source: draft-ietf-httpbis/08/draft-ietf-httpbis-p3-payload-08.xml @ 2438

Last change on this file since 2438 was 1500, checked in by julian.reschke@…, 9 years ago

fix mime types

  • Property svn:executable set to *
  • Property svn:mime-type set to text/xml
File size: 121.6 KB
Line 
1<?xml version="1.0" encoding="UTF-8"?>
2<!--
3    This XML document is the output of clean-for-DTD.xslt; a tool that strips
4    extensions to RFC2629(bis) from documents for processing with xml2rfc.
5-->
6<?xml-stylesheet type='text/xsl' href='../myxml2rfc.xslt'?>
7<?rfc toc="yes" ?>
8<?rfc symrefs="yes" ?>
9<?rfc sortrefs="yes" ?>
10<?rfc compact="yes"?>
11<?rfc subcompact="no" ?>
12<?rfc linkmailto="no" ?>
13<?rfc editing="no" ?>
14<?rfc comments="yes"?>
15<?rfc inline="yes"?>
16<!DOCTYPE rfc
17  PUBLIC "" "rfc2629.dtd">
18<rfc obsoletes="2616" category="std" ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p3-payload-08">
19<front>
20
21  <title abbrev="HTTP/1.1, Part 3">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
22
23  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
24    <organization abbrev="Day Software">Day Software</organization>
25    <address>
26      <postal>
27        <street>23 Corporate Plaza DR, Suite 280</street>
28        <city>Newport Beach</city>
29        <region>CA</region>
30        <code>92660</code>
31        <country>USA</country>
32      </postal>
33      <phone>+1-949-706-5300</phone>
34      <facsimile>+1-949-706-5305</facsimile>
35      <email>fielding@gbiv.com</email>
36      <uri>http://roy.gbiv.com/</uri>
37    </address>
38  </author>
39
40  <author initials="J." surname="Gettys" fullname="Jim Gettys">
41    <organization>One Laptop per Child</organization>
42    <address>
43      <postal>
44        <street>21 Oak Knoll Road</street>
45        <city>Carlisle</city>
46        <region>MA</region>
47        <code>01741</code>
48        <country>USA</country>
49      </postal>
50      <email>jg@laptop.org</email>
51      <uri>http://www.laptop.org/</uri>
52    </address>
53  </author>
54 
55  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
56    <organization abbrev="HP">Hewlett-Packard Company</organization>
57    <address>
58      <postal>
59        <street>HP Labs, Large Scale Systems Group</street>
60        <street>1501 Page Mill Road, MS 1177</street>
61        <city>Palo Alto</city>
62        <region>CA</region>
63        <code>94304</code>
64        <country>USA</country>
65      </postal>
66      <email>JeffMogul@acm.org</email>
67    </address>
68  </author>
69
70  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
71    <organization abbrev="Microsoft">Microsoft Corporation</organization>
72    <address>
73      <postal>
74        <street>1 Microsoft Way</street>
75        <city>Redmond</city>
76        <region>WA</region>
77        <code>98052</code>
78        <country>USA</country>
79      </postal>
80      <email>henrikn@microsoft.com</email>
81    </address>
82  </author>
83
84  <author initials="L." surname="Masinter" fullname="Larry Masinter">
85    <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
86    <address>
87      <postal>
88        <street>345 Park Ave</street>
89        <city>San Jose</city>
90        <region>CA</region>
91        <code>95110</code>
92        <country>USA</country>
93      </postal>
94      <email>LMM@acm.org</email>
95      <uri>http://larry.masinter.net/</uri>
96    </address>
97  </author>
98 
99  <author initials="P." surname="Leach" fullname="Paul J. Leach">
100    <organization abbrev="Microsoft">Microsoft Corporation</organization>
101    <address>
102      <postal>
103        <street>1 Microsoft Way</street>
104        <city>Redmond</city>
105        <region>WA</region>
106        <code>98052</code>
107      </postal>
108      <email>paulle@microsoft.com</email>
109    </address>
110  </author>
111   
112  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
113    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
114    <address>
115      <postal>
116        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
117        <street>The Stata Center, Building 32</street>
118        <street>32 Vassar Street</street>
119        <city>Cambridge</city>
120        <region>MA</region>
121        <code>02139</code>
122        <country>USA</country>
123      </postal>
124      <email>timbl@w3.org</email>
125      <uri>http://www.w3.org/People/Berners-Lee/</uri>
126    </address>
127  </author>
128
129  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
130    <organization abbrev="W3C">World Wide Web Consortium</organization>
131    <address>
132      <postal>
133        <street>W3C / ERCIM</street>
134        <street>2004, rte des Lucioles</street>
135        <city>Sophia-Antipolis</city>
136        <region>AM</region>
137        <code>06902</code>
138        <country>France</country>
139      </postal>
140      <email>ylafon@w3.org</email>
141      <uri>http://www.raubacapeu.net/people/yves/</uri>
142    </address>
143  </author>
144
145  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
146    <organization abbrev="greenbytes">greenbytes GmbH</organization>
147    <address>
148      <postal>
149        <street>Hafenweg 16</street>
150        <city>Muenster</city><region>NW</region><code>48155</code>
151        <country>Germany</country>
152      </postal>
153      <phone>+49 251 2807760</phone>
154      <facsimile>+49 251 2807761</facsimile>
155      <email>julian.reschke@greenbytes.de</email>
156      <uri>http://greenbytes.de/tech/webdav/</uri>
157    </address>
158  </author>
159
160  <date day="26" month="October" year="2009"/>
161  <workgroup>HTTPbis Working Group</workgroup>
162
163<abstract>
164<t>
165   The Hypertext Transfer Protocol (HTTP) is an application-level
166   protocol for distributed, collaborative, hypermedia information
167   systems. HTTP has been in use by the World Wide Web global information
168   initiative since 1990. This document is Part 3 of the seven-part specification
169   that defines the protocol referred to as "HTTP/1.1" and, taken together,
170   obsoletes RFC 2616.  Part 3 defines HTTP message content,
171   metadata, and content negotiation.
172</t>
173</abstract>
174
175<note title="Editorial Note (To be removed by RFC Editor)">
176  <t>
177    Discussion of this draft should take place on the HTTPBIS working group
178    mailing list (ietf-http-wg@w3.org). The current issues list is
179    at <eref target="http://tools.ietf.org/wg/httpbis/trac/report/11"/>
180    and related documents (including fancy diffs) can be found at
181    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
182  </t>
183  <t>
184    The changes in this draft are summarized in <xref target="changes.since.07"/>.
185  </t>
186</note>
187</front>
188<middle>
189<section title="Introduction" anchor="introduction">
190<t>
191   This document defines HTTP/1.1 message payloads (a.k.a., content), the
192   associated metadata header fields that define how the payload is intended
193   to be interpreted by a recipient, the request header fields that
194   may influence content selection, and the various selection algorithms
195   that are collectively referred to as HTTP content negotiation.
196</t>
197<t>
198   This document is currently disorganized in order to minimize the changes
199   between drafts and enable reviewers to see the smaller errata changes.
200   The next draft will reorganize the sections to better reflect the content.
201   In particular, the sections on entities will be renamed payload and moved
202   to the first half of the document, while the sections on content negotiation
203   and associated request header fields will be moved to the second half.  The
204   current mess reflects how widely dispersed these topics and associated
205   requirements had become in <xref target="RFC2616"/>.
206</t>
207
208<section title="Terminology" anchor="terminology">
209<t>
210   This specification uses a number of terms to refer to the roles
211   played by participants in, and objects of, the HTTP communication.
212</t>
213<t>
214  <iref item="content negotiation"/>
215  <?rfc needLines="4"?>content negotiation
216  <list>
217    <t>
218      The mechanism for selecting the appropriate representation when
219      servicing a request. The representation of entities in any response
220      can be negotiated (including error responses).
221    </t>
222  </list>
223</t>
224<t>
225  <iref item="entity"/>
226  <?rfc needLines="4"?>entity
227  <list>
228    <t>
229      The information transferred as the payload of a request or
230      response. An entity consists of metadata in the form of
231      entity-header fields and content in the form of an entity-body.
232    </t>
233  </list>
234</t>
235<t>
236  <iref item="representation"/>
237  <?rfc needLines="4"?>representation
238  <list>
239    <t>
240      An entity included with a response that is subject to content
241      negotiation. There may exist multiple
242      representations associated with a particular response status.
243    </t>
244  </list>
245</t>
246<t>
247  <iref item="variant"/>
248  <?rfc needLines="4"?>variant
249  <list>
250    <t>
251      A resource may have one, or more than one, representation(s)
252      associated with it at any given instant. Each of these
253      representations is termed a `variant'.  Use of the term `variant'
254      does not necessarily imply that the resource is subject to content
255      negotiation.
256    </t>
257  </list>
258</t>
259</section>
260
261<section title="Requirements" anchor="intro.requirements">
262<t>
263   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
264   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
265   document are to be interpreted as described in <xref target="RFC2119"/>.
266</t>
267<t>
268   An implementation is not compliant if it fails to satisfy one or more
269   of the MUST or REQUIRED level requirements for the protocols it
270   implements. An implementation that satisfies all the MUST or REQUIRED
271   level and all the SHOULD level requirements for its protocols is said
272   to be "unconditionally compliant"; one that satisfies all the MUST
273   level requirements but not all the SHOULD level requirements for its
274   protocols is said to be "conditionally compliant."
275</t>
276</section>
277
278<section title="Syntax Notation" anchor="notation">
279 
280 
281 
282 
283 
284 
285 
286<t>
287  This specification uses the ABNF syntax defined in Section 1.2 of <xref target="Part1"/> (which
288  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
289  <xref target="collected.abnf"/> shows the collected ABNF, with the list
290  rule expanded.
291</t>
292<t>
293  The following core rules are included by
294  reference, as defined in <xref target="RFC5234"/>, Appendix B.1:
295  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
296  DIGIT (decimal 0-9), DQUOTE (double quote),
297  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
298  OCTET (any 8-bit sequence of data), SP (space),
299  VCHAR (any visible USASCII character),
300  and WSP (whitespace).
301</t>
302
303<section title="Core Rules" anchor="core.rules">
304 
305 
306 
307<t>
308  The core rules below are defined in Section 1.2.2 of <xref target="Part1"/>:
309</t>
310<figure><artwork type="abnf2616"><![CDATA[
311  quoted-string  = <quoted-string, defined in [Part1], Section 1.2.2>
312  token          = <token, defined in [Part1], Section 1.2.2>
313  OWS            = <OWS, defined in [Part1], Section 1.2.2>
314]]></artwork></figure>
315</section>
316
317<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
318 
319 
320 
321 
322 
323 
324 
325 
326 
327<t>
328  The ABNF rules below are defined in other parts:
329</t>
330<figure><artwork type="abnf2616"><![CDATA[
331  absolute-URI   = <absolute-URI, defined in [Part1], Section 2.6>
332  Content-Length = <Content-Length, defined in [Part1], Section 9.2>
333  header-field   = <header-field, defined in [Part1], Section 3.2>
334  partial-URI    = <partial-URI, defined in [Part1], Section 2.6>
335  qvalue         = <qvalue, defined in [Part1], Section 6.4>
336]]></artwork></figure>
337<figure><artwork type="abnf2616"><![CDATA[
338  Last-Modified  = <Last-Modified, defined in [Part4], Section 6.6>
339]]></artwork></figure>
340<figure><artwork type="abnf2616"><![CDATA[
341  Content-Range  = <Content-Range, defined in [Part5], Section 5.2>
342]]></artwork></figure>
343<figure><artwork type="abnf2616"><![CDATA[
344  Expires        = <Expires, defined in [Part6], Section 3.3>
345]]></artwork></figure>
346</section>
347
348</section>
349
350</section>
351
352<section title="Protocol Parameters" anchor="protocol.parameters">
353
354<section title="Character Sets" anchor="character.sets">
355<t>
356   HTTP uses the same definition of the term "character set" as that
357   described for MIME:
358</t>
359<t>
360   The term "character set" is used in this document to refer to a
361   method used with one or more tables to convert a sequence of octets
362   into a sequence of characters. Note that unconditional conversion in
363   the other direction is not required, in that not all characters may
364   be available in a given character set and a character set may provide
365   more than one sequence of octets to represent a particular character.
366   This definition is intended to allow various kinds of character
367   encoding, from simple single-table mappings such as US-ASCII to
368   complex table switching methods such as those that use ISO-2022's
369   techniques. However, the definition associated with a MIME character
370   set name MUST fully specify the mapping to be performed from octets
371   to characters. In particular, use of external profiling information
372   to determine the exact mapping is not permitted.
373</t>
374<t><list>
375  <t>
376    Note: This use of the term "character set" is more commonly
377    referred to as a "character encoding." However, since HTTP and
378    MIME share the same registry, it is important that the terminology
379    also be shared.
380  </t>
381</list></t>
382<t anchor="rule.charset">
383 
384   HTTP character sets are identified by case-insensitive tokens. The
385   complete set of tokens is defined by the IANA Character Set registry
386   (<eref target="http://www.iana.org/assignments/character-sets"/>).
387</t>
388<figure><iref primary="true" item="Grammar" subitem="charset"/><artwork type="abnf2616"><![CDATA[
389  charset = token
390]]></artwork></figure>
391<t>
392   Although HTTP allows an arbitrary token to be used as a charset
393   value, any token that has a predefined value within the IANA
394   Character Set registry MUST represent the character set defined
395   by that registry. Applications SHOULD limit their use of character
396   sets to those defined by the IANA registry.
397</t>
398<t>
399   HTTP uses charset in two contexts: within an Accept-Charset request
400   header (in which the charset value is an unquoted token) and as the
401   value of a parameter in a Content-Type header (within a request or
402   response), in which case the parameter value of the charset parameter
403   may be quoted.
404</t>
405<t>
406   Implementors should be aware of IETF character set requirements <xref target="RFC3629"/>
407   <xref target="RFC2277"/>.
408</t>
409
410<section title="Missing Charset" anchor="missing.charset">
411<t>
412   Some HTTP/1.0 software has interpreted a Content-Type header without
413   charset parameter incorrectly to mean "recipient should guess."
414   Senders wishing to defeat this behavior MAY include a charset
415   parameter even when the charset is ISO-8859-1 (<xref target="ISO-8859-1"/>) and SHOULD do so when
416   it is known that it will not confuse the recipient.
417</t>
418<t>
419   Unfortunately, some older HTTP/1.0 clients did not deal properly with
420   an explicit charset parameter. HTTP/1.1 recipients MUST respect the
421   charset label provided by the sender; and those user agents that have
422   a provision to "guess" a charset MUST use the charset from the
423   content-type field if they support that charset, rather than the
424   recipient's preference, when initially displaying a document. See
425   <xref target="canonicalization.and.text.defaults"/>.
426</t>
427</section>
428</section>
429
430<section title="Content Codings" anchor="content.codings">
431 
432<t>
433   Content coding values indicate an encoding transformation that has
434   been or can be applied to an entity. Content codings are primarily
435   used to allow a document to be compressed or otherwise usefully
436   transformed without losing the identity of its underlying media type
437   and without loss of information. Frequently, the entity is stored in
438   coded form, transmitted directly, and only decoded by the recipient.
439</t>
440<figure><iref primary="true" item="Grammar" subitem="content-coding"/><artwork type="abnf2616"><![CDATA[
441  content-coding   = token
442]]></artwork></figure>
443<t>
444   All content-coding values are case-insensitive. HTTP/1.1 uses
445   content-coding values in the Accept-Encoding (<xref target="header.accept-encoding"/>) and
446   Content-Encoding (<xref target="header.content-encoding"/>) header fields. Although the value
447   describes the content-coding, what is more important is that it
448   indicates what decoding mechanism will be required to remove the
449   encoding.
450</t>
451<t>
452   compress<iref item="compress (Coding Format)"/><iref item="Coding Format" subitem="compress"/>
453  <list>
454    <t>
455      See Section 6.2.2.1 of <xref target="Part1"/>.
456    </t>
457  </list>
458</t>
459<t>
460   deflate<iref item="deflate (Coding Format)"/><iref item="Coding Format" subitem="deflate"/>
461  <list>
462    <t>
463      See Section 6.2.2.2 of <xref target="Part1"/>.
464    </t>
465  </list>
466</t>
467<t>
468   gzip<iref item="gzip (Coding Format)"/><iref item="Coding Format" subitem="gzip"/>
469  <list>
470    <t>
471      See Section 6.2.2.3 of <xref target="Part1"/>.
472    </t>
473  </list>
474</t>
475<t>
476   identity<iref item="identity (Coding Format)"/><iref item="Coding Format" subitem="identity"/>
477  <list><t>
478        The default (identity) encoding; the use of no transformation
479        whatsoever. This content-coding is used only in the Accept-Encoding
480        header, and SHOULD NOT  be used in the Content-Encoding
481        header.
482  </t></list>
483</t>
484
485<section title="Content Coding Registry" anchor="content.coding.registry">
486<t>
487   The HTTP Content Coding Registry defines the name space for the content
488   coding names.
489</t>
490<t>
491   Registrations MUST include the following fields:
492   <list style="symbols">
493     <t>Name</t>
494     <t>Description</t>
495     <t>Pointer to specification text</t>
496   </list>
497</t>
498<t>
499   Values to be added to this name space require expert review and a specification
500   (see "Expert Review" and "Specification Required" in
501   Section 4.1 of <xref target="RFC5226"/>), and MUST
502   conform to the purpose of content coding defined in this section.
503</t>
504<t>
505   The registry itself is maintained at
506   <eref target="http://www.iana.org/assignments/http-parameters"/>.
507</t>
508</section>
509
510</section>
511
512<section title="Media Types" anchor="media.types">
513 
514 
515 
516<t>
517   HTTP uses Internet Media Types <xref target="RFC2046"/> in the Content-Type (<xref target="header.content-type"/>)
518   and Accept (<xref target="header.accept"/>) header fields in order to provide
519   open and extensible data typing and type negotiation.
520</t>
521<figure><iref primary="true" item="Grammar" subitem="media-type"/><iref primary="true" item="Grammar" subitem="type"/><iref primary="true" item="Grammar" subitem="subtype"/><artwork type="abnf2616"><![CDATA[
522  media-type = type "/" subtype *( OWS ";" OWS parameter )
523  type       = token
524  subtype    = token
525]]></artwork></figure>
526<t anchor="rule.parameter">
527 
528 
529 
530   Parameters MAY follow the type/subtype in the form of attribute/value
531   pairs.
532</t>
533<figure><iref primary="true" item="Grammar" subitem="parameter"/><iref primary="true" item="Grammar" subitem="attribute"/><iref primary="true" item="Grammar" subitem="value"/><artwork type="abnf2616"><![CDATA[
534  parameter      = attribute "=" value
535  attribute      = token
536  value          = token / quoted-string
537]]></artwork></figure>
538<t>
539   The type, subtype, and parameter attribute names are case-insensitive.
540   Parameter values might or might not be case-sensitive, depending on the
541   semantics of the parameter name.  The presence or absence of a parameter might
542   be significant to the processing of a media-type, depending on its
543   definition within the media type registry.
544</t>
545<t>
546   A parameter value that matches the <xref target="core.rules" format="none">token</xref> production may be
547   transmitted as either a token or within a quoted-string. The quoted and
548   unquoted values are equivalent.
549</t>
550<t>
551   Note that some older HTTP applications do not recognize media type
552   parameters. When sending data to older HTTP applications,
553   implementations SHOULD only use media type parameters when they are
554   required by that type/subtype definition.
555</t>
556<t>
557   Media-type values are registered with the Internet Assigned Number
558   Authority (IANA). The media type registration process is
559   outlined in <xref target="RFC4288"/>. Use of non-registered media types is
560   discouraged.
561</t>
562
563<section title="Canonicalization and Text Defaults" anchor="canonicalization.and.text.defaults">
564<t>
565   Internet media types are registered with a canonical form. An
566   entity-body transferred via HTTP messages MUST be represented in the
567   appropriate canonical form prior to its transmission except for
568   "text" types, as defined in the next paragraph.
569</t>
570<t>
571   When in canonical form, media subtypes of the "text" type use CRLF as
572   the text line break. HTTP relaxes this requirement and allows the
573   transport of text media with plain CR or LF alone representing a line
574   break when it is done consistently for an entire entity-body. HTTP
575   applications MUST accept CRLF, bare CR, and bare LF as being
576   representative of a line break in text media received via HTTP. In
577   addition, if the text is represented in a character set that does not
578   use octets 13 and 10 for CR and LF respectively, as is the case for
579   some multi-byte character sets, HTTP allows the use of whatever octet
580   sequences are defined by that character set to represent the
581   equivalent of CR and LF for line breaks. This flexibility regarding
582   line breaks applies only to text media in the entity-body; a bare CR
583   or LF MUST NOT be substituted for CRLF within any of the HTTP control
584   structures (such as header fields and multipart boundaries).
585</t>
586<t>
587   If an entity-body is encoded with a content-coding, the underlying
588   data MUST be in a form defined above prior to being encoded.
589</t>
590<t>
591   The "charset" parameter is used with some media types to define the
592   character set (<xref target="character.sets"/>) of the data. When no explicit charset
593   parameter is provided by the sender, media subtypes of the "text"
594   type are defined to have a default charset value of "ISO-8859-1" when
595   received via HTTP. Data in character sets other than "ISO-8859-1" or
596   its subsets MUST be labeled with an appropriate charset value. See
597   <xref target="missing.charset"/> for compatibility problems.
598</t>
599</section>
600
601<section title="Multipart Types" anchor="multipart.types">
602<t>
603   MIME provides for a number of "multipart" types -- encapsulations of
604   one or more entities within a single message-body. All multipart
605   types share a common syntax, as defined in Section 5.1.1 of <xref target="RFC2046"/>,
606   and MUST include a boundary parameter as part of the media type
607   value. The message body is itself a protocol element and MUST
608   therefore use only CRLF to represent line breaks between body-parts.
609   Unlike in RFC 2046, the epilogue of any multipart message MUST be
610   empty; HTTP applications MUST NOT transmit the epilogue (even if the
611   original multipart contains an epilogue). These restrictions exist in
612   order to preserve the self-delimiting nature of a multipart message-body,
613   wherein the "end" of the message-body is indicated by the
614   ending multipart boundary.
615</t>
616<t>
617   In general, HTTP treats a multipart message-body no differently than
618   any other media type: strictly as payload. The one exception is the
619   "multipart/byteranges" type (Appendix A of <xref target="Part5"/>) when it appears in a 206
620   (Partial Content) response.
621   <!-- jre: re-insert removed text pointing to caching? -->
622   In all
623   other cases, an HTTP user agent SHOULD follow the same or similar
624   behavior as a MIME user agent would upon receipt of a multipart type.
625   The MIME header fields within each body-part of a multipart message-body
626   do not have any significance to HTTP beyond that defined by
627   their MIME semantics.
628</t>
629<t>
630   In general, an HTTP user agent SHOULD follow the same or similar
631   behavior as a MIME user agent would upon receipt of a multipart type.
632   If an application receives an unrecognized multipart subtype, the
633   application MUST treat it as being equivalent to "multipart/mixed".
634</t>
635<t><list>
636  <t>
637    Note: The "multipart/form-data" type has been specifically defined
638    for carrying form data suitable for processing via the POST
639    request method, as described in <xref target="RFC2388"/>.
640  </t>
641</list></t>
642</section>
643</section>
644
645<section title="Language Tags" anchor="language.tags">
646 
647<t>
648   A language tag, as defined in <xref target="RFC5646"/>, identifies a
649   natural language spoken, written, or otherwise conveyed by human beings for
650   communication of information to other human beings. Computer languages are
651   explicitly excluded. HTTP uses language tags within the Accept-Language and
652   Content-Language fields.
653</t>
654<t>
655   In summary, a language tag is composed of one or more parts: A primary
656   language subtag followed by a possibly empty series of subtags:
657</t>
658<figure><iref primary="true" item="Grammar" subitem="language-tag"/><artwork type="abnf2616"><![CDATA[
659  language-tag = <Language-Tag, defined in [RFC5646], Section 2.1>
660]]></artwork></figure>
661<t>
662   White space is not allowed within the tag and all tags are case-insensitive.
663   The name space of language subtags is administered by the IANA (see
664   <eref target="http://www.iana.org/assignments/language-subtag-registry"/>).
665</t>
666<figure>
667  <preamble>Example tags include:</preamble>
668<artwork type="example"><![CDATA[
669  en, en-US, es-419, az-Arab, x-pig-latin, man-Nkoo-GN
670]]></artwork>
671</figure>
672<t>
673   See <xref target="RFC5646"/> for further information.
674</t>
675</section>
676</section>
677
678<section title="Entity" anchor="entity">
679<t>
680   Request and Response messages MAY transfer an entity if not otherwise
681   restricted by the request method or response status code. An entity
682   consists of entity-header fields and an entity-body, although some
683   responses will only include the entity-headers.
684</t>
685<t>
686   In this section, both sender and recipient refer to either the client
687   or the server, depending on who sends and who receives the entity.
688</t>
689
690<section title="Entity Header Fields" anchor="entity.header.fields">
691 
692 
693<t>
694   Entity-header fields define metainformation about the entity-body or,
695   if no body is present, about the resource identified by the request.
696</t>
697<figure><iref primary="true" item="Grammar" subitem="entity-header"/><iref primary="true" item="Grammar" subitem="extension-header"/><artwork type="abnf2616"><![CDATA[
698  entity-header  = Content-Encoding         ; Section 5.5
699                 / Content-Language         ; Section 5.6
700                 / Content-Length           ; [Part1], Section 9.2
701                 / Content-Location         ; Section 5.7
702                 / Content-MD5              ; Section 5.8
703                 / Content-Range            ; [Part5], Section 5.2
704                 / Content-Type             ; Section 5.9
705                 / Expires                  ; [Part6], Section 3.3
706                 / Last-Modified            ; [Part4], Section 6.6
707                 / extension-header
708 
709  extension-header = header-field
710]]></artwork></figure>
711<t>
712   The extension-header mechanism allows additional entity-header fields
713   to be defined without changing the protocol, but these fields cannot
714   be assumed to be recognizable by the recipient. Unrecognized header
715   fields SHOULD be ignored by the recipient and MUST be forwarded by
716   transparent proxies.
717</t>
718</section>
719
720<section title="Entity Body" anchor="entity.body">
721 
722<t>
723   The entity-body (if any) sent with an HTTP request or response is in
724   a format and encoding defined by the entity-header fields.
725</t>
726<figure><iref primary="true" item="Grammar" subitem="entity-body"/><artwork type="abnf2616"><![CDATA[
727  entity-body    = *OCTET
728]]></artwork></figure>
729<t>
730   An entity-body is only present in a message when a message-body is
731   present, as described in Section 3.3 of <xref target="Part1"/>. The entity-body is obtained
732   from the message-body by decoding any Transfer-Encoding that might
733   have been applied to ensure safe and proper transfer of the message.
734</t>
735
736<section title="Type" anchor="type">
737<t>
738   When an entity-body is included with a message, the data type of that
739   body is determined via the header fields Content-Type and Content-Encoding.
740   These define a two-layer, ordered encoding model:
741</t>
742<figure><artwork type="example"><![CDATA[
743  entity-body := Content-Encoding( Content-Type( data ) )
744]]></artwork></figure>
745<t>
746   Content-Type specifies the media type of the underlying data. Any HTTP/1.1
747   message containing an entity-body SHOULD include a Content-Type header
748   field defining the media type of that body, unless that information is
749   unknown.  If the Content-Type header field is not present, it indicates that
750   the sender does not know the media type of the data; recipients MAY
751   either assume that it is "application/octet-stream" (<xref target="RFC2046"/>, Section 4.5.1)
752   or examine the content to determine its type.
753</t>
754<t>
755   Content-Encoding may be used to indicate any additional content
756   codings applied to the data, usually for the purpose of data
757   compression, that are a property of the requested resource.  There is
758   no default encoding.
759</t>
760</section>
761   
762<section title="Entity Length" anchor="entity.length">
763<t>
764   The entity-length of a message is the length of the message-body
765   before any transfer-codings have been applied. Section 3.4 of <xref target="Part1"/> defines
766   how the transfer-length of a message-body is determined.
767</t>
768</section>
769</section>
770</section>
771
772<section title="Content Negotiation" anchor="content.negotiation">
773<t>
774   Most HTTP responses include an entity which contains information for
775   interpretation by a human user. Naturally, it is desirable to supply
776   the user with the "best available" entity corresponding to the
777   request. Unfortunately for servers and caches, not all users have the
778   same preferences for what is "best," and not all user agents are
779   equally capable of rendering all entity types. For that reason, HTTP
780   has provisions for several mechanisms for "content negotiation" --
781   the process of selecting the best representation for a given response
782   when there are multiple representations available.
783</t>
784<t><list>
785  <t>
786    Note: This is not called "format negotiation" because the
787    alternate representations may be of the same media type, but use
788    different capabilities of that type, be in different languages,
789    etc.
790  </t>
791</list></t>
792<t>
793   Any response containing an entity-body MAY be subject to negotiation,
794   including error responses.
795</t>
796<t>
797   There are two kinds of content negotiation which are possible in
798   HTTP: server-driven and agent-driven negotiation. These two kinds of
799   negotiation are orthogonal and thus may be used separately or in
800   combination. One method of combination, referred to as transparent
801   negotiation, occurs when a cache uses the agent-driven negotiation
802   information provided by the origin server in order to provide
803   server-driven negotiation for subsequent requests.
804</t>
805
806<section title="Server-driven Negotiation" anchor="server-driven.negotiation">
807<t>
808   If the selection of the best representation for a response is made by
809   an algorithm located at the server, it is called server-driven
810   negotiation. Selection is based on the available representations of
811   the response (the dimensions over which it can vary; e.g. language,
812   content-coding, etc.) and the contents of particular header fields in
813   the request message or on other information pertaining to the request
814   (such as the network address of the client).
815</t>
816<t>
817   Server-driven negotiation is advantageous when the algorithm for
818   selecting from among the available representations is difficult to
819   describe to the user agent, or when the server desires to send its
820   "best guess" to the client along with the first response (hoping to
821   avoid the round-trip delay of a subsequent request if the "best
822   guess" is good enough for the user). In order to improve the server's
823   guess, the user agent MAY include request header fields (Accept,
824   Accept-Language, Accept-Encoding, etc.) which describe its
825   preferences for such a response.
826</t>
827<t>
828   Server-driven negotiation has disadvantages:
829  <list style="numbers">
830    <t>
831         It is impossible for the server to accurately determine what
832         might be "best" for any given user, since that would require
833         complete knowledge of both the capabilities of the user agent
834         and the intended use for the response (e.g., does the user want
835         to view it on screen or print it on paper?).
836    </t>
837    <t>
838         Having the user agent describe its capabilities in every
839         request can be both very inefficient (given that only a small
840         percentage of responses have multiple representations) and a
841         potential violation of the user's privacy.
842    </t>
843    <t>
844         It complicates the implementation of an origin server and the
845         algorithms for generating responses to a request.
846    </t>
847    <t>
848         It may limit a public cache's ability to use the same response
849         for multiple user's requests.
850    </t>
851  </list>
852</t>
853<t>
854   HTTP/1.1 includes the following request-header fields for enabling
855   server-driven negotiation through description of user agent
856   capabilities and user preferences: Accept (<xref target="header.accept"/>), Accept-Charset
857   (<xref target="header.accept-charset"/>), Accept-Encoding (<xref target="header.accept-encoding"/>), Accept-Language
858   (<xref target="header.accept-language"/>), and User-Agent (Section 9.9 of <xref target="Part2"/>). However, an
859   origin server is not limited to these dimensions and MAY vary the
860   response based on any aspect of the request, including information
861   outside the request-header fields or within extension header fields
862   not defined by this specification.
863</t>
864<t>
865   The Vary header field (Section 3.5 of <xref target="Part6"/>) can be used to express the parameters the
866   server uses to select a representation that is subject to server-driven
867   negotiation.
868</t>
869</section>
870
871<section title="Agent-driven Negotiation" anchor="agent-driven.negotiation">
872<t>
873   With agent-driven negotiation, selection of the best representation
874   for a response is performed by the user agent after receiving an
875   initial response from the origin server. Selection is based on a list
876   of the available representations of the response included within the
877   header fields or entity-body of the initial response, with each
878   representation identified by its own URI. Selection from among the
879   representations may be performed automatically (if the user agent is
880   capable of doing so) or manually by the user selecting from a
881   generated (possibly hypertext) menu.
882</t>
883<t>
884   Agent-driven negotiation is advantageous when the response would vary
885   over commonly-used dimensions (such as type, language, or encoding),
886   when the origin server is unable to determine a user agent's
887   capabilities from examining the request, and generally when public
888   caches are used to distribute server load and reduce network usage.
889</t>
890<t>
891   Agent-driven negotiation suffers from the disadvantage of needing a
892   second request to obtain the best alternate representation. This
893   second request is only efficient when caching is used. In addition,
894   this specification does not define any mechanism for supporting
895   automatic selection, though it also does not prevent any such
896   mechanism from being developed as an extension and used within
897   HTTP/1.1.
898</t>
899<t>
900   HTTP/1.1 defines the 300 (Multiple Choices) and 406 (Not Acceptable)
901   status codes for enabling agent-driven negotiation when the server is
902   unwilling or unable to provide a varying response using server-driven
903   negotiation.
904</t>
905</section>
906
907<section title="Transparent Negotiation" anchor="transparent.negotiation">
908<t>
909   Transparent negotiation is a combination of both server-driven and
910   agent-driven negotiation. When a cache is supplied with a form of the
911   list of available representations of the response (as in agent-driven
912   negotiation) and the dimensions of variance are completely understood
913   by the cache, then the cache becomes capable of performing server-driven
914   negotiation on behalf of the origin server for subsequent
915   requests on that resource.
916</t>
917<t>
918   Transparent negotiation has the advantage of distributing the
919   negotiation work that would otherwise be required of the origin
920   server and also removing the second request delay of agent-driven
921   negotiation when the cache is able to correctly guess the right
922   response.
923</t>
924<t>
925   This specification does not define any mechanism for transparent
926   negotiation, though it also does not prevent any such mechanism from
927   being developed as an extension that could be used within HTTP/1.1.
928</t>
929</section>
930</section>
931
932<section title="Header Field Definitions" anchor="header.fields">
933<t>
934   This section defines the syntax and semantics of HTTP/1.1 header fields
935   related to the payload of messages.
936</t>
937<t>
938   For entity-header fields, both sender and recipient refer to either the
939   client or the server, depending on who sends and who receives the entity.
940</t>
941
942<section title="Accept" anchor="header.accept">
943  <iref primary="true" item="Accept header"/>
944  <iref primary="true" item="Headers" subitem="Accept"/>
945 
946 
947 
948 
949 
950<t>
951   The "Accept" request-header field can be used by user agents to specify
952   response media types that are acceptable. Accept headers can be used to
953   indicate that the request is specifically limited to a small set of desired
954   types, as in the case of a request for an in-line image.
955</t>
956<figure><iref primary="true" item="Grammar" subitem="Accept"/><iref primary="true" item="Grammar" subitem="Accept-v"/><iref primary="true" item="Grammar" subitem="media-range"/><iref primary="true" item="Grammar" subitem="accept-params"/><iref primary="true" item="Grammar" subitem="accept-ext"/><artwork type="abnf2616"><![CDATA[
957  Accept   = "Accept" ":" OWS Accept-v
958  Accept-v = #( media-range [ accept-params ] )
959 
960  media-range    = ( "*/*"
961                   / ( type "/" "*" )
962                   / ( type "/" subtype )
963                   ) *( OWS ";" OWS parameter )
964  accept-params  = OWS ";" OWS "q=" qvalue *( accept-ext )
965  accept-ext     = OWS ";" OWS token
966                   [ "=" ( token / quoted-string ) ]
967]]></artwork></figure>
968<t>
969   The asterisk "*" character is used to group media types into ranges,
970   with "*/*" indicating all media types and "type/*" indicating all
971   subtypes of that type. The media-range MAY include media type
972   parameters that are applicable to that range.
973</t>
974<t>
975   Each media-range MAY be followed by one or more accept-params,
976   beginning with the "q" parameter for indicating a relative quality
977   factor. The first "q" parameter (if any) separates the media-range
978   parameter(s) from the accept-params. Quality factors allow the user
979   or user agent to indicate the relative degree of preference for that
980   media-range, using the qvalue scale from 0 to 1 (Section 6.4 of <xref target="Part1"/>). The
981   default value is q=1.
982</t>
983<t><list>
984  <t>
985    Note: Use of the "q" parameter name to separate media type
986    parameters from Accept extension parameters is due to historical
987    practice. Although this prevents any media type parameter named
988    "q" from being used with a media range, such an event is believed
989    to be unlikely given the lack of any "q" parameters in the IANA
990    media type registry and the rare usage of any media type
991    parameters in Accept. Future media types are discouraged from
992    registering any parameter named "q".
993  </t>
994</list></t>
995<t>
996   The example
997</t>
998<figure><artwork type="example"><![CDATA[
999  Accept: audio/*; q=0.2, audio/basic
1000]]></artwork></figure>
1001<t>
1002   SHOULD be interpreted as "I prefer audio/basic, but send me any audio
1003   type if it is the best available after an 80% mark-down in quality."
1004</t>
1005<t>
1006   If no Accept header field is present, then it is assumed that the
1007   client accepts all media types. If an Accept header field is present,
1008   and if the server cannot send a response which is acceptable
1009   according to the combined Accept field value, then the server SHOULD
1010   send a 406 (Not Acceptable) response.
1011</t>
1012<t>
1013   A more elaborate example is
1014</t>
1015<figure><artwork type="example"><![CDATA[
1016  Accept: text/plain; q=0.5, text/html,
1017          text/x-dvi; q=0.8, text/x-c
1018]]></artwork></figure>
1019<t>
1020   Verbally, this would be interpreted as "text/html and text/x-c are
1021   the preferred media types, but if they do not exist, then send the
1022   text/x-dvi entity, and if that does not exist, send the text/plain
1023   entity."
1024</t>
1025<t>
1026   Media ranges can be overridden by more specific media ranges or
1027   specific media types. If more than one media range applies to a given
1028   type, the most specific reference has precedence. For example,
1029</t>
1030<figure><artwork type="example"><![CDATA[
1031  Accept: text/*, text/html, text/html;level=1, */*
1032]]></artwork></figure>
1033<t>
1034   have the following precedence:
1035   <list style="numbers">
1036    <t>text/html;level=1</t>
1037    <t>text/html</t>
1038    <t>text/*</t>
1039    <t>*/*</t>
1040   </list>
1041</t>
1042<t>
1043   The media type quality factor associated with a given type is
1044   determined by finding the media range with the highest precedence
1045   which matches that type. For example,
1046</t>
1047<figure><artwork type="example"><![CDATA[
1048  Accept: text/*;q=0.3, text/html;q=0.7, text/html;level=1,
1049          text/html;level=2;q=0.4, */*;q=0.5
1050]]></artwork></figure>
1051<t>
1052   would cause the following values to be associated:
1053</t>
1054<texttable align="left">
1055  <ttcol>Media Type</ttcol><ttcol>Quality Value</ttcol>
1056  <c>text/html;level=1</c>    <c>1</c>
1057  <c>text/html</c>            <c>0.7</c>
1058  <c>text/plain</c>           <c>0.3</c>
1059  <c>image/jpeg</c>           <c>0.5</c>
1060  <c>text/html;level=2</c>    <c>0.4</c>
1061  <c>text/html;level=3</c>    <c>0.7</c>
1062</texttable>
1063<t>
1064      Note: A user agent might be provided with a default set of quality
1065      values for certain media ranges. However, unless the user agent is
1066      a closed system which cannot interact with other rendering agents,
1067      this default set ought to be configurable by the user.
1068</t>
1069</section>
1070
1071<section title="Accept-Charset" anchor="header.accept-charset">
1072  <iref primary="true" item="Accept-Charset header"/>
1073  <iref primary="true" item="Headers" subitem="Accept-Charset"/>
1074 
1075 
1076<t>
1077   The "Accept-Charset" request-header field can be used by user agents to
1078   indicate what response character sets are acceptable. This field allows
1079   clients capable of understanding more comprehensive or special-purpose
1080   character sets to signal that capability to a server which is capable of
1081   representing documents in those character sets.
1082</t>
1083<figure><iref primary="true" item="Grammar" subitem="Accept-Charset"/><iref primary="true" item="Grammar" subitem="Accept-Charset-v"/><artwork type="abnf2616"><![CDATA[
1084  Accept-Charset   = "Accept-Charset" ":" OWS
1085          Accept-Charset-v
1086  Accept-Charset-v = 1#( ( charset / "*" )
1087                         [ OWS ";" OWS "q=" qvalue ] )
1088]]></artwork></figure>
1089<t>
1090   Character set values are described in <xref target="character.sets"/>. Each charset MAY
1091   be given an associated quality value which represents the user's
1092   preference for that charset. The default value is q=1. An example is
1093</t>
1094<figure><artwork type="example"><![CDATA[
1095  Accept-Charset: iso-8859-5, unicode-1-1;q=0.8
1096]]></artwork></figure>
1097<t>
1098   The special value "*", if present in the Accept-Charset field,
1099   matches every character set (including ISO-8859-1) which is not
1100   mentioned elsewhere in the Accept-Charset field. If no "*" is present
1101   in an Accept-Charset field, then all character sets not explicitly
1102   mentioned get a quality value of 0, except for ISO-8859-1, which gets
1103   a quality value of 1 if not explicitly mentioned.
1104</t>
1105<t>
1106   If no Accept-Charset header is present, the default is that any
1107   character set is acceptable. If an Accept-Charset header is present,
1108   and if the server cannot send a response which is acceptable
1109   according to the Accept-Charset header, then the server SHOULD send
1110   an error response with the 406 (Not Acceptable) status code, though
1111   the sending of an unacceptable response is also allowed.
1112</t>
1113</section>
1114
1115<section title="Accept-Encoding" anchor="header.accept-encoding">
1116  <iref primary="true" item="Accept-Encoding header"/>
1117  <iref primary="true" item="Headers" subitem="Accept-Encoding"/>
1118 
1119 
1120 
1121<t>
1122   The "Accept-Encoding" request-header field can be used by user agents to
1123   indicate what response content-codings (<xref target="content.codings"/>)
1124   are acceptable in the response.
1125</t>
1126<figure><iref primary="true" item="Grammar" subitem="Accept-Encoding"/><iref primary="true" item="Grammar" subitem="Accept-Encoding-v"/><iref primary="true" item="Grammar" subitem="codings"/><artwork type="abnf2616"><![CDATA[
1127  Accept-Encoding    = "Accept-Encoding" ":" OWS
1128                     Accept-Encoding-v
1129  Accept-Encoding-v  =
1130                     #( codings [ OWS ";" OWS "q=" qvalue ] )
1131  codings            = ( content-coding / "*" )
1132]]></artwork></figure>
1133<t>
1134   Each codings value MAY be given an associated quality value which
1135   represents the preference for that encoding. The default value is q=1.
1136</t>
1137<t>
1138   Examples of its use are:
1139</t>
1140<figure><artwork type="example"><![CDATA[
1141  Accept-Encoding: compress, gzip
1142  Accept-Encoding:
1143  Accept-Encoding: *
1144  Accept-Encoding: compress;q=0.5, gzip;q=1.0
1145  Accept-Encoding: gzip;q=1.0, identity; q=0.5, *;q=0
1146]]></artwork></figure>
1147<t>
1148   A server tests whether a content-coding is acceptable, according to
1149   an Accept-Encoding field, using these rules:
1150  <list style="numbers">
1151      <t>If the content-coding is one of the content-codings listed in
1152         the Accept-Encoding field, then it is acceptable, unless it is
1153         accompanied by a qvalue of 0. (As defined in Section 6.4 of <xref target="Part1"/>, a
1154         qvalue of 0 means "not acceptable.")</t>
1155
1156      <t>The special "*" symbol in an Accept-Encoding field matches any
1157         available content-coding not explicitly listed in the header
1158         field.</t>
1159
1160      <t>If multiple content-codings are acceptable, then the acceptable
1161         content-coding with the highest non-zero qvalue is preferred.</t>
1162
1163      <t>The "identity" content-coding is always acceptable, unless
1164         specifically refused because the Accept-Encoding field includes
1165         "identity;q=0", or because the field includes "*;q=0" and does
1166         not explicitly include the "identity" content-coding. If the
1167         Accept-Encoding field-value is empty, then only the "identity"
1168         encoding is acceptable.</t>
1169  </list>
1170</t>
1171<t>
1172   If an Accept-Encoding field is present in a request, and if the
1173   server cannot send a response which is acceptable according to the
1174   Accept-Encoding header, then the server SHOULD send an error response
1175   with the 406 (Not Acceptable) status code.
1176</t>
1177<t>
1178   If no Accept-Encoding field is present in a request, the server MAY
1179   assume that the client will accept any content coding. In this case,
1180   if "identity" is one of the available content-codings, then the
1181   server SHOULD use the "identity" content-coding, unless it has
1182   additional information that a different content-coding is meaningful
1183   to the client.
1184</t>
1185<t><list>
1186  <t>
1187    Note: If the request does not include an Accept-Encoding field,
1188    and if the "identity" content-coding is unavailable, then
1189    content-codings commonly understood by HTTP/1.0 clients (i.e.,
1190    "gzip" and "compress") are preferred; some older clients
1191    improperly display messages sent with other content-codings.  The
1192    server might also make this decision based on information about
1193    the particular user-agent or client.
1194  </t>
1195</list></t>
1196<t><list>
1197  <t>
1198    Note: Most HTTP/1.0 applications do not recognize or obey qvalues
1199    associated with content-codings. This means that qvalues will not
1200    work and are not permitted with x-gzip or x-compress.
1201  </t>
1202</list></t>
1203</section>
1204
1205<section title="Accept-Language" anchor="header.accept-language">
1206  <iref primary="true" item="Accept-Language header"/>
1207  <iref primary="true" item="Headers" subitem="Accept-Language"/>
1208 
1209 
1210 
1211<t>
1212   The "Accept-Language" request-header field can be used by user agents to
1213   indicate the set of natural languages that are preferred in the response.
1214   Language tags are defined in <xref target="language.tags"/>.
1215</t>
1216<figure><iref primary="true" item="Grammar" subitem="Accept-Language"/><iref primary="true" item="Grammar" subitem="Accept-Language-v"/><iref primary="true" item="Grammar" subitem="language-range"/><artwork type="abnf2616"><![CDATA[
1217  Accept-Language   = "Accept-Language" ":" OWS
1218                    Accept-Language-v
1219  Accept-Language-v =
1220                    1#( language-range [ OWS ";" OWS "q=" qvalue ] )
1221  language-range    =
1222            <language-range, defined in [RFC4647], Section 2.1>
1223]]></artwork></figure>
1224<t>
1225   Each language-range can be given an associated quality value which
1226   represents an estimate of the user's preference for the languages
1227   specified by that range. The quality value defaults to "q=1". For
1228   example,
1229</t>
1230<figure><artwork type="example"><![CDATA[
1231  Accept-Language: da, en-gb;q=0.8, en;q=0.7
1232]]></artwork></figure>
1233<t>
1234   would mean: "I prefer Danish, but will accept British English and
1235   other types of English."
1236</t>
1237<t>
1238   For matching, the "Basic Filtering" matching scheme, defined in
1239   Section 3.3.1 of <xref target="RFC4647"/>, is used:
1240</t>
1241<t><list>
1242  <t>
1243     A language range matches a
1244     particular language tag if, in a case-insensitive comparison, it
1245     exactly equals the tag, or if it exactly equals a prefix of the tag
1246     such that the first character following the prefix is "-".
1247  </t>
1248</list></t>
1249<t>
1250   The special range "*", if present in the Accept-Language field,
1251   matches every tag not matched by any other range present in the
1252   Accept-Language field.
1253</t>
1254<t><list>
1255  <t>
1256    Note: This use of a prefix matching rule does not imply that
1257    language tags are assigned to languages in such a way that it is
1258    always true that if a user understands a language with a certain
1259    tag, then this user will also understand all languages with tags
1260    for which this tag is a prefix. The prefix rule simply allows the
1261    use of prefix tags if this is the case.
1262  </t>
1263</list></t>
1264<t>
1265   The language quality factor assigned to a language-tag by the
1266   Accept-Language field is the quality value of the longest language-range
1267   in the field that matches the language-tag. If no language-range
1268   in the field matches the tag, the language quality factor
1269   assigned is 0. If no Accept-Language header is present in the
1270   request, the server
1271   SHOULD assume that all languages are equally acceptable. If an
1272   Accept-Language header is present, then all languages which are
1273   assigned a quality factor greater than 0 are acceptable.
1274</t>
1275<t>
1276   It might be contrary to the privacy expectations of the user to send
1277   an Accept-Language header with the complete linguistic preferences of
1278   the user in every request. For a discussion of this issue, see
1279   <xref target="privacy.issues.connected.to.accept.headers"/>.
1280</t>
1281<t>
1282   As intelligibility is highly dependent on the individual user, it is
1283   recommended that client applications make the choice of linguistic
1284   preference available to the user. If the choice is not made
1285   available, then the Accept-Language header field MUST NOT be given in
1286   the request.
1287</t>
1288<t><list>
1289  <t>
1290    Note: When making the choice of linguistic preference available to
1291    the user, we remind implementors of  the fact that users are not
1292    familiar with the details of language matching as described above,
1293    and should provide appropriate guidance. As an example, users
1294    might assume that on selecting "en-gb", they will be served any
1295    kind of English document if British English is not available. A
1296    user agent might suggest in such a case to add "en" to get the
1297    best matching behavior.
1298  </t>
1299</list></t>
1300</section>
1301
1302<section title="Content-Encoding" anchor="header.content-encoding">
1303  <iref primary="true" item="Content-Encoding header"/>
1304  <iref primary="true" item="Headers" subitem="Content-Encoding"/>
1305 
1306 
1307<t>
1308   The "Content-Encoding" entity-header field indicates what content-codings
1309   have been applied to the entity-body, and thus what decoding mechanisms
1310   must be applied in order to obtain the media-type referenced by the
1311   Content-Type header field. Content-Encoding is primarily used to allow a
1312   document to be compressed without losing the identity of its underlying
1313   media type.
1314</t>
1315<figure><iref primary="true" item="Grammar" subitem="Content-Encoding"/><iref primary="true" item="Grammar" subitem="Content-Encoding-v"/><artwork type="abnf2616"><![CDATA[
1316  Content-Encoding   = "Content-Encoding" ":" OWS Content-Encoding-v
1317  Content-Encoding-v = 1#content-coding
1318]]></artwork></figure>
1319<t>
1320   Content codings are defined in <xref target="content.codings"/>. An example of its use is
1321</t>
1322<figure><artwork type="example"><![CDATA[
1323  Content-Encoding: gzip
1324]]></artwork></figure>
1325<t>
1326   The content-coding is a characteristic of the entity identified by
1327   the request-target. Typically, the entity-body is stored with this
1328   encoding and is only decoded before rendering or analogous usage.
1329   However, a non-transparent proxy MAY modify the content-coding if the
1330   new coding is known to be acceptable to the recipient, unless the
1331   "no-transform" cache-control directive is present in the message.
1332</t>
1333<t>
1334   If the content-coding of an entity is not "identity", then the
1335   response MUST include a Content-Encoding entity-header (<xref target="header.content-encoding"/>)
1336   that lists the non-identity content-coding(s) used.
1337</t>
1338<t>
1339   If the content-coding of an entity in a request message is not
1340   acceptable to the origin server, the server SHOULD respond with a
1341   status code of 415 (Unsupported Media Type).
1342</t>
1343<t>
1344   If multiple encodings have been applied to an entity, the content
1345   codings MUST be listed in the order in which they were applied.
1346   Additional information about the encoding parameters MAY be provided
1347   by other entity-header fields not defined by this specification.
1348</t>
1349</section>
1350
1351<section title="Content-Language" anchor="header.content-language">
1352  <iref primary="true" item="Content-Language header"/>
1353  <iref primary="true" item="Headers" subitem="Content-Language"/>
1354 
1355 
1356<t>
1357   The "Content-Language" entity-header field describes the natural
1358   language(s) of the intended audience for the entity. Note that this might
1359   not be equivalent to all the languages used within the entity-body.
1360</t>
1361<figure><iref primary="true" item="Grammar" subitem="Content-Language"/><iref primary="true" item="Grammar" subitem="Content-Language-v"/><artwork type="abnf2616"><![CDATA[
1362  Content-Language   = "Content-Language" ":" OWS Content-Language-v
1363  Content-Language-v = 1#language-tag
1364]]></artwork></figure>
1365<t>
1366   Language tags are defined in <xref target="language.tags"/>. The primary purpose of
1367   Content-Language is to allow a user to identify and differentiate
1368   entities according to the user's own preferred language. Thus, if the
1369   body content is intended only for a Danish-literate audience, the
1370   appropriate field is
1371</t>
1372<figure><artwork type="example"><![CDATA[
1373  Content-Language: da
1374]]></artwork></figure>
1375<t>
1376   If no Content-Language is specified, the default is that the content
1377   is intended for all language audiences. This might mean that the
1378   sender does not consider it to be specific to any natural language,
1379   or that the sender does not know for which language it is intended.
1380</t>
1381<t>
1382   Multiple languages MAY be listed for content that is intended for
1383   multiple audiences. For example, a rendition of the "Treaty of
1384   Waitangi," presented simultaneously in the original Maori and English
1385   versions, would call for
1386</t>
1387<figure><artwork type="example"><![CDATA[
1388  Content-Language: mi, en
1389]]></artwork></figure>
1390<t>
1391   However, just because multiple languages are present within an entity
1392   does not mean that it is intended for multiple linguistic audiences.
1393   An example would be a beginner's language primer, such as "A First
1394   Lesson in Latin," which is clearly intended to be used by an
1395   English-literate audience. In this case, the Content-Language would
1396   properly only include "en".
1397</t>
1398<t>
1399   Content-Language MAY be applied to any media type -- it is not
1400   limited to textual documents.
1401</t>
1402</section>
1403
1404<section title="Content-Location" anchor="header.content-location">
1405  <iref primary="true" item="Content-Location header"/>
1406  <iref primary="true" item="Headers" subitem="Content-Location"/>
1407 
1408 
1409<t>
1410   The "Content-Location" entity-header field is used to supply a URI for the
1411   entity in the message when it is accessible from a location separate from
1412   the requested resource's URI.
1413</t>
1414<t>
1415   A server SHOULD provide a Content-Location for the variant corresponding
1416   to the response entity, especially in the case where a resource has multiple
1417   entities associated with it, and those entities actually have separate
1418   locations by which they might be individually accessed, the server SHOULD
1419   provide a Content-Location for the particular variant which is returned.
1420</t>
1421<figure><iref primary="true" item="Grammar" subitem="Content-Location"/><iref primary="true" item="Grammar" subitem="Content-Location-v"/><artwork type="abnf2616"><![CDATA[
1422  Content-Location   = "Content-Location" ":" OWS
1423                    Content-Location-v
1424  Content-Location-v =
1425                    absolute-URI / partial-URI
1426]]></artwork></figure>
1427<t>
1428   The Content-Location value is not a replacement for the original
1429   requested URI; it is only a statement of the location of the resource
1430   corresponding to this particular entity at the time of the request.
1431   Future requests MAY specify the Content-Location URI as the request-target
1432   if the desire is to identify the source of that particular
1433   entity.
1434</t>
1435<t>
1436   Section 6.1 of <xref target="Part2"/> describes how clients may process the Content-Location header field.
1437</t>
1438<t>
1439   A cache cannot assume that an entity with a Content-Location
1440   different from the URI used to retrieve it can be used to respond to
1441   later requests on that Content-Location URI. However, the Content-Location
1442   can be used to differentiate between multiple entities
1443   retrieved from a single requested resource, as described in Section 2.6 of <xref target="Part6"/>.
1444</t>
1445<t>
1446   If the Content-Location is a relative URI, the relative URI is
1447   interpreted relative to the request-target.
1448</t>
1449<t>
1450   The meaning of the Content-Location header in requests is
1451   undefined; servers are free to ignore it in those cases.
1452</t>
1453</section>
1454
1455<section title="Content-MD5" anchor="header.content-md5">
1456  <iref primary="true" item="Content-MD5 header"/>
1457  <iref primary="true" item="Headers" subitem="Content-MD5"/>
1458 
1459 
1460<t>
1461   The "Content-MD5" entity-header field, as defined in <xref target="RFC1864"/>, is
1462   an MD5 digest of the entity-body that provides an end-to-end message
1463   integrity check (MIC) of the entity-body. Note that a MIC is good for
1464   detecting accidental modification of the entity-body in transit, but is not
1465   proof against malicious attacks.
1466</t>
1467<figure><iref primary="true" item="Grammar" subitem="Content-MD5"/><iref primary="true" item="Grammar" subitem="Content-MD5-v"/><artwork type="abnf2616"><![CDATA[
1468  Content-MD5   = "Content-MD5" ":" OWS Content-MD5-v
1469  Content-MD5-v = <base64 of 128 bit MD5 digest as per [RFC1864]>
1470]]></artwork></figure>
1471<t>
1472   The Content-MD5 header field MAY be generated by an origin server or
1473   client to function as an integrity check of the entity-body. Only
1474   origin servers or clients MAY generate the Content-MD5 header field;
1475   proxies and gateways MUST NOT generate it, as this would defeat its
1476   value as an end-to-end integrity check. Any recipient of the entity-body,
1477   including gateways and proxies, MAY check that the digest value
1478   in this header field matches that of the entity-body as received.
1479</t>
1480<t>
1481   The MD5 digest is computed based on the content of the entity-body,
1482   including any content-coding that has been applied, but not including
1483   any transfer-encoding applied to the message-body. If the message is
1484   received with a transfer-encoding, that encoding MUST be removed
1485   prior to checking the Content-MD5 value against the received entity.
1486</t>
1487<t>
1488   This has the result that the digest is computed on the octets of the
1489   entity-body exactly as, and in the order that, they would be sent if
1490   no transfer-encoding were being applied.
1491</t>
1492<t>
1493   HTTP extends RFC 1864 to permit the digest to be computed for MIME
1494   composite media-types (e.g., multipart/* and message/rfc822), but
1495   this does not change how the digest is computed as defined in the
1496   preceding paragraph.
1497</t>
1498<t>
1499   There are several consequences of this. The entity-body for composite
1500   types MAY contain many body-parts, each with its own MIME and HTTP
1501   headers (including Content-MD5, Content-Transfer-Encoding, and
1502   Content-Encoding headers). If a body-part has a Content-Transfer-Encoding
1503   or Content-Encoding header, it is assumed that the content
1504   of the body-part has had the encoding applied, and the body-part is
1505   included in the Content-MD5 digest as is -- i.e., after the
1506   application. The Transfer-Encoding header field is not allowed within
1507   body-parts.
1508</t>
1509<t>
1510   Conversion of all line breaks to CRLF MUST NOT be done before
1511   computing or checking the digest: the line break convention used in
1512   the text actually transmitted MUST be left unaltered when computing
1513   the digest.
1514</t>
1515<t><list>
1516  <t>
1517    Note: while the definition of Content-MD5 is exactly the same for
1518    HTTP as in RFC 1864 for MIME entity-bodies, there are several ways
1519    in which the application of Content-MD5 to HTTP entity-bodies
1520    differs from its application to MIME entity-bodies. One is that
1521    HTTP, unlike MIME, does not use Content-Transfer-Encoding, and
1522    does use Transfer-Encoding and Content-Encoding. Another is that
1523    HTTP more frequently uses binary content types than MIME, so it is
1524    worth noting that, in such cases, the byte order used to compute
1525    the digest is the transmission byte order defined for the type.
1526    Lastly, HTTP allows transmission of text types with any of several
1527    line break conventions and not just the canonical form using CRLF.
1528  </t>
1529</list></t>
1530</section>
1531
1532<section title="Content-Type" anchor="header.content-type">
1533  <iref primary="true" item="Content-Type header"/>
1534  <iref primary="true" item="Headers" subitem="Content-Type"/>
1535 
1536 
1537<t>
1538   The "Content-Type" entity-header field indicates the media type of the
1539   entity-body. In the case of responses to the HEAD method, the media type is
1540   that which would have been sent had the request been a GET.
1541</t>
1542<figure><iref primary="true" item="Grammar" subitem="Content-Type"/><iref primary="true" item="Grammar" subitem="Content-Type-v"/><artwork type="abnf2616"><![CDATA[
1543  Content-Type   = "Content-Type" ":" OWS Content-Type-v
1544  Content-Type-v = media-type
1545]]></artwork></figure>
1546<t>
1547   Media types are defined in <xref target="media.types"/>. An example of the field is
1548</t>
1549<figure><artwork type="example"><![CDATA[
1550  Content-Type: text/html; charset=ISO-8859-4
1551]]></artwork></figure>
1552<t>
1553   Further discussion of methods for identifying the media type of an
1554   entity is provided in <xref target="type"/>.
1555</t>
1556</section>
1557
1558</section>
1559
1560<section title="IANA Considerations" anchor="IANA.considerations">
1561<section title="Message Header Registration" anchor="message.header.registration">
1562<t>
1563   The Message Header Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> should be updated
1564   with the permanent registrations below (see <xref target="RFC3864"/>):
1565</t>
1566
1567<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
1568<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
1569   <ttcol>Header Field Name</ttcol>
1570   <ttcol>Protocol</ttcol>
1571   <ttcol>Status</ttcol>
1572   <ttcol>Reference</ttcol>
1573
1574   <c>Accept</c>
1575   <c>http</c>
1576   <c>standard</c>
1577   <c>
1578      <xref target="header.accept"/>
1579   </c>
1580   <c>Accept-Charset</c>
1581   <c>http</c>
1582   <c>standard</c>
1583   <c>
1584      <xref target="header.accept-charset"/>
1585   </c>
1586   <c>Accept-Encoding</c>
1587   <c>http</c>
1588   <c>standard</c>
1589   <c>
1590      <xref target="header.accept-encoding"/>
1591   </c>
1592   <c>Accept-Language</c>
1593   <c>http</c>
1594   <c>standard</c>
1595   <c>
1596      <xref target="header.accept-language"/>
1597   </c>
1598   <c>Content-Disposition</c>
1599   <c>http</c>
1600   <c/>
1601   <c>
1602      <xref target="content-disposition"/>
1603   </c>
1604   <c>Content-Encoding</c>
1605   <c>http</c>
1606   <c>standard</c>
1607   <c>
1608      <xref target="header.content-encoding"/>
1609   </c>
1610   <c>Content-Language</c>
1611   <c>http</c>
1612   <c>standard</c>
1613   <c>
1614      <xref target="header.content-language"/>
1615   </c>
1616   <c>Content-Location</c>
1617   <c>http</c>
1618   <c>standard</c>
1619   <c>
1620      <xref target="header.content-location"/>
1621   </c>
1622   <c>Content-MD5</c>
1623   <c>http</c>
1624   <c>standard</c>
1625   <c>
1626      <xref target="header.content-md5"/>
1627   </c>
1628   <c>Content-Type</c>
1629   <c>http</c>
1630   <c>standard</c>
1631   <c>
1632      <xref target="header.content-type"/>
1633   </c>
1634   <c>MIME-Version</c>
1635   <c>http</c>
1636   <c/>
1637   <c>
1638      <xref target="mime-version"/>
1639   </c>
1640</texttable>
1641<!--(END)-->
1642
1643<t>
1644   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
1645</t>
1646</section>
1647
1648<section title="Content Coding Registry" anchor="content.coding.registration">
1649<t>
1650   The registration procedure for HTTP Content Codings is now defined
1651   by <xref target="content.coding.registry"/> of this document.
1652</t>
1653<t>
1654   The HTTP Content Codings Registry located at <eref target="http://www.iana.org/assignments/http-parameters"/>
1655   should be updated with the registration below:
1656</t>
1657<texttable align="left" suppress-title="true" anchor="iana.content.coding.registration.table">
1658   <ttcol>Name</ttcol>
1659   <ttcol>Description</ttcol>
1660   <ttcol>Reference</ttcol>
1661   <c>compress</c>
1662   <c>UNIX "compress" program method</c>
1663   <c>
1664      Section 6.2.2.1 of <xref target="Part1"/>
1665   </c>
1666   <c>deflate</c>
1667   <c>"zlib" format <xref target="RFC1950"/> with "deflate" compression</c>
1668   <c>
1669      Section 6.2.2.2 of <xref target="Part1"/>
1670   </c>
1671   <c>gzip</c>
1672   <c>Same as GNU zip <xref target="RFC1952"/></c>
1673   <c>
1674      Section 6.2.2.3 of <xref target="Part1"/>
1675   </c>
1676   <c>identity</c>
1677   <c>No transformation</c>
1678   <c>
1679      <xref target="content.codings"/>
1680   </c>
1681</texttable>
1682</section>
1683
1684</section>
1685
1686<section title="Security Considerations" anchor="security.considerations">
1687<t>
1688   This section is meant to inform application developers, information
1689   providers, and users of the security limitations in HTTP/1.1 as
1690   described by this document. The discussion does not include
1691   definitive solutions to the problems revealed, though it does make
1692   some suggestions for reducing security risks.
1693</t>
1694
1695<section title="Privacy Issues Connected to Accept Headers" anchor="privacy.issues.connected.to.accept.headers">
1696<t>
1697   Accept request-headers can reveal information about the user to all
1698   servers which are accessed. The Accept-Language header in particular
1699   can reveal information the user would consider to be of a private
1700   nature, because the understanding of particular languages is often
1701   strongly correlated to the membership of a particular ethnic group.
1702   User agents which offer the option to configure the contents of an
1703   Accept-Language header to be sent in every request are strongly
1704   encouraged to let the configuration process include a message which
1705   makes the user aware of the loss of privacy involved.
1706</t>
1707<t>
1708   An approach that limits the loss of privacy would be for a user agent
1709   to omit the sending of Accept-Language headers by default, and to ask
1710   the user whether or not to start sending Accept-Language headers to a
1711   server if it detects, by looking for any Vary response-header fields
1712   generated by the server, that such sending could improve the quality
1713   of service.
1714</t>
1715<t>
1716   Elaborate user-customized accept header fields sent in every request,
1717   in particular if these include quality values, can be used by servers
1718   as relatively reliable and long-lived user identifiers. Such user
1719   identifiers would allow content providers to do click-trail tracking,
1720   and would allow collaborating content providers to match cross-server
1721   click-trails or form submissions of individual users. Note that for
1722   many users not behind a proxy, the network address of the host
1723   running the user agent will also serve as a long-lived user
1724   identifier. In environments where proxies are used to enhance
1725   privacy, user agents ought to be conservative in offering accept
1726   header configuration options to end users. As an extreme privacy
1727   measure, proxies could filter the accept headers in relayed requests.
1728   General purpose user agents which provide a high degree of header
1729   configurability SHOULD warn users about the loss of privacy which can
1730   be involved.
1731</t>
1732</section>
1733
1734<section title="Content-Disposition Issues" anchor="content-disposition.issues">
1735<t>
1736   <xref target="RFC2183"/>, from which the often implemented Content-Disposition
1737   (see <xref target="content-disposition"/>) header in HTTP is derived, has a number of very
1738   serious security considerations. Content-Disposition is not part of
1739   the HTTP standard, but since it is widely implemented, we are
1740   documenting its use and risks for implementors. See Section 5 of <xref target="RFC2183"/>
1741   for details.
1742</t>
1743</section>
1744
1745</section>
1746
1747<section title="Acknowledgments" anchor="ack">
1748</section>
1749</middle>
1750<back>
1751
1752<references title="Normative References">
1753
1754<reference anchor="ISO-8859-1">
1755  <front>
1756    <title>
1757     Information technology -- 8-bit single-byte coded graphic character sets -- Part 1: Latin alphabet No. 1
1758    </title>
1759    <author>
1760      <organization>International Organization for Standardization</organization>
1761    </author>
1762    <date year="1998"/>
1763  </front>
1764  <seriesInfo name="ISO/IEC" value="8859-1:1998"/>
1765</reference>
1766
1767<reference anchor="Part1">
1768  <front>
1769    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
1770    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1771      <organization abbrev="Day Software">Day Software</organization>
1772      <address><email>fielding@gbiv.com</email></address>
1773    </author>
1774    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1775      <organization>One Laptop per Child</organization>
1776      <address><email>jg@laptop.org</email></address>
1777    </author>
1778    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1779      <organization abbrev="HP">Hewlett-Packard Company</organization>
1780      <address><email>JeffMogul@acm.org</email></address>
1781    </author>
1782    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1783      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1784      <address><email>henrikn@microsoft.com</email></address>
1785    </author>
1786    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1787      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1788      <address><email>LMM@acm.org</email></address>
1789    </author>
1790    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1791      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1792      <address><email>paulle@microsoft.com</email></address>
1793    </author>
1794    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1795      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1796      <address><email>timbl@w3.org</email></address>
1797    </author>
1798    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1799      <organization abbrev="W3C">World Wide Web Consortium</organization>
1800      <address><email>ylafon@w3.org</email></address>
1801    </author>
1802    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1803      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1804      <address><email>julian.reschke@greenbytes.de</email></address>
1805    </author>
1806    <date month="October" year="2009"/>
1807  </front>
1808  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-08"/>
1809 
1810</reference>
1811
1812<reference anchor="Part2">
1813  <front>
1814    <title abbrev="HTTP/1.1">HTTP/1.1, part 2: Message Semantics</title>
1815    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1816      <organization abbrev="Day Software">Day Software</organization>
1817      <address><email>fielding@gbiv.com</email></address>
1818    </author>
1819    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1820      <organization>One Laptop per Child</organization>
1821      <address><email>jg@laptop.org</email></address>
1822    </author>
1823    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1824      <organization abbrev="HP">Hewlett-Packard Company</organization>
1825      <address><email>JeffMogul@acm.org</email></address>
1826    </author>
1827    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1828      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1829      <address><email>henrikn@microsoft.com</email></address>
1830    </author>
1831    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1832      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1833      <address><email>LMM@acm.org</email></address>
1834    </author>
1835    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1836      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1837      <address><email>paulle@microsoft.com</email></address>
1838    </author>
1839    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1840      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1841      <address><email>timbl@w3.org</email></address>
1842    </author>
1843    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1844      <organization abbrev="W3C">World Wide Web Consortium</organization>
1845      <address><email>ylafon@w3.org</email></address>
1846    </author>
1847    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1848      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1849      <address><email>julian.reschke@greenbytes.de</email></address>
1850    </author>
1851    <date month="October" year="2009"/>
1852  </front>
1853  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p2-semantics-08"/>
1854 
1855</reference>
1856
1857<reference anchor="Part4">
1858  <front>
1859    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
1860    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1861      <organization abbrev="Day Software">Day Software</organization>
1862      <address><email>fielding@gbiv.com</email></address>
1863    </author>
1864    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1865      <organization>One Laptop per Child</organization>
1866      <address><email>jg@laptop.org</email></address>
1867    </author>
1868    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1869      <organization abbrev="HP">Hewlett-Packard Company</organization>
1870      <address><email>JeffMogul@acm.org</email></address>
1871    </author>
1872    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1873      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1874      <address><email>henrikn@microsoft.com</email></address>
1875    </author>
1876    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1877      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1878      <address><email>LMM@acm.org</email></address>
1879    </author>
1880    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1881      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1882      <address><email>paulle@microsoft.com</email></address>
1883    </author>
1884    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1885      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1886      <address><email>timbl@w3.org</email></address>
1887    </author>
1888    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1889      <organization abbrev="W3C">World Wide Web Consortium</organization>
1890      <address><email>ylafon@w3.org</email></address>
1891    </author>
1892    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1893      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1894      <address><email>julian.reschke@greenbytes.de</email></address>
1895    </author>
1896    <date month="October" year="2009"/>
1897  </front>
1898  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-08"/>
1899 
1900</reference>
1901
1902<reference anchor="Part5">
1903  <front>
1904    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
1905    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1906      <organization abbrev="Day Software">Day Software</organization>
1907      <address><email>fielding@gbiv.com</email></address>
1908    </author>
1909    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1910      <organization>One Laptop per Child</organization>
1911      <address><email>jg@laptop.org</email></address>
1912    </author>
1913    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1914      <organization abbrev="HP">Hewlett-Packard Company</organization>
1915      <address><email>JeffMogul@acm.org</email></address>
1916    </author>
1917    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1918      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1919      <address><email>henrikn@microsoft.com</email></address>
1920    </author>
1921    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1922      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1923      <address><email>LMM@acm.org</email></address>
1924    </author>
1925    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1926      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1927      <address><email>paulle@microsoft.com</email></address>
1928    </author>
1929    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1930      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1931      <address><email>timbl@w3.org</email></address>
1932    </author>
1933    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1934      <organization abbrev="W3C">World Wide Web Consortium</organization>
1935      <address><email>ylafon@w3.org</email></address>
1936    </author>
1937    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1938      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1939      <address><email>julian.reschke@greenbytes.de</email></address>
1940    </author>
1941    <date month="October" year="2009"/>
1942  </front>
1943  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-08"/>
1944 
1945</reference>
1946
1947<reference anchor="Part6">
1948  <front>
1949    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
1950    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1951      <organization abbrev="Day Software">Day Software</organization>
1952      <address><email>fielding@gbiv.com</email></address>
1953    </author>
1954    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1955      <organization>One Laptop per Child</organization>
1956      <address><email>jg@laptop.org</email></address>
1957    </author>
1958    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1959      <organization abbrev="HP">Hewlett-Packard Company</organization>
1960      <address><email>JeffMogul@acm.org</email></address>
1961    </author>
1962    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1963      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1964      <address><email>henrikn@microsoft.com</email></address>
1965    </author>
1966    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1967      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1968      <address><email>LMM@acm.org</email></address>
1969    </author>
1970    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1971      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1972      <address><email>paulle@microsoft.com</email></address>
1973    </author>
1974    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1975      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1976      <address><email>timbl@w3.org</email></address>
1977    </author>
1978    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1979      <organization abbrev="W3C">World Wide Web Consortium</organization>
1980      <address><email>ylafon@w3.org</email></address>
1981    </author>
1982    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
1983      <address><email>mnot@mnot.net</email></address>
1984    </author>
1985    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1986      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1987      <address><email>julian.reschke@greenbytes.de</email></address>
1988    </author>
1989    <date month="October" year="2009"/>
1990  </front>
1991  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-08"/>
1992 
1993</reference>
1994
1995<reference anchor="RFC1864">
1996  <front>
1997    <title abbrev="Content-MD5 Header Field">The Content-MD5 Header Field</title>
1998    <author initials="J." surname="Myers" fullname="John G. Myers">
1999      <organization>Carnegie Mellon University</organization>
2000      <address><email>jgm+@cmu.edu</email></address>
2001    </author>
2002    <author initials="M." surname="Rose" fullname="Marshall T. Rose">
2003      <organization>Dover Beach Consulting, Inc.</organization>
2004      <address><email>mrose@dbc.mtview.ca.us</email></address>
2005    </author>
2006    <date month="October" year="1995"/>
2007  </front>
2008  <seriesInfo name="RFC" value="1864"/>
2009</reference>
2010
2011<reference anchor="RFC1950">
2012  <front>
2013    <title>ZLIB Compressed Data Format Specification version 3.3</title>
2014    <author initials="L.P." surname="Deutsch" fullname="L. Peter Deutsch">
2015      <organization>Aladdin Enterprises</organization>
2016      <address><email>ghost@aladdin.com</email></address>
2017    </author>
2018    <author initials="J-L." surname="Gailly" fullname="Jean-Loup Gailly"/>
2019    <date month="May" year="1996"/>
2020  </front>
2021  <seriesInfo name="RFC" value="1950"/>
2022  <annotation>
2023    RFC 1950 is an Informational RFC, thus it may be less stable than
2024    this specification. On the other hand, this downward reference was
2025    present since the publication of RFC 2068 in 1997 (<xref target="RFC2068"/>),
2026    therefore it is unlikely to cause problems in practice. See also
2027    <xref target="BCP97"/>.
2028  </annotation>
2029</reference>
2030
2031<reference anchor="RFC1952">
2032  <front>
2033    <title>GZIP file format specification version 4.3</title>
2034    <author initials="P." surname="Deutsch" fullname="L. Peter Deutsch">
2035      <organization>Aladdin Enterprises</organization>
2036      <address><email>ghost@aladdin.com</email></address>
2037    </author>
2038    <author initials="J-L." surname="Gailly" fullname="Jean-Loup Gailly">
2039      <address><email>gzip@prep.ai.mit.edu</email></address>
2040    </author>
2041    <author initials="M." surname="Adler" fullname="Mark Adler">
2042      <address><email>madler@alumni.caltech.edu</email></address>
2043    </author>
2044    <author initials="L.P." surname="Deutsch" fullname="L. Peter Deutsch">
2045      <address><email>ghost@aladdin.com</email></address>
2046    </author>
2047    <author initials="G." surname="Randers-Pehrson" fullname="Glenn Randers-Pehrson">
2048      <address><email>randeg@alumni.rpi.edu</email></address>
2049    </author>
2050    <date month="May" year="1996"/>
2051  </front>
2052  <seriesInfo name="RFC" value="1952"/>
2053  <annotation>
2054    RFC 1952 is an Informational RFC, thus it may be less stable than
2055    this specification. On the other hand, this downward reference was
2056    present since the publication of RFC 2068 in 1997 (<xref target="RFC2068"/>),
2057    therefore it is unlikely to cause problems in practice. See also
2058    <xref target="BCP97"/>.
2059  </annotation>
2060</reference>
2061
2062<reference anchor="RFC2045">
2063  <front>
2064    <title abbrev="Internet Message Bodies">Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies</title>
2065    <author initials="N." surname="Freed" fullname="Ned Freed">
2066      <organization>Innosoft International, Inc.</organization>
2067      <address><email>ned@innosoft.com</email></address>
2068    </author>
2069    <author initials="N.S." surname="Borenstein" fullname="Nathaniel S. Borenstein">
2070      <organization>First Virtual Holdings</organization>
2071      <address><email>nsb@nsb.fv.com</email></address>
2072    </author>
2073    <date month="November" year="1996"/>
2074  </front>
2075  <seriesInfo name="RFC" value="2045"/>
2076</reference>
2077
2078<reference anchor="RFC2046">
2079  <front>
2080    <title abbrev="Media Types">Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types</title>
2081    <author initials="N." surname="Freed" fullname="Ned Freed">
2082      <organization>Innosoft International, Inc.</organization>
2083      <address><email>ned@innosoft.com</email></address>
2084    </author>
2085    <author initials="N." surname="Borenstein" fullname="Nathaniel S. Borenstein">
2086      <organization>First Virtual Holdings</organization>
2087      <address><email>nsb@nsb.fv.com</email></address>
2088    </author>
2089    <date month="November" year="1996"/>
2090  </front>
2091  <seriesInfo name="RFC" value="2046"/>
2092</reference>
2093
2094<reference anchor="RFC2119">
2095  <front>
2096    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
2097    <author initials="S." surname="Bradner" fullname="Scott Bradner">
2098      <organization>Harvard University</organization>
2099      <address><email>sob@harvard.edu</email></address>
2100    </author>
2101    <date month="March" year="1997"/>
2102  </front>
2103  <seriesInfo name="BCP" value="14"/>
2104  <seriesInfo name="RFC" value="2119"/>
2105</reference>
2106
2107<reference anchor="RFC4647">
2108  <front>
2109    <title>Matching of Language Tags</title>
2110    <author initials="A." surname="Phillips" fullname="Addison Phillips" role="editor">
2111      <organization>Yahoo! Inc.</organization>
2112      <address><email>addison@inter-locale.com</email></address>
2113    </author>
2114    <author initials="M." surname="Davis" fullname="Mark Davis" role="editor">
2115      <organization>Google</organization>
2116      <address><email>mark.davis@macchiato.com</email></address>
2117    </author>
2118    <date year="2006" month="September"/>
2119  </front>
2120  <seriesInfo name="BCP" value="47"/>
2121  <seriesInfo name="RFC" value="4647"/>
2122</reference>
2123
2124<reference anchor="RFC5234">
2125  <front>
2126    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
2127    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
2128      <organization>Brandenburg InternetWorking</organization>
2129      <address>
2130      <postal>
2131      <street>675 Spruce Dr.</street>
2132      <city>Sunnyvale</city>
2133      <region>CA</region>
2134      <code>94086</code>
2135      <country>US</country></postal>
2136      <phone>+1.408.246.8253</phone>
2137      <email>dcrocker@bbiw.net</email></address> 
2138    </author>
2139    <author initials="P." surname="Overell" fullname="Paul Overell">
2140      <organization>THUS plc.</organization>
2141      <address>
2142      <postal>
2143      <street>1/2 Berkeley Square</street>
2144      <street>99 Berkely Street</street>
2145      <city>Glasgow</city>
2146      <code>G3 7HR</code>
2147      <country>UK</country></postal>
2148      <email>paul.overell@thus.net</email></address>
2149    </author>
2150    <date month="January" year="2008"/>
2151  </front>
2152  <seriesInfo name="STD" value="68"/>
2153  <seriesInfo name="RFC" value="5234"/>
2154</reference>
2155
2156<reference anchor="RFC5646">
2157  <front>
2158    <title>Tags for Identifying Languages</title>
2159    <author initials="A." surname="Phillips" fullname="Addison Phillips" role="editor">
2160      <organization>Lab126</organization>
2161      <address><email>addison@inter-locale.com</email></address>
2162    </author>
2163    <author initials="M." surname="Davis" fullname="Mark Davis" role="editor">
2164      <organization>Google</organization>
2165      <address><email>mark.davis@google.com</email></address>
2166    </author>
2167    <date month="September" year="2009"/>
2168  </front>
2169  <seriesInfo name="BCP" value="47"/>
2170  <seriesInfo name="RFC" value="5646"/>
2171</reference>
2172
2173</references>
2174
2175<references title="Informative References">
2176
2177<reference anchor="RFC1945">
2178  <front>
2179    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
2180    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2181      <organization>MIT, Laboratory for Computer Science</organization>
2182      <address><email>timbl@w3.org</email></address>
2183    </author>
2184    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
2185      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2186      <address><email>fielding@ics.uci.edu</email></address>
2187    </author>
2188    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2189      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
2190      <address><email>frystyk@w3.org</email></address>
2191    </author>
2192    <date month="May" year="1996"/>
2193  </front>
2194  <seriesInfo name="RFC" value="1945"/>
2195</reference>
2196
2197<reference anchor="RFC2049">
2198  <front>
2199    <title abbrev="MIME Conformance">Multipurpose Internet Mail Extensions (MIME) Part Five: Conformance Criteria and Examples</title>
2200    <author initials="N." surname="Freed" fullname="Ned Freed">
2201      <organization>Innosoft International, Inc.</organization>
2202      <address><email>ned@innosoft.com</email></address>
2203    </author>
2204    <author initials="N.S." surname="Borenstein" fullname="Nathaniel S. Borenstein">
2205      <organization>First Virtual Holdings</organization>
2206      <address><email>nsb@nsb.fv.com</email></address>
2207    </author>
2208    <date month="November" year="1996"/>
2209  </front>
2210  <seriesInfo name="RFC" value="2049"/>
2211</reference>
2212
2213<reference anchor="RFC2068">
2214  <front>
2215    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
2216    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
2217      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2218      <address><email>fielding@ics.uci.edu</email></address>
2219    </author>
2220    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2221      <organization>MIT Laboratory for Computer Science</organization>
2222      <address><email>jg@w3.org</email></address>
2223    </author>
2224    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2225      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
2226      <address><email>mogul@wrl.dec.com</email></address>
2227    </author>
2228    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2229      <organization>MIT Laboratory for Computer Science</organization>
2230      <address><email>frystyk@w3.org</email></address>
2231    </author>
2232    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2233      <organization>MIT Laboratory for Computer Science</organization>
2234      <address><email>timbl@w3.org</email></address>
2235    </author>
2236    <date month="January" year="1997"/>
2237  </front>
2238  <seriesInfo name="RFC" value="2068"/>
2239</reference>
2240
2241<reference anchor="RFC2076">
2242  <front>
2243    <title abbrev="Internet Message Headers">Common Internet Message Headers</title>
2244    <author initials="J." surname="Palme" fullname="Jacob Palme">
2245      <organization>Stockholm University/KTH</organization>
2246      <address><email>jpalme@dsv.su.se</email></address>
2247    </author>
2248    <date month="February" year="1997"/>
2249  </front>
2250  <seriesInfo name="RFC" value="2076"/>
2251</reference>
2252
2253<reference anchor="RFC2183">
2254  <front>
2255    <title abbrev="Content-Disposition">Communicating Presentation Information in Internet Messages: The Content-Disposition Header Field</title>
2256    <author initials="R." surname="Troost" fullname="Rens Troost">
2257      <organization>New Century Systems</organization>
2258      <address><email>rens@century.com</email></address>
2259    </author>
2260    <author initials="S." surname="Dorner" fullname="Steve Dorner">
2261      <organization>QUALCOMM Incorporated</organization>
2262      <address><email>sdorner@qualcomm.com</email></address>
2263    </author>
2264    <author initials="K." surname="Moore" fullname="Keith Moore">
2265      <organization>Department of Computer Science</organization>
2266      <address><email>moore@cs.utk.edu</email></address>
2267    </author>
2268    <date month="August" year="1997"/>
2269  </front>
2270  <seriesInfo name="RFC" value="2183"/>
2271</reference>
2272
2273<reference anchor="RFC2277">
2274  <front>
2275    <title abbrev="Charset Policy">IETF Policy on Character Sets and Languages</title>
2276    <author initials="H.T." surname="Alvestrand" fullname="Harald Tveit Alvestrand">
2277      <organization>UNINETT</organization>
2278      <address><email>Harald.T.Alvestrand@uninett.no</email></address>
2279    </author>
2280    <date month="January" year="1998"/>
2281  </front>
2282  <seriesInfo name="BCP" value="18"/>
2283  <seriesInfo name="RFC" value="2277"/>
2284</reference>
2285
2286<reference anchor="RFC2388">
2287  <front>
2288    <title abbrev="multipart/form-data">Returning Values from Forms:  multipart/form-data</title>
2289    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2290      <organization>Xerox Palo Alto Research Center</organization>
2291      <address><email>masinter@parc.xerox.com</email></address>
2292    </author>
2293    <date year="1998" month="August"/>
2294  </front>
2295  <seriesInfo name="RFC" value="2388"/>
2296</reference>
2297
2298<reference anchor="RFC2557">
2299  <front>
2300    <title abbrev="MIME Encapsulation of Aggregate Documents">MIME Encapsulation of Aggregate Documents, such as HTML (MHTML)</title>
2301    <author initials="F." surname="Palme" fullname="Jacob Palme">
2302      <organization>Stockholm University and KTH</organization>
2303      <address><email>jpalme@dsv.su.se</email></address>
2304    </author>
2305    <author initials="A." surname="Hopmann" fullname="Alex Hopmann">
2306      <organization>Microsoft Corporation</organization>
2307      <address><email>alexhop@microsoft.com</email></address>
2308    </author>
2309    <author initials="N." surname="Shelness" fullname="Nick Shelness">
2310      <organization>Lotus Development Corporation</organization>
2311      <address><email>Shelness@lotus.com</email></address>
2312    </author>
2313    <author initials="E." surname="Stefferud" fullname="Einar Stefferud">
2314      <address><email>stef@nma.com</email></address>
2315    </author>
2316    <date year="1999" month="March"/>
2317  </front>
2318  <seriesInfo name="RFC" value="2557"/>
2319</reference>
2320
2321<reference anchor="RFC2616">
2322  <front>
2323    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
2324    <author initials="R." surname="Fielding" fullname="R. Fielding">
2325      <organization>University of California, Irvine</organization>
2326      <address><email>fielding@ics.uci.edu</email></address>
2327    </author>
2328    <author initials="J." surname="Gettys" fullname="J. Gettys">
2329      <organization>W3C</organization>
2330      <address><email>jg@w3.org</email></address>
2331    </author>
2332    <author initials="J." surname="Mogul" fullname="J. Mogul">
2333      <organization>Compaq Computer Corporation</organization>
2334      <address><email>mogul@wrl.dec.com</email></address>
2335    </author>
2336    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
2337      <organization>MIT Laboratory for Computer Science</organization>
2338      <address><email>frystyk@w3.org</email></address>
2339    </author>
2340    <author initials="L." surname="Masinter" fullname="L. Masinter">
2341      <organization>Xerox Corporation</organization>
2342      <address><email>masinter@parc.xerox.com</email></address>
2343    </author>
2344    <author initials="P." surname="Leach" fullname="P. Leach">
2345      <organization>Microsoft Corporation</organization>
2346      <address><email>paulle@microsoft.com</email></address>
2347    </author>
2348    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
2349      <organization>W3C</organization>
2350      <address><email>timbl@w3.org</email></address>
2351    </author>
2352    <date month="June" year="1999"/>
2353  </front>
2354  <seriesInfo name="RFC" value="2616"/>
2355</reference>
2356
2357<reference anchor="RFC3629">
2358  <front>
2359    <title>UTF-8, a transformation format of ISO 10646</title>
2360    <author initials="F." surname="Yergeau" fullname="F. Yergeau">
2361      <organization>Alis Technologies</organization>
2362      <address><email>fyergeau@alis.com</email></address>
2363    </author>
2364    <date month="November" year="2003"/>
2365  </front>
2366  <seriesInfo name="RFC" value="3629"/>
2367  <seriesInfo name="STD" value="63"/>
2368</reference>
2369
2370<reference anchor="RFC3864">
2371  <front>
2372    <title>Registration Procedures for Message Header Fields</title>
2373    <author initials="G." surname="Klyne" fullname="G. Klyne">
2374      <organization>Nine by Nine</organization>
2375      <address><email>GK-IETF@ninebynine.org</email></address>
2376    </author>
2377    <author initials="M." surname="Nottingham" fullname="M. Nottingham">
2378      <organization>BEA Systems</organization>
2379      <address><email>mnot@pobox.com</email></address>
2380    </author>
2381    <author initials="J." surname="Mogul" fullname="J. Mogul">
2382      <organization>HP Labs</organization>
2383      <address><email>JeffMogul@acm.org</email></address>
2384    </author>
2385    <date year="2004" month="September"/>
2386  </front>
2387  <seriesInfo name="BCP" value="90"/>
2388  <seriesInfo name="RFC" value="3864"/>
2389</reference>
2390
2391<reference anchor="RFC4288">
2392  <front>
2393    <title>Media Type Specifications and Registration Procedures</title>
2394    <author initials="N." surname="Freed" fullname="N. Freed">
2395      <organization>Sun Microsystems</organization>
2396      <address>
2397        <email>ned.freed@mrochek.com</email>
2398      </address>
2399    </author>
2400    <author initials="J." surname="Klensin" fullname="J. Klensin">
2401      <address>
2402        <email>klensin+ietf@jck.com</email>
2403      </address>
2404    </author>
2405    <date year="2005" month="December"/>
2406  </front>
2407  <seriesInfo name="BCP" value="13"/>
2408  <seriesInfo name="RFC" value="4288"/>
2409</reference>
2410
2411<reference anchor="RFC5226">
2412  <front>
2413    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
2414    <author initials="T." surname="Narten" fullname="T. Narten">
2415      <organization>IBM</organization>
2416      <address><email>narten@us.ibm.com</email></address>
2417    </author>
2418    <author initials="H." surname="Alvestrand" fullname="H. Alvestrand">
2419      <organization>Google</organization>
2420      <address><email>Harald@Alvestrand.no</email></address>
2421    </author>
2422    <date year="2008" month="May"/>
2423  </front>
2424  <seriesInfo name="BCP" value="26"/>
2425  <seriesInfo name="RFC" value="5226"/>
2426</reference>
2427
2428<reference anchor="RFC5322">
2429  <front>
2430    <title>Internet Message Format</title>
2431    <author initials="P." surname="Resnick" fullname="P. Resnick">
2432      <organization>Qualcomm Incorporated</organization>
2433    </author>
2434    <date year="2008" month="October"/>
2435  </front>
2436  <seriesInfo name="RFC" value="5322"/>
2437</reference>
2438
2439<reference anchor="BCP97">
2440  <front>
2441    <title>Handling Normative References to Standards-Track Documents</title>
2442    <author initials="J." surname="Klensin" fullname="J. Klensin">
2443      <address>
2444        <email>klensin+ietf@jck.com</email>
2445      </address>
2446    </author>
2447    <author initials="S." surname="Hartman" fullname="S. Hartman">
2448      <organization>MIT</organization>
2449      <address>
2450        <email>hartmans-ietf@mit.edu</email>
2451      </address>
2452    </author>
2453    <date year="2007" month="June"/>
2454  </front>
2455  <seriesInfo name="BCP" value="97"/>
2456  <seriesInfo name="RFC" value="4897"/>
2457</reference>
2458
2459
2460</references>
2461
2462<section title="Differences Between HTTP Entities and RFC 2045 Entities" anchor="differences.between.http.entities.and.rfc.2045.entities">
2463<t>
2464   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
2465   allow entities to be transmitted in an open variety of
2466   representations and with extensible mechanisms. However, RFC 2045
2467   discusses mail, and HTTP has a few features that are different from
2468   those described in RFC 2045. These differences were carefully chosen
2469   to optimize performance over binary connections, to allow greater
2470   freedom in the use of new media types, to make date comparisons
2471   easier, and to acknowledge the practice of some early HTTP servers
2472   and clients.
2473</t>
2474<t>
2475   This appendix describes specific areas where HTTP differs from RFC
2476   2045. Proxies and gateways to strict MIME environments SHOULD be
2477   aware of these differences and provide the appropriate conversions
2478   where necessary. Proxies and gateways from MIME environments to HTTP
2479   also need to be aware of the differences because some conversions
2480   might be required.
2481</t>
2482
2483<section title="MIME-Version" anchor="mime-version">
2484  <iref primary="true" item="MIME-Version header"/>
2485  <iref primary="true" item="Headers" subitem="MIME-Version"/>
2486 
2487 
2488<t>
2489   HTTP is not a MIME-compliant protocol. However, HTTP/1.1 messages MAY
2490   include a single MIME-Version general-header field to indicate what
2491   version of the MIME protocol was used to construct the message. Use
2492   of the MIME-Version header field indicates that the message is in
2493   full compliance with the MIME protocol (as defined in <xref target="RFC2045"/>).
2494   Proxies/gateways are responsible for ensuring full compliance (where
2495   possible) when exporting HTTP messages to strict MIME environments.
2496</t>
2497<figure><iref primary="true" item="Grammar" subitem="MIME-Version"/><iref primary="true" item="Grammar" subitem="MIME-Version-v"/><artwork type="abnf2616"><![CDATA[
2498  MIME-Version   = "MIME-Version" ":" OWS MIME-Version-v
2499  MIME-Version-v = 1*DIGIT "." 1*DIGIT
2500]]></artwork></figure>
2501<t>
2502   MIME version "1.0" is the default for use in HTTP/1.1. However,
2503   HTTP/1.1 message parsing and semantics are defined by this document
2504   and not the MIME specification.
2505</t>
2506</section>
2507
2508<section title="Conversion to Canonical Form" anchor="conversion.to.canonical.form">
2509<t>
2510   <xref target="RFC2045"/> requires that an Internet mail entity be converted to
2511   canonical form prior to being transferred, as described in Section 4 of <xref target="RFC2049"/>.
2512   <xref target="canonicalization.and.text.defaults"/> of this document describes the forms
2513   allowed for subtypes of the "text" media type when transmitted over
2514   HTTP. <xref target="RFC2046"/> requires that content with a type of "text" represent
2515   line breaks as CRLF and forbids the use of CR or LF outside of line
2516   break sequences. HTTP allows CRLF, bare CR, and bare LF to indicate a
2517   line break within text content when a message is transmitted over
2518   HTTP.
2519</t>
2520<t>
2521   Where it is possible, a proxy or gateway from HTTP to a strict MIME
2522   environment SHOULD translate all line breaks within the text media
2523   types described in <xref target="canonicalization.and.text.defaults"/> of this document to the RFC 2049
2524   canonical form of CRLF. Note, however, that this might be complicated
2525   by the presence of a Content-Encoding and by the fact that HTTP
2526   allows the use of some character sets which do not use octets 13 and
2527   10 to represent CR and LF, as is the case for some multi-byte
2528   character sets.
2529</t>
2530<t>
2531   Implementors should note that conversion will break any cryptographic
2532   checksums applied to the original content unless the original content
2533   is already in canonical form. Therefore, the canonical form is
2534   recommended for any content that uses such checksums in HTTP.
2535</t>
2536</section>
2537
2538
2539<section title="Conversion of Date Formats" anchor="conversion.of.date.formats">
2540<t>
2541   HTTP/1.1 uses a restricted set of date formats (Section 6.1 of <xref target="Part1"/>) to
2542   simplify the process of date comparison. Proxies and gateways from
2543   other protocols SHOULD ensure that any Date header field present in a
2544   message conforms to one of the HTTP/1.1 formats and rewrite the date
2545   if necessary.
2546</t>
2547</section>
2548
2549<section title="Introduction of Content-Encoding" anchor="introduction.of.content-encoding">
2550<t>
2551   RFC 2045 does not include any concept equivalent to HTTP/1.1's
2552   Content-Encoding header field. Since this acts as a modifier on the
2553   media type, proxies and gateways from HTTP to MIME-compliant
2554   protocols MUST either change the value of the Content-Type header
2555   field or decode the entity-body before forwarding the message. (Some
2556   experimental applications of Content-Type for Internet mail have used
2557   a media-type parameter of ";conversions=&lt;content-coding&gt;" to perform
2558   a function equivalent to Content-Encoding. However, this parameter is
2559   not part of RFC 2045).
2560</t>
2561</section>
2562
2563<section title="No Content-Transfer-Encoding" anchor="no.content-transfer-encoding">
2564<t>
2565   HTTP does not use the Content-Transfer-Encoding field of RFC
2566   2045. Proxies and gateways from MIME-compliant protocols to HTTP MUST
2567   remove any Content-Transfer-Encoding
2568   prior to delivering the response message to an HTTP client.
2569</t>
2570<t>
2571   Proxies and gateways from HTTP to MIME-compliant protocols are
2572   responsible for ensuring that the message is in the correct format
2573   and encoding for safe transport on that protocol, where "safe
2574   transport" is defined by the limitations of the protocol being used.
2575   Such a proxy or gateway SHOULD label the data with an appropriate
2576   Content-Transfer-Encoding if doing so will improve the likelihood of
2577   safe transport over the destination protocol.
2578</t>
2579</section>
2580
2581<section title="Introduction of Transfer-Encoding" anchor="introduction.of.transfer-encoding">
2582<t>
2583   HTTP/1.1 introduces the Transfer-Encoding header field (Section 9.7 of <xref target="Part1"/>).
2584   Proxies/gateways MUST remove any transfer-coding prior to
2585   forwarding a message via a MIME-compliant protocol.
2586</t>
2587</section>
2588
2589<section title="MHTML and Line Length Limitations" anchor="mhtml.line.length">
2590<t>
2591   HTTP implementations which share code with MHTML <xref target="RFC2557"/> implementations
2592   need to be aware of MIME line length limitations. Since HTTP does not
2593   have this limitation, HTTP does not fold long lines. MHTML messages
2594   being transported by HTTP follow all conventions of MHTML, including
2595   line length limitations and folding, canonicalization, etc., since
2596   HTTP transports all message-bodies as payload (see <xref target="multipart.types"/>) and
2597   does not interpret the content or any MIME header lines that might be
2598   contained therein.
2599</t>
2600</section>
2601</section>
2602
2603<section title="Additional Features" anchor="additional.features">
2604<t>
2605   <xref target="RFC1945"/> and <xref target="RFC2068"/> document protocol elements used by some
2606   existing HTTP implementations, but not consistently and correctly
2607   across most HTTP/1.1 applications. Implementors are advised to be
2608   aware of these features, but cannot rely upon their presence in, or
2609   interoperability with, other HTTP/1.1 applications. Some of these
2610   describe proposed experimental features, and some describe features
2611   that experimental deployment found lacking that are now addressed in
2612   the base HTTP/1.1 specification.
2613</t>
2614<t>
2615   A number of other headers, such as Content-Disposition and Title,
2616   from SMTP and MIME are also often implemented (see <xref target="RFC2076"/>).
2617</t>
2618
2619<section title="Content-Disposition" anchor="content-disposition">
2620<iref item="Headers" subitem="Content-Disposition" primary="true"/>
2621<iref item="Content-Disposition header" primary="true"/>
2622 
2623 
2624 
2625 
2626 
2627 
2628 
2629<t>
2630   The "Content-Disposition" response-header field has been proposed as a
2631   means for the origin server to suggest a default filename if the user
2632   requests that the content is saved to a file. This usage is derived
2633   from the definition of Content-Disposition in <xref target="RFC2183"/>.
2634</t>
2635<figure><iref primary="true" item="Grammar" subitem="content-disposition"/><iref primary="true" item="Grammar" subitem="content-disposition-v"/><iref primary="true" item="Grammar" subitem="disposition-type"/><iref primary="true" item="Grammar" subitem="disposition-parm"/><iref primary="true" item="Grammar" subitem="filename-parm"/><iref primary="true" item="Grammar" subitem="disp-extension-token"/><iref primary="true" item="Grammar" subitem="disp-extension-parm"/><artwork type="abnf2616"><![CDATA[
2636  content-disposition = "Content-Disposition" ":" OWS
2637                        content-disposition-v
2638  content-disposition-v = disposition-type
2639                          *( OWS ";" OWS disposition-parm )
2640  disposition-type = "attachment" / disp-extension-token
2641  disposition-parm = filename-parm / disp-extension-parm
2642  filename-parm = "filename" "=" quoted-string
2643  disp-extension-token = token
2644  disp-extension-parm = token "=" ( token / quoted-string )
2645]]></artwork></figure>
2646<t>
2647   An example is
2648</t>
2649<figure><artwork type="example"><![CDATA[
2650  Content-Disposition: attachment; filename="fname.ext"
2651]]></artwork></figure>
2652<t>
2653   The receiving user agent SHOULD NOT  respect any directory path
2654   information present in the filename-parm parameter, which is the only
2655   parameter believed to apply to HTTP implementations at this time. The
2656   filename SHOULD be treated as a terminal component only.
2657</t>
2658<t>
2659   If this header is used in a response with the application/octet-stream
2660   content-type, the implied suggestion is that the user agent
2661   should not display the response, but directly enter a `save response
2662   as...' dialog.
2663</t>
2664<t>
2665   See <xref target="content-disposition.issues"/> for Content-Disposition security issues.
2666</t>
2667</section>
2668</section>
2669
2670<section title="Compatibility with Previous Versions" anchor="compatibility">
2671<section title="Changes from RFC 2068" anchor="changes.from.rfc.2068">
2672<t>
2673   Transfer-coding and message lengths all interact in ways that
2674   required fixing exactly when chunked encoding is used (to allow for
2675   transfer encoding that may not be self delimiting); it was important
2676   to straighten out exactly how message lengths are computed.
2677   (<xref target="entity.length"/>, see also <xref target="Part1"/>,
2678   <xref target="Part5"/> and <xref target="Part6"/>).
2679</t>
2680<t>
2681   Charset wildcarding is introduced to avoid explosion of character set
2682   names in accept headers. (<xref target="header.accept-charset"/>)
2683</t>
2684<t>
2685   Content-Base was deleted from the specification: it was not
2686   implemented widely, and there is no simple, safe way to introduce it
2687   without a robust extension mechanism. In addition, it is used in a
2688   similar, but not identical fashion in MHTML <xref target="RFC2557"/>.
2689</t>
2690<t>
2691   A content-coding of "identity" was introduced, to solve problems
2692   discovered in caching. (<xref target="content.codings"/>)
2693</t>
2694<t>
2695   The Alternates<iref item="Alternates header" primary="true"/><iref item="Headers" subitem="Alternate" primary="true"/>, Content-Version<iref item="Content-Version header" primary="true"/><iref item="Headers" subitem="Content-Version" primary="true"/>, Derived-From<iref item="Derived-From header" primary="true"/><iref item="Headers" subitem="Derived-From" primary="true"/>, Link<iref item="Link header" primary="true"/><iref item="Headers" subitem="Link" primary="true"/>, URI<iref item="URI header" primary="true"/><iref item="Headers" subitem="URI" primary="true"/>, Public<iref item="Public header" primary="true"/><iref item="Headers" subitem="Public" primary="true"/> and
2696   Content-Base<iref item="Content-Base header" primary="true"/><iref item="Headers" subitem="Content-Base" primary="true"/> header fields were defined in previous versions of this
2697   specification, but not commonly implemented. See Section 19.6.2 of <xref target="RFC2068"/>.
2698</t>
2699</section>
2700
2701<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
2702<t>
2703  Clarify contexts that charset is used in.
2704  (<xref target="character.sets"/>)
2705</t>
2706<t>
2707  Remove base URI setting semantics for Content-Location due to poor
2708  implementation support, which was caused by too many broken servers emitting
2709  bogus Content-Location headers, and also the potentially undesirable effect
2710  of potentially breaking relative links in content-negotiated resources.
2711  (<xref target="header.content-location"/>)
2712</t>
2713<t>
2714  Remove reference to non-existant identity transfer-coding value tokens.
2715  (<xref target="no.content-transfer-encoding"/>)
2716</t>
2717</section>
2718
2719</section>
2720
2721
2722<section title="Collected ABNF" anchor="collected.abnf">
2723<figure>
2724<artwork type="abnf" name="p3-payload.parsed-abnf"><![CDATA[
2725Accept = "Accept:" OWS Accept-v
2726Accept-Charset = "Accept-Charset:" OWS Accept-Charset-v
2727Accept-Charset-v = *( "," OWS ) ( charset / "*" ) [ OWS ";" OWS "q="
2728 qvalue ] *( OWS "," [ OWS ( charset / "*" ) [ OWS ";" OWS "q="
2729 qvalue ] ] )
2730Accept-Encoding = "Accept-Encoding:" OWS Accept-Encoding-v
2731Accept-Encoding-v = [ ( "," / ( codings [ OWS ";" OWS "q=" qvalue ] )
2732 ) *( OWS "," [ OWS codings [ OWS ";" OWS "q=" qvalue ] ] ) ]
2733Accept-Language = "Accept-Language:" OWS Accept-Language-v
2734Accept-Language-v = *( "," OWS ) language-range [ OWS ";" OWS "q="
2735 qvalue ] *( OWS "," [ OWS language-range [ OWS ";" OWS "q=" qvalue ]
2736 ] )
2737Accept-v = [ ( "," / ( media-range [ accept-params ] ) ) *( OWS "," [
2738 OWS media-range [ accept-params ] ] ) ]
2739
2740Content-Encoding = "Content-Encoding:" OWS Content-Encoding-v
2741Content-Encoding-v = *( "," OWS ) content-coding *( OWS "," [ OWS
2742 content-coding ] )
2743Content-Language = "Content-Language:" OWS Content-Language-v
2744Content-Language-v = *( "," OWS ) language-tag *( OWS "," [ OWS
2745 language-tag ] )
2746Content-Length = <Content-Length, defined in [Part1], Section 9.2>
2747Content-Location = "Content-Location:" OWS Content-Location-v
2748Content-Location-v = absolute-URI / partial-URI
2749Content-MD5 = "Content-MD5:" OWS Content-MD5-v
2750Content-MD5-v = <base64 of 128 bit MD5 digest as per [RFC1864]>
2751Content-Range = <Content-Range, defined in [Part5], Section 5.2>
2752Content-Type = "Content-Type:" OWS Content-Type-v
2753Content-Type-v = media-type
2754
2755Expires = <Expires, defined in [Part6], Section 3.3>
2756
2757Last-Modified = <Last-Modified, defined in [Part4], Section 6.6>
2758
2759MIME-Version = "MIME-Version:" OWS MIME-Version-v
2760MIME-Version-v = 1*DIGIT "." 1*DIGIT
2761
2762OWS = <OWS, defined in [Part1], Section 1.2.2>
2763
2764absolute-URI = <absolute-URI, defined in [Part1], Section 2.6>
2765accept-ext = OWS ";" OWS token [ "=" ( token / quoted-string ) ]
2766accept-params = OWS ";" OWS "q=" qvalue *accept-ext
2767attribute = token
2768
2769charset = token
2770codings = ( content-coding / "*" )
2771content-coding = token
2772content-disposition = "Content-Disposition:" OWS
2773 content-disposition-v
2774content-disposition-v = disposition-type *( OWS ";" OWS
2775 disposition-parm )
2776
2777disp-extension-parm = token "=" ( token / quoted-string )
2778disp-extension-token = token
2779disposition-parm = filename-parm / disp-extension-parm
2780disposition-type = "attachment" / disp-extension-token
2781
2782entity-body = *OCTET
2783entity-header = Content-Encoding / Content-Language / Content-Length
2784 / Content-Location / Content-MD5 / Content-Range / Content-Type /
2785 Expires / Last-Modified / extension-header
2786extension-header = header-field
2787
2788filename-parm = "filename=" quoted-string
2789
2790header-field = <header-field, defined in [Part1], Section 3.2>
2791
2792language-range = <language-range, defined in [RFC4647], Section 2.1>
2793language-tag = <Language-Tag, defined in [RFC5646], Section 2.1>
2794
2795media-range = ( "*/*" / ( type "/*" ) / ( type "/" subtype ) ) *( OWS
2796 ";" OWS parameter )
2797media-type = type "/" subtype *( OWS ";" OWS parameter )
2798
2799parameter = attribute "=" value
2800partial-URI = <partial-URI, defined in [Part1], Section 2.6>
2801
2802quoted-string = <quoted-string, defined in [Part1], Section 1.2.2>
2803qvalue = <qvalue, defined in [Part1], Section 6.4>
2804
2805subtype = token
2806
2807token = <token, defined in [Part1], Section 1.2.2>
2808type = token
2809
2810value = token / quoted-string
2811]]></artwork>
2812</figure>
2813<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline"><![CDATA[
2814; Accept defined but not used
2815; Accept-Charset defined but not used
2816; Accept-Encoding defined but not used
2817; Accept-Language defined but not used
2818; MIME-Version defined but not used
2819; content-disposition defined but not used
2820; entity-body defined but not used
2821; entity-header defined but not used
2822]]></artwork></figure></section>
2823
2824
2825<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
2826
2827<section title="Since RFC2616">
2828<t>
2829  Extracted relevant partitions from <xref target="RFC2616"/>.
2830</t>
2831</section>
2832
2833<section title="Since draft-ietf-httpbis-p3-payload-00">
2834<t>
2835  Closed issues:
2836  <list style="symbols">
2837    <t>
2838      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/8"/>:
2839      "Media Type Registrations"
2840      (<eref target="http://purl.org/NET/http-errata#media-reg"/>)
2841    </t>
2842    <t>
2843      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/14"/>:
2844      "Clarification regarding quoting of charset values"
2845      (<eref target="http://purl.org/NET/http-errata#charactersets"/>)
2846    </t>
2847    <t>
2848      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/16"/>:
2849      "Remove 'identity' token references"
2850      (<eref target="http://purl.org/NET/http-errata#identity"/>)
2851    </t>
2852    <t>
2853      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/25"/>:
2854      "Accept-Encoding BNF"
2855    </t>
2856    <t>
2857      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
2858      "Normative and Informative references"
2859    </t>
2860    <t>
2861      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/46"/>:
2862      "RFC1700 references"
2863    </t>
2864    <t>
2865      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/55"/>:
2866      "Updating to RFC4288"
2867    </t>
2868    <t>
2869      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
2870      "Informative references"
2871    </t>
2872    <t>
2873      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/66"/>:
2874      "ISO-8859-1 Reference"
2875    </t>
2876    <t>
2877      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/68"/>:
2878      "Encoding References Normative"
2879    </t>
2880    <t>
2881      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/86"/>:
2882      "Normative up-to-date references"
2883    </t>
2884  </list>
2885</t>
2886</section>
2887
2888<section title="Since draft-ietf-httpbis-p3-payload-01">
2889<t>
2890  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
2891  <list style="symbols">
2892    <t>
2893      Add explicit references to BNF syntax and rules imported from other parts of the specification.
2894    </t>
2895  </list>
2896</t>
2897</section>
2898
2899<section title="Since draft-ietf-httpbis-p3-payload-02" anchor="changes.since.02">
2900<t>
2901  Closed issues:
2902  <list style="symbols">
2903    <t>
2904      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/67"/>:
2905      "Quoting Charsets"
2906    </t>
2907    <t>
2908      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
2909      "Classification for Allow header"
2910    </t>
2911    <t>
2912      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/115"/>:
2913      "missing default for qvalue in description of Accept-Encoding"
2914    </t>
2915  </list>
2916</t>
2917<t>
2918  Ongoing work on IANA Message Header Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
2919  <list style="symbols">
2920    <t>
2921      Reference RFC 3984, and update header registrations for headers defined
2922      in this document.
2923    </t>
2924  </list>
2925</t>
2926</section>
2927
2928<section title="Since draft-ietf-httpbis-p3-payload-03" anchor="changes.since.03">
2929<t>
2930  Closed issues:
2931  <list style="symbols">
2932    <t>
2933      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/67"/>:
2934      "Quoting Charsets"
2935    </t>
2936    <t>
2937      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/113"/>:
2938      "language tag matching (Accept-Language) vs RFC4647"
2939    </t>
2940    <t>
2941      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/121"/>:
2942      "RFC 1806 has been replaced by RFC2183"
2943    </t>
2944  </list>
2945</t>
2946<t>
2947  Other changes:
2948  <list style="symbols">
2949    <t>
2950      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/68"/>:
2951      "Encoding References Normative" -- rephrase the annotation and reference
2952      <xref target="BCP97"/>.
2953    </t>
2954  </list>
2955</t>
2956 </section>
2957
2958<section title="Since draft-ietf-httpbis-p3-payload-04" anchor="changes.since.04">
2959<t>
2960  Closed issues:
2961  <list style="symbols">
2962    <t>
2963      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
2964      "RFC 2822 is updated by RFC 5322"
2965    </t>
2966  </list>
2967</t>
2968<t>
2969  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
2970  <list style="symbols">
2971    <t>
2972      Use "/" instead of "|" for alternatives.
2973    </t>
2974    <t>
2975      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
2976      whitespace ("OWS") and required whitespace ("RWS").
2977    </t>
2978    <t>
2979      Rewrite ABNFs to spell out whitespace rules, factor out
2980      header value format definitions.
2981    </t>
2982  </list>
2983</t>
2984</section>
2985
2986<section title="Since draft-ietf-httpbis-p3-payload-05" anchor="changes.since.05">
2987<t>
2988  Closed issues:
2989  <list style="symbols">
2990    <t>
2991      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/118"/>:
2992      "Join "Differences Between HTTP Entities and RFC 2045 Entities"?"
2993    </t>
2994  </list>
2995</t>
2996<t>
2997  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
2998  <list style="symbols">
2999    <t>
3000      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
3001    </t>
3002  </list>
3003</t>
3004<t>
3005  Other changes:
3006  <list style="symbols">
3007    <t>
3008      Move definition of quality values into Part 1.
3009    </t>
3010  </list>
3011</t>
3012</section>
3013
3014<section title="Since draft-ietf-httpbis-p3-payload-06" anchor="changes.since.06">
3015<t>
3016  Closed issues:
3017  <list style="symbols">
3018    <t>
3019      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/80"/>:
3020      "Content-Location isn't special"
3021    </t>
3022    <t>
3023      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/155"/>:
3024      "Content Sniffing"
3025    </t>
3026  </list>
3027</t>
3028</section>
3029
3030<section title="Since draft-ietf-httpbis-p3-payload-07" anchor="changes.since.07">
3031<t>
3032  Closed issues:
3033  <list style="symbols">
3034    <t>
3035      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/13"/>:
3036      "Updated reference for language tags"
3037    </t>
3038    <t>
3039      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
3040      "Clarify rules for determining what entities a response carries"
3041    </t>
3042    <t>
3043      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/154"/>:
3044      "Content-Location base-setting problems"
3045    </t>
3046    <t>
3047      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/155"/>:
3048      "Content Sniffing"
3049    </t>
3050    <t>
3051      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/188"/>:
3052      "pick IANA policy (RFC5226) for Transfer Coding / Content Coding"
3053    </t>
3054    <t>
3055      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/189"/>:
3056      "move definitions of gzip/deflate/compress to part 1"
3057    </t>
3058  </list>
3059</t>
3060<t>
3061  Partly resolved issues:
3062  <list style="symbols">
3063    <t>
3064      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/148"/>:
3065      "update IANA requirements wrt Transfer-Coding values" (add the
3066      IANA Considerations subsection)
3067    </t>
3068    <t>
3069      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/149"/>:
3070      "update IANA requirements wrt Content-Coding values" (add the
3071      IANA Considerations subsection)
3072    </t>
3073  </list>
3074</t>
3075</section>
3076
3077</section>
3078
3079</back>
3080</rfc>
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