 to represent CR and LF, respectively, as is the case for some multi-byte
2407   character encodings.
2408</t>
2409<t>
2410   Conversion will break any cryptographic
2411   checksums applied to the original content unless the original content
2412   is already in canonical form. Therefore, the canonical form is
2413   recommended for any content that uses such checksums in HTTP.
2414</t>
2415</section>
2416
2417
2418<section title="Conversion of Date Formats" anchor="conversion.of.date.formats">
2419<t>
2420   HTTP/1.1 uses a restricted set of date formats (&full-date;) to
2421   simplify the process of date comparison. Proxies and gateways from
2422   other protocols &SHOULD; ensure that any Date header field present in a
2423   message conforms to one of the HTTP/1.1 formats and rewrite the date
2424   if necessary.
2425</t>
2426</section>
2427
2428<section title="Introduction of Content-Encoding" anchor="introduction.of.content-encoding">
2429<t>
2430   MIME does not include any concept equivalent to HTTP/1.1's
2431   Content-Encoding header field. Since this acts as a modifier on the
2432   media type, proxies and gateways from HTTP to MIME-compliant
2433   protocols &MUST; either change the value of the Content-Type header
2434   field or decode the representation before forwarding the message. (Some
2435   experimental applications of Content-Type for Internet mail have used
2436   a media-type parameter of ";conversions=&lt;content-coding&gt;" to perform
2437   a function equivalent to Content-Encoding. However, this parameter is
2438   not part of the MIME standards).
2439</t>
2440</section>
2441
2442<section title="No Content-Transfer-Encoding" anchor="no.content-transfer-encoding">
2443<t>
2444   HTTP does not use the Content-Transfer-Encoding field of MIME.
2445   Proxies and gateways from MIME-compliant protocols to HTTP &MUST;
2446   remove any Content-Transfer-Encoding
2447   prior to delivering the response message to an HTTP client.
2448</t>
2449<t>
2450   Proxies and gateways from HTTP to MIME-compliant protocols are
2451   responsible for ensuring that the message is in the correct format
2452   and encoding for safe transport on that protocol, where "safe
2453   transport" is defined by the limitations of the protocol being used.
2454   Such a proxy or gateway &SHOULD; label the data with an appropriate
2455   Content-Transfer-Encoding if doing so will improve the likelihood of
2456   safe transport over the destination protocol.
2457</t>
2458</section>
2459
2460<section title="Introduction of Transfer-Encoding" anchor="introduction.of.transfer-encoding">
2461<t>
2462   HTTP/1.1 introduces the Transfer-Encoding header field (&header-transfer-encoding;).
2463   Proxies/gateways &MUST; remove any transfer-coding prior to
2464   forwarding a message via a MIME-compliant protocol.
2465</t>
2466</section>
2467
2468<section title="MHTML and Line Length Limitations" anchor="mhtml.line.length">
2469<t>
2470   HTTP implementations which share code with MHTML <xref target="RFC2557"/> implementations
2471   need to be aware of MIME line length limitations. Since HTTP does not
2472   have this limitation, HTTP does not fold long lines. MHTML messages
2473   being transported by HTTP follow all conventions of MHTML, including
2474   line length limitations and folding, canonicalization, etc., since
2475   HTTP transports all message-bodies as payload (see <xref target="multipart.types"/>) and
2476   does not interpret the content or any MIME header lines that might be
2477   contained therein.
2478</t>
2479</section>
2480</section>
2481
2482<section title="Additional Features" anchor="additional.features">
2483<t>
2484   <xref target="RFC1945"/> and <xref target="RFC2068"/> document protocol elements used by some
2485   existing HTTP implementations, but not consistently and correctly
2486   across most HTTP/1.1 applications. Implementors are advised to be
2487   aware of these features, but cannot rely upon their presence in, or
2488   interoperability with, other HTTP/1.1 applications. Some of these
2489   describe proposed experimental features, and some describe features
2490   that experimental deployment found lacking that are now addressed in
2491   the base HTTP/1.1 specification.
2492</t>
2493<t>
2494   A number of other header fields, such as Content-Disposition and Title,
2495   from SMTP and MIME are also often implemented (see <xref target="RFC6266"/>
2496   and <xref target="RFC2076"/>).
2497</t>
2498</section>
2499
2500<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
2501<t>
2502  Clarify contexts that charset is used in.
2503  (<xref target="character.sets"/>)
2504</t>
2505<t>
2506  Remove the default character encoding for text media types; the default
2507  now is whatever the media type definition says.
2508  (<xref target="canonicalization.and.text.defaults"/>)
2509</t>
2510<t>
2511  Change ABNF productions for header fields to only define the field value.
2512  (<xref target="header.field.definitions"/>)
2513</t>
2514<t>
2515  Remove definition of Content-MD5 header field because it was inconsistently
2516  implemented with respect to partial responses, and also because of known
2517  deficiencies in the hash algorithm itself (see <xref target="RFC6151"/> for details).
2518  (<xref target="header.field.definitions"/>)
2519</t>
2520<t>
2521  Remove ISO-8859-1 special-casing in Accept-Charset.
2522  (<xref target="header.accept-charset"/>)
2523</t>
2524<t>
2525  Remove base URI setting semantics for Content-Location due to poor
2526  implementation support, which was caused by too many broken servers emitting
2527  bogus Content-Location header fields, and also the potentially undesirable effect
2528  of potentially breaking relative links in content-negotiated resources.
2529  (<xref target="header.content-location"/>)
2530</t>
2531<t>
2532  Remove discussion of Content-Disposition header field, it is now defined
2533  by <xref target="RFC6266"/>.
2534  (<xref target="additional.features"/>)
2535</t>
2536<t>
2537  Remove reference to non-existant identity transfer-coding value tokens.
2538  (<xref target="no.content-transfer-encoding"/>)
2539</t>
2540</section>
2541
2542<?BEGININC p3-payload.abnf-appendix ?>
2543<section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf">
2544<figure>
2545<artwork type="abnf" name="p3-payload.parsed-abnf">
2546<x:ref>Accept</x:ref> = [ ( "," / ( media-range [ accept-params ] ) ) *( OWS "," [
2547 OWS media-range [ accept-params ] ] ) ]
2548<x:ref>Accept-Charset</x:ref> = *( "," OWS ) ( charset / "*" ) [ OWS ";" OWS "q="
2549 qvalue ] *( OWS "," [ OWS ( charset / "*" ) [ OWS ";" OWS "q="
2550 qvalue ] ] )
2551<x:ref>Accept-Encoding</x:ref> = [ ( "," / ( codings [ OWS ";" OWS "q=" qvalue ] ) )
2552 *( OWS "," [ OWS codings [ OWS ";" OWS "q=" qvalue ] ] ) ]
2553<x:ref>Accept-Language</x:ref> = *( "," OWS ) language-range [ OWS ";" OWS "q="
2554 qvalue ] *( OWS "," [ OWS language-range [ OWS ";" OWS "q=" qvalue ]
2555 ] )
2556
2557<x:ref>Content-Encoding</x:ref> = *( "," OWS ) content-coding *( OWS "," [ OWS
2558 content-coding ] )
2559<x:ref>Content-Language</x:ref> = *( "," OWS ) language-tag *( OWS "," [ OWS
2560 language-tag ] )
2561<x:ref>Content-Location</x:ref> = absolute-URI / partial-URI
2562<x:ref>Content-Type</x:ref> = media-type
2563
2564<x:ref>MIME-Version</x:ref> = 1*DIGIT "." 1*DIGIT
2565
2566<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
2567
2568<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.7&gt;
2569<x:ref>accept-ext</x:ref> = OWS ";" OWS token [ "=" word ]
2570<x:ref>accept-params</x:ref> = OWS ";" OWS "q=" qvalue *accept-ext
2571<x:ref>attribute</x:ref> = token
2572
2573<x:ref>charset</x:ref> = token
2574<x:ref>codings</x:ref> = content-coding / "identity" / "*"
2575<x:ref>content-coding</x:ref> = token
2576
2577<x:ref>language-range</x:ref> = &lt;language-range, defined in [RFC4647], Section 2.1&gt;
2578<x:ref>language-tag</x:ref> = &lt;Language-Tag, defined in [RFC5646], Section 2.1&gt;
2579
2580<x:ref>media-range</x:ref> = ( "*/*" / ( type "/*" ) / ( type "/" subtype ) ) *( OWS
2581 ";" OWS parameter )
2582<x:ref>media-type</x:ref> = type "/" subtype *( OWS ";" OWS parameter )
2583
2584<x:ref>parameter</x:ref> = attribute "=" value
2585<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.7&gt;
2586
2587<x:ref>qvalue</x:ref> = &lt;qvalue, defined in [Part1], Section 6.4&gt;
2588
2589<x:ref>subtype</x:ref> = token
2590
2591<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 3.2.3&gt;
2592<x:ref>type</x:ref> = token
2593
2594<x:ref>value</x:ref> = word
2595
2596<x:ref>word</x:ref> = &lt;word, defined in [Part1], Section 3.2.3&gt;
2597</artwork>
2598</figure>
2599<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
2600; Accept defined but not used
2601; Accept-Charset defined but not used
2602; Accept-Encoding defined but not used
2603; Accept-Language defined but not used
2604; Content-Encoding defined but not used
2605; Content-Language defined but not used
2606; Content-Location defined but not used
2607; Content-Type defined but not used
2608; MIME-Version defined but not used
2609</artwork></figure></section>
2610<?ENDINC p3-payload.abnf-appendix ?>
2611
2612<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
2613
2614<section title="Since RFC 2616">
2615<t>
2616  Extracted relevant partitions from <xref target="RFC2616"/>.
2617</t>
2618</section>
2619
2620<section title="Since draft-ietf-httpbis-p3-payload-00">
2621<t>
2622  Closed issues:
2623  <list style="symbols"> 
2624    <t>
2625      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/8"/>:
2626      "Media Type Registrations"
2627      (<eref target="http://purl.org/NET/http-errata#media-reg"/>)
2628    </t>
2629    <t>
2630      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/14"/>:
2631      "Clarification regarding quoting of charset values"
2632      (<eref target="http://purl.org/NET/http-errata#charactersets"/>)
2633    </t>
2634    <t>
2635      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/16"/>:
2636      "Remove 'identity' token references"
2637      (<eref target="http://purl.org/NET/http-errata#identity"/>)
2638    </t>
2639    <t>
2640      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/25"/>:
2641      "Accept-Encoding BNF"
2642    </t>
2643    <t>
2644      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
2645      "Normative and Informative references"
2646    </t>
2647    <t>
2648      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/46"/>:
2649      "RFC1700 references"
2650    </t>
2651    <t>
2652      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/55"/>:
2653      "Updating to RFC4288"
2654    </t>
2655    <t>
2656      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
2657      "Informative references"
2658    </t>
2659    <t>
2660      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/66"/>:
2661      "ISO-8859-1 Reference"
2662    </t>
2663    <t>
2664      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/68"/>:
2665      "Encoding References Normative"
2666    </t>
2667    <t>
2668      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/86"/>:
2669      "Normative up-to-date references"
2670    </t>
2671  </list>
2672</t>
2673</section>
2674
2675<section title="Since draft-ietf-httpbis-p3-payload-01">
2676<t>
2677  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
2678  <list style="symbols"> 
2679    <t>
2680      Add explicit references to BNF syntax and rules imported from other parts of the specification.
2681    </t>
2682  </list>
2683</t>
2684</section>
2685
2686<section title="Since draft-ietf-httpbis-p3-payload-02" anchor="changes.since.02">
2687<t>
2688  Closed issues:
2689  <list style="symbols"> 
2690    <t>
2691      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/67"/>:
2692      "Quoting Charsets"
2693    </t>
2694    <t>
2695      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
2696      "Classification for Allow header"
2697    </t>
2698    <t>
2699      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/115"/>:
2700      "missing default for qvalue in description of Accept-Encoding"
2701    </t>
2702  </list>
2703</t>
2704<t>
2705  Ongoing work on IANA Message Header Field Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
2706  <list style="symbols"> 
2707    <t>
2708      Reference RFC 3984, and update header field registrations for headers defined
2709      in this document.
2710    </t>
2711  </list>
2712</t>
2713</section>
2714
2715<section title="Since draft-ietf-httpbis-p3-payload-03" anchor="changes.since.03">
2716<t>
2717  Closed issues:
2718  <list style="symbols"> 
2719    <t>
2720      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/67"/>:
2721      "Quoting Charsets"
2722    </t>
2723    <t>
2724      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/113"/>:
2725      "language tag matching (Accept-Language) vs RFC4647"
2726    </t>
2727    <t>
2728      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/121"/>:
2729      "RFC 1806 has been replaced by RFC2183"
2730    </t>
2731  </list>
2732</t>
2733<t>
2734  Other changes:
2735  <list style="symbols"> 
2736    <t>
2737      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/68"/>:
2738      "Encoding References Normative" &mdash; rephrase the annotation and reference
2739      <xref target="BCP97"/>.
2740    </t>
2741  </list>
2742</t>
2743 </section>
2744
2745<section title="Since draft-ietf-httpbis-p3-payload-04" anchor="changes.since.04">
2746<t>
2747  Closed issues:
2748  <list style="symbols"> 
2749    <t>
2750      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
2751      "RFC 2822 is updated by RFC 5322"
2752    </t>
2753  </list>
2754</t>
2755<t>
2756  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
2757  <list style="symbols"> 
2758    <t>
2759      Use "/" instead of "|" for alternatives.
2760    </t>
2761    <t>
2762      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
2763      whitespace ("OWS") and required whitespace ("RWS").
2764    </t>
2765    <t>
2766      Rewrite ABNFs to spell out whitespace rules, factor out
2767      header field value format definitions.
2768    </t>
2769  </list>
2770</t>
2771</section>
2772
2773<section title="Since draft-ietf-httpbis-p3-payload-05" anchor="changes.since.05">
2774<t>
2775  Closed issues:
2776  <list style="symbols"> 
2777    <t>
2778      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/118"/>:
2779      "Join "Differences Between HTTP Entities and RFC 2045 Entities"?"
2780    </t>
2781  </list>
2782</t>
2783<t>
2784  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
2785  <list style="symbols"> 
2786    <t>
2787      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
2788    </t>
2789  </list>
2790</t>
2791<t>
2792  Other changes:
2793  <list style="symbols"> 
2794    <t>
2795      Move definition of quality values into Part 1.
2796    </t>
2797  </list>
2798</t>
2799</section>
2800
2801<section title="Since draft-ietf-httpbis-p3-payload-06" anchor="changes.since.06">
2802<t>
2803  Closed issues:
2804  <list style="symbols"> 
2805    <t>
2806      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/80"/>:
2807      "Content-Location isn't special"
2808    </t>
2809    <t>
2810      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/155"/>:
2811      "Content Sniffing"
2812    </t>
2813  </list>
2814</t>
2815</section>
2816
2817<section title="Since draft-ietf-httpbis-p3-payload-07" anchor="changes.since.07">
2818<t>
2819  Closed issues:
2820  <list style="symbols"> 
2821    <t>
2822      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/13"/>:
2823      "Updated reference for language tags"
2824    </t>
2825    <t>
2826      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
2827      "Clarify rules for determining what entities a response carries"
2828    </t>
2829    <t>
2830      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/154"/>:
2831      "Content-Location base-setting problems"
2832    </t>
2833    <t>
2834      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/155"/>:
2835      "Content Sniffing"
2836    </t>
2837    <t>
2838      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/188"/>:
2839      "pick IANA policy (RFC5226) for Transfer Coding / Content Coding"
2840    </t>
2841    <t>
2842      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/189"/>:
2843      "move definitions of gzip/deflate/compress to part 1"
2844    </t>
2845  </list>
2846</t>
2847<t>
2848  Partly resolved issues:
2849  <list style="symbols"> 
2850    <t>
2851      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/148"/>:
2852      "update IANA requirements wrt Transfer-Coding values" (add the
2853      IANA Considerations subsection)
2854    </t>
2855    <t>
2856      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/149"/>:
2857      "update IANA requirements wrt Content-Coding values" (add the
2858      IANA Considerations subsection)
2859    </t>
2860  </list>
2861</t>
2862</section>
2863
2864<section title="Since draft-ietf-httpbis-p3-payload-08" anchor="changes.since.08">
2865<t>
2866  Closed issues:
2867  <list style="symbols"> 
2868    <t>
2869      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/81"/>:
2870      "Content Negotiation for media types"
2871    </t>
2872    <t>
2873      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/181"/>:
2874      "Accept-Language: which RFC4647 filtering?"
2875    </t>
2876  </list>
2877</t>
2878</section>
2879
2880<section title="Since draft-ietf-httpbis-p3-payload-09" anchor="changes.since.09">
2881<t>
2882  Closed issues:
2883  <list style="symbols"> 
2884    <t>
2885      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/122"/>:
2886      "MIME-Version not listed in P1, general header fields"
2887    </t>
2888    <t>
2889      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/143"/>:
2890      "IANA registry for content/transfer encodings"
2891    </t>
2892    <t>
2893      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/155"/>:
2894      "Content Sniffing"
2895    </t>
2896    <t>
2897      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/200"/>:
2898      "use of term "word" when talking about header structure"
2899    </t>
2900  </list>
2901</t>
2902<t>
2903  Partly resolved issues:
2904  <list style="symbols"> 
2905    <t>
2906      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196"/>:
2907      "Term for the requested resource's URI"
2908    </t>
2909  </list>
2910</t>
2911</section>
2912
2913<section title="Since draft-ietf-httpbis-p3-payload-10" anchor="changes.since.10">
2914<t>
2915  Closed issues:
2916  <list style="symbols"> 
2917    <t>
2918      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/69"/>:
2919      "Clarify 'Requested Variant'"
2920    </t>
2921    <t>
2922      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/80"/>:
2923      "Content-Location isn't special"
2924    </t>
2925    <t>
2926      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/90"/>:
2927      "Delimiting messages with multipart/byteranges"
2928    </t>
2929    <t>
2930      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/109"/>:
2931      "Clarify entity / representation / variant terminology"
2932    </t>
2933    <t>
2934      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/136"/>:
2935      "confusing req. language for Content-Location"
2936    </t>
2937    <t>
2938      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/167"/>:
2939      "Content-Location on 304 responses"
2940    </t>
2941    <t>
2942      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/183"/>:
2943      "'requested resource' in content-encoding definition"
2944    </t>
2945    <t>
2946      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/220"/>:
2947      "consider removing the 'changes from 2068' sections"
2948    </t>
2949  </list>
2950</t>
2951<t>
2952  Partly resolved issues:
2953  <list style="symbols"> 
2954    <t>
2955      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/178"/>:
2956      "Content-MD5 and partial responses"
2957    </t>
2958  </list>
2959</t>
2960</section>
2961
2962<section title="Since draft-ietf-httpbis-p3-payload-11" anchor="changes.since.11">
2963<t>
2964  Closed issues:
2965  <list style="symbols"> 
2966    <t>
2967      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/123"/>:
2968      "Factor out Content-Disposition"
2969    </t>
2970  </list>
2971</t>
2972</section>
2973
2974<section title="Since draft-ietf-httpbis-p3-payload-12" anchor="changes.since.12">
2975<t>
2976  Closed issues:
2977  <list style="symbols"> 
2978    <t>
2979      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/224"/>:
2980      "Header Classification"
2981    </t>
2982    <t>
2983      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
2984      "untangle ABNFs for header fields"
2985    </t>
2986    <t>
2987      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/277"/>:
2988      "potentially misleading MAY in media-type def"
2989    </t>
2990  </list>
2991</t>
2992</section>
2993
2994<section title="Since draft-ietf-httpbis-p3-payload-13" anchor="changes.since.13">
2995<t>
2996  Closed issues:
2997  <list style="symbols"> 
2998    <t>
2999      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/20"/>:
3000      "Default charsets for text media types"
3001    </t>
3002    <t>
3003      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/178"/>:
3004      "Content-MD5 and partial responses"
3005    </t>
3006    <t>
3007      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
3008      "untangle ABNFs for header fields"
3009    </t>
3010    <t>
3011      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/281"/>:
3012      "confusing undefined parameter in media range example"
3013    </t>
3014  </list>
3015</t>
3016</section>
3017
3018<section title="Since draft-ietf-httpbis-p3-payload-14" anchor="changes.since.14">
3019<t>
3020  None.
3021</t>
3022</section>
3023
3024<section title="Since draft-ietf-httpbis-p3-payload-15" anchor="changes.since.15">
3025<t>
3026  Closed issues:
3027  <list style="symbols"> 
3028    <t>
3029      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/285"/>:
3030      "Strength of requirements on Accept re: 406"
3031    </t>
3032  </list>
3033</t>
3034</section>
3035
3036<section title="Since draft-ietf-httpbis-p3-payload-16" anchor="changes.since.16">
3037<t>
3038  None yet.
3039</t>
3040</section>
3041
3042</section>
3043
3044</back>
3045</rfc>
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