source: draft-ietf-httpbis/15/p3-payload.xml @ 1691

Last change on this file since 1691 was 1500, checked in by julian.reschke@…, 9 years ago

fix mime types

  • Property svn:eol-style set to native
  • Property svn:mime-type set to text/xml
File size: 122.2 KB
[29]1<?xml version="1.0" encoding="utf-8"?>
[101]2<?xml-stylesheet type='text/xsl' href='../myxml2rfc.xslt'?>
[8]3<!DOCTYPE rfc [
4  <!ENTITY MAY "<bcp14 xmlns=''>MAY</bcp14>">
5  <!ENTITY MUST "<bcp14 xmlns=''>MUST</bcp14>">
6  <!ENTITY MUST-NOT "<bcp14 xmlns=''>MUST NOT</bcp14>">
7  <!ENTITY OPTIONAL "<bcp14 xmlns=''>OPTIONAL</bcp14>">
8  <!ENTITY RECOMMENDED "<bcp14 xmlns=''>RECOMMENDED</bcp14>">
9  <!ENTITY REQUIRED "<bcp14 xmlns=''>REQUIRED</bcp14>">
10  <!ENTITY SHALL "<bcp14 xmlns=''>SHALL</bcp14>">
11  <!ENTITY SHALL-NOT "<bcp14 xmlns=''>SHALL NOT</bcp14>">
12  <!ENTITY SHOULD "<bcp14 xmlns=''>SHOULD</bcp14>">
13  <!ENTITY SHOULD-NOT "<bcp14 xmlns=''>SHOULD NOT</bcp14>">
[1326]14  <!ENTITY ID-VERSION "15">
[1321]15  <!ENTITY ID-MONTH "July">
[1099]16  <!ENTITY ID-YEAR "2011">
[1101]17  <!ENTITY mdash "&#8212;">
[424]18  <!ENTITY notation                 "<xref target='Part1' x:rel='#notation' xmlns:x=''/>">
[205]19  <!ENTITY notation-abnf            "<xref target='Part1' x:rel='#notation.abnf' xmlns:x=''/>">
20  <!ENTITY basic-rules              "<xref target='Part1' x:rel='#basic.rules' xmlns:x=''/>">
[115]21  <!ENTITY caching-neg-resp         "<xref target='Part6' x:rel='#caching.negotiated.responses' xmlns:x=''/>">
[31]22  <!ENTITY header-transfer-encoding "<xref target='Part1' x:rel='#header.transfer-encoding' xmlns:x=''/>">
23  <!ENTITY header-content-length    "<xref target='Part1' x:rel='#header.content-length' xmlns:x=''/>">
24  <!ENTITY header-content-range     "<xref target='Part5' x:rel='#header.content-range' xmlns:x=''/>">
25  <!ENTITY header-expires           "<xref target='Part6' x:rel='#header.expires' xmlns:x=''/>">
26  <!ENTITY header-last-modified     "<xref target='Part4' x:rel='#header.last-modified' xmlns:x=''/>">
27  <!ENTITY header-user-agent        "<xref target='Part2' x:rel='#header.user-agent' xmlns:x=''/>">
[115]28  <!ENTITY header-vary              "<xref target='Part6' x:rel='#header.vary' xmlns:x=''/>">
[31]29  <!ENTITY message-body             "<xref target='Part1' x:rel='#message.body' xmlns:x=''/>">
30  <!ENTITY multipart-byteranges     "<xref target='Part5' x:rel='' xmlns:x=''/>">
[580]31  <!ENTITY full-date                "<xref target='Part1' x:rel='' xmlns:x=''/>">
[457]32  <!ENTITY qvalue                   "<xref target='Part1' x:rel='#quality.values' xmlns:x=''/>">
[374]33  <!ENTITY uri                      "<xref target='Part1' x:rel='#uri' xmlns:x=''/>">
[823]34  <!ENTITY effective-request-uri    "<xref target='Part1' x:rel='#effective.request.uri' xmlns:x=''/>">
[808]35  <!ENTITY compression-codings      "<xref target='Part1' x:rel='#compression.codings' xmlns:x=''/>">
36  <!ENTITY transfer-codings         "<xref target='Part1' x:rel='#transfer.codings' xmlns:x=''/>">
[673]37  <!ENTITY compress-coding          "<xref target='Part1' x:rel='#compress.coding' xmlns:x=''/>">
38  <!ENTITY deflate-coding           "<xref target='Part1' x:rel='#deflate.coding' xmlns:x=''/>">
39  <!ENTITY gzip-coding              "<xref target='Part1' x:rel='#gzip.coding' xmlns:x=''/>">
[716]40  <!ENTITY response-representation  "<xref target='Part2' x:rel='#identifying.response.associated.with.representation' xmlns:x=''/>">
42<?rfc toc="yes" ?>
[29]43<?rfc symrefs="yes" ?>
44<?rfc sortrefs="yes" ?>
[8]45<?rfc compact="yes"?>
46<?rfc subcompact="no" ?>
47<?rfc linkmailto="no" ?>
48<?rfc editing="no" ?>
[203]49<?rfc comments="yes"?>
50<?rfc inline="yes"?>
[799]51<?rfc rfcedstyle="yes"?>
[8]52<?rfc-ext allow-markup-in-artwork="yes" ?>
53<?rfc-ext include-references-in-index="yes" ?>
[308]54<rfc obsoletes="2616" category="std" x:maturity-level="draft"
[446]55     ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p3-payload-&ID-VERSION;"
[153]56     xmlns:x=''>
[120]59  <title abbrev="HTTP/1.1, Part 3">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
[29]61  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
[1106]62    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[8]63    <address>
64      <postal>
[1106]65        <street>345 Park Ave</street>
66        <city>San Jose</city>
[8]67        <region>CA</region>
[1106]68        <code>95110</code>
[29]69        <country>USA</country>
[8]70      </postal>
[29]71      <email></email>
72      <uri></uri>
[8]73    </address>
74  </author>
[29]76  <author initials="J." surname="Gettys" fullname="Jim Gettys">
[844]77    <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
[8]78    <address>
79      <postal>
[29]80        <street>21 Oak Knoll Road</street>
81        <city>Carlisle</city>
[8]82        <region>MA</region>
[29]83        <code>01741</code>
84        <country>USA</country>
[8]85      </postal>
[844]86      <email></email>
87      <uri></uri>
[8]88    </address>
89  </author>
91  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
[29]92    <organization abbrev="HP">Hewlett-Packard Company</organization>
[8]93    <address>
94      <postal>
[29]95        <street>HP Labs, Large Scale Systems Group</street>
96        <street>1501 Page Mill Road, MS 1177</street>
[8]97        <city>Palo Alto</city>
98        <region>CA</region>
[29]99        <code>94304</code>
100        <country>USA</country>
[8]101      </postal>
[29]102      <email></email>
[8]103    </address>
104  </author>
106  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
[29]107    <organization abbrev="Microsoft">Microsoft Corporation</organization>
[8]108    <address>
109      <postal>
[29]110        <street>1 Microsoft Way</street>
111        <city>Redmond</city>
112        <region>WA</region>
113        <code>98052</code>
114        <country>USA</country>
[8]115      </postal>
[29]116      <email></email>
[8]117    </address>
118  </author>
120  <author initials="L." surname="Masinter" fullname="Larry Masinter">
[1106]121    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[8]122    <address>
123      <postal>
[29]124        <street>345 Park Ave</street>
125        <city>San Jose</city>
[8]126        <region>CA</region>
[29]127        <code>95110</code>
128        <country>USA</country>
[8]129      </postal>
[29]130      <email></email>
131      <uri></uri>
[8]132    </address>
133  </author>
135  <author initials="P." surname="Leach" fullname="Paul J. Leach">
136    <organization abbrev="Microsoft">Microsoft Corporation</organization>
137    <address>
138      <postal>
139        <street>1 Microsoft Way</street>
140        <city>Redmond</city>
141        <region>WA</region>
142        <code>98052</code>
143      </postal>
144      <email></email>
145    </address>
146  </author>
148  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
149    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
150    <address>
151      <postal>
[34]152        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
153        <street>The Stata Center, Building 32</street>
154        <street>32 Vassar Street</street>
[8]155        <city>Cambridge</city>
156        <region>MA</region>
157        <code>02139</code>
[29]158        <country>USA</country>
[8]159      </postal>
160      <email></email>
[34]161      <uri></uri>
[8]162    </address>
163  </author>
[95]165  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
[94]166    <organization abbrev="W3C">World Wide Web Consortium</organization>
167    <address>
168      <postal>
169        <street>W3C / ERCIM</street>
170        <street>2004, rte des Lucioles</street>
171        <city>Sophia-Antipolis</city>
172        <region>AM</region>
173        <code>06902</code>
174        <country>France</country>
175      </postal>
176      <email></email>
177      <uri></uri>
178    </address>
179  </author>
[95]181  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
182    <organization abbrev="greenbytes">greenbytes GmbH</organization>
183    <address>
184      <postal>
185        <street>Hafenweg 16</street>
186        <city>Muenster</city><region>NW</region><code>48155</code>
187        <country>Germany</country>
188      </postal>
[609]189      <phone>+49 251 2807760</phone>
190      <facsimile>+49 251 2807761</facsimile>
191      <email></email>
192      <uri></uri>
[95]193    </address>
194  </author>
[1326]196  <date month="&ID-MONTH;" year="&ID-YEAR;" day="11"/>
[440]197  <workgroup>HTTPbis Working Group</workgroup>
201   The Hypertext Transfer Protocol (HTTP) is an application-level
202   protocol for distributed, collaborative, hypermedia information
[29]203   systems. HTTP has been in use by the World Wide Web global information
[35]204   initiative since 1990. This document is Part 3 of the seven-part specification
[29]205   that defines the protocol referred to as "HTTP/1.1" and, taken together,
[42]206   obsoletes RFC 2616.  Part 3 defines HTTP message content,
[29]207   metadata, and content negotiation.
211<note title="Editorial Note (To be removed by RFC Editor)">
212  <t>
213    Discussion of this draft should take place on the HTTPBIS working group
[1268]214    mailing list (, which is archived at
215    <eref target=""/>.
216  </t>
217  <t>
218    The current issues list is at
219    <eref target=""/> and related
220    documents (including fancy diffs) can be found at
[324]221    <eref target=""/>.
[36]222  </t>
[153]223  <t>
[1271]224    The changes in this draft are summarized in <xref target="changes.since.14"/>.
[153]225  </t>
229<section title="Introduction" anchor="introduction">
[163]231   This document defines HTTP/1.1 message payloads (a.k.a., content), the
[161]232   associated metadata header fields that define how the payload is intended
233   to be interpreted by a recipient, the request header fields that
[908]234   might influence content selection, and the various selection algorithms
[161]235   that are collectively referred to as HTTP content negotiation.
238   This document is currently disorganized in order to minimize the changes
239   between drafts and enable reviewers to see the smaller errata changes.
[980]240   A future draft will reorganize the sections to better reflect the content.
[161]241   In particular, the sections on entities will be renamed payload and moved
242   to the first half of the document, while the sections on content negotiation
243   and associated request header fields will be moved to the second half.  The
244   current mess reflects how widely dispersed these topics and associated
245   requirements had become in <xref target="RFC2616"/>.
[660]248<section title="Terminology" anchor="terminology">
250   This specification uses a number of terms to refer to the roles
251   played by participants in, and objects of, the HTTP communication.
254  <iref item="content negotiation"/>
255  <x:dfn>content negotiation</x:dfn>
256  <list>
257    <t>
258      The mechanism for selecting the appropriate representation when
[856]259      servicing a request. The representation in any response
[660]260      can be negotiated (including error responses).
261    </t>
262  </list>
[96]266<section title="Requirements" anchor="intro.requirements">
268   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
269   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
270   document are to be interpreted as described in <xref target="RFC2119"/>.
273   An implementation is not compliant if it fails to satisfy one or more
[847]274   of the "MUST" or "REQUIRED" level requirements for the protocols it
275   implements. An implementation that satisfies all the "MUST" or "REQUIRED"
276   level and all the "SHOULD" level requirements for its protocols is said
277   to be "unconditionally compliant"; one that satisfies all the "MUST"
278   level requirements but not all the "SHOULD" level requirements for its
279   protocols is said to be "conditionally compliant".
[424]283<section title="Syntax Notation" anchor="notation">
[425]284  <x:anchor-alias value="ALPHA"/>
285  <x:anchor-alias value="CR"/>
286  <x:anchor-alias value="DIGIT"/>
287  <x:anchor-alias value="LF"/>
288  <x:anchor-alias value="OCTET"/>
289  <x:anchor-alias value="VCHAR"/>
290  <x:anchor-alias value="WSP"/>
[543]292  This specification uses the ABNF syntax defined in &notation; (which
293  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
294  <xref target="collected.abnf"/> shows the collected ABNF, with the list
295  rule expanded.
[425]298  The following core rules are included by
299  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
300  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
301  DIGIT (decimal 0-9), DQUOTE (double quote),
302  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
303  OCTET (any 8-bit sequence of data), SP (space),
304  VCHAR (any visible USASCII character),
305  and WSP (whitespace).
308<section title="Core Rules" anchor="core.rules">
[229]309  <x:anchor-alias value="token"/>
[810]310  <x:anchor-alias value="word"/>
[357]311  <x:anchor-alias value="OWS"/>
[424]313  The core rules below are defined in &basic-rules;:
315<figure><artwork type="abnf2616">
[229]316  <x:ref>token</x:ref>          = &lt;token, defined in &basic-rules;&gt;
[810]317  <x:ref>word</x:ref>           = &lt;word, defined in &basic-rules;&gt;
[357]318  <x:ref>OWS</x:ref>            = &lt;OWS, defined in &basic-rules;&gt;
322<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
[374]323  <x:anchor-alias value="absolute-URI"/>
[391]324  <x:anchor-alias value="partial-URI"/>
[457]325  <x:anchor-alias value="qvalue"/>
[206]327  The ABNF rules below are defined in other parts:
[207]329<figure><!--Part1--><artwork type="abnf2616">
[374]330  <x:ref>absolute-URI</x:ref>   = &lt;absolute-URI, defined in &uri;&gt;
[391]331  <x:ref>partial-URI</x:ref>    = &lt;partial-URI, defined in &uri;&gt;
[457]332  <x:ref>qvalue</x:ref>         = &lt;qvalue, defined in &qvalue;&gt;
[8]340<section title="Protocol Parameters" anchor="protocol.parameters">
[1176]342<section title="Character Encodings (charset)" anchor="character.sets">
[1176]344   HTTP uses charset names to indicate the character encoding of a
345   textual representation.
[229]347<t anchor="rule.charset">
348  <x:anchor-alias value="charset"/>
[1176]349   A character encoding is identified by a case-insensitive token. The
[8]350   complete set of tokens is defined by the IANA Character Set registry
[91]351   (<eref target=""/>).
353<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="charset"/>
[229]354  <x:ref>charset</x:ref> = <x:ref>token</x:ref>
357   Although HTTP allows an arbitrary token to be used as a charset
358   value, any token that has a predefined value within the IANA
[1176]359   Character Set registry &MUST; represent the character encoding defined
[8]360   by that registry. Applications &SHOULD; limit their use of character
[1176]361   encodings to those defined within the IANA registry.
[81]364   HTTP uses charset in two contexts: within an Accept-Charset request
[994]365   header field (in which the charset value is an unquoted token) and as the
366   value of a parameter in a Content-Type header field (within a request or
[81]367   response), in which case the parameter value of the charset parameter
[908]368   can be quoted.
[969]371   Implementors need to be aware of IETF character set requirements <xref target="RFC3629"/>
[8]372   <xref target="RFC2277"/>.
376<section title="Content Codings" anchor="content.codings">
[229]377  <x:anchor-alias value="content-coding"/>
379   Content coding values indicate an encoding transformation that has
[866]380   been or can be applied to a representation. Content codings are primarily
381   used to allow a representation to be compressed or otherwise usefully
[8]382   transformed without losing the identity of its underlying media type
[866]383   and without loss of information. Frequently, the representation is stored in
[8]384   coded form, transmitted directly, and only decoded by the recipient.
386<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="content-coding"/>
[229]387  <x:ref>content-coding</x:ref>   = <x:ref>token</x:ref>
390   All content-coding values are case-insensitive. HTTP/1.1 uses
391   content-coding values in the Accept-Encoding (<xref target="header.accept-encoding"/>) and
392   Content-Encoding (<xref target="header.content-encoding"/>) header fields. Although the value
393   describes the content-coding, what is more important is that it
394   indicates what decoding mechanism will be required to remove the
395   encoding.
[673]398   compress<iref item="compress (Coding Format)"/><iref item="Coding Format" subitem="compress"/>
399  <list>
400    <t>
401      See &compress-coding;.
402    </t>
403  </list>
[673]406   deflate<iref item="deflate (Coding Format)"/><iref item="Coding Format" subitem="deflate"/>
[8]407  <list>
408    <t>
[673]409      See &deflate-coding;.
[8]410    </t>
411  </list>
[673]414   gzip<iref item="gzip (Coding Format)"/><iref item="Coding Format" subitem="gzip"/>
415  <list>
416    <t>
417      See &gzip-coding;.
418    </t>
419  </list>
[673]422   identity<iref item="identity (Coding Format)"/><iref item="Coding Format" subitem="identity"/>
[8]423  <list><t>
424        The default (identity) encoding; the use of no transformation
425        whatsoever. This content-coding is used only in the Accept-Encoding
[994]426        header field, and &SHOULD-NOT;  be used in the Content-Encoding
427        header field.
[8]428  </t></list>
431<section title="Content Coding Registry" anchor="content.coding.registry">
[670]433   The HTTP Content Coding Registry defines the name space for the content
434   coding names.
437   Registrations &MUST; include the following fields:
438   <list style="symbols">
439     <t>Name</t>
440     <t>Description</t>
441     <t>Pointer to specification text</t>
442   </list>
[808]445   Names of content codings &MUST-NOT; overlap with names of transfer codings
446   (&transfer-codings;), unless the encoding transformation is identical (as it
447   is the case for the compression codings defined in
448   &compression-codings;).
[942]451   Values to be added to this name space require a specification
452   (see "Specification Required" in
[670]453   <xref target="RFC5226" x:fmt="of" x:sec="4.1"/>), and &MUST;
[8]454   conform to the purpose of content coding defined in this section.
457   The registry itself is maintained at
458   <eref target=""/>.
[8]464<section title="Media Types" anchor="media.types">
[229]465  <x:anchor-alias value="media-type"/>
466  <x:anchor-alias value="type"/>
467  <x:anchor-alias value="subtype"/>
[152]469   HTTP uses Internet Media Types <xref target="RFC2046"/> in the Content-Type (<xref target="header.content-type"/>)
[8]470   and Accept (<xref target="header.accept"/>) header fields in order to provide
471   open and extensible data typing and type negotiation.
473<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="media-type"/><iref primary="true" item="Grammar" subitem="type"/><iref primary="true" item="Grammar" subitem="subtype"/>
[357]474  <x:ref>media-type</x:ref> = <x:ref>type</x:ref> "/" <x:ref>subtype</x:ref> *( <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> <x:ref>parameter</x:ref> )
475  <x:ref>type</x:ref>       = <x:ref>token</x:ref>
476  <x:ref>subtype</x:ref>    = <x:ref>token</x:ref>
[229]478<t anchor="rule.parameter">
479  <x:anchor-alias value="attribute"/>
480  <x:anchor-alias value="parameter"/>
481  <x:anchor-alias value="value"/>
[1153]482   The type/subtype &MAY; be followed by parameters in the form of
483   attribute/value pairs.
[29]485<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="parameter"/><iref primary="true" item="Grammar" subitem="attribute"/><iref primary="true" item="Grammar" subitem="value"/>
[250]486  <x:ref>parameter</x:ref>      = <x:ref>attribute</x:ref> "=" <x:ref>value</x:ref>
487  <x:ref>attribute</x:ref>      = <x:ref>token</x:ref>
[810]488  <x:ref>value</x:ref>          = <x:ref>word</x:ref>
491   The type, subtype, and parameter attribute names are case-insensitive.
[370]492   Parameter values might or might not be case-sensitive, depending on the
493   semantics of the parameter name.  The presence or absence of a parameter might
[8]494   be significant to the processing of a media-type, depending on its
495   definition within the media type registry.
[908]498   A parameter value that matches the <x:ref>token</x:ref> production can be
[297]499   transmitted as either a token or within a quoted-string. The quoted and
500   unquoted values are equivalent.
[8]503   Note that some older HTTP applications do not recognize media type
504   parameters. When sending data to older HTTP applications,
505   implementations &SHOULD; only use media type parameters when they are
506   required by that type/subtype definition.
509   Media-type values are registered with the Internet Assigned Number
[91]510   Authority (IANA). The media type registration process is
[115]511   outlined in <xref target="RFC4288"/>. Use of non-registered media types is
[8]512   discouraged.
515<section title="Canonicalization and Text Defaults" anchor="canonicalization.and.text.defaults">
[874]517   Internet media types are registered with a canonical form. A
518   representation transferred via HTTP messages &MUST; be in the
[8]519   appropriate canonical form prior to its transmission except for
520   "text" types, as defined in the next paragraph.
523   When in canonical form, media subtypes of the "text" type use CRLF as
524   the text line break. HTTP relaxes this requirement and allows the
525   transport of text media with plain CR or LF alone representing a line
[874]526   break when it is done consistently for an entire representation. HTTP
527   applications &MUST; accept CRLF, bare CR, and bare LF as indicating
528   a line break in text media received via HTTP. In
529   addition, if the text is in a character encoding that does not
[8]530   use octets 13 and 10 for CR and LF respectively, as is the case for
[874]531   some multi-byte character encodings, HTTP allows the use of whatever octet
532   sequences are defined by that character encoding to represent the
[8]533   equivalent of CR and LF for line breaks. This flexibility regarding
[874]534   line breaks applies only to text media in the payload body; a bare CR
[8]535   or LF &MUST-NOT; be substituted for CRLF within any of the HTTP control
536   structures (such as header fields and multipart boundaries).
[874]539   If a representation is encoded with a content-coding, the underlying
[8]540   data &MUST; be in a form defined above prior to being encoded.
544<section title="Multipart Types" anchor="multipart.types">
[1101]546   MIME provides for a number of "multipart" types &mdash; encapsulations of
[874]547   one or more representations within a single message-body. All multipart
[97]548   types share a common syntax, as defined in <xref target="RFC2046" x:sec="5.1.1" x:fmt="of"/>,
549   and &MUST; include a boundary parameter as part of the media type
[8]550   value. The message body is itself a protocol element and &MUST;
551   therefore use only CRLF to represent line breaks between body-parts.
554   In general, HTTP treats a multipart message-body no differently than
[852]555   any other media type: strictly as payload.  HTTP does not use the
556   multipart boundary as an indicator of message-body length.
[97]557   <!-- jre: re-insert removed text pointing to caching? -->
[852]558   In all other respects, an HTTP user agent &SHOULD; follow the same or similar
[8]559   behavior as a MIME user agent would upon receipt of a multipart type.
560   The MIME header fields within each body-part of a multipart message-body
561   do not have any significance to HTTP beyond that defined by
562   their MIME semantics.
565   If an application receives an unrecognized multipart subtype, the
566   application &MUST; treat it as being equivalent to "multipart/mixed".
569  <t>
570    <x:h>Note:</x:h> The "multipart/form-data" type has been specifically defined
571    for carrying form data suitable for processing via the POST
572    request method, as described in <xref target="RFC2388"/>.
573  </t>
578<section title="Language Tags" anchor="language.tags">
[229]579  <x:anchor-alias value="language-tag"/>
[690]581   A language tag, as defined in <xref target="RFC5646"/>, identifies a
[613]582   natural language spoken, written, or otherwise conveyed by human beings for
583   communication of information to other human beings. Computer languages are
584   explicitly excluded. HTTP uses language tags within the Accept-Language and
585   Content-Language fields.
[613]588   In summary, a language tag is composed of one or more parts: A primary
589   language subtag followed by a possibly empty series of subtags:
[613]591<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="language-tag"/>
[690]592  <x:ref>language-tag</x:ref> = &lt;Language-Tag, defined in <xref target="RFC5646" x:sec="2.1"/>&gt;
595   White space is not allowed within the tag and all tags are case-insensitive.
[613]596   The name space of language subtags is administered by the IANA (see
597   <eref target=""/>).
600  <preamble>Example tags include:</preamble>
601<artwork type="example">
602  en, en-US, es-419, az-Arab, x-pig-latin, man-Nkoo-GN
[690]606   See <xref target="RFC5646"/> for further information.
[965]611<section title="Payload" anchor="payload">
[965]613   HTTP messages &MAY; transfer a payload if not otherwise restricted by
614   the request method or response status code.  The payload consists of
615   metadata, in the form of header fields, and data, in the form of the
616   sequence of octets in the message-body after any transfer-coding has
617   been decoded.
[965]619<iref item="payload"/>
621   A "<x:dfn>payload</x:dfn>" in HTTP is always a partial or complete
622   representation of some resource.  We use separate terms for payload
623   and representation because some messages contain only the associated
624   representation's header fields (e.g., responses to HEAD) or only some
625   part(s) of the representation (e.g., the 206 status code).
627<section title="Payload Header Fields" anchor="payload.header.fields">
628  <x:anchor-alias value="payload-header"/>
[965]630   HTTP header fields that specifically define the payload, rather than the
631   associated representation, are referred to as "payload header fields".
632   The following payload header fields are defined by HTTP/1.1:
[1138]634<texttable align="left">
635  <ttcol>Header Field Name</ttcol>
636  <ttcol>Defined in...</ttcol>
638  <c>Content-Length</c> <c>&header-content-length;</c>
639  <c>Content-Range</c> <c>&header-content-range;</c>
[874]643<section title="Payload Body" anchor="payload.body">
644  <x:anchor-alias value="payload-body"/>
[874]646   A payload body is only present in a message when a message-body is
647   present, as described in &message-body;. The payload body is obtained
[8]648   from the message-body by decoding any Transfer-Encoding that might
649   have been applied to ensure safe and proper transfer of the message.
[965]654<section title="Representation" anchor="representation">
655<iref item="representation"/>
[965]657   A "<x:dfn>representation</x:dfn>" is information in a format that can be readily
658   communicated from one party to another.  A resource representation
659   is information that reflects the state of that resource, as observed
660   at some point in the past (e.g., in a response to GET) or to be
661   desired at some point in the future (e.g., in a PUT request).
664   Most, but not all, representations transferred via HTTP are intended
665   to be a representation of the target resource (the resource identified
666   by the effective request URI).  The precise semantics of a representation
667   are determined by the type of message (request or response), the request
668   method, the response status code, and the representation metadata.
669   For example, the above semantic is true for the representation in any
670   200 (OK) response to GET and for the representation in any PUT request.
671   A 200 response to PUT, in contrast, contains either a representation
672   that describes the successful action or a representation of the target
673   resource, with the latter indicated by a Content-Location header field
674   with the same value as the effective request URI.  Likewise, response
675   messages with an error status code usually contain a representation that
676   describes the error and what next steps are suggested for resolving it.
679<section title="Representation Header Fields" anchor="representation.header.fields">
680  <x:anchor-alias value="representation-header"/>
682   Representation header fields define metadata about the representation data
683   enclosed in the message-body or, if no message-body is present, about
684   the representation that would have been transferred in a 200 response
685   to a simultaneous GET request with the same effective request URI.
688   The following header fields are defined as representation metadata:
[1138]690<texttable align="left">
691  <ttcol>Header Field Name</ttcol>
692  <ttcol>Defined in...</ttcol>
694  <c>Content-Encoding</c> <c><xref target="header.content-encoding"/></c>
695  <c>Content-Language</c> <c><xref target="header.content-language"/></c>
696  <c>Content-Location</c> <c><xref target="header.content-location"/></c>
697  <c>Content-Type</c> <c><xref target="header.content-type"/></c>
698  <c>Expires</c> <c>&header-expires;</c>
699  <c>Last-Modified</c> <c>&header-last-modified;</c>
703<section title="Representation Data" anchor="">
704  <x:anchor-alias value="representation-data"/>
706   The representation body associated with an HTTP message is
707   either provided as the payload body of the message or
708   referred to by the message semantics and the effective request
709   URI.  The representation data is in a format and encoding defined by
710   the representation metadata header fields.
713   The data type of the representation data
714   is determined via the header fields Content-Type and Content-Encoding.
[8]715   These define a two-layer, ordered encoding model:
717<figure><artwork type="example">
[965]718  representation-data := Content-Encoding( Content-Type( bits ) )
[965]721   Content-Type specifies the media type of the underlying data, which
722   defines both the data format and how that data &SHOULD; be processed
723   by the recipient (within the scope of the request method semantics).
724   Any HTTP/1.1 message containing a payload body &SHOULD; include a
725   Content-Type header field defining the media type of the associated
726   representation unless that metadata is unknown to the sender.
[831]727   If the Content-Type header field is not present, it indicates that
[965]728   the sender does not know the media type of the representation;
729   recipients &MAY; either assume that the media type is
730   "application/octet-stream" (<xref target="RFC2046" x:fmt="," x:sec="4.5.1"/>)
[592]731   or examine the content to determine its type.
[965]734   In practice, resource owners do not always properly configure their origin
735   server to provide the correct Content-Type for a given representation,
736   with the result that some clients will examine a response body's content
737   and override the specified type.
[908]738   Clients that do so risk drawing incorrect conclusions, which might expose
[965]739   additional security risks (e.g., "privilege escalation").  Furthermore,
740   it is impossible to determine the sender's intent by examining the data
741   format: many data formats match multiple media types that differ only in
742   processing semantics.  Implementers are encouraged to provide a means of
743   disabling such "content sniffing" when it is used.
[908]746   Content-Encoding is used to indicate any additional content
[8]747   codings applied to the data, usually for the purpose of data
[965]748   compression, that are a property of the representation.  If
749   Content-Encoding is not present, then there is no additional
750   encoding beyond that defined by the Content-Type.
755<section title="Content Negotiation" anchor="content.negotiation">
[745]757   HTTP responses include a representation which contains information for
758   interpretation, whether by a human user or for further processing.
759   Often, the server has different ways of representing the
760   same information; for example, in different formats, languages,
761   or using different character encodings.
[745]764   HTTP clients and their users might have different or variable
765   capabilities, characteristics or preferences which would influence
766   which representation, among those available from the server,
767   would be best for the server to deliver. For this reason, HTTP
[1101]768   provides mechanisms for "content negotiation" &mdash; a process of
[745]769   allowing selection of a representation of a given resource,
770   when more than one is available.
[745]773   This specification defines two patterns of content negotiation;
774   "server-driven", where the server selects the representation based
775   upon the client's stated preferences, and "agent-driven" negotiation,
776   where the server provides a list of representations for the client to
777   choose from, based upon their metadata. In addition,  there are
778   other patterns: some applications use an "active content" pattern,
779   where the server returns active content which runs on the client
780   and, based on client available parameters, selects additional
781   resources to invoke. "Transparent Content Negotiation" (<xref target="RFC2295"/>)
782   has also been proposed.
785   These patterns are all widely used, and have trade-offs in applicability
786   and practicality. In particular, when the number of preferences or
787   capabilities to be expressed by a client are large (such as when many
788   different formats are supported by a user-agent), server-driven
[908]789   negotiation becomes unwieldy, and might not be appropriate. Conversely,
[745]790   when the number of representations to choose from is very large,
[908]791   agent-driven negotiation might not be appropriate.
794   Note that in all cases, the supplier of representations has the
795   responsibility for determining which representations might be
796   considered to be the "same information".
799<section title="Server-driven Negotiation" anchor="server-driven.negotiation">
801   If the selection of the best representation for a response is made by
802   an algorithm located at the server, it is called server-driven
803   negotiation. Selection is based on the available representations of
[763]804   the response (the dimensions over which it can vary; e.g., language,
[8]805   content-coding, etc.) and the contents of particular header fields in
806   the request message or on other information pertaining to the request
807   (such as the network address of the client).
810   Server-driven negotiation is advantageous when the algorithm for
811   selecting from among the available representations is difficult to
812   describe to the user agent, or when the server desires to send its
813   "best guess" to the client along with the first response (hoping to
814   avoid the round-trip delay of a subsequent request if the "best
815   guess" is good enough for the user). In order to improve the server's
816   guess, the user agent &MAY; include request header fields (Accept,
817   Accept-Language, Accept-Encoding, etc.) which describe its
818   preferences for such a response.
821   Server-driven negotiation has disadvantages:
822  <list style="numbers">
823    <t>
824         It is impossible for the server to accurately determine what
825         might be "best" for any given user, since that would require
826         complete knowledge of both the capabilities of the user agent
827         and the intended use for the response (e.g., does the user want
828         to view it on screen or print it on paper?).
829    </t>
830    <t>
831         Having the user agent describe its capabilities in every
832         request can be both very inefficient (given that only a small
833         percentage of responses have multiple representations) and a
834         potential violation of the user's privacy.
835    </t>
836    <t>
837         It complicates the implementation of an origin server and the
838         algorithms for generating responses to a request.
839    </t>
840    <t>
[908]841         It might limit a public cache's ability to use the same response
[8]842         for multiple user's requests.
843    </t>
844  </list>
[1163]847   HTTP/1.1 includes the following header fields for enabling
[8]848   server-driven negotiation through description of user agent
849   capabilities and user preferences: Accept (<xref target="header.accept"/>), Accept-Charset
850   (<xref target="header.accept-charset"/>), Accept-Encoding (<xref target="header.accept-encoding"/>), Accept-Language
[745]851   (<xref target="header.accept-language"/>), and User-Agent (&header-user-agent;).
852   However, an origin server is not limited to these dimensions and &MAY; vary
[1163]853   the response based on any aspect of the request, including aspects
854   of the connection (e.g., IP address) or information within extension
855   header fields not defined by this specification.
858  <t>
859    <x:h>Note:</x:h> In practice, User-Agent based negotiation is fragile,
860    because new clients might not be recognized.
861  </t>
[115]864   The Vary header field (&header-vary;) can be used to express the parameters the
[8]865   server uses to select a representation that is subject to server-driven
[29]866   negotiation.
870<section title="Agent-driven Negotiation" anchor="agent-driven.negotiation">
872   With agent-driven negotiation, selection of the best representation
873   for a response is performed by the user agent after receiving an
874   initial response from the origin server. Selection is based on a list
875   of the available representations of the response included within the
[874]876   header fields or body of the initial response, with each
[8]877   representation identified by its own URI. Selection from among the
[908]878   representations can be performed automatically (if the user agent is
[8]879   capable of doing so) or manually by the user selecting from a
880   generated (possibly hypertext) menu.
883   Agent-driven negotiation is advantageous when the response would vary
884   over commonly-used dimensions (such as type, language, or encoding),
885   when the origin server is unable to determine a user agent's
886   capabilities from examining the request, and generally when public
887   caches are used to distribute server load and reduce network usage.
890   Agent-driven negotiation suffers from the disadvantage of needing a
891   second request to obtain the best alternate representation. This
892   second request is only efficient when caching is used. In addition,
893   this specification does not define any mechanism for supporting
894   automatic selection, though it also does not prevent any such
895   mechanism from being developed as an extension and used within
896   HTTP/1.1.
[745]899   This specification defines the 300 (Multiple Choices) and 406 (Not Acceptable)
[8]900   status codes for enabling agent-driven negotiation when the server is
901   unwilling or unable to provide a varying response using server-driven
902   negotiation.
[8]907<section title="Header Field Definitions" anchor="header.fields">
[117]909   This section defines the syntax and semantics of HTTP/1.1 header fields
910   related to the payload of messages.
[8]913<section title="Accept" anchor="header.accept">
[1120]914  <iref primary="true" item="Accept header field" x:for-anchor=""/>
915  <iref primary="true" item="Header Fields" subitem="Accept" x:for-anchor=""/>
[229]916  <x:anchor-alias value="Accept"/>
[370]917  <x:anchor-alias value="accept-ext"/>
[229]918  <x:anchor-alias value="accept-params"/>
919  <x:anchor-alias value="media-range"/>
[1163]921   The "Accept" header field can be used by user agents to specify
[994]922   response media types that are acceptable. Accept header fields can be used to
[698]923   indicate that the request is specifically limited to a small set of desired
924   types, as in the case of a request for an in-line image.
[1234]926<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Accept"/><iref primary="true" item="Grammar" subitem="media-range"/><iref primary="true" item="Grammar" subitem="accept-params"/><iref primary="true" item="Grammar" subitem="accept-ext"/>
927  <x:ref>Accept</x:ref> = #( <x:ref>media-range</x:ref> [ <x:ref>accept-params</x:ref> ] )
[229]929  <x:ref>media-range</x:ref>    = ( "*/*"
[334]930                   / ( <x:ref>type</x:ref> "/" "*" )
931                   / ( <x:ref>type</x:ref> "/" <x:ref>subtype</x:ref> )
[370]932                   ) *( <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> <x:ref>parameter</x:ref> )
933  <x:ref>accept-params</x:ref>  = <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> "q=" <x:ref>qvalue</x:ref> *( <x:ref>accept-ext</x:ref> )
[1039]934  <x:ref>accept-ext</x:ref>     = <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> <x:ref>token</x:ref> [ "=" <x:ref>word</x:ref> ]
937   The asterisk "*" character is used to group media types into ranges,
938   with "*/*" indicating all media types and "type/*" indicating all
939   subtypes of that type. The media-range &MAY; include media type
940   parameters that are applicable to that range.
943   Each media-range &MAY; be followed by one or more accept-params,
944   beginning with the "q" parameter for indicating a relative quality
945   factor. The first "q" parameter (if any) separates the media-range
946   parameter(s) from the accept-params. Quality factors allow the user
947   or user agent to indicate the relative degree of preference for that
[457]948   media-range, using the qvalue scale from 0 to 1 (&qvalue;). The
[8]949   default value is q=1.
952  <t>
953    <x:h>Note:</x:h> Use of the "q" parameter name to separate media type
954    parameters from Accept extension parameters is due to historical
955    practice. Although this prevents any media type parameter named
956    "q" from being used with a media range, such an event is believed
957    to be unlikely given the lack of any "q" parameters in the IANA
958    media type registry and the rare usage of any media type
959    parameters in Accept. Future media types are discouraged from
960    registering any parameter named "q".
961  </t>
964   The example
966<figure><artwork type="example">
[357]967  Accept: audio/*; q=0.2, audio/basic
970   &SHOULD; be interpreted as "I prefer audio/basic, but send me any audio
[879]971   type if it is the best available after an 80% mark-down in quality".
974   If no Accept header field is present, then it is assumed that the
975   client accepts all media types. If an Accept header field is present,
976   and if the server cannot send a response which is acceptable
977   according to the combined Accept field value, then the server &SHOULD;
[137]978   send a 406 (Not Acceptable) response.
981   A more elaborate example is
983<figure><artwork type="example">
[357]984  Accept: text/plain; q=0.5, text/html,
985          text/x-dvi; q=0.8, text/x-c
988   Verbally, this would be interpreted as "text/html and text/x-c are
989   the preferred media types, but if they do not exist, then send the
[866]990   text/x-dvi representation, and if that does not exist, send the text/plain
[879]991   representation".
994   Media ranges can be overridden by more specific media ranges or
995   specific media types. If more than one media range applies to a given
996   type, the most specific reference has precedence. For example,
998<figure><artwork type="example">
[1244]999  Accept: text/*, text/plain, text/plain;format=flowed, */*
1002   have the following precedence:
[459]1003   <list style="numbers">
[1244]1004    <t>text/plain;format=flowed</t>
1005    <t>text/plain</t>
[459]1006    <t>text/*</t>
1007    <t>*/*</t>
1008   </list>
1011   The media type quality factor associated with a given type is
1012   determined by finding the media range with the highest precedence
1013   which matches that type. For example,
1015<figure><artwork type="example">
[357]1016  Accept: text/*;q=0.3, text/html;q=0.7, text/html;level=1,
1017          text/html;level=2;q=0.4, */*;q=0.5
1020   would cause the following values to be associated:
[459]1022<texttable align="left">
1023  <ttcol>Media Type</ttcol><ttcol>Quality Value</ttcol>
1024  <c>text/html;level=1</c>    <c>1</c>
1025  <c>text/html</c>            <c>0.7</c>
1026  <c>text/plain</c>           <c>0.3</c>
1027  <c>image/jpeg</c>           <c>0.5</c>
1028  <c>text/html;level=2</c>    <c>0.4</c>
1029  <c>text/html;level=3</c>    <c>0.7</c>
1032      <x:h>Note:</x:h> A user agent might be provided with a default set of quality
1033      values for certain media ranges. However, unless the user agent is
1034      a closed system which cannot interact with other rendering agents,
1035      this default set ought to be configurable by the user.
1039<section title="Accept-Charset" anchor="header.accept-charset">
[1120]1040  <iref primary="true" item="Accept-Charset header field" x:for-anchor=""/>
1041  <iref primary="true" item="Header Fields" subitem="Accept-Charset" x:for-anchor=""/>
[229]1042  <x:anchor-alias value="Accept-Charset"/>
[1163]1044   The "Accept-Charset" header field can be used by user agents to
[1176]1045   indicate what character encodings are acceptable in a response
1046   payload. This field allows
[8]1047   clients capable of understanding more comprehensive or special-purpose
[1176]1048   character encodings to signal that capability to a server which is capable of
1049   representing documents in those character encodings.
[1234]1051<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Accept-Charset"/>
1052  <x:ref>Accept-Charset</x:ref> = 1#( ( <x:ref>charset</x:ref> / "*" )
[376]1053                         [ <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> "q=" <x:ref>qvalue</x:ref> ] )
[1176]1056   Character encoding values (a.k.a., charsets) are described in
1057   <xref target="character.sets"/>. Each charset &MAY; be given an
1058   associated quality value which represents the user's preference
1059   for that charset. The default value is q=1. An example is
1061<figure><artwork type="example">
[357]1062  Accept-Charset: iso-8859-5, unicode-1-1;q=0.8
1065   The special value "*", if present in the Accept-Charset field,
[1240]1066   matches every character encoding which is not mentioned elsewhere in the
1067   Accept-Charset field. If no "*" is present in an Accept-Charset field, then
1068   all character encodings not explicitly mentioned get a quality value of 0.
[994]1071   If no Accept-Charset header field is present, the default is that any
[1176]1072   character encoding is acceptable. If an Accept-Charset header field is present,
[8]1073   and if the server cannot send a response which is acceptable
[994]1074   according to the Accept-Charset header field, then the server &SHOULD; send
[137]1075   an error response with the 406 (Not Acceptable) status code, though
[8]1076   the sending of an unacceptable response is also allowed.
1080<section title="Accept-Encoding" anchor="header.accept-encoding">
[1120]1081  <iref primary="true" item="Accept-Encoding header field" x:for-anchor=""/>
1082  <iref primary="true" item="Header Fields" subitem="Accept-Encoding" x:for-anchor=""/>
[229]1083  <x:anchor-alias value="Accept-Encoding"/>
1084  <x:anchor-alias value="codings"/>
[1163]1086   The "Accept-Encoding" header field can be used by user agents to
[698]1087   indicate what response content-codings (<xref target="content.codings"/>)
1088   are acceptable in the response.
[1234]1090<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Accept-Encoding"/><iref primary="true" item="Grammar" subitem="codings"/>
1091  <x:ref>Accept-Encoding</x:ref>  = #( <x:ref>codings</x:ref> [ <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> "q=" <x:ref>qvalue</x:ref> ] )
1092  <x:ref>codings</x:ref>          = ( <x:ref>content-coding</x:ref> / "*" )
[248]1095   Each codings value &MAY; be given an associated quality value which
1096   represents the preference for that encoding. The default value is q=1.
[8]1099   Examples of its use are:
1101<figure><artwork type="example">
[357]1102  Accept-Encoding: compress, gzip
1103  Accept-Encoding:
1104  Accept-Encoding: *
1105  Accept-Encoding: compress;q=0.5, gzip;q=1.0
1106  Accept-Encoding: gzip;q=1.0, identity; q=0.5, *;q=0
1109   A server tests whether a content-coding is acceptable, according to
1110   an Accept-Encoding field, using these rules:
1111  <list style="numbers">
1112      <t>If the content-coding is one of the content-codings listed in
1113         the Accept-Encoding field, then it is acceptable, unless it is
[457]1114         accompanied by a qvalue of 0. (As defined in &qvalue;, a
[879]1115         qvalue of 0 means "not acceptable".)</t>
1117      <t>The special "*" symbol in an Accept-Encoding field matches any
1118         available content-coding not explicitly listed in the header
1119         field.</t>
1121      <t>If multiple content-codings are acceptable, then the acceptable
1122         content-coding with the highest non-zero qvalue is preferred.</t>
1124      <t>The "identity" content-coding is always acceptable, unless
1125         specifically refused because the Accept-Encoding field includes
1126         "identity;q=0", or because the field includes "*;q=0" and does
1127         not explicitly include the "identity" content-coding. If the
1128         Accept-Encoding field-value is empty, then only the "identity"
1129         encoding is acceptable.</t>
1130  </list>
1133   If an Accept-Encoding field is present in a request, and if the
1134   server cannot send a response which is acceptable according to the
[994]1135   Accept-Encoding header field, then the server &SHOULD; send an error response
[8]1136   with the 406 (Not Acceptable) status code.
1139   If no Accept-Encoding field is present in a request, the server &MAY;
1140   assume that the client will accept any content coding. In this case,
1141   if "identity" is one of the available content-codings, then the
1142   server &SHOULD; use the "identity" content-coding, unless it has
1143   additional information that a different content-coding is meaningful
1144   to the client.
1147  <t>
1148    <x:h>Note:</x:h> If the request does not include an Accept-Encoding field,
1149    and if the "identity" content-coding is unavailable, then
1150    content-codings commonly understood by HTTP/1.0 clients (i.e.,
1151    "gzip" and "compress") are preferred; some older clients
1152    improperly display messages sent with other content-codings.  The
1153    server might also make this decision based on information about
1154    the particular user-agent or client.
1155  </t>
1158  <t>
1159    <x:h>Note:</x:h> Most HTTP/1.0 applications do not recognize or obey qvalues
1160    associated with content-codings. This means that qvalues will not
1161    work and are not permitted with x-gzip or x-compress.
1162  </t>
1166<section title="Accept-Language" anchor="header.accept-language">
[1120]1167  <iref primary="true" item="Accept-Language header field" x:for-anchor=""/>
1168  <iref primary="true" item="Header Fields" subitem="Accept-Language" x:for-anchor=""/>
[229]1169  <x:anchor-alias value="Accept-Language"/>
1170  <x:anchor-alias value="language-range"/>
[1163]1172   The "Accept-Language" header field can be used by user agents to
[698]1173   indicate the set of natural languages that are preferred in the response.
1174   Language tags are defined in <xref target="language.tags"/>.
[1234]1176<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Accept-Language"/><iref primary="true" item="Grammar" subitem="language-range"/>
1177  <x:ref>Accept-Language</x:ref> =
[370]1178                    1#( <x:ref>language-range</x:ref> [ <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> "q=" <x:ref>qvalue</x:ref> ] )
[1234]1179  <x:ref>language-range</x:ref>  =
[303]1180            &lt;language-range, defined in <xref target="RFC4647" x:fmt="," x:sec="2.1"/>&gt;
[303]1183   Each language-range can be given an associated quality value which
[8]1184   represents an estimate of the user's preference for the languages
1185   specified by that range. The quality value defaults to "q=1". For
1186   example,
1188<figure><artwork type="example">
[357]1189  Accept-Language: da, en-gb;q=0.8, en;q=0.7
1192   would mean: "I prefer Danish, but will accept British English and
[879]1193   other types of English".
[724]1194   (see also <xref target="RFC4647" x:sec="2.3" x:fmt="of"/>)
[724]1197   For matching, <xref target="RFC4647" x:sec="3" x:fmt="of"/> defines
1198   several matching schemes. Implementations can offer the most appropriate
1199   matching scheme for their requirements.
1202  <t>
[756]1203    <x:h>Note:</x:h> The "Basic Filtering" scheme (<xref target="RFC4647"
[724]1204    x:fmt="," x:sec="3.3.1"/>) is identical to the matching scheme that was
1205    previously defined in <xref target="RFC2616" x:fmt="of" x:sec="14.4"/>.
[563]1206  </t>
1209   It might be contrary to the privacy expectations of the user to send
[994]1210   an Accept-Language header field with the complete linguistic preferences of
[8]1211   the user in every request. For a discussion of this issue, see
[994]1212   <xref target=""/>.
1215   As intelligibility is highly dependent on the individual user, it is
1216   recommended that client applications make the choice of linguistic
1217   preference available to the user. If the choice is not made
1218   available, then the Accept-Language header field &MUST-NOT; be given in
1219   the request.
1222  <t>
1223    <x:h>Note:</x:h> When making the choice of linguistic preference available to
1224    the user, we remind implementors of  the fact that users are not
1225    familiar with the details of language matching as described above,
[969]1226    and ought to be provided appropriate guidance. As an example, users
[563]1227    might assume that on selecting "en-gb", they will be served any
1228    kind of English document if British English is not available. A
1229    user agent might suggest in such a case to add "en" to get the
1230    best matching behavior.
1231  </t>
1235<section title="Content-Encoding" anchor="header.content-encoding">
[1120]1236  <iref primary="true" item="Content-Encoding header field" x:for-anchor=""/>
1237  <iref primary="true" item="Header Fields" subitem="Content-Encoding" x:for-anchor=""/>
[229]1238  <x:anchor-alias value="Content-Encoding"/>
[965]1240   The "Content-Encoding" header field indicates what content-codings
[866]1241   have been applied to the representation, and thus what decoding mechanisms
[698]1242   must be applied in order to obtain the media-type referenced by the
1243   Content-Type header field. Content-Encoding is primarily used to allow a
[866]1244   representation to be compressed without losing the identity of its underlying
[698]1245   media type.
[1234]1247<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Encoding"/>
1248  <x:ref>Content-Encoding</x:ref> = 1#<x:ref>content-coding</x:ref>
1251   Content codings are defined in <xref target="content.codings"/>. An example of its use is
1253<figure><artwork type="example">
[357]1254  Content-Encoding: gzip
[866]1257   The content-coding is a characteristic of the representation.
1258   Typically, the representation body is stored with this
[8]1259   encoding and is only decoded before rendering or analogous usage.
[1107]1260   However, a transforming proxy &MAY; modify the content-coding if the
[8]1261   new coding is known to be acceptable to the recipient, unless the
1262   "no-transform" cache-control directive is present in the message.
[866]1265   If the content-coding of a representation is not "identity", then the
1266   representation metadata &MUST; include a Content-Encoding header
1267   field (<xref target="header.content-encoding"/>)
[8]1268   that lists the non-identity content-coding(s) used.
[874]1271   If the content-coding of a representation in a request message is not
[8]1272   acceptable to the origin server, the server &SHOULD; respond with a
1273   status code of 415 (Unsupported Media Type).
[866]1276   If multiple encodings have been applied to a representation, the content
[8]1277   codings &MUST; be listed in the order in which they were applied.
1278   Additional information about the encoding parameters &MAY; be provided
[866]1279   by other header fields not defined by this specification.
1283<section title="Content-Language" anchor="header.content-language">
[1120]1284  <iref primary="true" item="Content-Language header field" x:for-anchor=""/>
1285  <iref primary="true" item="Header Fields" subitem="Content-Language" x:for-anchor=""/>
[229]1286  <x:anchor-alias value="Content-Language"/>
[965]1288   The "Content-Language" header field describes the natural
[866]1289   language(s) of the intended audience for the representation. Note that this might
[874]1290   not be equivalent to all the languages used within the representation.
[1234]1292<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Language"/>
1293  <x:ref>Content-Language</x:ref> = 1#<x:ref>language-tag</x:ref>
1296   Language tags are defined in <xref target="language.tags"/>. The primary purpose of
1297   Content-Language is to allow a user to identify and differentiate
[866]1298   representations according to the user's own preferred language. Thus, if the
[8]1299   body content is intended only for a Danish-literate audience, the
1300   appropriate field is
1302<figure><artwork type="example">
[357]1303  Content-Language: da
1306   If no Content-Language is specified, the default is that the content
1307   is intended for all language audiences. This might mean that the
1308   sender does not consider it to be specific to any natural language,
1309   or that the sender does not know for which language it is intended.
1312   Multiple languages &MAY; be listed for content that is intended for
1313   multiple audiences. For example, a rendition of the "Treaty of
[879]1314   Waitangi", presented simultaneously in the original Maori and English
[8]1315   versions, would call for
1317<figure><artwork type="example">
[357]1318  Content-Language: mi, en
[866]1321   However, just because multiple languages are present within a representation
[8]1322   does not mean that it is intended for multiple linguistic audiences.
1323   An example would be a beginner's language primer, such as "A First
[879]1324   Lesson in Latin", which is clearly intended to be used by an
[8]1325   English-literate audience. In this case, the Content-Language would
1326   properly only include "en".
[1101]1329   Content-Language &MAY; be applied to any media type &mdash; it is not
[8]1330   limited to textual documents.
1334<section title="Content-Location" anchor="header.content-location">
[1120]1335  <iref primary="true" item="Content-Location header field" x:for-anchor=""/>
1336  <iref primary="true" item="Header Fields" subitem="Content-Location" x:for-anchor=""/>
[229]1337  <x:anchor-alias value="Content-Location"/>
[856]1339   The "Content-Location" header field supplies a URI that can be used
1340   as a specific identifier for the representation in this message.
1341   In other words, if one were to perform a GET on this URI at the time
1342   of this message's generation, then a 200 response would contain the
1343   same representation that is enclosed as payload in this message.
[1234]1345<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Location"/>
1346  <x:ref>Content-Location</x:ref> = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
[972]1349   The Content-Location value is not a replacement for the effective
[856]1350   Request URI (&effective-request-uri;).  It is representation metadata.
1351   It has the same syntax and semantics as the header field of the same name
[858]1352   defined for MIME body parts in <xref target="RFC2557" x:fmt="of" x:sec="4"/>.
[856]1353   However, its appearance in an HTTP message has some special implications
1354   for HTTP recipients.
[856]1357   If Content-Location is included in a response message and its value
[965]1358   is the same as the effective request URI, then the response payload
[856]1359   &SHOULD; be considered the current representation of that resource.
1360   For a GET or HEAD request, this is the same as the default semantics
1361   when no Content-Location is provided by the server.  For a state-changing
[1161]1362   request like PUT or POST, it implies that the server's response contains
[856]1363   the new representation of that resource, thereby distinguishing it from
1364   representations that might only report about the action (e.g., "It worked!").
1365   This allows authoring applications to update their local copies without
1366   the need for a subsequent GET request.
[856]1369   If Content-Location is included in a response message and its value
[965]1370   differs from the effective request URI, then the origin server is
[856]1371   informing recipients that this representation has its own, presumably
1372   more specific, identifier.  For a GET or HEAD request, this is an
[965]1373   indication that the effective request URI identifies a resource that
[856]1374   is subject to content negotiation and the representation selected for
1375   this response can also be found at the identified URI.  For other
1376   methods, such a Content-Location indicates that this representation
1377   contains a report on the action's status and the same report is
1378   available (for future access with GET) at the given URI.  For
[1161]1379   example, a purchase transaction made via a POST request might
[856]1380   include a receipt document as the payload of the 200 response;
1381   the Content-Location value provides an identifier for retrieving
1382   a copy of that same receipt in the future.
1385   If Content-Location is included in a request message, then it &MAY;
1386   be interpreted by the origin server as an indication of where the
1387   user agent originally obtained the content of the enclosed
1388   representation (prior to any subsequent modification of the content
1389   by that user agent).  In other words, the user agent is providing
1390   the same representation metadata that it received with the original
1391   representation.  However, such interpretation &MUST-NOT; be used to
1392   alter the semantics of the method requested by the client.  For
1393   example, if a client makes a PUT request on a negotiated resource
1394   and the origin server accepts that PUT (without redirection), then the
1395   new set of values for that resource is expected to be consistent with
1396   the one representation supplied in that PUT; the Content-Location
1397   cannot be used as a form of reverse content selection that
1398   identifies only one of the negotiated representations to be updated.
1399   If the user agent had wanted the latter semantics, it would have applied
1400   the PUT directly to the Content-Location URI.
1403   A Content-Location field received in a request message is transitory
1404   information that &SHOULD-NOT; be saved with other representation
1405   metadata for use in later responses.  The Content-Location's value
1406   might be saved for use in other contexts, such as within source links
1407   or other metadata.
1410   A cache cannot assume that a representation with a Content-Location
[8]1411   different from the URI used to retrieve it can be used to respond to
[856]1412   later requests on that Content-Location URI.
[965]1415   If the Content-Location value is a partial URI, the partial URI is
1416   interpreted relative to the effective request URI.
1420<section title="Content-Type" anchor="header.content-type">
[1120]1421  <iref primary="true" item="Content-Type header field" x:for-anchor=""/>
1422  <iref primary="true" item="Header Fields" subitem="Content-Type" x:for-anchor=""/>
[229]1423  <x:anchor-alias value="Content-Type"/>
[965]1425   The "Content-Type" header field indicates the media type of the
[874]1426   representation. In the case of responses to the HEAD method, the media type is
[698]1427   that which would have been sent had the request been a GET.
[1234]1429<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Type"/>
1430  <x:ref>Content-Type</x:ref> = <x:ref>media-type</x:ref>
1433   Media types are defined in <xref target="media.types"/>. An example of the field is
1435<figure><artwork type="example">
[357]1436  Content-Type: text/html; charset=ISO-8859-4
[965]1439   Further discussion of Content-Type is provided in <xref target=""/>.
[29]1445<section title="IANA Considerations" anchor="IANA.considerations">
[921]1446<section title="Header Field Registration" anchor="header.field.registration">
[969]1448   The Message Header Field Registry located at <eref target=""/> shall be updated
[290]1449   with the permanent registrations below (see <xref target="RFC3864"/>):
[680]1451<?BEGININC p3-payload.iana-headers ?>
[253]1452<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
[290]1453<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
[253]1454   <ttcol>Header Field Name</ttcol>
1455   <ttcol>Protocol</ttcol>
1456   <ttcol>Status</ttcol>
1457   <ttcol>Reference</ttcol>
1459   <c>Accept</c>
1460   <c>http</c>
1461   <c>standard</c>
1462   <c>
1463      <xref target="header.accept"/>
1464   </c>
1465   <c>Accept-Charset</c>
1466   <c>http</c>
1467   <c>standard</c>
1468   <c>
1469      <xref target="header.accept-charset"/>
1470   </c>
1471   <c>Accept-Encoding</c>
1472   <c>http</c>
1473   <c>standard</c>
1474   <c>
1475      <xref target="header.accept-encoding"/>
1476   </c>
1477   <c>Accept-Language</c>
1478   <c>http</c>
1479   <c>standard</c>
1480   <c>
1481      <xref target="header.accept-language"/>
1482   </c>
1483   <c>Content-Encoding</c>
1484   <c>http</c>
1485   <c>standard</c>
1486   <c>
1487      <xref target="header.content-encoding"/>
1488   </c>
1489   <c>Content-Language</c>
1490   <c>http</c>
1491   <c>standard</c>
1492   <c>
1493      <xref target="header.content-language"/>
1494   </c>
1495   <c>Content-Location</c>
1496   <c>http</c>
1497   <c>standard</c>
1498   <c>
1499      <xref target="header.content-location"/>
1500   </c>
1501   <c>Content-Type</c>
1502   <c>http</c>
1503   <c>standard</c>
1504   <c>
1505      <xref target="header.content-type"/>
1506   </c>
[291]1507   <c>MIME-Version</c>
1508   <c>http</c>
[937]1509   <c>standard</c>
[291]1510   <c>
1511      <xref target="mime-version"/>
1512   </c>
[680]1515<?ENDINC p3-payload.iana-headers ?>
[290]1517   The change controller is: "IETF ( - Internet Engineering Task Force".
[668]1521<section title="Content Coding Registry" anchor="content.coding.registration">
1523   The registration procedure for HTTP Content Codings is now defined
[670]1524   by <xref target="content.coding.registry"/> of this document.
1527   The HTTP Content Codings Registry located at <eref target=""/>
[969]1528   shall be updated with the registration below:
1530<texttable align="left" suppress-title="true" anchor="iana.content.coding.registration.table">
[670]1531   <ttcol>Name</ttcol>
[668]1532   <ttcol>Description</ttcol>
1533   <ttcol>Reference</ttcol>
1534   <c>compress</c>
1535   <c>UNIX "compress" program method</c>
1536   <c>
[673]1537      &compress-coding;
[668]1538   </c>
1539   <c>deflate</c>
[806]1540   <c>"deflate" compression mechanism (<xref target="RFC1951"/>) used inside
1541   the "zlib" data format (<xref target="RFC1950"/>)
1542   </c>
[668]1543   <c>
[673]1544      &deflate-coding;
[668]1545   </c>
1546   <c>gzip</c>
1547   <c>Same as GNU zip <xref target="RFC1952"/></c>
1548   <c>
[673]1549      &gzip-coding;
[668]1550   </c>
1551   <c>identity</c>
1552   <c>No transformation</c>
1553   <c>
1554      <xref target="content.codings"/>
1555   </c>
[8]1561<section title="Security Considerations" anchor="security.considerations">
1563   This section is meant to inform application developers, information
1564   providers, and users of the security limitations in HTTP/1.1 as
1565   described by this document. The discussion does not include
1566   definitive solutions to the problems revealed, though it does make
1567   some suggestions for reducing security risks.
[994]1570<section title="Privacy Issues Connected to Accept Header Fields" anchor="">
[1163]1572   Accept headers fields can reveal information about the user to all
[994]1573   servers which are accessed. The Accept-Language header field in particular
[8]1574   can reveal information the user would consider to be of a private
1575   nature, because the understanding of particular languages is often
1576   strongly correlated to the membership of a particular ethnic group.
1577   User agents which offer the option to configure the contents of an
[994]1578   Accept-Language header field to be sent in every request are strongly
[8]1579   encouraged to let the configuration process include a message which
1580   makes the user aware of the loss of privacy involved.
1583   An approach that limits the loss of privacy would be for a user agent
[994]1584   to omit the sending of Accept-Language header fields by default, and to ask
1585   the user whether or not to start sending Accept-Language header fields to a
[1163]1586   server if it detects, by looking for any Vary header fields
[8]1587   generated by the server, that such sending could improve the quality
1588   of service.
1591   Elaborate user-customized accept header fields sent in every request,
1592   in particular if these include quality values, can be used by servers
1593   as relatively reliable and long-lived user identifiers. Such user
1594   identifiers would allow content providers to do click-trail tracking,
1595   and would allow collaborating content providers to match cross-server
1596   click-trails or form submissions of individual users. Note that for
1597   many users not behind a proxy, the network address of the host
1598   running the user agent will also serve as a long-lived user
1599   identifier. In environments where proxies are used to enhance
1600   privacy, user agents ought to be conservative in offering accept
1601   header configuration options to end users. As an extreme privacy
[994]1602   measure, proxies could filter the accept header fields in relayed requests.
[8]1603   General purpose user agents which provide a high degree of header
1604   configurability &SHOULD; warn users about the loss of privacy which can
1605   be involved.
1611<section title="Acknowledgments" anchor="ack">
[119]1616<references title="Normative References">
[31]1618<reference anchor="Part1">
[119]1619  <front>
1620    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
1621    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
[1106]1622      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[119]1623      <address><email></email></address>
1624    </author>
1625    <author initials="J." surname="Gettys" fullname="Jim Gettys">
[844]1626      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1627      <address><email></email></address>
[119]1628    </author>
1629    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1630      <organization abbrev="HP">Hewlett-Packard Company</organization>
1631      <address><email></email></address>
1632    </author>
1633    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1634      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1635      <address><email></email></address>
1636    </author>
1637    <author initials="L." surname="Masinter" fullname="Larry Masinter">
[1106]1638      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[119]1639      <address><email></email></address>
1640    </author>
1641    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1642      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1643      <address><email></email></address>
1644    </author>
1645    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1646      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1647      <address><email></email></address>
1648    </author>
1649    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1650      <organization abbrev="W3C">World Wide Web Consortium</organization>
1651      <address><email></email></address>
1652    </author>
1653    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1654      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1655      <address><email></email></address>
1656    </author>
1657    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1658  </front>
1659  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
1660  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
1663<reference anchor="Part2">
[119]1664  <front>
1665    <title abbrev="HTTP/1.1">HTTP/1.1, part 2: Message Semantics</title>
1666    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
[1106]1667      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[119]1668      <address><email></email></address>
1669    </author>
1670    <author initials="J." surname="Gettys" fullname="Jim Gettys">
[844]1671      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1672      <address><email></email></address>
[119]1673    </author>
1674    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1675      <organization abbrev="HP">Hewlett-Packard Company</organization>
1676      <address><email></email></address>
1677    </author>
1678    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1679      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1680      <address><email></email></address>
1681    </author>
1682    <author initials="L." surname="Masinter" fullname="Larry Masinter">
[1106]1683      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[119]1684      <address><email></email></address>
1685    </author>
1686    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1687      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1688      <address><email></email></address>
1689    </author>
1690    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1691      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1692      <address><email></email></address>
1693    </author>
1694    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1695      <organization abbrev="W3C">World Wide Web Consortium</organization>
1696      <address><email></email></address>
1697    </author>
1698    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1699      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1700      <address><email></email></address>
1701    </author>
1702    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1703  </front>
1704  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"/>
1705  <x:source href="p2-semantics.xml" basename="p2-semantics"/>
1708<reference anchor="Part4">
[119]1709  <front>
1710    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
1711    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
[1106]1712      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[119]1713      <address><email></email></address>
1714    </author>
1715    <author initials="J." surname="Gettys" fullname="Jim Gettys">
[844]1716      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1717      <address><email></email></address>
[119]1718    </author>
1719    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1720      <organization abbrev="HP">Hewlett-Packard Company</organization>
1721      <address><email></email></address>
1722    </author>
1723    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1724      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1725      <address><email></email></address>
1726    </author>
1727    <author initials="L." surname="Masinter" fullname="Larry Masinter">
[1106]1728      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[119]1729      <address><email></email></address>
1730    </author>
1731    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1732      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1733      <address><email></email></address>
1734    </author>
1735    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1736      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1737      <address><email></email></address>
1738    </author>
1739    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1740      <organization abbrev="W3C">World Wide Web Consortium</organization>
1741      <address><email></email></address>
1742    </author>
1743    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1744      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1745      <address><email></email></address>
1746    </author>
1747    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1748  </front>
1749  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
1750  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
1753<reference anchor="Part5">
[119]1754  <front>
1755    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
1756    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
[1106]1757      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[119]1758      <address><email></email></address>
1759    </author>
1760    <author initials="J." surname="Gettys" fullname="Jim Gettys">
[844]1761      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1762      <address><email></email></address>
[119]1763    </author>
1764    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1765      <organization abbrev="HP">Hewlett-Packard Company</organization>
1766      <address><email></email></address>
1767    </author>
1768    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1769      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1770      <address><email></email></address>
1771    </author>
1772    <author initials="L." surname="Masinter" fullname="Larry Masinter">
[1106]1773      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[119]1774      <address><email></email></address>
1775    </author>
1776    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1777      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1778      <address><email></email></address>
1779    </author>
1780    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1781      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1782      <address><email></email></address>
1783    </author>
1784    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1785      <organization abbrev="W3C">World Wide Web Consortium</organization>
1786      <address><email></email></address>
1787    </author>
1788    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1789      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1790      <address><email></email></address>
1791    </author>
1792    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1793  </front>
1794  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
1795  <x:source href="p5-range.xml" basename="p5-range"/>
1798<reference anchor="Part6">
[119]1799  <front>
1800    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
1801    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
[1106]1802      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[119]1803      <address><email></email></address>
1804    </author>
1805    <author initials="J." surname="Gettys" fullname="Jim Gettys">
[844]1806      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1807      <address><email></email></address>
[119]1808    </author>
1809    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1810      <organization abbrev="HP">Hewlett-Packard Company</organization>
1811      <address><email></email></address>
1812    </author>
1813    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1814      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1815      <address><email></email></address>
1816    </author>
1817    <author initials="L." surname="Masinter" fullname="Larry Masinter">
[1106]1818      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[119]1819      <address><email></email></address>
1820    </author>
1821    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1822      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1823      <address><email></email></address>
1824    </author>
1825    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1826      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1827      <address><email></email></address>
1828    </author>
1829    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1830      <organization abbrev="W3C">World Wide Web Consortium</organization>
1831      <address><email></email></address>
1832    </author>
[601]1833    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
1834      <address><email></email></address>
1835    </author>
[119]1836    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1837      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1838      <address><email></email></address>
1839    </author>
1840    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1841  </front>
1842  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
1843  <x:source href="p6-cache.xml" basename="p6-cache"/>
[122]1846<reference anchor="RFC1950">
1847  <front>
1848    <title>ZLIB Compressed Data Format Specification version 3.3</title>
1849    <author initials="L.P." surname="Deutsch" fullname="L. Peter Deutsch">
1850      <organization>Aladdin Enterprises</organization>
1851      <address><email></email></address>
1852    </author>
[713]1853    <author initials="J-L." surname="Gailly" fullname="Jean-Loup Gailly"/>
[122]1854    <date month="May" year="1996"/>
1855  </front>
1856  <seriesInfo name="RFC" value="1950"/>
1857  <annotation>
[908]1858    RFC 1950 is an Informational RFC, thus it might be less stable than
[122]1859    this specification. On the other hand, this downward reference was
[277]1860    present since the publication of RFC 2068 in 1997 (<xref target="RFC2068"/>),
1861    therefore it is unlikely to cause problems in practice. See also
1862    <xref target="BCP97"/>.
[122]1863  </annotation>
[806]1866<reference anchor="RFC1951">
1867  <front>
1868    <title>DEFLATE Compressed Data Format Specification version 1.3</title>
1869    <author initials="P." surname="Deutsch" fullname="L. Peter Deutsch">
1870      <organization>Aladdin Enterprises</organization>
1871      <address><email></email></address>
1872    </author>
1873    <date month="May" year="1996"/>
1874  </front>
1875  <seriesInfo name="RFC" value="1951"/>
1876  <annotation>
[908]1877    RFC 1951 is an Informational RFC, thus it might be less stable than
[806]1878    this specification. On the other hand, this downward reference was
1879    present since the publication of RFC 2068 in 1997 (<xref target="RFC2068"/>),
1880    therefore it is unlikely to cause problems in practice. See also
1881    <xref target="BCP97"/>.
1882  </annotation>
[122]1885<reference anchor="RFC1952">
1886  <front>
1887    <title>GZIP file format specification version 4.3</title>
1888    <author initials="P." surname="Deutsch" fullname="L. Peter Deutsch">
1889      <organization>Aladdin Enterprises</organization>
1890      <address><email></email></address>
1891    </author>
1892    <author initials="J-L." surname="Gailly" fullname="Jean-Loup Gailly">
1893      <address><email></email></address>
1894    </author>
1895    <author initials="M." surname="Adler" fullname="Mark Adler">
1896      <address><email></email></address>
1897    </author>
1898    <author initials="L.P." surname="Deutsch" fullname="L. Peter Deutsch">
1899      <address><email></email></address>
1900    </author>
1901    <author initials="G." surname="Randers-Pehrson" fullname="Glenn Randers-Pehrson">
1902      <address><email></email></address>
1903    </author>
1904    <date month="May" year="1996"/>
1905  </front>
1906  <seriesInfo name="RFC" value="1952"/>
1907  <annotation>
[908]1908    RFC 1952 is an Informational RFC, thus it might be less stable than
[122]1909    this specification. On the other hand, this downward reference was
[277]1910    present since the publication of RFC 2068 in 1997 (<xref target="RFC2068"/>),
1911    therefore it is unlikely to cause problems in practice. See also
1912    <xref target="BCP97"/>.
[122]1913  </annotation>
[131]1916<reference anchor="RFC2045">
1917  <front>
1918    <title abbrev="Internet Message Bodies">Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies</title>
1919    <author initials="N." surname="Freed" fullname="Ned Freed">
1920      <organization>Innosoft International, Inc.</organization>
1921      <address><email></email></address>
1922    </author>
1923    <author initials="N.S." surname="Borenstein" fullname="Nathaniel S. Borenstein">
1924      <organization>First Virtual Holdings</organization>
1925      <address><email></email></address>
1926    </author>
1927    <date month="November" year="1996"/>
1928  </front>
1929  <seriesInfo name="RFC" value="2045"/>
1932<reference anchor="RFC2046">
1933  <front>
1934    <title abbrev="Media Types">Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types</title>
1935    <author initials="N." surname="Freed" fullname="Ned Freed">
1936      <organization>Innosoft International, Inc.</organization>
1937      <address><email></email></address>
1938    </author>
1939    <author initials="N." surname="Borenstein" fullname="Nathaniel S. Borenstein">
1940      <organization>First Virtual Holdings</organization>
1941      <address><email></email></address>
1942    </author>
1943    <date month="November" year="1996"/>
1944  </front>
1945  <seriesInfo name="RFC" value="2046"/>
[119]1948<reference anchor="RFC2119">
1949  <front>
1950    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
1951    <author initials="S." surname="Bradner" fullname="Scott Bradner">
1952      <organization>Harvard University</organization>
1953      <address><email></email></address>
1954    </author>
1955    <date month="March" year="1997"/>
1956  </front>
1957  <seriesInfo name="BCP" value="14"/>
1958  <seriesInfo name="RFC" value="2119"/>
[303]1961<reference anchor='RFC4647'>
1962  <front>
1963    <title>Matching of Language Tags</title>
1964    <author initials='A.' surname='Phillips' fullname='Addison Phillips' role="editor">
1965      <organization>Yahoo! Inc.</organization>
1966      <address><email></email></address>
1967    </author>
1968    <author initials='M.' surname='Davis' fullname='Mark Davis' role="editor">
1969      <organization>Google</organization>
1970      <address><email></email></address>
1971    </author>
1972    <date year='2006' month='September' />
1973  </front>
1974  <seriesInfo name='BCP' value='47' />
1975  <seriesInfo name='RFC' value='4647' />
[425]1978<reference anchor="RFC5234">
1979  <front>
1980    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
1981    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
1982      <organization>Brandenburg InternetWorking</organization>
1983      <address>
[728]1984        <email></email>
1985      </address> 
[425]1986    </author>
1987    <author initials="P." surname="Overell" fullname="Paul Overell">
1988      <organization>THUS plc.</organization>
1989      <address>
[728]1990        <email></email>
1991      </address>
[425]1992    </author>
1993    <date month="January" year="2008"/>
1994  </front>
1995  <seriesInfo name="STD" value="68"/>
1996  <seriesInfo name="RFC" value="5234"/>
[690]1999<reference anchor='RFC5646'>
[613]2000  <front>
2001    <title>Tags for Identifying Languages</title>
2002    <author initials='A.' surname='Phillips' fullname='Addison Phillips' role='editor'>
2003      <organization>Lab126</organization>
2004      <address><email></email></address>
2005    </author>
2006    <author initials='M.' surname='Davis' fullname='Mark Davis' role='editor'>
2007      <organization>Google</organization>
2008      <address><email></email></address>
2009    </author>
[690]2010    <date month='September' year='2009' />
[613]2011  </front>
[690]2012  <seriesInfo name='BCP' value='47' />
2013  <seriesInfo name='RFC' value='5646' />
2018<references title="Informative References">
[129]2020<reference anchor="RFC1945">
2021  <front>
2022    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
2023    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2024      <organization>MIT, Laboratory for Computer Science</organization>
2025      <address><email></email></address>
2026    </author>
2027    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
2028      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2029      <address><email></email></address>
2030    </author>
2031    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2032      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
2033      <address><email></email></address>
2034    </author>
2035    <date month="May" year="1996"/>
2036  </front>
2037  <seriesInfo name="RFC" value="1945"/>
2040<reference anchor="RFC2049">
2041  <front>
2042    <title abbrev="MIME Conformance">Multipurpose Internet Mail Extensions (MIME) Part Five: Conformance Criteria and Examples</title>
2043    <author initials="N." surname="Freed" fullname="Ned Freed">
2044      <organization>Innosoft International, Inc.</organization>
2045      <address><email></email></address>
2046    </author>
2047    <author initials="N.S." surname="Borenstein" fullname="Nathaniel S. Borenstein">
2048      <organization>First Virtual Holdings</organization>
2049      <address><email></email></address>
2050    </author>
2051    <date month="November" year="1996"/>
2052  </front>
2053  <seriesInfo name="RFC" value="2049"/>
[133]2056<reference anchor="RFC2068">
2057  <front>
2058    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
2059    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
2060      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2061      <address><email></email></address>
2062    </author>
2063    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2064      <organization>MIT Laboratory for Computer Science</organization>
2065      <address><email></email></address>
2066    </author>
2067    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2068      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
2069      <address><email></email></address>
2070    </author>
2071    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2072      <organization>MIT Laboratory for Computer Science</organization>
2073      <address><email></email></address>
2074    </author>
2075    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2076      <organization>MIT Laboratory for Computer Science</organization>
2077      <address><email></email></address>
2078    </author>
2079    <date month="January" year="1997"/>
2080  </front>
2081  <seriesInfo name="RFC" value="2068"/>
[129]2084<reference anchor="RFC2076">
2085  <front>
2086    <title abbrev="Internet Message Headers">Common Internet Message Headers</title>
2087    <author initials="J." surname="Palme" fullname="Jacob Palme">
2088      <organization>Stockholm University/KTH</organization>
2089      <address><email></email></address>
2090    </author>
2091    <date month="February" year="1997"/>
2092  </front>
2093  <seriesInfo name="RFC" value="2076"/>
2096<reference anchor="RFC2277">
2097  <front>
2098    <title abbrev="Charset Policy">IETF Policy on Character Sets and Languages</title>
2099    <author initials="H.T." surname="Alvestrand" fullname="Harald Tveit Alvestrand">
2100      <organization>UNINETT</organization>
2101      <address><email></email></address>
2102    </author>
2103    <date month="January" year="1998"/>
2104  </front>
2105  <seriesInfo name="BCP" value="18"/>
2106  <seriesInfo name="RFC" value="2277"/>
[745]2109<reference anchor='RFC2295'>
2110  <front>
2111    <title abbrev='HTTP Content Negotiation'>Transparent Content Negotiation in HTTP</title>
2112    <author initials='K.' surname='Holtman' fullname='Koen Holtman'>
2113      <organization>Technische Universiteit Eindhoven</organization>
2114      <address>
2115        <email></email>
2116      </address>
2117    </author>
2118    <author initials='A.H.' surname='Mutz' fullname='Andrew H. Mutz'>
2119      <organization>Hewlett-Packard Company</organization>
2120      <address>
2121        <email></email>
2122      </address>
2123    </author>
2124    <date year='1998' month='March'/>
2125  </front>
2126  <seriesInfo name='RFC' value='2295'/>
[129]2129<reference anchor="RFC2388">
2130  <front>
2131    <title abbrev="multipart/form-data">Returning Values from Forms:  multipart/form-data</title>
2132    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2133      <organization>Xerox Palo Alto Research Center</organization>
2134      <address><email></email></address>
2135    </author>
2136    <date year="1998" month="August"/>
2137  </front>
2138  <seriesInfo name="RFC" value="2388"/>
2141<reference anchor="RFC2557">
2142  <front>
2143    <title abbrev="MIME Encapsulation of Aggregate Documents">MIME Encapsulation of Aggregate Documents, such as HTML (MHTML)</title>
2144    <author initials="F." surname="Palme" fullname="Jacob Palme">
2145      <organization>Stockholm University and KTH</organization>
2146      <address><email></email></address>
2147    </author>
2148    <author initials="A." surname="Hopmann" fullname="Alex Hopmann">
2149      <organization>Microsoft Corporation</organization>
2150      <address><email></email></address>
2151    </author>
2152    <author initials="N." surname="Shelness" fullname="Nick Shelness">
2153      <organization>Lotus Development Corporation</organization>
2154      <address><email></email></address>
2155    </author>
2156    <author initials="E." surname="Stefferud" fullname="Einar Stefferud">
2157      <address><email></email></address>
2158    </author>
2159    <date year="1999" month="March"/>
2160  </front>
2161  <seriesInfo name="RFC" value="2557"/>
[119]2164<reference anchor="RFC2616">
2165  <front>
2166    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
2167    <author initials="R." surname="Fielding" fullname="R. Fielding">
2168      <organization>University of California, Irvine</organization>
2169      <address><email></email></address>
2170    </author>
2171    <author initials="J." surname="Gettys" fullname="J. Gettys">
2172      <organization>W3C</organization>
2173      <address><email></email></address>
2174    </author>
2175    <author initials="J." surname="Mogul" fullname="J. Mogul">
2176      <organization>Compaq Computer Corporation</organization>
2177      <address><email></email></address>
2178    </author>
2179    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
2180      <organization>MIT Laboratory for Computer Science</organization>
2181      <address><email></email></address>
2182    </author>
2183    <author initials="L." surname="Masinter" fullname="L. Masinter">
2184      <organization>Xerox Corporation</organization>
2185      <address><email></email></address>
2186    </author>
2187    <author initials="P." surname="Leach" fullname="P. Leach">
2188      <organization>Microsoft Corporation</organization>
2189      <address><email></email></address>
2190    </author>
2191    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
2192      <organization>W3C</organization>
2193      <address><email></email></address>
2194    </author>
2195    <date month="June" year="1999"/>
2196  </front>
2197  <seriesInfo name="RFC" value="2616"/>
[129]2200<reference anchor="RFC3629">
2201  <front>
2202    <title>UTF-8, a transformation format of ISO 10646</title>
2203    <author initials="F." surname="Yergeau" fullname="F. Yergeau">
2204      <organization>Alis Technologies</organization>
2205      <address><email></email></address>
2206    </author>
2207    <date month="November" year="2003"/>
2208  </front>
[1003]2209  <seriesInfo name="STD" value="63"/>
[129]2210  <seriesInfo name="RFC" value="3629"/>
[253]2213<reference anchor='RFC3864'>
2214  <front>
2215    <title>Registration Procedures for Message Header Fields</title>
2216    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
2217      <organization>Nine by Nine</organization>
2218      <address><email></email></address>
2219    </author>
2220    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
2221      <organization>BEA Systems</organization>
2222      <address><email></email></address>
2223    </author>
2224    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
2225      <organization>HP Labs</organization>
2226      <address><email></email></address>
2227    </author>
2228    <date year='2004' month='September' />
2229  </front>
2230  <seriesInfo name='BCP' value='90' />
2231  <seriesInfo name='RFC' value='3864' />
[200]2234<reference anchor="RFC4288">
2235  <front>
2236    <title>Media Type Specifications and Registration Procedures</title>
2237    <author initials="N." surname="Freed" fullname="N. Freed">
2238      <organization>Sun Microsystems</organization>
2239      <address>
2240        <email></email>
2241      </address>
2242    </author>
2243    <author initials="J." surname="Klensin" fullname="J. Klensin">
2244      <address>
2245        <email></email>
2246      </address>
2247    </author>
2248    <date year="2005" month="December"/>
2249  </front>
2250  <seriesInfo name="BCP" value="13"/>
2251  <seriesInfo name="RFC" value="4288"/>
[670]2254<reference anchor='RFC5226'>
2255  <front>
2256    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
2257    <author initials='T.' surname='Narten' fullname='T. Narten'>
2258      <organization>IBM</organization>
2259      <address><email></email></address>
2260    </author>
2261    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
2262      <organization>Google</organization>
2263      <address><email></email></address>
2264    </author>
2265    <date year='2008' month='May' />
2266  </front>
2267  <seriesInfo name='BCP' value='26' />
2268  <seriesInfo name='RFC' value='5226' />
[327]2271<reference anchor="RFC5322">
2272  <front>
2273    <title>Internet Message Format</title>
2274    <author initials="P." surname="Resnick" fullname="P. Resnick">
2275      <organization>Qualcomm Incorporated</organization>
2276    </author>
2277    <date year="2008" month="October"/>
2278  </front>
2279  <seriesInfo name="RFC" value="5322"/>
[1267]2282<reference anchor="RFC6151">
2283  <front>
2284    <title>Updated Security Considerations for the MD5 Message-Digest and the HMAC-MD5 Algorithms</title>
2285    <author initials="S." surname="Turner" fullname="S. Turner"/>
2286    <author initials="L." surname="Chen" fullname="L. Chen"/>
2287    <date year="2011" month="March" />
[1308]2288  </front>
[1267]2289  <seriesInfo name="RFC" value="6151" />
[277]2292<reference anchor='BCP97'>
2293  <front>
2294    <title>Handling Normative References to Standards-Track Documents</title>
2295    <author initials='J.' surname='Klensin' fullname='J. Klensin'>
2296      <address>
2297        <email></email>
2298      </address>
2299    </author>
2300    <author initials='S.' surname='Hartman' fullname='S. Hartman'>
2301      <organization>MIT</organization>
2302      <address>
2303        <email></email>
2304      </address>
2305    </author>
2306    <date year='2007' month='June' />
2307  </front>
2308  <seriesInfo name='BCP' value='97' />
2309  <seriesInfo name='RFC' value='4897' />
[1307]2312<reference anchor="RFC6266">
[1308]2313  <front>
[1259]2314    <title abbrev="Content-Disposition in HTTP">Use of the Content-Disposition Header Field
2315    in the Hypertext Transfer Protocol (HTTP)</title>
2316    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke">
2317      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2318      <address>
[1308]2319        <email></email>
[1259]2320      </address>
2321    </author>
[1307]2322    <date month="June" year="2011"/>
[1259]2323  </front>
[1307]2324  <seriesInfo name='RFC' value='6266' />
[874]2329<section title="Differences between HTTP and MIME" anchor="differences.between.http.and.mime">
[327]2331   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
[874]2332   allow a message-body to be transmitted in an open variety of
[8]2333   representations and with extensible mechanisms. However, RFC 2045
2334   discusses mail, and HTTP has a few features that are different from
[874]2335   those described in MIME. These differences were carefully chosen
[8]2336   to optimize performance over binary connections, to allow greater
2337   freedom in the use of new media types, to make date comparisons
2338   easier, and to acknowledge the practice of some early HTTP servers
2339   and clients.
[874]2342   This appendix describes specific areas where HTTP differs from MIME.
2343   Proxies and gateways to strict MIME environments &SHOULD; be
[8]2344   aware of these differences and provide the appropriate conversions
2345   where necessary. Proxies and gateways from MIME environments to HTTP
2346   also need to be aware of the differences because some conversions
2347   might be required.
[8]2350<section title="MIME-Version" anchor="mime-version">
[1120]2351  <iref primary="true" item="MIME-Version header field" x:for-anchor=""/>
2352  <iref primary="true" item="Header Fields" subitem="MIME-Version" x:for-anchor=""/>
[229]2353  <x:anchor-alias value="MIME-Version"/>
2355   HTTP is not a MIME-compliant protocol. However, HTTP/1.1 messages &MAY;
[1163]2356   include a single MIME-Version header field to indicate what
[8]2357   version of the MIME protocol was used to construct the message. Use
2358   of the MIME-Version header field indicates that the message is in
[115]2359   full compliance with the MIME protocol (as defined in <xref target="RFC2045"/>).
[8]2360   Proxies/gateways are responsible for ensuring full compliance (where
2361   possible) when exporting HTTP messages to strict MIME environments.
[1234]2363<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="MIME-Version"/>
2364  <x:ref>MIME-Version</x:ref> = 1*<x:ref>DIGIT</x:ref> "." 1*<x:ref>DIGIT</x:ref>
2367   MIME version "1.0" is the default for use in HTTP/1.1. However,
2368   HTTP/1.1 message parsing and semantics are defined by this document
2369   and not the MIME specification.
2373<section title="Conversion to Canonical Form" anchor="">
[874]2375   MIME requires that an Internet mail body-part be converted to
[115]2376   canonical form prior to being transferred, as described in <xref target="RFC2049" x:fmt="of" x:sec="4"/>.
[97]2377   <xref target="canonicalization.and.text.defaults"/> of this document describes the forms
[8]2378   allowed for subtypes of the "text" media type when transmitted over
[97]2379   HTTP. <xref target="RFC2046"/> requires that content with a type of "text" represent
[8]2380   line breaks as CRLF and forbids the use of CR or LF outside of line
2381   break sequences. HTTP allows CRLF, bare CR, and bare LF to indicate a
2382   line break within text content when a message is transmitted over
2383   HTTP.
2386   Where it is possible, a proxy or gateway from HTTP to a strict MIME
2387   environment &SHOULD; translate all line breaks within the text media
[1176]2388   types described in <xref target="canonicalization.and.text.defaults"/>
2389   of this document to the RFC 2049
[8]2390   canonical form of CRLF. Note, however, that this might be complicated
2391   by the presence of a Content-Encoding and by the fact that HTTP
[1176]2392   allows the use of some character encodings which do not use octets 13 and
2393   10 to represent CR and LF, respectively, as is the case for some multi-byte
2394   character encodings.
[969]2397   Conversion will break any cryptographic
[8]2398   checksums applied to the original content unless the original content
2399   is already in canonical form. Therefore, the canonical form is
2400   recommended for any content that uses such checksums in HTTP.
2405<section title="Conversion of Date Formats" anchor="">
2407   HTTP/1.1 uses a restricted set of date formats (&full-date;) to
2408   simplify the process of date comparison. Proxies and gateways from
2409   other protocols &SHOULD; ensure that any Date header field present in a
2410   message conforms to one of the HTTP/1.1 formats and rewrite the date
2411   if necessary.
[8]2415<section title="Introduction of Content-Encoding" anchor="introduction.of.content-encoding">
[874]2417   MIME does not include any concept equivalent to HTTP/1.1's
[8]2418   Content-Encoding header field. Since this acts as a modifier on the
2419   media type, proxies and gateways from HTTP to MIME-compliant
2420   protocols &MUST; either change the value of the Content-Type header
[874]2421   field or decode the representation before forwarding the message. (Some
[8]2422   experimental applications of Content-Type for Internet mail have used
2423   a media-type parameter of ";conversions=&lt;content-coding&gt;" to perform
2424   a function equivalent to Content-Encoding. However, this parameter is
[874]2425   not part of the MIME standards).
2429<section title="No Content-Transfer-Encoding" anchor="no.content-transfer-encoding">
[874]2431   HTTP does not use the Content-Transfer-Encoding field of MIME.
2432   Proxies and gateways from MIME-compliant protocols to HTTP &MUST;
[85]2433   remove any Content-Transfer-Encoding
[8]2434   prior to delivering the response message to an HTTP client.
2437   Proxies and gateways from HTTP to MIME-compliant protocols are
2438   responsible for ensuring that the message is in the correct format
2439   and encoding for safe transport on that protocol, where "safe
2440   transport" is defined by the limitations of the protocol being used.
2441   Such a proxy or gateway &SHOULD; label the data with an appropriate
2442   Content-Transfer-Encoding if doing so will improve the likelihood of
2443   safe transport over the destination protocol.
2447<section title="Introduction of Transfer-Encoding" anchor="introduction.of.transfer-encoding">
[29]2449   HTTP/1.1 introduces the Transfer-Encoding header field (&header-transfer-encoding;).
[8]2450   Proxies/gateways &MUST; remove any transfer-coding prior to
2451   forwarding a message via a MIME-compliant protocol.
2455<section title="MHTML and Line Length Limitations" anchor="mhtml.line.length">
[129]2457   HTTP implementations which share code with MHTML <xref target="RFC2557"/> implementations
[8]2458   need to be aware of MIME line length limitations. Since HTTP does not
2459   have this limitation, HTTP does not fold long lines. MHTML messages
2460   being transported by HTTP follow all conventions of MHTML, including
2461   line length limitations and folding, canonicalization, etc., since
2462   HTTP transports all message-bodies as payload (see <xref target="multipart.types"/>) and
2463   does not interpret the content or any MIME header lines that might be
2464   contained therein.
2469<section title="Additional Features" anchor="additional.features">
[97]2471   <xref target="RFC1945"/> and <xref target="RFC2068"/> document protocol elements used by some
[8]2472   existing HTTP implementations, but not consistently and correctly
2473   across most HTTP/1.1 applications. Implementors are advised to be
2474   aware of these features, but cannot rely upon their presence in, or
2475   interoperability with, other HTTP/1.1 applications. Some of these
2476   describe proposed experimental features, and some describe features
2477   that experimental deployment found lacking that are now addressed in
2478   the base HTTP/1.1 specification.
[994]2481   A number of other header fields, such as Content-Disposition and Title,
[1307]2482   from SMTP and MIME are also often implemented (see <xref target="RFC6266"/>
2483   and <xref target="RFC2076"/>).
[99]2487<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
2489  Clarify contexts that charset is used in.
2490  (<xref target="character.sets"/>)
[1240]2493  Remove the default character encoding for text media types; the default
2494  now is whatever the media type definition says.
2495  (<xref target="canonicalization.and.text.defaults"/>)
[1234]2498  Change ABNF productions for header fields to only define the field value.
2499  (<xref target="header.fields"/>)
[1308]2502  Remove definition of Content-MD5 header field because it was inconsistently
2503  implemented with respect to partial responses, and also because of known
2504  deficiencies in the hash algorithm itself (see <xref target="RFC6151"/> for details).
[1267]2505  (<xref target="header.fields"/>)
[1240]2508  Remove ISO-8859-1 special-casing in Accept-Charset.
2509  (<xref target="header.accept-charset"/>)
[712]2512  Remove base URI setting semantics for Content-Location due to poor
[714]2513  implementation support, which was caused by too many broken servers emitting
[994]2514  bogus Content-Location header fields, and also the potentially undesirable effect
[714]2515  of potentially breaking relative links in content-negotiated resources.
[712]2516  (<xref target="header.content-location"/>)
[1308]2519  Remove discussion of Content-Disposition header field, it is now defined
2520  by <xref target="RFC6266"/>.
[1259]2521  (<xref target="additional.features"/>)
[104]2524  Remove reference to non-existant identity transfer-coding value tokens.
2525  (<xref target="no.content-transfer-encoding"/>)
[680]2529<?BEGININC p3-payload.abnf-appendix ?>
[427]2530<section xmlns:x="" title="Collected ABNF" anchor="collected.abnf">
2532<artwork type="abnf" name="p3-payload.parsed-abnf">
[1234]2533<x:ref>Accept</x:ref> = [ ( "," / ( media-range [ accept-params ] ) ) *( OWS "," [
2534 OWS media-range [ accept-params ] ] ) ]
2535<x:ref>Accept-Charset</x:ref> = *( "," OWS ) ( charset / "*" ) [ OWS ";" OWS "q="
[425]2536 qvalue ] *( OWS "," [ OWS ( charset / "*" ) [ OWS ";" OWS "q="
2537 qvalue ] ] )
[1234]2538<x:ref>Accept-Encoding</x:ref> = [ ( "," / ( codings [ OWS ";" OWS "q=" qvalue ] ) )
2539 *( OWS "," [ OWS codings [ OWS ";" OWS "q=" qvalue ] ] ) ]
2540<x:ref>Accept-Language</x:ref> = *( "," OWS ) language-range [ OWS ";" OWS "q="
[425]2541 qvalue ] *( OWS "," [ OWS language-range [ OWS ";" OWS "q=" qvalue ]
2542 ] )
[1234]2544<x:ref>Content-Encoding</x:ref> = *( "," OWS ) content-coding *( OWS "," [ OWS
[425]2545 content-coding ] )
[1234]2546<x:ref>Content-Language</x:ref> = *( "," OWS ) language-tag *( OWS "," [ OWS
[425]2547 language-tag ] )
[1234]2548<x:ref>Content-Location</x:ref> = absolute-URI / partial-URI
2549<x:ref>Content-Type</x:ref> = media-type
[1234]2551<x:ref>MIME-Version</x:ref> = 1*DIGIT "." 1*DIGIT
2553<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
[1318]2555<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.7&gt;
[810]2556<x:ref>accept-ext</x:ref> = OWS ";" OWS token [ "=" word ]
[427]2557<x:ref>accept-params</x:ref> = OWS ";" OWS "q=" qvalue *accept-ext
2558<x:ref>attribute</x:ref> = token
2560<x:ref>charset</x:ref> = token
2561<x:ref>codings</x:ref> = ( content-coding / "*" )
2562<x:ref>content-coding</x:ref> = token
[427]2564<x:ref>language-range</x:ref> = &lt;language-range, defined in [RFC4647], Section 2.1&gt;
[690]2565<x:ref>language-tag</x:ref> = &lt;Language-Tag, defined in [RFC5646], Section 2.1&gt;
2567<x:ref>media-range</x:ref> = ( "*/*" / ( type "/*" ) / ( type "/" subtype ) ) *( OWS
[425]2568 ";" OWS parameter )
[427]2569<x:ref>media-type</x:ref> = type "/" subtype *( OWS ";" OWS parameter )
2571<x:ref>parameter</x:ref> = attribute "=" value
[1318]2572<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.7&gt;
[678]2574<x:ref>qvalue</x:ref> = &lt;qvalue, defined in [Part1], Section 6.4&gt;
2576<x:ref>subtype</x:ref> = token
2578<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 1.2.2&gt;
2579<x:ref>type</x:ref> = token
[810]2581<x:ref>value</x:ref> = word
2583<x:ref>word</x:ref> = &lt;word, defined in [Part1], Section 1.2.2&gt;
[532]2586<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
2587; Accept defined but not used
[425]2588; Accept-Charset defined but not used
2589; Accept-Encoding defined but not used
2590; Accept-Language defined but not used
[968]2591; Content-Encoding defined but not used
2592; Content-Language defined but not used
2593; Content-Location defined but not used
2594; Content-Type defined but not used
[425]2595; MIME-Version defined but not used
[680]2597<?ENDINC p3-payload.abnf-appendix ?>
[252]2599<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
[1002]2601<section title="Since RFC 2616">
2603  Extracted relevant partitions from <xref target="RFC2616"/>.
2607<section title="Since draft-ietf-httpbis-p3-payload-00">
[116]2609  Closed issues:
2610  <list style="symbols">
2611    <t>
[324]2612      <eref target=""/>:
[116]2613      "Media Type Registrations"
2614      (<eref target=""/>)
2615    </t>
2616    <t>
[324]2617      <eref target=""/>:
[116]2618      "Clarification regarding quoting of charset values"
2619      (<eref target=""/>)
2620    </t>
2621    <t>
[324]2622      <eref target=""/>:
[116]2623      "Remove 'identity' token references"
2624      (<eref target=""/>)
2625    </t>
2626    <t>
[324]2627      <eref target=""/>:
[126]2628      "Accept-Encoding BNF"
2629    </t>
2630    <t>
[324]2631      <eref target=""/>:
[152]2632      "Normative and Informative references"
2633    </t>
2634    <t>
[324]2635      <eref target=""/>:
[116]2636      "RFC1700 references"
2637    </t>
[122]2638    <t>
[324]2639      <eref target=""/>:
[200]2640      "Updating to RFC4288"
2641    </t>
2642    <t>
[324]2643      <eref target=""/>:
[129]2644      "Informative references"
2645    </t>
2646    <t>
[324]2647      <eref target=""/>:
[123]2648      "ISO-8859-1 Reference"
2649    </t>
2650    <t>
[324]2651      <eref target=""/>:
[122]2652      "Encoding References Normative"
2653    </t>
[131]2654    <t>
[324]2655      <eref target=""/>:
[131]2656      "Normative up-to-date references"
2657    </t>
[116]2658  </list>
[170]2662<section title="Since draft-ietf-httpbis-p3-payload-01">
[324]2664  Ongoing work on ABNF conversion (<eref target=""/>):
[205]2665  <list style="symbols">
2666    <t>
2667      Add explicit references to BNF syntax and rules imported from other parts of the specification.
2668    </t>
2669  </list>
[252]2673<section title="Since draft-ietf-httpbis-p3-payload-02" anchor="changes.since.02">
[232]2675  Closed issues:
2676  <list style="symbols">
2677    <t>
[324]2678      <eref target=""/>:
[251]2679      "Quoting Charsets"
2680    </t>
2681    <t>
[324]2682      <eref target=""/>:
[232]2683      "Classification for Allow header"
2684    </t>
[248]2685    <t>
[324]2686      <eref target=""/>:
[248]2687      "missing default for qvalue in description of Accept-Encoding"
2688    </t>
[232]2689  </list>
[994]2692  Ongoing work on IANA Message Header Field Registration (<eref target=""/>):
[253]2693  <list style="symbols">
2694    <t>
[994]2695      Reference RFC 3984, and update header field registrations for headers defined
[253]2696      in this document.
2697    </t>
2698  </list>
[267]2702<section title="Since draft-ietf-httpbis-p3-payload-03" anchor="changes.since.03">
[269]2704  Closed issues:
2705  <list style="symbols">
2706    <t>
[297]2707      <eref target=""/>:
2708      "Quoting Charsets"
2709    </t>
2710    <t>
[303]2711      <eref target=""/>:
2712      "language tag matching (Accept-Language) vs RFC4647"
2713    </t>
2714    <t>
[277]2715      <eref target=""/>:
[269]2716      "RFC 1806 has been replaced by RFC2183"
2717    </t>
2718  </list>
2721  Other changes:
2722  <list style="symbols">
2723    <t>
2724      <eref target=""/>:
[1101]2725      "Encoding References Normative" &mdash; rephrase the annotation and reference
[277]2726      <xref target="BCP97"/>.
2727    </t>
2728  </list>
[269]2730 </section>
[323]2732<section title="Since draft-ietf-httpbis-p3-payload-04" anchor="changes.since.04">
[327]2734  Closed issues:
2735  <list style="symbols">
2736    <t>
2737      <eref target=""/>:
2738      "RFC 2822 is updated by RFC 5322"
2739    </t>
2740  </list>
2743  Ongoing work on ABNF conversion (<eref target=""/>):
2744  <list style="symbols">
2745    <t>
2746      Use "/" instead of "|" for alternatives.
2747    </t>
[357]2748    <t>
2749      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
2750      whitespace ("OWS") and required whitespace ("RWS").
2751    </t>
2752    <t>
2753      Rewrite ABNFs to spell out whitespace rules, factor out
[994]2754      header field value format definitions.
[357]2755    </t>
[334]2756  </list>
[382]2760<section title="Since draft-ietf-httpbis-p3-payload-05" anchor="changes.since.05">
[385]2762  Closed issues:
2763  <list style="symbols">
2764    <t>
2765      <eref target=""/>:
2766      "Join "Differences Between HTTP Entities and RFC 2045 Entities"?"
2767    </t>
2768  </list>
[543]2771  Final work on ABNF conversion (<eref target=""/>):
[421]2772  <list style="symbols">
2773    <t>
[424]2774      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
[421]2775    </t>
2776  </list>
2779  Other changes:
2780  <list style="symbols">
2781    <t>
2782      Move definition of quality values into Part 1.
2783    </t>
2784  </list>
[547]2788<section title="Since draft-ietf-httpbis-p3-payload-06" anchor="changes.since.06">
[577]2790  Closed issues:
2791  <list style="symbols">
2792    <t>
2793      <eref target=""/>:
2794      "Content-Location isn't special"
2795    </t>
[592]2796    <t>
2797      <eref target=""/>:
2798      "Content Sniffing"
2799    </t>
[577]2800  </list>
[604]2804<section title="Since draft-ietf-httpbis-p3-payload-07" anchor="changes.since.07">
[613]2806  Closed issues:
2807  <list style="symbols">
2808    <t>
[670]2809      <eref target=""/>:
[613]2810      "Updated reference for language tags"
2811    </t>
[663]2812    <t>
[716]2813      <eref target=""/>:
2814      "Clarify rules for determining what entities a response carries"
2815    </t>
2816    <t>
[712]2817      <eref target=""/>:
2818      "Content-Location base-setting problems"
2819    </t>
2820    <t>
[663]2821      <eref target=""/>:
2822      "Content Sniffing"
2823    </t>
[670]2824    <t>
2825      <eref target=""/>:
2826      "pick IANA policy (RFC5226) for Transfer Coding / Content Coding"
2827    </t>
[673]2828    <t>
2829      <eref target=""/>:
2830      "move definitions of gzip/deflate/compress to part 1"
2831    </t>
[613]2832  </list>
2835  Partly resolved issues:
2836  <list style="symbols">
2837    <t>
2838      <eref target=""/>:
2839      "update IANA requirements wrt Transfer-Coding values" (add the
2840      IANA Considerations subsection)
2841    </t>
[668]2842    <t>
2843      <eref target=""/>:
2844      "update IANA requirements wrt Content-Coding values" (add the
2845      IANA Considerations subsection)
2846    </t>
[667]2847  </list>
[720]2851<section title="Since draft-ietf-httpbis-p3-payload-08" anchor="changes.since.08">
[724]2853  Closed issues:
2854  <list style="symbols">
2855    <t>
[745]2856      <eref target=""/>:
2857      "Content Negotiation for media types"
2858    </t>
2859    <t>
[724]2860      <eref target=""/>:
2861      "Accept-Language: which RFC4647 filtering?"
2862    </t>
2863  </list>
[773]2867<section title="Since draft-ietf-httpbis-p3-payload-09" anchor="changes.since.09">
[808]2869  Closed issues:
2870  <list style="symbols">
2871    <t>
[937]2872      <eref target=""/>:
2873      "MIME-Version not listed in P1, general header fields"
2874    </t>
2875    <t>
[808]2876      <eref target=""/>:
2877      "IANA registry for content/transfer encodings"
2878    </t>
[810]2879    <t>
[831]2880      <eref target=""/>:
2881      "Content Sniffing"
2882    </t>
2883    <t>
[810]2884      <eref target=""/>:
2885      "use of term "word" when talking about header structure"
2886    </t>
[808]2887  </list>
2890  Partly resolved issues:
2891  <list style="symbols">
2892    <t>
2893      <eref target=""/>:
2894      "Term for the requested resource's URI"
2895    </t>
2896  </list>
[841]2900<section title="Since draft-ietf-httpbis-p3-payload-10" anchor="changes.since.10">
[854]2902  Closed issues:
2903  <list style="symbols">
2904    <t>
[858]2905      <eref target=""/>:
2906      "Clarify 'Requested Variant'"
2907    </t>
2908    <t>
2909      <eref target=""/>:
2910      "Content-Location isn't special"
2911    </t>
2912    <t>
[854]2913      <eref target=""/>:
2914      "Delimiting messages with multipart/byteranges"
2915    </t>
[858]2916    <t>
2917      <eref target=""/>:
2918      "Clarify entity / representation / variant terminology"
2919    </t>
2920    <t>
2921      <eref target=""/>:
2922      "confusing req. language for Content-Location"
2923    </t>
2924    <t>
2925      <eref target=""/>:
2926      "Content-Location on 304 responses"
2927    </t>
[882]2928    <t>
2929      <eref target=""/>:
2930      "'requested resource' in content-encoding definition"
2931    </t>
[911]2932    <t>
2933      <eref target=""/>:
2934      "consider removing the 'changes from 2068' sections"
2935    </t>
[854]2936  </list>
2939  Partly resolved issues:
2940  <list style="symbols">
2941    <t>
2942      <eref target=""/>:
2943      "Content-MD5 and partial responses"
2944    </t>
2945  </list>
[973]2949<section title="Since draft-ietf-httpbis-p3-payload-11" anchor="changes.since.11">
[987]2951  Closed issues:
2952  <list style="symbols">
2953    <t>
2954      <eref target=""/>:
2955      "Factor out Content-Disposition"
2956    </t>
2957  </list>
[1052]2961<section title="Since draft-ietf-httpbis-p3-payload-12" anchor="changes.since.12">
[1153]2963  Closed issues:
2964  <list style="symbols">
2965    <t>
[1165]2966      <eref target=""/>:
2967      "Header Classification"
2968    </t>
2969    <t>
[1167]2970      <eref target=""/>:
2971      "untangle ABNFs for header fields"
2972    </t>
2973    <t>
[1153]2974      <eref target=""/>:
2975      "potentially misleading MAY in media-type def"
2976    </t>
2977  </list>
[1180]2981<section title="Since draft-ietf-httpbis-p3-payload-13" anchor="changes.since.13">
[1234]2983  Closed issues:
2984  <list style="symbols">
2985    <t>
[1240]2986      <eref target=""/>:
2987      "Default charsets for text media types"
2988    </t>
2989    <t>
[1267]2990      <eref target=""/>:
2991      "Content-MD5 and partial responses"
2992    </t>
2993    <t>
[1234]2994      <eref target=""/>:
2995      "untangle ABNFs for header fields"
2996    </t>
[1244]2997    <t>
2998      <eref target=""/>:
2999      "confusing undefined parameter in media range example"
3000    </t>
[1234]3001  </list>
[1271]3005<section title="Since draft-ietf-httpbis-p3-payload-14" anchor="changes.since.14">
[1328]3007  None.
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