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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<?rfc rfcedstyle="yes"?>
17<!DOCTYPE rfc
18  PUBLIC "" "rfc2629.dtd">
19<rfc obsoletes="2616" category="std" ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p3-payload-10">
20<front>
21
22  <title abbrev="HTTP/1.1, Part 3">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
23
24  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
25    <organization abbrev="Day Software">Day Software</organization>
26    <address>
27      <postal>
28        <street>23 Corporate Plaza DR, Suite 280</street>
29        <city>Newport Beach</city>
30        <region>CA</region>
31        <code>92660</code>
32        <country>USA</country>
33      </postal>
34      <phone>+1-949-706-5300</phone>
35      <facsimile>+1-949-706-5305</facsimile>
36      <email>fielding@gbiv.com</email>
37      <uri>http://roy.gbiv.com/</uri>
38    </address>
39  </author>
40
41  <author initials="J." surname="Gettys" fullname="Jim Gettys">
42    <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
43    <address>
44      <postal>
45        <street>21 Oak Knoll Road</street>
46        <city>Carlisle</city>
47        <region>MA</region>
48        <code>01741</code>
49        <country>USA</country>
50      </postal>
51      <email>jg@freedesktop.org</email>
52      <uri>http://gettys.wordpress.com/</uri>
53    </address>
54  </author>
55 
56  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
57    <organization abbrev="HP">Hewlett-Packard Company</organization>
58    <address>
59      <postal>
60        <street>HP Labs, Large Scale Systems Group</street>
61        <street>1501 Page Mill Road, MS 1177</street>
62        <city>Palo Alto</city>
63        <region>CA</region>
64        <code>94304</code>
65        <country>USA</country>
66      </postal>
67      <email>JeffMogul@acm.org</email>
68    </address>
69  </author>
70
71  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
72    <organization abbrev="Microsoft">Microsoft Corporation</organization>
73    <address>
74      <postal>
75        <street>1 Microsoft Way</street>
76        <city>Redmond</city>
77        <region>WA</region>
78        <code>98052</code>
79        <country>USA</country>
80      </postal>
81      <email>henrikn@microsoft.com</email>
82    </address>
83  </author>
84
85  <author initials="L." surname="Masinter" fullname="Larry Masinter">
86    <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
87    <address>
88      <postal>
89        <street>345 Park Ave</street>
90        <city>San Jose</city>
91        <region>CA</region>
92        <code>95110</code>
93        <country>USA</country>
94      </postal>
95      <email>LMM@acm.org</email>
96      <uri>http://larry.masinter.net/</uri>
97    </address>
98  </author>
99 
100  <author initials="P." surname="Leach" fullname="Paul J. Leach">
101    <organization abbrev="Microsoft">Microsoft Corporation</organization>
102    <address>
103      <postal>
104        <street>1 Microsoft Way</street>
105        <city>Redmond</city>
106        <region>WA</region>
107        <code>98052</code>
108      </postal>
109      <email>paulle@microsoft.com</email>
110    </address>
111  </author>
112   
113  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
114    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
115    <address>
116      <postal>
117        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
118        <street>The Stata Center, Building 32</street>
119        <street>32 Vassar Street</street>
120        <city>Cambridge</city>
121        <region>MA</region>
122        <code>02139</code>
123        <country>USA</country>
124      </postal>
125      <email>timbl@w3.org</email>
126      <uri>http://www.w3.org/People/Berners-Lee/</uri>
127    </address>
128  </author>
129
130  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
131    <organization abbrev="W3C">World Wide Web Consortium</organization>
132    <address>
133      <postal>
134        <street>W3C / ERCIM</street>
135        <street>2004, rte des Lucioles</street>
136        <city>Sophia-Antipolis</city>
137        <region>AM</region>
138        <code>06902</code>
139        <country>France</country>
140      </postal>
141      <email>ylafon@w3.org</email>
142      <uri>http://www.raubacapeu.net/people/yves/</uri>
143    </address>
144  </author>
145
146  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
147    <organization abbrev="greenbytes">greenbytes GmbH</organization>
148    <address>
149      <postal>
150        <street>Hafenweg 16</street>
151        <city>Muenster</city><region>NW</region><code>48155</code>
152        <country>Germany</country>
153      </postal>
154      <phone>+49 251 2807760</phone>
155      <facsimile>+49 251 2807761</facsimile>
156      <email>julian.reschke@greenbytes.de</email>
157      <uri>http://greenbytes.de/tech/webdav/</uri>
158    </address>
159  </author>
160
161  <date month="July" year="2010" day="12"/>
162  <workgroup>HTTPbis Working Group</workgroup>
163
164<abstract>
165<t>
166   The Hypertext Transfer Protocol (HTTP) is an application-level
167   protocol for distributed, collaborative, hypermedia information
168   systems. HTTP has been in use by the World Wide Web global information
169   initiative since 1990. This document is Part 3 of the seven-part specification
170   that defines the protocol referred to as "HTTP/1.1" and, taken together,
171   obsoletes RFC 2616.  Part 3 defines HTTP message content,
172   metadata, and content negotiation.
173</t>
174</abstract>
175
176<note title="Editorial Note (To be removed by RFC Editor)">
177  <t>
178    Discussion of this draft should take place on the HTTPBIS working group
179    mailing list (ietf-http-wg@w3.org). The current issues list is
180    at <eref target="http://tools.ietf.org/wg/httpbis/trac/report/3"/>
181    and related documents (including fancy diffs) can be found at
182    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
183  </t>
184  <t>
185    The changes in this draft are summarized in <xref target="changes.since.09"/>.
186  </t>
187</note>
188</front>
189<middle>
190<section title="Introduction" anchor="introduction">
191<t>
192   This document defines HTTP/1.1 message payloads (a.k.a., content), the
193   associated metadata header fields that define how the payload is intended
194   to be interpreted by a recipient, the request header fields that
195   may influence content selection, and the various selection algorithms
196   that are collectively referred to as HTTP content negotiation.
197</t>
198<t>
199   This document is currently disorganized in order to minimize the changes
200   between drafts and enable reviewers to see the smaller errata changes.
201   The next draft will reorganize the sections to better reflect the content.
202   In particular, the sections on entities will be renamed payload and moved
203   to the first half of the document, while the sections on content negotiation
204   and associated request header fields will be moved to the second half.  The
205   current mess reflects how widely dispersed these topics and associated
206   requirements had become in <xref target="RFC2616"/>.
207</t>
208
209<section title="Terminology" anchor="terminology">
210<t>
211   This specification uses a number of terms to refer to the roles
212   played by participants in, and objects of, the HTTP communication.
213</t>
214<t>
215  <iref item="content negotiation"/>
216  <?rfc needLines="4"?>content negotiation
217  <list>
218    <t>
219      The mechanism for selecting the appropriate representation when
220      servicing a request. The representation of entities in any response
221      can be negotiated (including error responses).
222    </t>
223  </list>
224</t>
225<t>
226  <iref item="entity"/>
227  <?rfc needLines="4"?>entity
228  <list>
229    <t>
230      The information transferred as the payload of a request or
231      response. An entity consists of metadata in the form of
232      entity-header fields and content in the form of an entity-body.
233    </t>
234  </list>
235</t>
236<t>
237  <iref item="representation"/>
238  <?rfc needLines="4"?>representation
239  <list>
240    <t>
241      An entity included with a response that is subject to content
242      negotiation. There may exist multiple
243      representations associated with a particular response status.
244    </t>
245  </list>
246</t>
247<t>
248  <iref item="variant"/>
249  <?rfc needLines="4"?>variant
250  <list>
251    <t>
252      A resource may have one, or more than one, representation(s)
253      associated with it at any given instant. Each of these
254      representations is termed a "variant".  Use of the term "variant"
255      does not necessarily imply that the resource is subject to content
256      negotiation.
257    </t>
258  </list>
259</t>
260</section>
261
262<section title="Requirements" anchor="intro.requirements">
263<t>
264   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
265   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
266   document are to be interpreted as described in <xref target="RFC2119"/>.
267</t>
268<t>
269   An implementation is not compliant if it fails to satisfy one or more
270   of the "MUST" or "REQUIRED" level requirements for the protocols it
271   implements. An implementation that satisfies all the "MUST" or "REQUIRED"
272   level and all the "SHOULD" level requirements for its protocols is said
273   to be "unconditionally compliant"; one that satisfies all the "MUST"
274   level requirements but not all the "SHOULD" level requirements for its
275   protocols is said to be "conditionally compliant".
276</t>
277</section>
278
279<section title="Syntax Notation" anchor="notation">
280 
281 
282 
283 
284 
285 
286 
287<t>
288  This specification uses the ABNF syntax defined in Section 1.2 of <xref target="Part1"/> (which
289  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
290  <xref target="collected.abnf"/> shows the collected ABNF, with the list
291  rule expanded.
292</t>
293<t>
294  The following core rules are included by
295  reference, as defined in <xref target="RFC5234"/>, Appendix B.1:
296  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
297  DIGIT (decimal 0-9), DQUOTE (double quote),
298  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
299  OCTET (any 8-bit sequence of data), SP (space),
300  VCHAR (any visible USASCII character),
301  and WSP (whitespace).
302</t>
303
304<section title="Core Rules" anchor="core.rules">
305 
306 
307 
308 
309<t>
310  The core rules below are defined in Section 1.2.2 of <xref target="Part1"/>:
311</t>
312<figure><artwork type="abnf2616"><![CDATA[
313  quoted-string  = <quoted-string, defined in [Part1], Section 1.2.2>
314  token          = <token, defined in [Part1], Section 1.2.2>
315  word           = <word, defined in [Part1], Section 1.2.2>
316  OWS            = <OWS, defined in [Part1], Section 1.2.2>
317]]></artwork></figure>
318</section>
319
320<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
321 
322 
323 
324 
325 
326 
327 
328 
329 
330<t>
331  The ABNF rules below are defined in other parts:
332</t>
333<figure><artwork type="abnf2616"><![CDATA[
334  absolute-URI   = <absolute-URI, defined in [Part1], Section 2.6>
335  Content-Length = <Content-Length, defined in [Part1], Section 9.2>
336  header-field   = <header-field, defined in [Part1], Section 3.2>
337  partial-URI    = <partial-URI, defined in [Part1], Section 2.6>
338  qvalue         = <qvalue, defined in [Part1], Section 6.4>
339]]></artwork></figure>
340<figure><artwork type="abnf2616"><![CDATA[
341  Last-Modified  = <Last-Modified, defined in [Part4], Section 6.6>
342]]></artwork></figure>
343<figure><artwork type="abnf2616"><![CDATA[
344  Content-Range  = <Content-Range, defined in [Part5], Section 5.2>
345]]></artwork></figure>
346<figure><artwork type="abnf2616"><![CDATA[
347  Expires        = <Expires, defined in [Part6], Section 3.3>
348]]></artwork></figure>
349</section>
350
351</section>
352
353</section>
354
355<section title="Protocol Parameters" anchor="protocol.parameters">
356
357<section title="Character Sets" anchor="character.sets">
358<t>
359   HTTP uses the same definition of the term "character set" as that
360   described for MIME:
361</t>
362<t>
363   The term "character set" is used in this document to refer to a
364   method used with one or more tables to convert a sequence of octets
365   into a sequence of characters. Note that unconditional conversion in
366   the other direction is not required, in that not all characters may
367   be available in a given character set and a character set may provide
368   more than one sequence of octets to represent a particular character.
369   This definition is intended to allow various kinds of character
370   encoding, from simple single-table mappings such as US-ASCII to
371   complex table switching methods such as those that use ISO-2022's
372   techniques. However, the definition associated with a MIME character
373   set name MUST fully specify the mapping to be performed from octets
374   to characters. In particular, use of external profiling information
375   to determine the exact mapping is not permitted.
376</t>
377<t><list>
378  <t>
379    Note: This use of the term "character set" is more commonly
380    referred to as a "character encoding." However, since HTTP and
381    MIME share the same registry, it is important that the terminology
382    also be shared.
383  </t>
384</list></t>
385<t anchor="rule.charset">
386 
387   HTTP character sets are identified by case-insensitive tokens. The
388   complete set of tokens is defined by the IANA Character Set registry
389   (<eref target="http://www.iana.org/assignments/character-sets"/>).
390</t>
391<figure><iref primary="true" item="Grammar" subitem="charset"/><artwork type="abnf2616"><![CDATA[
392  charset = token
393]]></artwork></figure>
394<t>
395   Although HTTP allows an arbitrary token to be used as a charset
396   value, any token that has a predefined value within the IANA
397   Character Set registry MUST represent the character set defined
398   by that registry. Applications SHOULD limit their use of character
399   sets to those defined by the IANA registry.
400</t>
401<t>
402   HTTP uses charset in two contexts: within an Accept-Charset request
403   header (in which the charset value is an unquoted token) and as the
404   value of a parameter in a Content-Type header (within a request or
405   response), in which case the parameter value of the charset parameter
406   may be quoted.
407</t>
408<t>
409   Implementors should be aware of IETF character set requirements <xref target="RFC3629"/>
410   <xref target="RFC2277"/>.
411</t>
412
413<section title="Missing Charset" anchor="missing.charset">
414<t>
415   Some HTTP/1.0 software has interpreted a Content-Type header without
416   charset parameter incorrectly to mean "recipient should guess."
417   Senders wishing to defeat this behavior MAY include a charset
418   parameter even when the charset is ISO-8859-1 (<xref target="ISO-8859-1"/>) and SHOULD do so when
419   it is known that it will not confuse the recipient.
420</t>
421<t>
422   Unfortunately, some older HTTP/1.0 clients did not deal properly with
423   an explicit charset parameter. HTTP/1.1 recipients MUST respect the
424   charset label provided by the sender; and those user agents that have
425   a provision to "guess" a charset MUST use the charset from the
426   content-type field if they support that charset, rather than the
427   recipient's preference, when initially displaying a document. See
428   <xref target="canonicalization.and.text.defaults"/>.
429</t>
430</section>
431</section>
432
433<section title="Content Codings" anchor="content.codings">
434 
435<t>
436   Content coding values indicate an encoding transformation that has
437   been or can be applied to an entity. Content codings are primarily
438   used to allow a document to be compressed or otherwise usefully
439   transformed without losing the identity of its underlying media type
440   and without loss of information. Frequently, the entity is stored in
441   coded form, transmitted directly, and only decoded by the recipient.
442</t>
443<figure><iref primary="true" item="Grammar" subitem="content-coding"/><artwork type="abnf2616"><![CDATA[
444  content-coding   = token
445]]></artwork></figure>
446<t>
447   All content-coding values are case-insensitive. HTTP/1.1 uses
448   content-coding values in the Accept-Encoding (<xref target="header.accept-encoding"/>) and
449   Content-Encoding (<xref target="header.content-encoding"/>) header fields. Although the value
450   describes the content-coding, what is more important is that it
451   indicates what decoding mechanism will be required to remove the
452   encoding.
453</t>
454<t>
455   compress<iref item="compress (Coding Format)"/><iref item="Coding Format" subitem="compress"/>
456  <list>
457    <t>
458      See Section 6.2.2.1 of <xref target="Part1"/>.
459    </t>
460  </list>
461</t>
462<t>
463   deflate<iref item="deflate (Coding Format)"/><iref item="Coding Format" subitem="deflate"/>
464  <list>
465    <t>
466      See Section 6.2.2.2 of <xref target="Part1"/>.
467    </t>
468  </list>
469</t>
470<t>
471   gzip<iref item="gzip (Coding Format)"/><iref item="Coding Format" subitem="gzip"/>
472  <list>
473    <t>
474      See Section 6.2.2.3 of <xref target="Part1"/>.
475    </t>
476  </list>
477</t>
478<t>
479   identity<iref item="identity (Coding Format)"/><iref item="Coding Format" subitem="identity"/>
480  <list><t>
481        The default (identity) encoding; the use of no transformation
482        whatsoever. This content-coding is used only in the Accept-Encoding
483        header, and SHOULD NOT  be used in the Content-Encoding
484        header.
485  </t></list>
486</t>
487
488<section title="Content Coding Registry" anchor="content.coding.registry">
489<t>
490   The HTTP Content Coding Registry defines the name space for the content
491   coding names.
492</t>
493<t>
494   Registrations MUST include the following fields:
495   <list style="symbols">
496     <t>Name</t>
497     <t>Description</t>
498     <t>Pointer to specification text</t>
499   </list>
500</t>
501<t>
502   Names of content codings MUST NOT overlap with names of transfer codings
503   (Section 6.2 of <xref target="Part1"/>), unless the encoding transformation is identical (as it
504   is the case for the compression codings defined in
505   Section 6.2.2 of <xref target="Part1"/>).
506</t>
507<t>
508   Values to be added to this name space require expert review and a specification
509   (see "Expert Review" and "Specification Required" in
510   Section 4.1 of <xref target="RFC5226"/>), and MUST
511   conform to the purpose of content coding defined in this section.
512</t>
513<t>
514   The registry itself is maintained at
515   <eref target="http://www.iana.org/assignments/http-parameters"/>.
516</t>
517</section>
518
519</section>
520
521<section title="Media Types" anchor="media.types">
522 
523 
524 
525<t>
526   HTTP uses Internet Media Types <xref target="RFC2046"/> in the Content-Type (<xref target="header.content-type"/>)
527   and Accept (<xref target="header.accept"/>) header fields in order to provide
528   open and extensible data typing and type negotiation.
529</t>
530<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[
531  media-type = type "/" subtype *( OWS ";" OWS parameter )
532  type       = token
533  subtype    = token
534]]></artwork></figure>
535<t anchor="rule.parameter">
536 
537 
538 
539   Parameters MAY follow the type/subtype in the form of attribute/value
540   pairs.
541</t>
542<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[
543  parameter      = attribute "=" value
544  attribute      = token
545  value          = word
546]]></artwork></figure>
547<t>
548   The type, subtype, and parameter attribute names are case-insensitive.
549   Parameter values might or might not be case-sensitive, depending on the
550   semantics of the parameter name.  The presence or absence of a parameter might
551   be significant to the processing of a media-type, depending on its
552   definition within the media type registry.
553</t>
554<t>
555   A parameter value that matches the <xref target="core.rules" format="none">token</xref> production may be
556   transmitted as either a token or within a quoted-string. The quoted and
557   unquoted values are equivalent.
558</t>
559<t>
560   Note that some older HTTP applications do not recognize media type
561   parameters. When sending data to older HTTP applications,
562   implementations SHOULD only use media type parameters when they are
563   required by that type/subtype definition.
564</t>
565<t>
566   Media-type values are registered with the Internet Assigned Number
567   Authority (IANA). The media type registration process is
568   outlined in <xref target="RFC4288"/>. Use of non-registered media types is
569   discouraged.
570</t>
571
572<section title="Canonicalization and Text Defaults" anchor="canonicalization.and.text.defaults">
573<t>
574   Internet media types are registered with a canonical form. An
575   entity-body transferred via HTTP messages MUST be represented in the
576   appropriate canonical form prior to its transmission except for
577   "text" types, as defined in the next paragraph.
578</t>
579<t>
580   When in canonical form, media subtypes of the "text" type use CRLF as
581   the text line break. HTTP relaxes this requirement and allows the
582   transport of text media with plain CR or LF alone representing a line
583   break when it is done consistently for an entire entity-body. HTTP
584   applications MUST accept CRLF, bare CR, and bare LF as being
585   representative of a line break in text media received via HTTP. In
586   addition, if the text is represented in a character set that does not
587   use octets 13 and 10 for CR and LF respectively, as is the case for
588   some multi-byte character sets, HTTP allows the use of whatever octet
589   sequences are defined by that character set to represent the
590   equivalent of CR and LF for line breaks. This flexibility regarding
591   line breaks applies only to text media in the entity-body; a bare CR
592   or LF MUST NOT be substituted for CRLF within any of the HTTP control
593   structures (such as header fields and multipart boundaries).
594</t>
595<t>
596   If an entity-body is encoded with a content-coding, the underlying
597   data MUST be in a form defined above prior to being encoded.
598</t>
599<t>
600   The "charset" parameter is used with some media types to define the
601   character set (<xref target="character.sets"/>) of the data. When no explicit charset
602   parameter is provided by the sender, media subtypes of the "text"
603   type are defined to have a default charset value of "ISO-8859-1" when
604   received via HTTP. Data in character sets other than "ISO-8859-1" or
605   its subsets MUST be labeled with an appropriate charset value. See
606   <xref target="missing.charset"/> for compatibility problems.
607</t>
608</section>
609
610<section title="Multipart Types" anchor="multipart.types">
611<t>
612   MIME provides for a number of "multipart" types -- encapsulations of
613   one or more entities within a single message-body. All multipart
614   types share a common syntax, as defined in Section 5.1.1 of <xref target="RFC2046"/>,
615   and MUST include a boundary parameter as part of the media type
616   value. The message body is itself a protocol element and MUST
617   therefore use only CRLF to represent line breaks between body-parts.
618   Unlike in RFC 2046, the epilogue of any multipart message MUST be
619   empty; HTTP applications MUST NOT transmit the epilogue (even if the
620   original multipart contains an epilogue). These restrictions exist in
621   order to preserve the self-delimiting nature of a multipart message-body,
622   wherein the "end" of the message-body is indicated by the
623   ending multipart boundary.
624</t>
625<t>
626   In general, HTTP treats a multipart message-body no differently than
627   any other media type: strictly as payload. The one exception is the
628   "multipart/byteranges" type (Appendix A of <xref target="Part5"/>) when it appears in a 206
629   (Partial Content) response.
630   <!-- jre: re-insert removed text pointing to caching? -->
631   In all
632   other cases, an HTTP user agent SHOULD follow the same or similar
633   behavior as a MIME user agent would upon receipt of a multipart type.
634   The MIME header fields within each body-part of a multipart message-body
635   do not have any significance to HTTP beyond that defined by
636   their MIME semantics.
637</t>
638<t>
639   In general, an HTTP user agent SHOULD follow the same or similar
640   behavior as a MIME user agent would upon receipt of a multipart type.
641   If an application receives an unrecognized multipart subtype, the
642   application MUST treat it as being equivalent to "multipart/mixed".
643</t>
644<t><list>
645  <t>
646    Note: The "multipart/form-data" type has been specifically defined
647    for carrying form data suitable for processing via the POST
648    request method, as described in <xref target="RFC2388"/>.
649  </t>
650</list></t>
651</section>
652</section>
653
654<section title="Language Tags" anchor="language.tags">
655 
656<t>
657   A language tag, as defined in <xref target="RFC5646"/>, identifies a
658   natural language spoken, written, or otherwise conveyed by human beings for
659   communication of information to other human beings. Computer languages are
660   explicitly excluded. HTTP uses language tags within the Accept-Language and
661   Content-Language fields.
662</t>
663<t>
664   In summary, a language tag is composed of one or more parts: A primary
665   language subtag followed by a possibly empty series of subtags:
666</t>
667<figure><iref primary="true" item="Grammar" subitem="language-tag"/><artwork type="abnf2616"><![CDATA[
668  language-tag = <Language-Tag, defined in [RFC5646], Section 2.1>
669]]></artwork></figure>
670<t>
671   White space is not allowed within the tag and all tags are case-insensitive.
672   The name space of language subtags is administered by the IANA (see
673   <eref target="http://www.iana.org/assignments/language-subtag-registry"/>).
674</t>
675<figure>
676  <preamble>Example tags include:</preamble>
677<artwork type="example"><![CDATA[
678  en, en-US, es-419, az-Arab, x-pig-latin, man-Nkoo-GN
679]]></artwork>
680</figure>
681<t>
682   See <xref target="RFC5646"/> for further information.
683</t>
684</section>
685</section>
686
687<section title="Entity" anchor="entity">
688<t>
689   Request and Response messages MAY transfer an entity if not otherwise
690   restricted by the request method or response status code. An entity
691   consists of entity-header fields and an entity-body, although some
692   responses will only include the entity-headers.
693</t>
694<t>
695   In this section, both sender and recipient refer to either the client
696   or the server, depending on who sends and who receives the entity.
697</t>
698
699<section title="Entity Header Fields" anchor="entity.header.fields">
700 
701 
702<t>
703   Entity-header fields define metainformation about the entity-body or,
704   if no body is present, about the resource identified by the request.
705</t>
706<figure><iref primary="true" item="Grammar" subitem="entity-header"/><iref primary="true" item="Grammar" subitem="extension-header"/><artwork type="abnf2616"><![CDATA[
707  entity-header  = Content-Encoding         ; Section 5.5
708                 / Content-Language         ; Section 5.6
709                 / Content-Length           ; [Part1], Section 9.2
710                 / Content-Location         ; Section 5.7
711                 / Content-MD5              ; Section 5.8
712                 / Content-Range            ; [Part5], Section 5.2
713                 / Content-Type             ; Section 5.9
714                 / Expires                  ; [Part6], Section 3.3
715                 / Last-Modified            ; [Part4], Section 6.6
716                 / extension-header
717 
718  extension-header = header-field
719]]></artwork></figure>
720<t>
721   The extension-header mechanism allows additional entity-header fields
722   to be defined without changing the protocol, but these fields cannot
723   be assumed to be recognizable by the recipient. Unrecognized header
724   fields SHOULD be ignored by the recipient and MUST be forwarded by
725   transparent proxies.
726</t>
727</section>
728
729<section title="Entity Body" anchor="entity.body">
730 
731<t>
732   The entity-body (if any) sent with an HTTP request or response is in
733   a format and encoding defined by the entity-header fields.
734</t>
735<figure><iref primary="true" item="Grammar" subitem="entity-body"/><artwork type="abnf2616"><![CDATA[
736  entity-body    = *OCTET
737]]></artwork></figure>
738<t>
739   An entity-body is only present in a message when a message-body is
740   present, as described in Section 3.3 of <xref target="Part1"/>. The entity-body is obtained
741   from the message-body by decoding any Transfer-Encoding that might
742   have been applied to ensure safe and proper transfer of the message.
743</t>
744
745<section title="Type" anchor="type">
746<t>
747   When an entity-body is included with a message, the data type of that
748   body is determined via the header fields Content-Type and Content-Encoding.
749   These define a two-layer, ordered encoding model:
750</t>
751<figure><artwork type="example"><![CDATA[
752  entity-body := Content-Encoding( Content-Type( data ) )
753]]></artwork></figure>
754<t>
755   Content-Type specifies the media type of the underlying data. Any HTTP/1.1
756   message containing an entity-body SHOULD include a Content-Type header
757   field defining the media type of that body, unless that information is
758   unknown.
759</t>
760<t>   
761   If the Content-Type header field is not present, it indicates that
762   the sender does not know the media type of the data; recipients MAY
763   either assume that it is "application/octet-stream" (<xref target="RFC2046"/>, Section 4.5.1)
764   or examine the content to determine its type.
765</t>
766<t>
767   In practice, currently-deployed servers sometimes provide a Content-Type
768   header which does not correctly convey the intended interpretation of the
769   content sent, with the result that some clients will examine the response
770   body's content and override the specified type.
771</t>
772<t>
773   Client that do so risk drawing incorrect conclusions, which may expose
774   additional security risks (e.g., "privilege escalation"). Implementers are
775   encouraged to provide a means of disabling such "content sniffing" when it
776   is used.
777</t>
778<t>
779   Content-Encoding may be used to indicate any additional content
780   codings applied to the data, usually for the purpose of data
781   compression, that are a property of the requested resource.  There is
782   no default encoding.
783</t>
784</section>
785   
786<section title="Entity Length" anchor="entity.length">
787<t>
788   The entity-length of a message is the length of the message-body
789   before any transfer-codings have been applied. Section 3.4 of <xref target="Part1"/> defines
790   how the transfer-length of a message-body is determined.
791</t>
792</section>
793</section>
794</section>
795
796<section title="Content Negotiation" anchor="content.negotiation">
797<t>
798   HTTP responses include a representation which contains information for
799   interpretation, whether by a human user or for further processing.
800   Often, the server has different ways of representing the
801   same information; for example, in different formats, languages,
802   or using different character encodings.
803</t>
804<t>
805   HTTP clients and their users might have different or variable
806   capabilities, characteristics or preferences which would influence
807   which representation, among those available from the server,
808   would be best for the server to deliver. For this reason, HTTP
809   provides mechanisms for "content negotiation" -- a process of
810   allowing selection of a representation of a given resource,
811   when more than one is available.
812</t>
813<t>
814   This specification defines two patterns of content negotiation;
815   "server-driven", where the server selects the representation based
816   upon the client's stated preferences, and "agent-driven" negotiation,
817   where the server provides a list of representations for the client to
818   choose from, based upon their metadata. In addition,  there are
819   other patterns: some applications use an "active content" pattern,
820   where the server returns active content which runs on the client
821   and, based on client available parameters, selects additional
822   resources to invoke. "Transparent Content Negotiation" (<xref target="RFC2295"/>)
823   has also been proposed.
824</t>
825<t>
826   These patterns are all widely used, and have trade-offs in applicability
827   and practicality. In particular, when the number of preferences or
828   capabilities to be expressed by a client are large (such as when many
829   different formats are supported by a user-agent), server-driven
830   negotiation becomes unwieldy, and may not be appropriate. Conversely,
831   when the number of representations to choose from is very large,
832   agent-driven negotiation may not be appropriate.
833</t>
834<t>
835   Note that in all cases, the supplier of representations has the
836   responsibility for determining which representations might be
837   considered to be the "same information".
838</t>
839
840<section title="Server-driven Negotiation" anchor="server-driven.negotiation">
841<t>
842   If the selection of the best representation for a response is made by
843   an algorithm located at the server, it is called server-driven
844   negotiation. Selection is based on the available representations of
845   the response (the dimensions over which it can vary; e.g., language,
846   content-coding, etc.) and the contents of particular header fields in
847   the request message or on other information pertaining to the request
848   (such as the network address of the client).
849</t>
850<t>
851   Server-driven negotiation is advantageous when the algorithm for
852   selecting from among the available representations is difficult to
853   describe to the user agent, or when the server desires to send its
854   "best guess" to the client along with the first response (hoping to
855   avoid the round-trip delay of a subsequent request if the "best
856   guess" is good enough for the user). In order to improve the server's
857   guess, the user agent MAY include request header fields (Accept,
858   Accept-Language, Accept-Encoding, etc.) which describe its
859   preferences for such a response.
860</t>
861<t>
862   Server-driven negotiation has disadvantages:
863  <list style="numbers">
864    <t>
865         It is impossible for the server to accurately determine what
866         might be "best" for any given user, since that would require
867         complete knowledge of both the capabilities of the user agent
868         and the intended use for the response (e.g., does the user want
869         to view it on screen or print it on paper?).
870    </t>
871    <t>
872         Having the user agent describe its capabilities in every
873         request can be both very inefficient (given that only a small
874         percentage of responses have multiple representations) and a
875         potential violation of the user's privacy.
876    </t>
877    <t>
878         It complicates the implementation of an origin server and the
879         algorithms for generating responses to a request.
880    </t>
881    <t>
882         It may limit a public cache's ability to use the same response
883         for multiple user's requests.
884    </t>
885  </list>
886</t>
887<t>
888   HTTP/1.1 includes the following request-header fields for enabling
889   server-driven negotiation through description of user agent
890   capabilities and user preferences: Accept (<xref target="header.accept"/>), Accept-Charset
891   (<xref target="header.accept-charset"/>), Accept-Encoding (<xref target="header.accept-encoding"/>), Accept-Language
892   (<xref target="header.accept-language"/>), and User-Agent (Section 9.9 of <xref target="Part2"/>).
893   However, an origin server is not limited to these dimensions and MAY vary
894   the response based on any aspect of the request, including information
895   outside the request-header fields or within extension header fields
896   not defined by this specification.
897</t>
898<t><list>
899  <t>
900    Note: In practice, User-Agent based negotiation is fragile,
901    because new clients might not be recognized.
902  </t>
903</list></t>
904<t>
905   The Vary header field (Section 3.5 of <xref target="Part6"/>) can be used to express the parameters the
906   server uses to select a representation that is subject to server-driven
907   negotiation.
908</t>
909</section>
910
911<section title="Agent-driven Negotiation" anchor="agent-driven.negotiation">
912<t>
913   With agent-driven negotiation, selection of the best representation
914   for a response is performed by the user agent after receiving an
915   initial response from the origin server. Selection is based on a list
916   of the available representations of the response included within the
917   header fields or entity-body of the initial response, with each
918   representation identified by its own URI. Selection from among the
919   representations may be performed automatically (if the user agent is
920   capable of doing so) or manually by the user selecting from a
921   generated (possibly hypertext) menu.
922</t>
923<t>
924   Agent-driven negotiation is advantageous when the response would vary
925   over commonly-used dimensions (such as type, language, or encoding),
926   when the origin server is unable to determine a user agent's
927   capabilities from examining the request, and generally when public
928   caches are used to distribute server load and reduce network usage.
929</t>
930<t>
931   Agent-driven negotiation suffers from the disadvantage of needing a
932   second request to obtain the best alternate representation. This
933   second request is only efficient when caching is used. In addition,
934   this specification does not define any mechanism for supporting
935   automatic selection, though it also does not prevent any such
936   mechanism from being developed as an extension and used within
937   HTTP/1.1.
938</t>
939<t>
940   This specification defines the 300 (Multiple Choices) and 406 (Not Acceptable)
941   status codes for enabling agent-driven negotiation when the server is
942   unwilling or unable to provide a varying response using server-driven
943   negotiation.
944</t>
945</section>
946</section>
947
948<section title="Header Field Definitions" anchor="header.fields">
949<t>
950   This section defines the syntax and semantics of HTTP/1.1 header fields
951   related to the payload of messages.
952</t>
953<t>
954   For entity-header fields, both sender and recipient refer to either the
955   client or the server, depending on who sends and who receives the entity.
956</t>
957
958<section title="Accept" anchor="header.accept">
959  <iref primary="true" item="Accept header"/>
960  <iref primary="true" item="Headers" subitem="Accept"/>
961 
962 
963 
964 
965 
966<t>
967   The "Accept" request-header field can be used by user agents to specify
968   response media types that are acceptable. Accept headers can be used to
969   indicate that the request is specifically limited to a small set of desired
970   types, as in the case of a request for an in-line image.
971</t>
972<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[
973  Accept   = "Accept" ":" OWS Accept-v
974  Accept-v = #( media-range [ accept-params ] )
975 
976  media-range    = ( "*/*"
977                   / ( type "/" "*" )
978                   / ( type "/" subtype )
979                   ) *( OWS ";" OWS parameter )
980  accept-params  = OWS ";" OWS "q=" qvalue *( accept-ext )
981  accept-ext     = OWS ";" OWS token
982                   [ "=" word ]
983]]></artwork></figure>
984<t>
985   The asterisk "*" character is used to group media types into ranges,
986   with "*/*" indicating all media types and "type/*" indicating all
987   subtypes of that type. The media-range MAY include media type
988   parameters that are applicable to that range.
989</t>
990<t>
991   Each media-range MAY be followed by one or more accept-params,
992   beginning with the "q" parameter for indicating a relative quality
993   factor. The first "q" parameter (if any) separates the media-range
994   parameter(s) from the accept-params. Quality factors allow the user
995   or user agent to indicate the relative degree of preference for that
996   media-range, using the qvalue scale from 0 to 1 (Section 6.4 of <xref target="Part1"/>). The
997   default value is q=1.
998</t>
999<t><list>
1000  <t>
1001    Note: Use of the "q" parameter name to separate media type
1002    parameters from Accept extension parameters is due to historical
1003    practice. Although this prevents any media type parameter named
1004    "q" from being used with a media range, such an event is believed
1005    to be unlikely given the lack of any "q" parameters in the IANA
1006    media type registry and the rare usage of any media type
1007    parameters in Accept. Future media types are discouraged from
1008    registering any parameter named "q".
1009  </t>
1010</list></t>
1011<t>
1012   The example
1013</t>
1014<figure><artwork type="example"><![CDATA[
1015  Accept: audio/*; q=0.2, audio/basic
1016]]></artwork></figure>
1017<t>
1018   SHOULD be interpreted as "I prefer audio/basic, but send me any audio
1019   type if it is the best available after an 80% mark-down in quality."
1020</t>
1021<t>
1022   If no Accept header field is present, then it is assumed that the
1023   client accepts all media types. If an Accept header field is present,
1024   and if the server cannot send a response which is acceptable
1025   according to the combined Accept field value, then the server SHOULD
1026   send a 406 (Not Acceptable) response.
1027</t>
1028<t>
1029   A more elaborate example is
1030</t>
1031<figure><artwork type="example"><![CDATA[
1032  Accept: text/plain; q=0.5, text/html,
1033          text/x-dvi; q=0.8, text/x-c
1034]]></artwork></figure>
1035<t>
1036   Verbally, this would be interpreted as "text/html and text/x-c are
1037   the preferred media types, but if they do not exist, then send the
1038   text/x-dvi entity, and if that does not exist, send the text/plain
1039   entity."
1040</t>
1041<t>
1042   Media ranges can be overridden by more specific media ranges or
1043   specific media types. If more than one media range applies to a given
1044   type, the most specific reference has precedence. For example,
1045</t>
1046<figure><artwork type="example"><![CDATA[
1047  Accept: text/*, text/html, text/html;level=1, */*
1048]]></artwork></figure>
1049<t>
1050   have the following precedence:
1051   <list style="numbers">
1052    <t>text/html;level=1</t>
1053    <t>text/html</t>
1054    <t>text/*</t>
1055    <t>*/*</t>
1056   </list>
1057</t>
1058<t>
1059   The media type quality factor associated with a given type is
1060   determined by finding the media range with the highest precedence
1061   which matches that type. For example,
1062</t>
1063<figure><artwork type="example"><![CDATA[
1064  Accept: text/*;q=0.3, text/html;q=0.7, text/html;level=1,
1065          text/html;level=2;q=0.4, */*;q=0.5
1066]]></artwork></figure>
1067<t>
1068   would cause the following values to be associated:
1069</t>
1070<texttable align="left">
1071  <ttcol>Media Type</ttcol><ttcol>Quality Value</ttcol>
1072  <c>text/html;level=1</c>    <c>1</c>
1073  <c>text/html</c>            <c>0.7</c>
1074  <c>text/plain</c>           <c>0.3</c>
1075  <c>image/jpeg</c>           <c>0.5</c>
1076  <c>text/html;level=2</c>    <c>0.4</c>
1077  <c>text/html;level=3</c>    <c>0.7</c>
1078</texttable>
1079<t>
1080      Note: A user agent might be provided with a default set of quality
1081      values for certain media ranges. However, unless the user agent is
1082      a closed system which cannot interact with other rendering agents,
1083      this default set ought to be configurable by the user.
1084</t>
1085</section>
1086
1087<section title="Accept-Charset" anchor="header.accept-charset">
1088  <iref primary="true" item="Accept-Charset header"/>
1089  <iref primary="true" item="Headers" subitem="Accept-Charset"/>
1090 
1091 
1092<t>
1093   The "Accept-Charset" request-header field can be used by user agents to
1094   indicate what response character sets are acceptable. This field allows
1095   clients capable of understanding more comprehensive or special-purpose
1096   character sets to signal that capability to a server which is capable of
1097   representing documents in those character sets.
1098</t>
1099<figure><iref primary="true" item="Grammar" subitem="Accept-Charset"/><iref primary="true" item="Grammar" subitem="Accept-Charset-v"/><artwork type="abnf2616"><![CDATA[
1100  Accept-Charset   = "Accept-Charset" ":" OWS
1101          Accept-Charset-v
1102  Accept-Charset-v = 1#( ( charset / "*" )
1103                         [ OWS ";" OWS "q=" qvalue ] )
1104]]></artwork></figure>
1105<t>
1106   Character set values are described in <xref target="character.sets"/>. Each charset MAY
1107   be given an associated quality value which represents the user's
1108   preference for that charset. The default value is q=1. An example is
1109</t>
1110<figure><artwork type="example"><![CDATA[
1111  Accept-Charset: iso-8859-5, unicode-1-1;q=0.8
1112]]></artwork></figure>
1113<t>
1114   The special value "*", if present in the Accept-Charset field,
1115   matches every character set (including ISO-8859-1) which is not
1116   mentioned elsewhere in the Accept-Charset field. If no "*" is present
1117   in an Accept-Charset field, then all character sets not explicitly
1118   mentioned get a quality value of 0, except for ISO-8859-1, which gets
1119   a quality value of 1 if not explicitly mentioned.
1120</t>
1121<t>
1122   If no Accept-Charset header is present, the default is that any
1123   character set is acceptable. If an Accept-Charset header is present,
1124   and if the server cannot send a response which is acceptable
1125   according to the Accept-Charset header, then the server SHOULD send
1126   an error response with the 406 (Not Acceptable) status code, though
1127   the sending of an unacceptable response is also allowed.
1128</t>
1129</section>
1130
1131<section title="Accept-Encoding" anchor="header.accept-encoding">
1132  <iref primary="true" item="Accept-Encoding header"/>
1133  <iref primary="true" item="Headers" subitem="Accept-Encoding"/>
1134 
1135 
1136 
1137<t>
1138   The "Accept-Encoding" request-header field can be used by user agents to
1139   indicate what response content-codings (<xref target="content.codings"/>)
1140   are acceptable in the response.
1141</t>
1142<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[
1143  Accept-Encoding    = "Accept-Encoding" ":" OWS
1144                     Accept-Encoding-v
1145  Accept-Encoding-v  =
1146                     #( codings [ OWS ";" OWS "q=" qvalue ] )
1147  codings            = ( content-coding / "*" )
1148]]></artwork></figure>
1149<t>
1150   Each codings value MAY be given an associated quality value which
1151   represents the preference for that encoding. The default value is q=1.
1152</t>
1153<t>
1154   Examples of its use are:
1155</t>
1156<figure><artwork type="example"><![CDATA[
1157  Accept-Encoding: compress, gzip
1158  Accept-Encoding:
1159  Accept-Encoding: *
1160  Accept-Encoding: compress;q=0.5, gzip;q=1.0
1161  Accept-Encoding: gzip;q=1.0, identity; q=0.5, *;q=0
1162]]></artwork></figure>
1163<t>
1164   A server tests whether a content-coding is acceptable, according to
1165   an Accept-Encoding field, using these rules:
1166  <list style="numbers">
1167      <t>If the content-coding is one of the content-codings listed in
1168         the Accept-Encoding field, then it is acceptable, unless it is
1169         accompanied by a qvalue of 0. (As defined in Section 6.4 of <xref target="Part1"/>, a
1170         qvalue of 0 means "not acceptable.")</t>
1171
1172      <t>The special "*" symbol in an Accept-Encoding field matches any
1173         available content-coding not explicitly listed in the header
1174         field.</t>
1175
1176      <t>If multiple content-codings are acceptable, then the acceptable
1177         content-coding with the highest non-zero qvalue is preferred.</t>
1178
1179      <t>The "identity" content-coding is always acceptable, unless
1180         specifically refused because the Accept-Encoding field includes
1181         "identity;q=0", or because the field includes "*;q=0" and does
1182         not explicitly include the "identity" content-coding. If the
1183         Accept-Encoding field-value is empty, then only the "identity"
1184         encoding is acceptable.</t>
1185  </list>
1186</t>
1187<t>
1188   If an Accept-Encoding field is present in a request, and if the
1189   server cannot send a response which is acceptable according to the
1190   Accept-Encoding header, then the server SHOULD send an error response
1191   with the 406 (Not Acceptable) status code.
1192</t>
1193<t>
1194   If no Accept-Encoding field is present in a request, the server MAY
1195   assume that the client will accept any content coding. In this case,
1196   if "identity" is one of the available content-codings, then the
1197   server SHOULD use the "identity" content-coding, unless it has
1198   additional information that a different content-coding is meaningful
1199   to the client.
1200</t>
1201<t><list>
1202  <t>
1203    Note: If the request does not include an Accept-Encoding field,
1204    and if the "identity" content-coding is unavailable, then
1205    content-codings commonly understood by HTTP/1.0 clients (i.e.,
1206    "gzip" and "compress") are preferred; some older clients
1207    improperly display messages sent with other content-codings.  The
1208    server might also make this decision based on information about
1209    the particular user-agent or client.
1210  </t>
1211</list></t>
1212<t><list>
1213  <t>
1214    Note: Most HTTP/1.0 applications do not recognize or obey qvalues
1215    associated with content-codings. This means that qvalues will not
1216    work and are not permitted with x-gzip or x-compress.
1217  </t>
1218</list></t>
1219</section>
1220
1221<section title="Accept-Language" anchor="header.accept-language">
1222  <iref primary="true" item="Accept-Language header"/>
1223  <iref primary="true" item="Headers" subitem="Accept-Language"/>
1224 
1225 
1226 
1227<t>
1228   The "Accept-Language" request-header field can be used by user agents to
1229   indicate the set of natural languages that are preferred in the response.
1230   Language tags are defined in <xref target="language.tags"/>.
1231</t>
1232<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[
1233  Accept-Language   = "Accept-Language" ":" OWS
1234                    Accept-Language-v
1235  Accept-Language-v =
1236                    1#( language-range [ OWS ";" OWS "q=" qvalue ] )
1237  language-range    =
1238            <language-range, defined in [RFC4647], Section 2.1>
1239]]></artwork></figure>
1240<t>
1241   Each language-range can be given an associated quality value which
1242   represents an estimate of the user's preference for the languages
1243   specified by that range. The quality value defaults to "q=1". For
1244   example,
1245</t>
1246<figure><artwork type="example"><![CDATA[
1247  Accept-Language: da, en-gb;q=0.8, en;q=0.7
1248]]></artwork></figure>
1249<t>
1250   would mean: "I prefer Danish, but will accept British English and
1251   other types of English."
1252   (see also Section 2.3 of <xref target="RFC4647"/>)
1253</t>
1254<t>
1255   For matching, Section 3 of <xref target="RFC4647"/> defines
1256   several matching schemes. Implementations can offer the most appropriate
1257   matching scheme for their requirements.
1258</t>
1259<t><list>
1260  <t>
1261    Note: The "Basic Filtering" scheme (<xref target="RFC4647"/>, Section 3.3.1) is identical to the matching scheme that was
1262    previously defined in Section 14.4 of <xref target="RFC2616"/>.
1263  </t>
1264</list></t>
1265<t>
1266   It might be contrary to the privacy expectations of the user to send
1267   an Accept-Language header with the complete linguistic preferences of
1268   the user in every request. For a discussion of this issue, see
1269   <xref target="privacy.issues.connected.to.accept.headers"/>.
1270</t>
1271<t>
1272   As intelligibility is highly dependent on the individual user, it is
1273   recommended that client applications make the choice of linguistic
1274   preference available to the user. If the choice is not made
1275   available, then the Accept-Language header field MUST NOT be given in
1276   the request.
1277</t>
1278<t><list>
1279  <t>
1280    Note: When making the choice of linguistic preference available to
1281    the user, we remind implementors of  the fact that users are not
1282    familiar with the details of language matching as described above,
1283    and should provide appropriate guidance. As an example, users
1284    might assume that on selecting "en-gb", they will be served any
1285    kind of English document if British English is not available. A
1286    user agent might suggest in such a case to add "en" to get the
1287    best matching behavior.
1288  </t>
1289</list></t>
1290</section>
1291
1292<section title="Content-Encoding" anchor="header.content-encoding">
1293  <iref primary="true" item="Content-Encoding header"/>
1294  <iref primary="true" item="Headers" subitem="Content-Encoding"/>
1295 
1296 
1297<t>
1298   The "Content-Encoding" entity-header field indicates what content-codings
1299   have been applied to the entity-body, and thus what decoding mechanisms
1300   must be applied in order to obtain the media-type referenced by the
1301   Content-Type header field. Content-Encoding is primarily used to allow a
1302   document to be compressed without losing the identity of its underlying
1303   media type.
1304</t>
1305<figure><iref primary="true" item="Grammar" subitem="Content-Encoding"/><iref primary="true" item="Grammar" subitem="Content-Encoding-v"/><artwork type="abnf2616"><![CDATA[
1306  Content-Encoding   = "Content-Encoding" ":" OWS Content-Encoding-v
1307  Content-Encoding-v = 1#content-coding
1308]]></artwork></figure>
1309<t>
1310   Content codings are defined in <xref target="content.codings"/>. An example of its use is
1311</t>
1312<figure><artwork type="example"><![CDATA[
1313  Content-Encoding: gzip
1314]]></artwork></figure>
1315<t>
1316   The content-coding is a characteristic of the entity identified by
1317   the Effective Request URI (Section 4.3 of <xref target="Part1"/>). Typically, the entity-body is stored with this
1318   encoding and is only decoded before rendering or analogous usage.
1319   However, a non-transparent proxy MAY modify the content-coding if the
1320   new coding is known to be acceptable to the recipient, unless the
1321   "no-transform" cache-control directive is present in the message.
1322</t>
1323<t>
1324   If the content-coding of an entity is not "identity", then the
1325   response MUST include a Content-Encoding entity-header (<xref target="header.content-encoding"/>)
1326   that lists the non-identity content-coding(s) used.
1327</t>
1328<t>
1329   If the content-coding of an entity in a request message is not
1330   acceptable to the origin server, the server SHOULD respond with a
1331   status code of 415 (Unsupported Media Type).
1332</t>
1333<t>
1334   If multiple encodings have been applied to an entity, the content
1335   codings MUST be listed in the order in which they were applied.
1336   Additional information about the encoding parameters MAY be provided
1337   by other entity-header fields not defined by this specification.
1338</t>
1339</section>
1340
1341<section title="Content-Language" anchor="header.content-language">
1342  <iref primary="true" item="Content-Language header"/>
1343  <iref primary="true" item="Headers" subitem="Content-Language"/>
1344 
1345 
1346<t>
1347   The "Content-Language" entity-header field describes the natural
1348   language(s) of the intended audience for the entity. Note that this might
1349   not be equivalent to all the languages used within the entity-body.
1350</t>
1351<figure><iref primary="true" item="Grammar" subitem="Content-Language"/><iref primary="true" item="Grammar" subitem="Content-Language-v"/><artwork type="abnf2616"><![CDATA[
1352  Content-Language   = "Content-Language" ":" OWS Content-Language-v
1353  Content-Language-v = 1#language-tag
1354]]></artwork></figure>
1355<t>
1356   Language tags are defined in <xref target="language.tags"/>. The primary purpose of
1357   Content-Language is to allow a user to identify and differentiate
1358   entities according to the user's own preferred language. Thus, if the
1359   body content is intended only for a Danish-literate audience, the
1360   appropriate field is
1361</t>
1362<figure><artwork type="example"><![CDATA[
1363  Content-Language: da
1364]]></artwork></figure>
1365<t>
1366   If no Content-Language is specified, the default is that the content
1367   is intended for all language audiences. This might mean that the
1368   sender does not consider it to be specific to any natural language,
1369   or that the sender does not know for which language it is intended.
1370</t>
1371<t>
1372   Multiple languages MAY be listed for content that is intended for
1373   multiple audiences. For example, a rendition of the "Treaty of
1374   Waitangi," presented simultaneously in the original Maori and English
1375   versions, would call for
1376</t>
1377<figure><artwork type="example"><![CDATA[
1378  Content-Language: mi, en
1379]]></artwork></figure>
1380<t>
1381   However, just because multiple languages are present within an entity
1382   does not mean that it is intended for multiple linguistic audiences.
1383   An example would be a beginner's language primer, such as "A First
1384   Lesson in Latin," which is clearly intended to be used by an
1385   English-literate audience. In this case, the Content-Language would
1386   properly only include "en".
1387</t>
1388<t>
1389   Content-Language MAY be applied to any media type -- it is not
1390   limited to textual documents.
1391</t>
1392</section>
1393
1394<section title="Content-Location" anchor="header.content-location">
1395  <iref primary="true" item="Content-Location header"/>
1396  <iref primary="true" item="Headers" subitem="Content-Location"/>
1397 
1398 
1399<t>
1400   The "Content-Location" entity-header field is used to supply a URI for the
1401   entity in the message when it is accessible from a location separate from
1402   the requested resource's URI.
1403</t>
1404<t>
1405   A server SHOULD provide a Content-Location for the variant corresponding
1406   to the response entity, especially in the case where a resource has multiple
1407   entities associated with it, and those entities actually have separate
1408   locations by which they might be individually accessed, the server SHOULD
1409   provide a Content-Location for the particular variant which is returned.
1410</t>
1411<figure><iref primary="true" item="Grammar" subitem="Content-Location"/><iref primary="true" item="Grammar" subitem="Content-Location-v"/><artwork type="abnf2616"><![CDATA[
1412  Content-Location   = "Content-Location" ":" OWS
1413                    Content-Location-v
1414  Content-Location-v =
1415                    absolute-URI / partial-URI
1416]]></artwork></figure>
1417<t>
1418   The Content-Location value is not a replacement for the Effective
1419   Request URI (Section 4.3 of <xref target="Part1"/>); it is only a statement of the location of the resource
1420   corresponding to this particular entity at the time of the request.
1421   Future requests MAY may be addressed to the Content-Location URI
1422   if the desire is to identify the source of that particular
1423   entity.
1424</t>
1425<t>
1426   Section 6.1 of <xref target="Part2"/> describes how clients may process the Content-Location header field.
1427</t>
1428<t>
1429   A cache cannot assume that an entity with a Content-Location
1430   different from the URI used to retrieve it can be used to respond to
1431   later requests on that Content-Location URI. However, the Content-Location
1432   can be used to differentiate between multiple entities
1433   retrieved from a single requested resource, as described in Section 2.7 of <xref target="Part6"/>.
1434</t>
1435<t>
1436   If the Content-Location is a relative URI, the relative URI is
1437   interpreted relative to the Effective Request URI.
1438</t>
1439<t>
1440   The meaning of the Content-Location header in requests is
1441   undefined; servers are free to ignore it in those cases.
1442</t>
1443</section>
1444
1445<section title="Content-MD5" anchor="header.content-md5">
1446  <iref primary="true" item="Content-MD5 header"/>
1447  <iref primary="true" item="Headers" subitem="Content-MD5"/>
1448 
1449 
1450<t>
1451   The "Content-MD5" entity-header field, as defined in <xref target="RFC1864"/>, is
1452   an MD5 digest of the entity-body that provides an end-to-end message
1453   integrity check (MIC) of the entity-body. Note that a MIC is good for
1454   detecting accidental modification of the entity-body in transit, but is not
1455   proof against malicious attacks.
1456</t>
1457<figure><iref primary="true" item="Grammar" subitem="Content-MD5"/><iref primary="true" item="Grammar" subitem="Content-MD5-v"/><artwork type="abnf2616"><![CDATA[
1458  Content-MD5   = "Content-MD5" ":" OWS Content-MD5-v
1459  Content-MD5-v = <base64 of 128 bit MD5 digest as per [RFC1864]>
1460]]></artwork></figure>
1461<t>
1462   The Content-MD5 header field MAY be generated by an origin server or
1463   client to function as an integrity check of the entity-body. Only
1464   origin servers or clients MAY generate the Content-MD5 header field;
1465   proxies and gateways MUST NOT generate it, as this would defeat its
1466   value as an end-to-end integrity check. Any recipient of the entity-body,
1467   including gateways and proxies, MAY check that the digest value
1468   in this header field matches that of the entity-body as received.
1469</t>
1470<t>
1471   The MD5 digest is computed based on the content of the entity-body,
1472   including any content-coding that has been applied, but not including
1473   any transfer-encoding applied to the message-body. If the message is
1474   received with a transfer-encoding, that encoding MUST be removed
1475   prior to checking the Content-MD5 value against the received entity.
1476</t>
1477<t>
1478   This has the result that the digest is computed on the octets of the
1479   entity-body exactly as, and in the order that, they would be sent if
1480   no transfer-encoding were being applied.
1481</t>
1482<t>
1483   HTTP extends RFC 1864 to permit the digest to be computed for MIME
1484   composite media-types (e.g., multipart/* and message/rfc822), but
1485   this does not change how the digest is computed as defined in the
1486   preceding paragraph.
1487</t>
1488<t>
1489   There are several consequences of this. The entity-body for composite
1490   types MAY contain many body-parts, each with its own MIME and HTTP
1491   headers (including Content-MD5, Content-Transfer-Encoding, and
1492   Content-Encoding headers). If a body-part has a Content-Transfer-Encoding
1493   or Content-Encoding header, it is assumed that the content
1494   of the body-part has had the encoding applied, and the body-part is
1495   included in the Content-MD5 digest as is -- i.e., after the
1496   application. The Transfer-Encoding header field is not allowed within
1497   body-parts.
1498</t>
1499<t>
1500   Conversion of all line breaks to CRLF MUST NOT be done before
1501   computing or checking the digest: the line break convention used in
1502   the text actually transmitted MUST be left unaltered when computing
1503   the digest.
1504</t>
1505<t><list>
1506  <t>
1507    Note: While the definition of Content-MD5 is exactly the same for
1508    HTTP as in RFC 1864 for MIME entity-bodies, there are several ways
1509    in which the application of Content-MD5 to HTTP entity-bodies
1510    differs from its application to MIME entity-bodies. One is that
1511    HTTP, unlike MIME, does not use Content-Transfer-Encoding, and
1512    does use Transfer-Encoding and Content-Encoding. Another is that
1513    HTTP more frequently uses binary content types than MIME, so it is
1514    worth noting that, in such cases, the byte order used to compute
1515    the digest is the transmission byte order defined for the type.
1516    Lastly, HTTP allows transmission of text types with any of several
1517    line break conventions and not just the canonical form using CRLF.
1518  </t>
1519</list></t>
1520</section>
1521
1522<section title="Content-Type" anchor="header.content-type">
1523  <iref primary="true" item="Content-Type header"/>
1524  <iref primary="true" item="Headers" subitem="Content-Type"/>
1525 
1526 
1527<t>
1528   The "Content-Type" entity-header field indicates the media type of the
1529   entity-body. In the case of responses to the HEAD method, the media type is
1530   that which would have been sent had the request been a GET.
1531</t>
1532<figure><iref primary="true" item="Grammar" subitem="Content-Type"/><iref primary="true" item="Grammar" subitem="Content-Type-v"/><artwork type="abnf2616"><![CDATA[
1533  Content-Type   = "Content-Type" ":" OWS Content-Type-v
1534  Content-Type-v = media-type
1535]]></artwork></figure>
1536<t>
1537   Media types are defined in <xref target="media.types"/>. An example of the field is
1538</t>
1539<figure><artwork type="example"><![CDATA[
1540  Content-Type: text/html; charset=ISO-8859-4
1541]]></artwork></figure>
1542<t>
1543   Further discussion of methods for identifying the media type of an
1544   entity is provided in <xref target="type"/>.
1545</t>
1546</section>
1547
1548</section>
1549
1550<section title="IANA Considerations" anchor="IANA.considerations">
1551<section title="Message Header Registration" anchor="message.header.registration">
1552<t>
1553   The Message Header Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> should be updated
1554   with the permanent registrations below (see <xref target="RFC3864"/>):
1555</t>
1556
1557<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
1558<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
1559   <ttcol>Header Field Name</ttcol>
1560   <ttcol>Protocol</ttcol>
1561   <ttcol>Status</ttcol>
1562   <ttcol>Reference</ttcol>
1563
1564   <c>Accept</c>
1565   <c>http</c>
1566   <c>standard</c>
1567   <c>
1568      <xref target="header.accept"/>
1569   </c>
1570   <c>Accept-Charset</c>
1571   <c>http</c>
1572   <c>standard</c>
1573   <c>
1574      <xref target="header.accept-charset"/>
1575   </c>
1576   <c>Accept-Encoding</c>
1577   <c>http</c>
1578   <c>standard</c>
1579   <c>
1580      <xref target="header.accept-encoding"/>
1581   </c>
1582   <c>Accept-Language</c>
1583   <c>http</c>
1584   <c>standard</c>
1585   <c>
1586      <xref target="header.accept-language"/>
1587   </c>
1588   <c>Content-Disposition</c>
1589   <c>http</c>
1590   <c/>
1591   <c>
1592      <xref target="content-disposition"/>
1593   </c>
1594   <c>Content-Encoding</c>
1595   <c>http</c>
1596   <c>standard</c>
1597   <c>
1598      <xref target="header.content-encoding"/>
1599   </c>
1600   <c>Content-Language</c>
1601   <c>http</c>
1602   <c>standard</c>
1603   <c>
1604      <xref target="header.content-language"/>
1605   </c>
1606   <c>Content-Location</c>
1607   <c>http</c>
1608   <c>standard</c>
1609   <c>
1610      <xref target="header.content-location"/>
1611   </c>
1612   <c>Content-MD5</c>
1613   <c>http</c>
1614   <c>standard</c>
1615   <c>
1616      <xref target="header.content-md5"/>
1617   </c>
1618   <c>Content-Type</c>
1619   <c>http</c>
1620   <c>standard</c>
1621   <c>
1622      <xref target="header.content-type"/>
1623   </c>
1624   <c>MIME-Version</c>
1625   <c>http</c>
1626   <c/>
1627   <c>
1628      <xref target="mime-version"/>
1629   </c>
1630</texttable>
1631<!--(END)-->
1632
1633<t>
1634   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
1635</t>
1636</section>
1637
1638<section title="Content Coding Registry" anchor="content.coding.registration">
1639<t>
1640   The registration procedure for HTTP Content Codings is now defined
1641   by <xref target="content.coding.registry"/> of this document.
1642</t>
1643<t>
1644   The HTTP Content Codings Registry located at <eref target="http://www.iana.org/assignments/http-parameters"/>
1645   should be updated with the registration below:
1646</t>
1647<texttable align="left" suppress-title="true" anchor="iana.content.coding.registration.table">
1648   <ttcol>Name</ttcol>
1649   <ttcol>Description</ttcol>
1650   <ttcol>Reference</ttcol>
1651   <c>compress</c>
1652   <c>UNIX "compress" program method</c>
1653   <c>
1654      Section 6.2.2.1 of <xref target="Part1"/>
1655   </c>
1656   <c>deflate</c>
1657   <c>"deflate" compression mechanism (<xref target="RFC1951"/>) used inside
1658   the "zlib" data format (<xref target="RFC1950"/>)
1659   </c>
1660   <c>
1661      Section 6.2.2.2 of <xref target="Part1"/>
1662   </c>
1663   <c>gzip</c>
1664   <c>Same as GNU zip <xref target="RFC1952"/></c>
1665   <c>
1666      Section 6.2.2.3 of <xref target="Part1"/>
1667   </c>
1668   <c>identity</c>
1669   <c>No transformation</c>
1670   <c>
1671      <xref target="content.codings"/>
1672   </c>
1673</texttable>
1674</section>
1675
1676</section>
1677
1678<section title="Security Considerations" anchor="security.considerations">
1679<t>
1680   This section is meant to inform application developers, information
1681   providers, and users of the security limitations in HTTP/1.1 as
1682   described by this document. The discussion does not include
1683   definitive solutions to the problems revealed, though it does make
1684   some suggestions for reducing security risks.
1685</t>
1686
1687<section title="Privacy Issues Connected to Accept Headers" anchor="privacy.issues.connected.to.accept.headers">
1688<t>
1689   Accept request-headers can reveal information about the user to all
1690   servers which are accessed. The Accept-Language header in particular
1691   can reveal information the user would consider to be of a private
1692   nature, because the understanding of particular languages is often
1693   strongly correlated to the membership of a particular ethnic group.
1694   User agents which offer the option to configure the contents of an
1695   Accept-Language header to be sent in every request are strongly
1696   encouraged to let the configuration process include a message which
1697   makes the user aware of the loss of privacy involved.
1698</t>
1699<t>
1700   An approach that limits the loss of privacy would be for a user agent
1701   to omit the sending of Accept-Language headers by default, and to ask
1702   the user whether or not to start sending Accept-Language headers to a
1703   server if it detects, by looking for any Vary response-header fields
1704   generated by the server, that such sending could improve the quality
1705   of service.
1706</t>
1707<t>
1708   Elaborate user-customized accept header fields sent in every request,
1709   in particular if these include quality values, can be used by servers
1710   as relatively reliable and long-lived user identifiers. Such user
1711   identifiers would allow content providers to do click-trail tracking,
1712   and would allow collaborating content providers to match cross-server
1713   click-trails or form submissions of individual users. Note that for
1714   many users not behind a proxy, the network address of the host
1715   running the user agent will also serve as a long-lived user
1716   identifier. In environments where proxies are used to enhance
1717   privacy, user agents ought to be conservative in offering accept
1718   header configuration options to end users. As an extreme privacy
1719   measure, proxies could filter the accept headers in relayed requests.
1720   General purpose user agents which provide a high degree of header
1721   configurability SHOULD warn users about the loss of privacy which can
1722   be involved.
1723</t>
1724</section>
1725
1726<section title="Content-Disposition Issues" anchor="content-disposition.issues">
1727<t>
1728   <xref target="RFC2183"/>, from which the often implemented Content-Disposition
1729   (see <xref target="content-disposition"/>) header in HTTP is derived, has a number of very
1730   serious security considerations. Content-Disposition is not part of
1731   the HTTP standard, but since it is widely implemented, we are
1732   documenting its use and risks for implementors. See Section 5 of <xref target="RFC2183"/>
1733   for details.
1734</t>
1735</section>
1736
1737</section>
1738
1739<section title="Acknowledgments" anchor="ack">
1740</section>
1741</middle>
1742<back>
1743
1744<references title="Normative References">
1745
1746<reference anchor="ISO-8859-1">
1747  <front>
1748    <title>
1749     Information technology -- 8-bit single-byte coded graphic character sets -- Part 1: Latin alphabet No. 1
1750    </title>
1751    <author>
1752      <organization>International Organization for Standardization</organization>
1753    </author>
1754    <date year="1998"/>
1755  </front>
1756  <seriesInfo name="ISO/IEC" value="8859-1:1998"/>
1757</reference>
1758
1759<reference anchor="Part1">
1760  <front>
1761    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
1762    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1763      <organization abbrev="Day Software">Day Software</organization>
1764      <address><email>fielding@gbiv.com</email></address>
1765    </author>
1766    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1767      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1768      <address><email>jg@freedesktop.org</email></address>
1769    </author>
1770    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1771      <organization abbrev="HP">Hewlett-Packard Company</organization>
1772      <address><email>JeffMogul@acm.org</email></address>
1773    </author>
1774    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1775      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1776      <address><email>henrikn@microsoft.com</email></address>
1777    </author>
1778    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1779      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1780      <address><email>LMM@acm.org</email></address>
1781    </author>
1782    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1783      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1784      <address><email>paulle@microsoft.com</email></address>
1785    </author>
1786    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1787      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1788      <address><email>timbl@w3.org</email></address>
1789    </author>
1790    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1791      <organization abbrev="W3C">World Wide Web Consortium</organization>
1792      <address><email>ylafon@w3.org</email></address>
1793    </author>
1794    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1795      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1796      <address><email>julian.reschke@greenbytes.de</email></address>
1797    </author>
1798    <date month="July" year="2010"/>
1799  </front>
1800  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-10"/>
1801 
1802</reference>
1803
1804<reference anchor="Part2">
1805  <front>
1806    <title abbrev="HTTP/1.1">HTTP/1.1, part 2: Message Semantics</title>
1807    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1808      <organization abbrev="Day Software">Day Software</organization>
1809      <address><email>fielding@gbiv.com</email></address>
1810    </author>
1811    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1812      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1813      <address><email>jg@freedesktop.org</email></address>
1814    </author>
1815    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1816      <organization abbrev="HP">Hewlett-Packard Company</organization>
1817      <address><email>JeffMogul@acm.org</email></address>
1818    </author>
1819    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1820      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1821      <address><email>henrikn@microsoft.com</email></address>
1822    </author>
1823    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1824      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1825      <address><email>LMM@acm.org</email></address>
1826    </author>
1827    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1828      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1829      <address><email>paulle@microsoft.com</email></address>
1830    </author>
1831    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1832      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1833      <address><email>timbl@w3.org</email></address>
1834    </author>
1835    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1836      <organization abbrev="W3C">World Wide Web Consortium</organization>
1837      <address><email>ylafon@w3.org</email></address>
1838    </author>
1839    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1840      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1841      <address><email>julian.reschke@greenbytes.de</email></address>
1842    </author>
1843    <date month="July" year="2010"/>
1844  </front>
1845  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p2-semantics-10"/>
1846 
1847</reference>
1848
1849<reference anchor="Part4">
1850  <front>
1851    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
1852    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1853      <organization abbrev="Day Software">Day Software</organization>
1854      <address><email>fielding@gbiv.com</email></address>
1855    </author>
1856    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1857      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1858      <address><email>jg@freedesktop.org</email></address>
1859    </author>
1860    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1861      <organization abbrev="HP">Hewlett-Packard Company</organization>
1862      <address><email>JeffMogul@acm.org</email></address>
1863    </author>
1864    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1865      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1866      <address><email>henrikn@microsoft.com</email></address>
1867    </author>
1868    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1869      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1870      <address><email>LMM@acm.org</email></address>
1871    </author>
1872    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1873      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1874      <address><email>paulle@microsoft.com</email></address>
1875    </author>
1876    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1877      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1878      <address><email>timbl@w3.org</email></address>
1879    </author>
1880    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1881      <organization abbrev="W3C">World Wide Web Consortium</organization>
1882      <address><email>ylafon@w3.org</email></address>
1883    </author>
1884    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1885      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1886      <address><email>julian.reschke@greenbytes.de</email></address>
1887    </author>
1888    <date month="July" year="2010"/>
1889  </front>
1890  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-10"/>
1891 
1892</reference>
1893
1894<reference anchor="Part5">
1895  <front>
1896    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
1897    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1898      <organization abbrev="Day Software">Day Software</organization>
1899      <address><email>fielding@gbiv.com</email></address>
1900    </author>
1901    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1902      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1903      <address><email>jg@freedesktop.org</email></address>
1904    </author>
1905    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1906      <organization abbrev="HP">Hewlett-Packard Company</organization>
1907      <address><email>JeffMogul@acm.org</email></address>
1908    </author>
1909    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1910      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1911      <address><email>henrikn@microsoft.com</email></address>
1912    </author>
1913    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1914      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1915      <address><email>LMM@acm.org</email></address>
1916    </author>
1917    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1918      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1919      <address><email>paulle@microsoft.com</email></address>
1920    </author>
1921    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1922      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1923      <address><email>timbl@w3.org</email></address>
1924    </author>
1925    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1926      <organization abbrev="W3C">World Wide Web Consortium</organization>
1927      <address><email>ylafon@w3.org</email></address>
1928    </author>
1929    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1930      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1931      <address><email>julian.reschke@greenbytes.de</email></address>
1932    </author>
1933    <date month="July" year="2010"/>
1934  </front>
1935  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-10"/>
1936 
1937</reference>
1938
1939<reference anchor="Part6">
1940  <front>
1941    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
1942    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1943      <organization abbrev="Day Software">Day Software</organization>
1944      <address><email>fielding@gbiv.com</email></address>
1945    </author>
1946    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1947      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1948      <address><email>jg@freedesktop.org</email></address>
1949    </author>
1950    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1951      <organization abbrev="HP">Hewlett-Packard Company</organization>
1952      <address><email>JeffMogul@acm.org</email></address>
1953    </author>
1954    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1955      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1956      <address><email>henrikn@microsoft.com</email></address>
1957    </author>
1958    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1959      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1960      <address><email>LMM@acm.org</email></address>
1961    </author>
1962    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1963      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1964      <address><email>paulle@microsoft.com</email></address>
1965    </author>
1966    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1967      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1968      <address><email>timbl@w3.org</email></address>
1969    </author>
1970    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1971      <organization abbrev="W3C">World Wide Web Consortium</organization>
1972      <address><email>ylafon@w3.org</email></address>
1973    </author>
1974    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
1975      <address><email>mnot@mnot.net</email></address>
1976    </author>
1977    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1978      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1979      <address><email>julian.reschke@greenbytes.de</email></address>
1980    </author>
1981    <date month="July" year="2010"/>
1982  </front>
1983  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-10"/>
1984 
1985</reference>
1986
1987<reference anchor="RFC1864">
1988  <front>
1989    <title abbrev="Content-MD5 Header Field">The Content-MD5 Header Field</title>
1990    <author initials="J." surname="Myers" fullname="John G. Myers">
1991      <organization>Carnegie Mellon University</organization>
1992      <address><email>jgm+@cmu.edu</email></address>
1993    </author>
1994    <author initials="M." surname="Rose" fullname="Marshall T. Rose">
1995      <organization>Dover Beach Consulting, Inc.</organization>
1996      <address><email>mrose@dbc.mtview.ca.us</email></address>
1997    </author>
1998    <date month="October" year="1995"/>
1999  </front>
2000  <seriesInfo name="RFC" value="1864"/>
2001</reference>
2002
2003<reference anchor="RFC1950">
2004  <front>
2005    <title>ZLIB Compressed Data Format Specification version 3.3</title>
2006    <author initials="L.P." surname="Deutsch" fullname="L. Peter Deutsch">
2007      <organization>Aladdin Enterprises</organization>
2008      <address><email>ghost@aladdin.com</email></address>
2009    </author>
2010    <author initials="J-L." surname="Gailly" fullname="Jean-Loup Gailly"/>
2011    <date month="May" year="1996"/>
2012  </front>
2013  <seriesInfo name="RFC" value="1950"/>
2014  <annotation>
2015    RFC 1950 is an Informational RFC, thus it may be less stable than
2016    this specification. On the other hand, this downward reference was
2017    present since the publication of RFC 2068 in 1997 (<xref target="RFC2068"/>),
2018    therefore it is unlikely to cause problems in practice. See also
2019    <xref target="BCP97"/>.
2020  </annotation>
2021</reference>
2022
2023<reference anchor="RFC1951">
2024  <front>
2025    <title>DEFLATE Compressed Data Format Specification version 1.3</title>
2026    <author initials="P." surname="Deutsch" fullname="L. Peter Deutsch">
2027      <organization>Aladdin Enterprises</organization>
2028      <address><email>ghost@aladdin.com</email></address>
2029    </author>
2030    <date month="May" year="1996"/>
2031  </front>
2032  <seriesInfo name="RFC" value="1951"/>
2033  <annotation>
2034    RFC 1951 is an Informational RFC, thus it may be less stable than
2035    this specification. On the other hand, this downward reference was
2036    present since the publication of RFC 2068 in 1997 (<xref target="RFC2068"/>),
2037    therefore it is unlikely to cause problems in practice. See also
2038    <xref target="BCP97"/>.
2039  </annotation>
2040</reference>
2041
2042<reference anchor="RFC1952">
2043  <front>
2044    <title>GZIP file format specification version 4.3</title>
2045    <author initials="P." surname="Deutsch" fullname="L. Peter Deutsch">
2046      <organization>Aladdin Enterprises</organization>
2047      <address><email>ghost@aladdin.com</email></address>
2048    </author>
2049    <author initials="J-L." surname="Gailly" fullname="Jean-Loup Gailly">
2050      <address><email>gzip@prep.ai.mit.edu</email></address>
2051    </author>
2052    <author initials="M." surname="Adler" fullname="Mark Adler">
2053      <address><email>madler@alumni.caltech.edu</email></address>
2054    </author>
2055    <author initials="L.P." surname="Deutsch" fullname="L. Peter Deutsch">
2056      <address><email>ghost@aladdin.com</email></address>
2057    </author>
2058    <author initials="G." surname="Randers-Pehrson" fullname="Glenn Randers-Pehrson">
2059      <address><email>randeg@alumni.rpi.edu</email></address>
2060    </author>
2061    <date month="May" year="1996"/>
2062  </front>
2063  <seriesInfo name="RFC" value="1952"/>
2064  <annotation>
2065    RFC 1952 is an Informational RFC, thus it may be less stable than
2066    this specification. On the other hand, this downward reference was
2067    present since the publication of RFC 2068 in 1997 (<xref target="RFC2068"/>),
2068    therefore it is unlikely to cause problems in practice. See also
2069    <xref target="BCP97"/>.
2070  </annotation>
2071</reference>
2072
2073<reference anchor="RFC2045">
2074  <front>
2075    <title abbrev="Internet Message Bodies">Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies</title>
2076    <author initials="N." surname="Freed" fullname="Ned Freed">
2077      <organization>Innosoft International, Inc.</organization>
2078      <address><email>ned@innosoft.com</email></address>
2079    </author>
2080    <author initials="N.S." surname="Borenstein" fullname="Nathaniel S. Borenstein">
2081      <organization>First Virtual Holdings</organization>
2082      <address><email>nsb@nsb.fv.com</email></address>
2083    </author>
2084    <date month="November" year="1996"/>
2085  </front>
2086  <seriesInfo name="RFC" value="2045"/>
2087</reference>
2088
2089<reference anchor="RFC2046">
2090  <front>
2091    <title abbrev="Media Types">Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types</title>
2092    <author initials="N." surname="Freed" fullname="Ned Freed">
2093      <organization>Innosoft International, Inc.</organization>
2094      <address><email>ned@innosoft.com</email></address>
2095    </author>
2096    <author initials="N." surname="Borenstein" fullname="Nathaniel S. Borenstein">
2097      <organization>First Virtual Holdings</organization>
2098      <address><email>nsb@nsb.fv.com</email></address>
2099    </author>
2100    <date month="November" year="1996"/>
2101  </front>
2102  <seriesInfo name="RFC" value="2046"/>
2103</reference>
2104
2105<reference anchor="RFC2119">
2106  <front>
2107    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
2108    <author initials="S." surname="Bradner" fullname="Scott Bradner">
2109      <organization>Harvard University</organization>
2110      <address><email>sob@harvard.edu</email></address>
2111    </author>
2112    <date month="March" year="1997"/>
2113  </front>
2114  <seriesInfo name="BCP" value="14"/>
2115  <seriesInfo name="RFC" value="2119"/>
2116</reference>
2117
2118<reference anchor="RFC4647">
2119  <front>
2120    <title>Matching of Language Tags</title>
2121    <author initials="A." surname="Phillips" fullname="Addison Phillips" role="editor">
2122      <organization>Yahoo! Inc.</organization>
2123      <address><email>addison@inter-locale.com</email></address>
2124    </author>
2125    <author initials="M." surname="Davis" fullname="Mark Davis" role="editor">
2126      <organization>Google</organization>
2127      <address><email>mark.davis@macchiato.com</email></address>
2128    </author>
2129    <date year="2006" month="September"/>
2130  </front>
2131  <seriesInfo name="BCP" value="47"/>
2132  <seriesInfo name="RFC" value="4647"/>
2133</reference>
2134
2135<reference anchor="RFC5234">
2136  <front>
2137    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
2138    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
2139      <organization>Brandenburg InternetWorking</organization>
2140      <address>
2141        <email>dcrocker@bbiw.net</email>
2142      </address> 
2143    </author>
2144    <author initials="P." surname="Overell" fullname="Paul Overell">
2145      <organization>THUS plc.</organization>
2146      <address>
2147        <email>paul.overell@thus.net</email>
2148      </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="RFC2295">
2287  <front>
2288    <title abbrev="HTTP Content Negotiation">Transparent Content Negotiation in HTTP</title>
2289    <author initials="K." surname="Holtman" fullname="Koen Holtman">
2290      <organization>Technische Universiteit Eindhoven</organization>
2291      <address>
2292        <email>koen@win.tue.nl</email>
2293      </address>
2294    </author>
2295    <author initials="A.H." surname="Mutz" fullname="Andrew H. Mutz">
2296      <organization>Hewlett-Packard Company</organization>
2297      <address>
2298        <email>mutz@hpl.hp.com</email>
2299      </address>
2300    </author>
2301    <date year="1998" month="March"/>
2302  </front>
2303  <seriesInfo name="RFC" value="2295"/>
2304</reference>
2305
2306<reference anchor="RFC2388">
2307  <front>
2308    <title abbrev="multipart/form-data">Returning Values from Forms:  multipart/form-data</title>
2309    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2310      <organization>Xerox Palo Alto Research Center</organization>
2311      <address><email>masinter@parc.xerox.com</email></address>
2312    </author>
2313    <date year="1998" month="August"/>
2314  </front>
2315  <seriesInfo name="RFC" value="2388"/>
2316</reference>
2317
2318<reference anchor="RFC2557">
2319  <front>
2320    <title abbrev="MIME Encapsulation of Aggregate Documents">MIME Encapsulation of Aggregate Documents, such as HTML (MHTML)</title>
2321    <author initials="F." surname="Palme" fullname="Jacob Palme">
2322      <organization>Stockholm University and KTH</organization>
2323      <address><email>jpalme@dsv.su.se</email></address>
2324    </author>
2325    <author initials="A." surname="Hopmann" fullname="Alex Hopmann">
2326      <organization>Microsoft Corporation</organization>
2327      <address><email>alexhop@microsoft.com</email></address>
2328    </author>
2329    <author initials="N." surname="Shelness" fullname="Nick Shelness">
2330      <organization>Lotus Development Corporation</organization>
2331      <address><email>Shelness@lotus.com</email></address>
2332    </author>
2333    <author initials="E." surname="Stefferud" fullname="Einar Stefferud">
2334      <address><email>stef@nma.com</email></address>
2335    </author>
2336    <date year="1999" month="March"/>
2337  </front>
2338  <seriesInfo name="RFC" value="2557"/>
2339</reference>
2340
2341<reference anchor="RFC2616">
2342  <front>
2343    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
2344    <author initials="R." surname="Fielding" fullname="R. Fielding">
2345      <organization>University of California, Irvine</organization>
2346      <address><email>fielding@ics.uci.edu</email></address>
2347    </author>
2348    <author initials="J." surname="Gettys" fullname="J. Gettys">
2349      <organization>W3C</organization>
2350      <address><email>jg@w3.org</email></address>
2351    </author>
2352    <author initials="J." surname="Mogul" fullname="J. Mogul">
2353      <organization>Compaq Computer Corporation</organization>
2354      <address><email>mogul@wrl.dec.com</email></address>
2355    </author>
2356    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
2357      <organization>MIT Laboratory for Computer Science</organization>
2358      <address><email>frystyk@w3.org</email></address>
2359    </author>
2360    <author initials="L." surname="Masinter" fullname="L. Masinter">
2361      <organization>Xerox Corporation</organization>
2362      <address><email>masinter@parc.xerox.com</email></address>
2363    </author>
2364    <author initials="P." surname="Leach" fullname="P. Leach">
2365      <organization>Microsoft Corporation</organization>
2366      <address><email>paulle@microsoft.com</email></address>
2367    </author>
2368    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
2369      <organization>W3C</organization>
2370      <address><email>timbl@w3.org</email></address>
2371    </author>
2372    <date month="June" year="1999"/>
2373  </front>
2374  <seriesInfo name="RFC" value="2616"/>
2375</reference>
2376
2377<reference anchor="RFC3629">
2378  <front>
2379    <title>UTF-8, a transformation format of ISO 10646</title>
2380    <author initials="F." surname="Yergeau" fullname="F. Yergeau">
2381      <organization>Alis Technologies</organization>
2382      <address><email>fyergeau@alis.com</email></address>
2383    </author>
2384    <date month="November" year="2003"/>
2385  </front>
2386  <seriesInfo name="RFC" value="3629"/>
2387  <seriesInfo name="STD" value="63"/>
2388</reference>
2389
2390<reference anchor="RFC3864">
2391  <front>
2392    <title>Registration Procedures for Message Header Fields</title>
2393    <author initials="G." surname="Klyne" fullname="G. Klyne">
2394      <organization>Nine by Nine</organization>
2395      <address><email>GK-IETF@ninebynine.org</email></address>
2396    </author>
2397    <author initials="M." surname="Nottingham" fullname="M. Nottingham">
2398      <organization>BEA Systems</organization>
2399      <address><email>mnot@pobox.com</email></address>
2400    </author>
2401    <author initials="J." surname="Mogul" fullname="J. Mogul">
2402      <organization>HP Labs</organization>
2403      <address><email>JeffMogul@acm.org</email></address>
2404    </author>
2405    <date year="2004" month="September"/>
2406  </front>
2407  <seriesInfo name="BCP" value="90"/>
2408  <seriesInfo name="RFC" value="3864"/>
2409</reference>
2410
2411<reference anchor="RFC4288">
2412  <front>
2413    <title>Media Type Specifications and Registration Procedures</title>
2414    <author initials="N." surname="Freed" fullname="N. Freed">
2415      <organization>Sun Microsystems</organization>
2416      <address>
2417        <email>ned.freed@mrochek.com</email>
2418      </address>
2419    </author>
2420    <author initials="J." surname="Klensin" fullname="J. Klensin">
2421      <address>
2422        <email>klensin+ietf@jck.com</email>
2423      </address>
2424    </author>
2425    <date year="2005" month="December"/>
2426  </front>
2427  <seriesInfo name="BCP" value="13"/>
2428  <seriesInfo name="RFC" value="4288"/>
2429</reference>
2430
2431<reference anchor="RFC5226">
2432  <front>
2433    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
2434    <author initials="T." surname="Narten" fullname="T. Narten">
2435      <organization>IBM</organization>
2436      <address><email>narten@us.ibm.com</email></address>
2437    </author>
2438    <author initials="H." surname="Alvestrand" fullname="H. Alvestrand">
2439      <organization>Google</organization>
2440      <address><email>Harald@Alvestrand.no</email></address>
2441    </author>
2442    <date year="2008" month="May"/>
2443  </front>
2444  <seriesInfo name="BCP" value="26"/>
2445  <seriesInfo name="RFC" value="5226"/>
2446</reference>
2447
2448<reference anchor="RFC5322">
2449  <front>
2450    <title>Internet Message Format</title>
2451    <author initials="P." surname="Resnick" fullname="P. Resnick">
2452      <organization>Qualcomm Incorporated</organization>
2453    </author>
2454    <date year="2008" month="October"/>
2455  </front> 
2456  <seriesInfo name="RFC" value="5322"/>
2457</reference>
2458
2459<reference anchor="BCP97">
2460  <front>
2461    <title>Handling Normative References to Standards-Track Documents</title>
2462    <author initials="J." surname="Klensin" fullname="J. Klensin">
2463      <address>
2464        <email>klensin+ietf@jck.com</email>
2465      </address>
2466    </author>
2467    <author initials="S." surname="Hartman" fullname="S. Hartman">
2468      <organization>MIT</organization>
2469      <address>
2470        <email>hartmans-ietf@mit.edu</email>
2471      </address>
2472    </author>
2473    <date year="2007" month="June"/>
2474  </front>
2475  <seriesInfo name="BCP" value="97"/>
2476  <seriesInfo name="RFC" value="4897"/>
2477</reference>
2478
2479
2480</references>
2481
2482<section title="Differences Between HTTP Entities and RFC 2045 Entities" anchor="differences.between.http.entities.and.rfc.2045.entities">
2483<t>
2484   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
2485   allow entities to be transmitted in an open variety of
2486   representations and with extensible mechanisms. However, RFC 2045
2487   discusses mail, and HTTP has a few features that are different from
2488   those described in RFC 2045. These differences were carefully chosen
2489   to optimize performance over binary connections, to allow greater
2490   freedom in the use of new media types, to make date comparisons
2491   easier, and to acknowledge the practice of some early HTTP servers
2492   and clients.
2493</t>
2494<t>
2495   This appendix describes specific areas where HTTP differs from RFC
2496   2045. Proxies and gateways to strict MIME environments SHOULD be
2497   aware of these differences and provide the appropriate conversions
2498   where necessary. Proxies and gateways from MIME environments to HTTP
2499   also need to be aware of the differences because some conversions
2500   might be required.
2501</t>
2502
2503<section title="MIME-Version" anchor="mime-version">
2504  <iref primary="true" item="MIME-Version header"/>
2505  <iref primary="true" item="Headers" subitem="MIME-Version"/>
2506 
2507 
2508<t>
2509   HTTP is not a MIME-compliant protocol. However, HTTP/1.1 messages MAY
2510   include a single MIME-Version general-header field to indicate what
2511   version of the MIME protocol was used to construct the message. Use
2512   of the MIME-Version header field indicates that the message is in
2513   full compliance with the MIME protocol (as defined in <xref target="RFC2045"/>).
2514   Proxies/gateways are responsible for ensuring full compliance (where
2515   possible) when exporting HTTP messages to strict MIME environments.
2516</t>
2517<figure><iref primary="true" item="Grammar" subitem="MIME-Version"/><iref primary="true" item="Grammar" subitem="MIME-Version-v"/><artwork type="abnf2616"><![CDATA[
2518  MIME-Version   = "MIME-Version" ":" OWS MIME-Version-v
2519  MIME-Version-v = 1*DIGIT "." 1*DIGIT
2520]]></artwork></figure>
2521<t>
2522   MIME version "1.0" is the default for use in HTTP/1.1. However,
2523   HTTP/1.1 message parsing and semantics are defined by this document
2524   and not the MIME specification.
2525</t>
2526</section>
2527
2528<section title="Conversion to Canonical Form" anchor="conversion.to.canonical.form">
2529<t>
2530   <xref target="RFC2045"/> requires that an Internet mail entity be converted to
2531   canonical form prior to being transferred, as described in Section 4 of <xref target="RFC2049"/>.
2532   <xref target="canonicalization.and.text.defaults"/> of this document describes the forms
2533   allowed for subtypes of the "text" media type when transmitted over
2534   HTTP. <xref target="RFC2046"/> requires that content with a type of "text" represent
2535   line breaks as CRLF and forbids the use of CR or LF outside of line
2536   break sequences. HTTP allows CRLF, bare CR, and bare LF to indicate a
2537   line break within text content when a message is transmitted over
2538   HTTP.
2539</t>
2540<t>
2541   Where it is possible, a proxy or gateway from HTTP to a strict MIME
2542   environment SHOULD translate all line breaks within the text media
2543   types described in <xref target="canonicalization.and.text.defaults"/> of this document to the RFC 2049
2544   canonical form of CRLF. Note, however, that this might be complicated
2545   by the presence of a Content-Encoding and by the fact that HTTP
2546   allows the use of some character sets which do not use octets 13 and
2547   10 to represent CR and LF, as is the case for some multi-byte
2548   character sets.
2549</t>
2550<t>
2551   Implementors should note that conversion will break any cryptographic
2552   checksums applied to the original content unless the original content
2553   is already in canonical form. Therefore, the canonical form is
2554   recommended for any content that uses such checksums in HTTP.
2555</t>
2556</section>
2557
2558
2559<section title="Conversion of Date Formats" anchor="conversion.of.date.formats">
2560<t>
2561   HTTP/1.1 uses a restricted set of date formats (Section 6.1 of <xref target="Part1"/>) to
2562   simplify the process of date comparison. Proxies and gateways from
2563   other protocols SHOULD ensure that any Date header field present in a
2564   message conforms to one of the HTTP/1.1 formats and rewrite the date
2565   if necessary.
2566</t>
2567</section>
2568
2569<section title="Introduction of Content-Encoding" anchor="introduction.of.content-encoding">
2570<t>
2571   RFC 2045 does not include any concept equivalent to HTTP/1.1's
2572   Content-Encoding header field. Since this acts as a modifier on the
2573   media type, proxies and gateways from HTTP to MIME-compliant
2574   protocols MUST either change the value of the Content-Type header
2575   field or decode the entity-body before forwarding the message. (Some
2576   experimental applications of Content-Type for Internet mail have used
2577   a media-type parameter of ";conversions=&lt;content-coding&gt;" to perform
2578   a function equivalent to Content-Encoding. However, this parameter is
2579   not part of RFC 2045).
2580</t>
2581</section>
2582
2583<section title="No Content-Transfer-Encoding" anchor="no.content-transfer-encoding">
2584<t>
2585   HTTP does not use the Content-Transfer-Encoding field of RFC
2586   2045. Proxies and gateways from MIME-compliant protocols to HTTP MUST
2587   remove any Content-Transfer-Encoding
2588   prior to delivering the response message to an HTTP client.
2589</t>
2590<t>
2591   Proxies and gateways from HTTP to MIME-compliant protocols are
2592   responsible for ensuring that the message is in the correct format
2593   and encoding for safe transport on that protocol, where "safe
2594   transport" is defined by the limitations of the protocol being used.
2595   Such a proxy or gateway SHOULD label the data with an appropriate
2596   Content-Transfer-Encoding if doing so will improve the likelihood of
2597   safe transport over the destination protocol.
2598</t>
2599</section>
2600
2601<section title="Introduction of Transfer-Encoding" anchor="introduction.of.transfer-encoding">
2602<t>
2603   HTTP/1.1 introduces the Transfer-Encoding header field (Section 9.7 of <xref target="Part1"/>).
2604   Proxies/gateways MUST remove any transfer-coding prior to
2605   forwarding a message via a MIME-compliant protocol.
2606</t>
2607</section>
2608
2609<section title="MHTML and Line Length Limitations" anchor="mhtml.line.length">
2610<t>
2611   HTTP implementations which share code with MHTML <xref target="RFC2557"/> implementations
2612   need to be aware of MIME line length limitations. Since HTTP does not
2613   have this limitation, HTTP does not fold long lines. MHTML messages
2614   being transported by HTTP follow all conventions of MHTML, including
2615   line length limitations and folding, canonicalization, etc., since
2616   HTTP transports all message-bodies as payload (see <xref target="multipart.types"/>) and
2617   does not interpret the content or any MIME header lines that might be
2618   contained therein.
2619</t>
2620</section>
2621</section>
2622
2623<section title="Additional Features" anchor="additional.features">
2624<t>
2625   <xref target="RFC1945"/> and <xref target="RFC2068"/> document protocol elements used by some
2626   existing HTTP implementations, but not consistently and correctly
2627   across most HTTP/1.1 applications. Implementors are advised to be
2628   aware of these features, but cannot rely upon their presence in, or
2629   interoperability with, other HTTP/1.1 applications. Some of these
2630   describe proposed experimental features, and some describe features
2631   that experimental deployment found lacking that are now addressed in
2632   the base HTTP/1.1 specification.
2633</t>
2634<t>
2635   A number of other headers, such as Content-Disposition and Title,
2636   from SMTP and MIME are also often implemented (see <xref target="RFC2076"/>).
2637</t>
2638
2639<section title="Content-Disposition" anchor="content-disposition">
2640<iref item="Headers" subitem="Content-Disposition" primary="true"/>
2641<iref item="Content-Disposition header" primary="true"/>
2642 
2643 
2644 
2645 
2646 
2647 
2648 
2649<t>
2650   The "Content-Disposition" response-header field has been proposed as a
2651   means for the origin server to suggest a default filename if the user
2652   requests that the content is saved to a file. This usage is derived
2653   from the definition of Content-Disposition in <xref target="RFC2183"/>.
2654</t>
2655<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[
2656  content-disposition = "Content-Disposition" ":" OWS
2657                        content-disposition-v
2658  content-disposition-v = disposition-type
2659                          *( OWS ";" OWS disposition-parm )
2660  disposition-type = "attachment" / disp-extension-token
2661  disposition-parm = filename-parm / disp-extension-parm
2662  filename-parm = "filename" "=" quoted-string
2663  disp-extension-token = token
2664  disp-extension-parm = token "=" word
2665]]></artwork></figure>
2666<t>
2667   An example is
2668</t>
2669<figure><artwork type="example"><![CDATA[
2670  Content-Disposition: attachment; filename="fname.ext"
2671]]></artwork></figure>
2672<t>
2673   The receiving user agent SHOULD NOT  respect any directory path
2674   information present in the filename-parm parameter, which is the only
2675   parameter believed to apply to HTTP implementations at this time. The
2676   filename SHOULD be treated as a terminal component only.
2677</t>
2678<t>
2679   If this header is used in a response with the application/octet-stream
2680   content-type, the implied suggestion is that the user agent
2681   should not display the response, but directly enter a "save response
2682   as..." dialog.
2683</t>
2684<t>
2685   See <xref target="content-disposition.issues"/> for Content-Disposition security issues.
2686</t>
2687</section>
2688</section>
2689
2690<section title="Compatibility with Previous Versions" anchor="compatibility">
2691<section title="Changes from RFC 2068" anchor="changes.from.rfc.2068">
2692<t>
2693   Transfer-coding and message lengths all interact in ways that
2694   required fixing exactly when chunked encoding is used (to allow for
2695   transfer encoding that may not be self delimiting); it was important
2696   to straighten out exactly how message lengths are computed.
2697   (<xref target="entity.length"/>, see also <xref target="Part1"/>,
2698   <xref target="Part5"/> and <xref target="Part6"/>).
2699</t>
2700<t>
2701   Charset wildcarding is introduced to avoid explosion of character set
2702   names in accept headers. (<xref target="header.accept-charset"/>)
2703</t>
2704<t>
2705   Content-Base was deleted from the specification: it was not
2706   implemented widely, and there is no simple, safe way to introduce it
2707   without a robust extension mechanism. In addition, it is used in a
2708   similar, but not identical fashion in MHTML <xref target="RFC2557"/>.
2709</t>
2710<t>
2711   A content-coding of "identity" was introduced, to solve problems
2712   discovered in caching. (<xref target="content.codings"/>)
2713</t>
2714<t>
2715   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
2716   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
2717   specification, but not commonly implemented. See Section 19.6.2 of <xref target="RFC2068"/>.
2718</t>
2719</section>
2720
2721<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
2722<t>
2723  Clarify contexts that charset is used in.
2724  (<xref target="character.sets"/>)
2725</t>
2726<t>
2727  Remove base URI setting semantics for Content-Location due to poor
2728  implementation support, which was caused by too many broken servers emitting
2729  bogus Content-Location headers, and also the potentially undesirable effect
2730  of potentially breaking relative links in content-negotiated resources.
2731  (<xref target="header.content-location"/>)
2732</t>
2733<t>
2734  Remove reference to non-existant identity transfer-coding value tokens.
2735  (<xref target="no.content-transfer-encoding"/>)
2736</t>
2737</section>
2738
2739</section>
2740
2741
2742<section title="Collected ABNF" anchor="collected.abnf">
2743<figure>
2744<artwork type="abnf" name="p3-payload.parsed-abnf"><![CDATA[
2745Accept = "Accept:" OWS Accept-v
2746Accept-Charset = "Accept-Charset:" OWS Accept-Charset-v
2747Accept-Charset-v = *( "," OWS ) ( charset / "*" ) [ OWS ";" OWS "q="
2748 qvalue ] *( OWS "," [ OWS ( charset / "*" ) [ OWS ";" OWS "q="
2749 qvalue ] ] )
2750Accept-Encoding = "Accept-Encoding:" OWS Accept-Encoding-v
2751Accept-Encoding-v = [ ( "," / ( codings [ OWS ";" OWS "q=" qvalue ] )
2752 ) *( OWS "," [ OWS codings [ OWS ";" OWS "q=" qvalue ] ] ) ]
2753Accept-Language = "Accept-Language:" OWS Accept-Language-v
2754Accept-Language-v = *( "," OWS ) language-range [ OWS ";" OWS "q="
2755 qvalue ] *( OWS "," [ OWS language-range [ OWS ";" OWS "q=" qvalue ]
2756 ] )
2757Accept-v = [ ( "," / ( media-range [ accept-params ] ) ) *( OWS "," [
2758 OWS media-range [ accept-params ] ] ) ]
2759
2760Content-Encoding = "Content-Encoding:" OWS Content-Encoding-v
2761Content-Encoding-v = *( "," OWS ) content-coding *( OWS "," [ OWS
2762 content-coding ] )
2763Content-Language = "Content-Language:" OWS Content-Language-v
2764Content-Language-v = *( "," OWS ) language-tag *( OWS "," [ OWS
2765 language-tag ] )
2766Content-Length = <Content-Length, defined in [Part1], Section 9.2>
2767Content-Location = "Content-Location:" OWS Content-Location-v
2768Content-Location-v = absolute-URI / partial-URI
2769Content-MD5 = "Content-MD5:" OWS Content-MD5-v
2770Content-MD5-v = <base64 of 128 bit MD5 digest as per [RFC1864]>
2771Content-Range = <Content-Range, defined in [Part5], Section 5.2>
2772Content-Type = "Content-Type:" OWS Content-Type-v
2773Content-Type-v = media-type
2774
2775Expires = <Expires, defined in [Part6], Section 3.3>
2776
2777Last-Modified = <Last-Modified, defined in [Part4], Section 6.6>
2778
2779MIME-Version = "MIME-Version:" OWS MIME-Version-v
2780MIME-Version-v = 1*DIGIT "." 1*DIGIT
2781
2782OWS = <OWS, defined in [Part1], Section 1.2.2>
2783
2784absolute-URI = <absolute-URI, defined in [Part1], Section 2.6>
2785accept-ext = OWS ";" OWS token [ "=" word ]
2786accept-params = OWS ";" OWS "q=" qvalue *accept-ext
2787attribute = token
2788
2789charset = token
2790codings = ( content-coding / "*" )
2791content-coding = token
2792content-disposition = "Content-Disposition:" OWS
2793 content-disposition-v
2794content-disposition-v = disposition-type *( OWS ";" OWS
2795 disposition-parm )
2796
2797disp-extension-parm = token "=" word
2798disp-extension-token = token
2799disposition-parm = filename-parm / disp-extension-parm
2800disposition-type = "attachment" / disp-extension-token
2801
2802entity-body = *OCTET
2803entity-header = Content-Encoding / Content-Language / Content-Length
2804 / Content-Location / Content-MD5 / Content-Range / Content-Type /
2805 Expires / Last-Modified / extension-header
2806extension-header = header-field
2807
2808filename-parm = "filename=" quoted-string
2809
2810header-field = <header-field, defined in [Part1], Section 3.2>
2811
2812language-range = <language-range, defined in [RFC4647], Section 2.1>
2813language-tag = <Language-Tag, defined in [RFC5646], Section 2.1>
2814
2815media-range = ( "*/*" / ( type "/*" ) / ( type "/" subtype ) ) *( OWS
2816 ";" OWS parameter )
2817media-type = type "/" subtype *( OWS ";" OWS parameter )
2818
2819parameter = attribute "=" value
2820partial-URI = <partial-URI, defined in [Part1], Section 2.6>
2821
2822quoted-string = <quoted-string, defined in [Part1], Section 1.2.2>
2823qvalue = <qvalue, defined in [Part1], Section 6.4>
2824
2825subtype = token
2826
2827token = <token, defined in [Part1], Section 1.2.2>
2828type = token
2829
2830value = word
2831
2832word = <word, defined in [Part1], Section 1.2.2>
2833]]></artwork>
2834</figure>
2835<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline"><![CDATA[
2836; Accept defined but not used
2837; Accept-Charset defined but not used
2838; Accept-Encoding defined but not used
2839; Accept-Language defined but not used
2840; MIME-Version defined but not used
2841; content-disposition defined but not used
2842; entity-body defined but not used
2843; entity-header defined but not used
2844]]></artwork></figure></section>
2845
2846
2847<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
2848
2849<section title="Since RFC2616">
2850<t>
2851  Extracted relevant partitions from <xref target="RFC2616"/>.
2852</t>
2853</section>
2854
2855<section title="Since draft-ietf-httpbis-p3-payload-00">
2856<t>
2857  Closed issues:
2858  <list style="symbols"> 
2859    <t>
2860      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/8"/>:
2861      "Media Type Registrations"
2862      (<eref target="http://purl.org/NET/http-errata#media-reg"/>)
2863    </t>
2864    <t>
2865      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/14"/>:
2866      "Clarification regarding quoting of charset values"
2867      (<eref target="http://purl.org/NET/http-errata#charactersets"/>)
2868    </t>
2869    <t>
2870      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/16"/>:
2871      "Remove 'identity' token references"
2872      (<eref target="http://purl.org/NET/http-errata#identity"/>)
2873    </t>
2874    <t>
2875      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/25"/>:
2876      "Accept-Encoding BNF"
2877    </t>
2878    <t>
2879      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
2880      "Normative and Informative references"
2881    </t>
2882    <t>
2883      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/46"/>:
2884      "RFC1700 references"
2885    </t>
2886    <t>
2887      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/55"/>:
2888      "Updating to RFC4288"
2889    </t>
2890    <t>
2891      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
2892      "Informative references"
2893    </t>
2894    <t>
2895      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/66"/>:
2896      "ISO-8859-1 Reference"
2897    </t>
2898    <t>
2899      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/68"/>:
2900      "Encoding References Normative"
2901    </t>
2902    <t>
2903      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/86"/>:
2904      "Normative up-to-date references"
2905    </t>
2906  </list>
2907</t>
2908</section>
2909
2910<section title="Since draft-ietf-httpbis-p3-payload-01">
2911<t>
2912  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
2913  <list style="symbols"> 
2914    <t>
2915      Add explicit references to BNF syntax and rules imported from other parts of the specification.
2916    </t>
2917  </list>
2918</t>
2919</section>
2920
2921<section title="Since draft-ietf-httpbis-p3-payload-02" anchor="changes.since.02">
2922<t>
2923  Closed issues:
2924  <list style="symbols"> 
2925    <t>
2926      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/67"/>:
2927      "Quoting Charsets"
2928    </t>
2929    <t>
2930      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
2931      "Classification for Allow header"
2932    </t>
2933    <t>
2934      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/115"/>:
2935      "missing default for qvalue in description of Accept-Encoding"
2936    </t>
2937  </list>
2938</t>
2939<t>
2940  Ongoing work on IANA Message Header Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
2941  <list style="symbols"> 
2942    <t>
2943      Reference RFC 3984, and update header registrations for headers defined
2944      in this document.
2945    </t>
2946  </list>
2947</t>
2948</section>
2949
2950<section title="Since draft-ietf-httpbis-p3-payload-03" anchor="changes.since.03">
2951<t>
2952  Closed issues:
2953  <list style="symbols"> 
2954    <t>
2955      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/67"/>:
2956      "Quoting Charsets"
2957    </t>
2958    <t>
2959      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/113"/>:
2960      "language tag matching (Accept-Language) vs RFC4647"
2961    </t>
2962    <t>
2963      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/121"/>:
2964      "RFC 1806 has been replaced by RFC2183"
2965    </t>
2966  </list>
2967</t>
2968<t>
2969  Other changes:
2970  <list style="symbols"> 
2971    <t>
2972      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/68"/>:
2973      "Encoding References Normative" -- rephrase the annotation and reference
2974      <xref target="BCP97"/>.
2975    </t>
2976  </list>
2977</t>
2978 </section>
2979
2980<section title="Since draft-ietf-httpbis-p3-payload-04" anchor="changes.since.04">
2981<t>
2982  Closed issues:
2983  <list style="symbols"> 
2984    <t>
2985      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
2986      "RFC 2822 is updated by RFC 5322"
2987    </t>
2988  </list>
2989</t>
2990<t>
2991  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
2992  <list style="symbols"> 
2993    <t>
2994      Use "/" instead of "|" for alternatives.
2995    </t>
2996    <t>
2997      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
2998      whitespace ("OWS") and required whitespace ("RWS").
2999    </t>
3000    <t>
3001      Rewrite ABNFs to spell out whitespace rules, factor out
3002      header value format definitions.
3003    </t>
3004  </list>
3005</t>
3006</section>
3007
3008<section title="Since draft-ietf-httpbis-p3-payload-05" anchor="changes.since.05">
3009<t>
3010  Closed issues:
3011  <list style="symbols"> 
3012    <t>
3013      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/118"/>:
3014      "Join "Differences Between HTTP Entities and RFC 2045 Entities"?"
3015    </t>
3016  </list>
3017</t>
3018<t>
3019  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3020  <list style="symbols"> 
3021    <t>
3022      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
3023    </t>
3024  </list>
3025</t>
3026<t>
3027  Other changes:
3028  <list style="symbols"> 
3029    <t>
3030      Move definition of quality values into Part 1.
3031    </t>
3032  </list>
3033</t>
3034</section>
3035
3036<section title="Since draft-ietf-httpbis-p3-payload-06" anchor="changes.since.06">
3037<t>
3038  Closed issues:
3039  <list style="symbols"> 
3040    <t>
3041      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/80"/>:
3042      "Content-Location isn't special"
3043    </t>
3044    <t>
3045      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/155"/>:
3046      "Content Sniffing"
3047    </t>
3048  </list>
3049</t>
3050</section>
3051
3052<section title="Since draft-ietf-httpbis-p3-payload-07" anchor="changes.since.07">
3053<t>
3054  Closed issues:
3055  <list style="symbols"> 
3056    <t>
3057      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/13"/>:
3058      "Updated reference for language tags"
3059    </t>
3060    <t>
3061      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
3062      "Clarify rules for determining what entities a response carries"
3063    </t>
3064    <t>
3065      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/154"/>:
3066      "Content-Location base-setting problems"
3067    </t>
3068    <t>
3069      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/155"/>:
3070      "Content Sniffing"
3071    </t>
3072    <t>
3073      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/188"/>:
3074      "pick IANA policy (RFC5226) for Transfer Coding / Content Coding"
3075    </t>
3076    <t>
3077      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/189"/>:
3078      "move definitions of gzip/deflate/compress to part 1"
3079    </t>
3080  </list>
3081</t>
3082<t>
3083  Partly resolved issues:
3084  <list style="symbols"> 
3085    <t>
3086      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/148"/>:
3087      "update IANA requirements wrt Transfer-Coding values" (add the
3088      IANA Considerations subsection)
3089    </t>
3090    <t>
3091      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/149"/>:
3092      "update IANA requirements wrt Content-Coding values" (add the
3093      IANA Considerations subsection)
3094    </t>
3095  </list>
3096</t>
3097</section>
3098
3099<section title="Since draft-ietf-httpbis-p3-payload-08" anchor="changes.since.08">
3100<t>
3101  Closed issues:
3102  <list style="symbols"> 
3103    <t>
3104      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/81"/>:
3105      "Content Negotiation for media types"
3106    </t>
3107    <t>
3108      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/181"/>:
3109      "Accept-Language: which RFC4647 filtering?"
3110    </t>
3111  </list>
3112</t>
3113</section>
3114
3115<section title="Since draft-ietf-httpbis-p3-payload-09" anchor="changes.since.09">
3116<t>
3117  Closed issues:
3118  <list style="symbols"> 
3119    <t>
3120      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/143"/>:
3121      "IANA registry for content/transfer encodings"
3122    </t>
3123    <t>
3124      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/155"/>:
3125      "Content Sniffing"
3126    </t>
3127    <t>
3128      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/200"/>:
3129      "use of term "word" when talking about header structure"
3130    </t>
3131  </list>
3132</t>
3133<t>
3134  Partly resolved issues:
3135  <list style="symbols"> 
3136    <t>
3137      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196"/>:
3138      "Term for the requested resource's URI"
3139    </t>
3140  </list>
3141</t>
3142</section>
3143
3144</section>
3145
3146</back>
3147</rfc>
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