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4Network Working Group                                   R. Fielding, Ed.
5Internet-Draft                                              Day Software
6Obsoletes: 2616 (if approved)                                  J. Gettys
7Intended status: Standards Track                    One Laptop per Child
8Expires: August 27, 2008                                        J. Mogul
9                                                                      HP
10                                                              H. Frystyk
11                                                               Microsoft
12                                                             L. Masinter
13                                                           Adobe Systems
14                                                                P. Leach
15                                                               Microsoft
16                                                          T. Berners-Lee
17                                                                 W3C/MIT
18                                                           Y. Lafon, Ed.
19                                                                     W3C
20                                                         J. Reschke, Ed.
21                                                              greenbytes
22                                                       February 24, 2008
23
24
25       HTTP/1.1, part 3: Message Payload and Content Negotiation
26                    draft-ietf-httpbis-p3-payload-02
27
28Status of this Memo
29
30   By submitting this Internet-Draft, each author represents that any
31   applicable patent or other IPR claims of which he or she is aware
32   have been or will be disclosed, and any of which he or she becomes
33   aware will be disclosed, in accordance with Section 6 of BCP 79.
34
35   Internet-Drafts are working documents of the Internet Engineering
36   Task Force (IETF), its areas, and its working groups.  Note that
37   other groups may also distribute working documents as Internet-
38   Drafts.
39
40   Internet-Drafts are draft documents valid for a maximum of six months
41   and may be updated, replaced, or obsoleted by other documents at any
42   time.  It is inappropriate to use Internet-Drafts as reference
43   material or to cite them other than as "work in progress."
44
45   The list of current Internet-Drafts can be accessed at
46   http://www.ietf.org/ietf/1id-abstracts.txt.
47
48   The list of Internet-Draft Shadow Directories can be accessed at
49   http://www.ietf.org/shadow.html.
50
51   This Internet-Draft will expire on August 27, 2008.
52
53
54
55Fielding, et al.         Expires August 27, 2008                [Page 1]
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57Internet-Draft              HTTP/1.1, Part 3               February 2008
58
59
60Copyright Notice
61
62   Copyright (C) The IETF Trust (2008).
63
64Abstract
65
66   The Hypertext Transfer Protocol (HTTP) is an application-level
67   protocol for distributed, collaborative, hypermedia information
68   systems.  HTTP has been in use by the World Wide Web global
69   information initiative since 1990.  This document is Part 3 of the
70   seven-part specification that defines the protocol referred to as
71   "HTTP/1.1" and, taken together, obsoletes RFC 2616.  Part 3 defines
72   HTTP message content, metadata, and content negotiation.
73
74Editorial Note (To be removed by RFC Editor)
75
76   Discussion of this draft should take place on the HTTPBIS working
77   group mailing list (ietf-http-wg@w3.org).  The current issues list is
78   at <http://www.tools.ietf.org/wg/httpbis/trac/report/11> and related
79   documents (including fancy diffs) can be found at
80   <http://www.tools.ietf.org/wg/httpbis/>.
81
82   This draft incorporates those issue resolutions that were either
83   collected in the original RFC2616 errata list
84   (<http://purl.org/NET/http-errata>), or which were agreed upon on the
85   mailing list between October 2006 and November 2007 (as published in
86   "draft-lafon-rfc2616bis-03").
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113Internet-Draft              HTTP/1.1, Part 3               February 2008
114
115
116Table of Contents
117
118   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  5
119     1.1.  Requirements . . . . . . . . . . . . . . . . . . . . . . .  5
120   2.  Notational Conventions and Generic Grammar . . . . . . . . . .  5
121   3.  Protocol Parameters  . . . . . . . . . . . . . . . . . . . . .  6
122     3.1.  Character Sets . . . . . . . . . . . . . . . . . . . . . .  6
123       3.1.1.  Missing Charset  . . . . . . . . . . . . . . . . . . .  7
124     3.2.  Content Codings  . . . . . . . . . . . . . . . . . . . . .  7
125     3.3.  Media Types  . . . . . . . . . . . . . . . . . . . . . . .  9
126       3.3.1.  Canonicalization and Text Defaults . . . . . . . . . .  9
127       3.3.2.  Multipart Types  . . . . . . . . . . . . . . . . . . . 10
128     3.4.  Quality Values . . . . . . . . . . . . . . . . . . . . . . 11
129     3.5.  Language Tags  . . . . . . . . . . . . . . . . . . . . . . 11
130   4.  Entity . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
131     4.1.  Entity Header Fields . . . . . . . . . . . . . . . . . . . 12
132     4.2.  Entity Body  . . . . . . . . . . . . . . . . . . . . . . . 12
133       4.2.1.  Type . . . . . . . . . . . . . . . . . . . . . . . . . 13
134       4.2.2.  Entity Length  . . . . . . . . . . . . . . . . . . . . 13
135   5.  Content Negotiation  . . . . . . . . . . . . . . . . . . . . . 13
136     5.1.  Server-driven Negotiation  . . . . . . . . . . . . . . . . 14
137     5.2.  Agent-driven Negotiation . . . . . . . . . . . . . . . . . 15
138     5.3.  Transparent Negotiation  . . . . . . . . . . . . . . . . . 16
139   6.  Header Field Definitions . . . . . . . . . . . . . . . . . . . 16
140     6.1.  Accept . . . . . . . . . . . . . . . . . . . . . . . . . . 16
141     6.2.  Accept-Charset . . . . . . . . . . . . . . . . . . . . . . 18
142     6.3.  Accept-Encoding  . . . . . . . . . . . . . . . . . . . . . 19
143     6.4.  Accept-Language  . . . . . . . . . . . . . . . . . . . . . 20
144     6.5.  Content-Encoding . . . . . . . . . . . . . . . . . . . . . 22
145     6.6.  Content-Language . . . . . . . . . . . . . . . . . . . . . 22
146     6.7.  Content-Location . . . . . . . . . . . . . . . . . . . . . 23
147     6.8.  Content-MD5  . . . . . . . . . . . . . . . . . . . . . . . 24
148     6.9.  Content-Type . . . . . . . . . . . . . . . . . . . . . . . 25
149   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 26
150   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 26
151     8.1.  Privacy Issues Connected to Accept Headers . . . . . . . . 26
152     8.2.  Content-Disposition Issues . . . . . . . . . . . . . . . . 27
153   9.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 27
154   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 27
155     10.1. Normative References . . . . . . . . . . . . . . . . . . . 27
156     10.2. Informative References . . . . . . . . . . . . . . . . . . 29
157   Appendix A.  Differences Between HTTP Entities and RFC 2045
158                Entities  . . . . . . . . . . . . . . . . . . . . . . 30
159     A.1.  MIME-Version . . . . . . . . . . . . . . . . . . . . . . . 30
160     A.2.  Conversion to Canonical Form . . . . . . . . . . . . . . . 30
161     A.3.  Introduction of Content-Encoding . . . . . . . . . . . . . 31
162     A.4.  No Content-Transfer-Encoding . . . . . . . . . . . . . . . 31
163     A.5.  Introduction of Transfer-Encoding  . . . . . . . . . . . . 31
164
165
166
167Fielding, et al.         Expires August 27, 2008                [Page 3]
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172     A.6.  MHTML and Line Length Limitations  . . . . . . . . . . . . 32
173   Appendix B.  Additional Features . . . . . . . . . . . . . . . . . 32
174     B.1.  Content-Disposition  . . . . . . . . . . . . . . . . . . . 32
175   Appendix C.  Compatibility with Previous Versions  . . . . . . . . 33
176     C.1.  Changes from RFC 2068  . . . . . . . . . . . . . . . . . . 33
177     C.2.  Changes from RFC 2616  . . . . . . . . . . . . . . . . . . 33
178   Appendix D.  Change Log (to be removed by RFC Editor before
179                publication)  . . . . . . . . . . . . . . . . . . . . 34
180     D.1.  Since RFC2616  . . . . . . . . . . . . . . . . . . . . . . 34
181     D.2.  Since draft-ietf-httpbis-p3-payload-00 . . . . . . . . . . 34
182     D.3.  Since draft-ietf-httpbis-p3-payload-01 . . . . . . . . . . 35
183   Index  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
184   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 37
185   Intellectual Property and Copyright Statements . . . . . . . . . . 40
186
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225Internet-Draft              HTTP/1.1, Part 3               February 2008
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227
2281.  Introduction
229
230   This document defines HTTP/1.1 message payloads (a.k.a., content),
231   the associated metadata header fields that define how the payload is
232   intended to be interpreted by a recipient, the request header fields
233   that may influence content selection, and the various selection
234   algorithms that are collectively referred to as HTTP content
235   negotiation.
236
237   This document is currently disorganized in order to minimize the
238   changes between drafts and enable reviewers to see the smaller errata
239   changes.  The next draft will reorganize the sections to better
240   reflect the content.  In particular, the sections on entities will be
241   renamed payload and moved to the first half of the document, while
242   the sections on content negotiation and associated request header
243   fields will be moved to the second half.  The current mess reflects
244   how widely dispersed these topics and associated requirements had
245   become in [RFC2616].
246
2471.1.  Requirements
248
249   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
250   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
251   document are to be interpreted as described in [RFC2119].
252
253   An implementation is not compliant if it fails to satisfy one or more
254   of the MUST or REQUIRED level requirements for the protocols it
255   implements.  An implementation that satisfies all the MUST or
256   REQUIRED level and all the SHOULD level requirements for its
257   protocols is said to be "unconditionally compliant"; one that
258   satisfies all the MUST level requirements but not all the SHOULD
259   level requirements for its protocols is said to be "conditionally
260   compliant."
261
262
2632.  Notational Conventions and Generic Grammar
264
265   This specification uses the ABNF syntax defined in Section 2.1 of
266   [Part1] and the core rules defined in Section 2.2 of [Part1]:
267   [[abnf.dep: ABNF syntax and basic rules will be adopted from RFC
268   5234, see <http://tools.ietf.org/wg/httpbis/trac/ticket/36>.]]
269
270     ALPHA          = <ALPHA, defined in [Part1], Section 2.2>
271     DIGIT          = <DIGIT, defined in [Part1], Section 2.2>
272     OCTET          = <OCTET, defined in [Part1], Section 2.2>
273
274
275     quoted-string  = <quoted-string, defined in [Part1], Section 2.2>
276
277
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283
284     token          = <token, defined in [Part1], Section 2.2>
285
286   The ABNF rules below are defined in other parts:
287
288     absoluteURI    = <absoluteURI, defined in [Part1], Section 3.2.1>
289     Content-Length = <Content-Length, defined in [Part1], Section 8.2>
290     relativeURI    = <relativeURI, defined in [Part1], Section 3.2.1>
291     message-header = <message-header, defined in [Part1], Section 4.2>
292
293
294     Allow          = <Allow, defined in [Part2], Section 10.1>
295
296
297     Last-Modified  = <Last-Modified, defined in [Part4], Section 7.6>
298
299
300     Content-Range  = <Content-Range, defined in [Part5], Section 6.2>
301
302
303     Expires        = <Expires, defined in [Part6], Section 16.3>
304
305
3063.  Protocol Parameters
307
3083.1.  Character Sets
309
310   HTTP uses the same definition of the term "character set" as that
311   described for MIME:
312
313   The term "character set" is used in this document to refer to a
314   method used with one or more tables to convert a sequence of octets
315   into a sequence of characters.  Note that unconditional conversion in
316   the other direction is not required, in that not all characters may
317   be available in a given character set and a character set may provide
318   more than one sequence of octets to represent a particular character.
319   This definition is intended to allow various kinds of character
320   encoding, from simple single-table mappings such as US-ASCII to
321   complex table switching methods such as those that use ISO-2022's
322   techniques.  However, the definition associated with a MIME character
323   set name MUST fully specify the mapping to be performed from octets
324   to characters.  In particular, use of external profiling information
325   to determine the exact mapping is not permitted.
326
327      Note: This use of the term "character set" is more commonly
328      referred to as a "character encoding."  However, since HTTP and
329      MIME share the same registry, it is important that the terminology
330      also be shared.
331
332
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339
340   HTTP character sets are identified by case-insensitive tokens.  The
341   complete set of tokens is defined by the IANA Character Set registry
342   (<http://www.iana.org/assignments/character-sets>).
343
344     charset = token
345
346   Although HTTP allows an arbitrary token to be used as a charset
347   value, any token that has a predefined value within the IANA
348   Character Set registry MUST represent the character set defined by
349   that registry.  Applications SHOULD limit their use of character sets
350   to those defined by the IANA registry.
351
352   HTTP uses charset in two contexts: within an Accept-Charset request
353   header (in which the charset value is an unquoted token) and as the
354   value of a parameter in a Content-Type header (within a request or
355   response), in which case the parameter value of the charset parameter
356   may be quoted.
357
358   Implementors should be aware of IETF character set requirements
359   [RFC3629] [RFC2277].
360
3613.1.1.  Missing Charset
362
363   Some HTTP/1.0 software has interpreted a Content-Type header without
364   charset parameter incorrectly to mean "recipient should guess."
365   Senders wishing to defeat this behavior MAY include a charset
366   parameter even when the charset is ISO-8859-1 ([ISO-8859-1]) and
367   SHOULD do so when it is known that it will not confuse the recipient.
368
369   Unfortunately, some older HTTP/1.0 clients did not deal properly with
370   an explicit charset parameter.  HTTP/1.1 recipients MUST respect the
371   charset label provided by the sender; and those user agents that have
372   a provision to "guess" a charset MUST use the charset from the
373   content-type field if they support that charset, rather than the
374   recipient's preference, when initially displaying a document.  See
375   Section 3.3.1.
376
3773.2.  Content Codings
378
379   Content coding values indicate an encoding transformation that has
380   been or can be applied to an entity.  Content codings are primarily
381   used to allow a document to be compressed or otherwise usefully
382   transformed without losing the identity of its underlying media type
383   and without loss of information.  Frequently, the entity is stored in
384   coded form, transmitted directly, and only decoded by the recipient.
385
386     content-coding   = token
387
388
389
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395
396   All content-coding values are case-insensitive.  HTTP/1.1 uses
397   content-coding values in the Accept-Encoding (Section 6.3) and
398   Content-Encoding (Section 6.5) header fields.  Although the value
399   describes the content-coding, what is more important is that it
400   indicates what decoding mechanism will be required to remove the
401   encoding.
402
403   The Internet Assigned Numbers Authority (IANA) acts as a registry for
404   content-coding value tokens.  Initially, the registry contains the
405   following tokens:
406
407   gzip
408
409      An encoding format produced by the file compression program "gzip"
410      (GNU zip) as described in [RFC1952].  This format is a Lempel-Ziv
411      coding (LZ77) with a 32 bit CRC.
412
413   compress
414
415      The encoding format produced by the common UNIX file compression
416      program "compress".  This format is an adaptive Lempel-Ziv-Welch
417      coding (LZW).
418
419      Use of program names for the identification of encoding formats is
420      not desirable and is discouraged for future encodings.  Their use
421      here is representative of historical practice, not good design.
422      For compatibility with previous implementations of HTTP,
423      applications SHOULD consider "x-gzip" and "x-compress" to be
424      equivalent to "gzip" and "compress" respectively.
425
426   deflate
427
428      The "zlib" format defined in [RFC1950] in combination with the
429      "deflate" compression mechanism described in [RFC1951].
430
431   identity
432
433      The default (identity) encoding; the use of no transformation
434      whatsoever.  This content-coding is used only in the Accept-
435      Encoding header, and SHOULD NOT be used in the Content-Encoding
436      header.
437
438   New content-coding value tokens SHOULD be registered; to allow
439   interoperability between clients and servers, specifications of the
440   content coding algorithms needed to implement a new value SHOULD be
441   publicly available and adequate for independent implementation, and
442   conform to the purpose of content coding defined in this section.
443
444
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451
4523.3.  Media Types
453
454   HTTP uses Internet Media Types [RFC2046] in the Content-Type
455   (Section 6.9) and Accept (Section 6.1) header fields in order to
456   provide open and extensible data typing and type negotiation.
457
458     media-type     = type "/" subtype *( ";" parameter )
459     type           = token
460     subtype        = token
461
462   Parameters MAY follow the type/subtype in the form of attribute/value
463   pairs.
464
465     parameter               = attribute "=" value
466     attribute               = token
467     value                   = token | quoted-string
468
469   The type, subtype, and parameter attribute names are case-
470   insensitive.  Parameter values might or might not be case-sensitive,
471   depending on the semantics of the parameter name.  Linear white space
472   (LWS) MUST NOT be used between the type and subtype, nor between an
473   attribute and its value.  The presence or absence of a parameter
474   might be significant to the processing of a media-type, depending on
475   its definition within the media type registry.
476
477   Note that some older HTTP applications do not recognize media type
478   parameters.  When sending data to older HTTP applications,
479   implementations SHOULD only use media type parameters when they are
480   required by that type/subtype definition.
481
482   Media-type values are registered with the Internet Assigned Number
483   Authority (IANA).  The media type registration process is outlined in
484   [RFC4288].  Use of non-registered media types is discouraged.
485
4863.3.1.  Canonicalization and Text Defaults
487
488   Internet media types are registered with a canonical form.  An
489   entity-body transferred via HTTP messages MUST be represented in the
490   appropriate canonical form prior to its transmission except for
491   "text" types, as defined in the next paragraph.
492
493   When in canonical form, media subtypes of the "text" type use CRLF as
494   the text line break.  HTTP relaxes this requirement and allows the
495   transport of text media with plain CR or LF alone representing a line
496   break when it is done consistently for an entire entity-body.  HTTP
497   applications MUST accept CRLF, bare CR, and bare LF as being
498   representative of a line break in text media received via HTTP.  In
499   addition, if the text is represented in a character set that does not
500
501
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507
508   use octets 13 and 10 for CR and LF respectively, as is the case for
509   some multi-byte character sets, HTTP allows the use of whatever octet
510   sequences are defined by that character set to represent the
511   equivalent of CR and LF for line breaks.  This flexibility regarding
512   line breaks applies only to text media in the entity-body; a bare CR
513   or LF MUST NOT be substituted for CRLF within any of the HTTP control
514   structures (such as header fields and multipart boundaries).
515
516   If an entity-body is encoded with a content-coding, the underlying
517   data MUST be in a form defined above prior to being encoded.
518
519   The "charset" parameter is used with some media types to define the
520   character set (Section 3.1) of the data.  When no explicit charset
521   parameter is provided by the sender, media subtypes of the "text"
522   type are defined to have a default charset value of "ISO-8859-1" when
523   received via HTTP.  Data in character sets other than "ISO-8859-1" or
524   its subsets MUST be labeled with an appropriate charset value.  See
525   Section 3.1.1 for compatibility problems.
526
5273.3.2.  Multipart Types
528
529   MIME provides for a number of "multipart" types -- encapsulations of
530   one or more entities within a single message-body.  All multipart
531   types share a common syntax, as defined in Section 5.1.1 of
532   [RFC2046], and MUST include a boundary parameter as part of the media
533   type value.  The message body is itself a protocol element and MUST
534   therefore use only CRLF to represent line breaks between body-parts.
535   Unlike in RFC 2046, the epilogue of any multipart message MUST be
536   empty; HTTP applications MUST NOT transmit the epilogue (even if the
537   original multipart contains an epilogue).  These restrictions exist
538   in order to preserve the self-delimiting nature of a multipart
539   message-body, wherein the "end" of the message-body is indicated by
540   the ending multipart boundary.
541
542   In general, HTTP treats a multipart message-body no differently than
543   any other media type: strictly as payload.  The one exception is the
544   "multipart/byteranges" type (Appendix A of [Part5]) when it appears
545   in a 206 (Partial Content) response.  In all other cases, an HTTP
546   user agent SHOULD follow the same or similar behavior as a MIME user
547   agent would upon receipt of a multipart type.  The MIME header fields
548   within each body-part of a multipart message-body do not have any
549   significance to HTTP beyond that defined by their MIME semantics.
550
551   In general, an HTTP user agent SHOULD follow the same or similar
552   behavior as a MIME user agent would upon receipt of a multipart type.
553   If an application receives an unrecognized multipart subtype, the
554   application MUST treat it as being equivalent to "multipart/mixed".
555
556
557
558
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563
564      Note: The "multipart/form-data" type has been specifically defined
565      for carrying form data suitable for processing via the POST
566      request method, as described in [RFC2388].
567
5683.4.  Quality Values
569
570   HTTP content negotiation (Section 5) uses short "floating point"
571   numbers to indicate the relative importance ("weight") of various
572   negotiable parameters.  A weight is normalized to a real number in
573   the range 0 through 1, where 0 is the minimum and 1 the maximum
574   value.  If a parameter has a quality value of 0, then content with
575   this parameter is `not acceptable' for the client.  HTTP/1.1
576   applications MUST NOT generate more than three digits after the
577   decimal point.  User configuration of these values SHOULD also be
578   limited in this fashion.
579
580     qvalue         = ( "0" [ "." 0*3DIGIT ] )
581                    | ( "1" [ "." 0*3("0") ] )
582
583   "Quality values" is a misnomer, since these values merely represent
584   relative degradation in desired quality.
585
5863.5.  Language Tags
587
588   A language tag identifies a natural language spoken, written, or
589   otherwise conveyed by human beings for communication of information
590   to other human beings.  Computer languages are explicitly excluded.
591   HTTP uses language tags within the Accept-Language and Content-
592   Language fields.
593
594   The syntax and registry of HTTP language tags is the same as that
595   defined by [RFC1766].  In summary, a language tag is composed of 1 or
596   more parts: A primary language tag and a possibly empty series of
597   subtags:
598
599     language-tag  = primary-tag *( "-" subtag )
600     primary-tag   = 1*8ALPHA
601     subtag        = 1*8ALPHA
602
603   White space is not allowed within the tag and all tags are case-
604   insensitive.  The name space of language tags is administered by the
605   IANA.  Example tags include:
606
607       en, en-US, en-cockney, i-cherokee, x-pig-latin
608
609   where any two-letter primary-tag is an ISO-639 language abbreviation
610   and any two-letter initial subtag is an ISO-3166 country code.  (The
611   last three tags above are not registered tags; all but the last are
612
613
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619
620   examples of tags which could be registered in future.)
621
622
6234.  Entity
624
625   Request and Response messages MAY transfer an entity if not otherwise
626   restricted by the request method or response status code.  An entity
627   consists of entity-header fields and an entity-body, although some
628   responses will only include the entity-headers.
629
630   In this section, both sender and recipient refer to either the client
631   or the server, depending on who sends and who receives the entity.
632
6334.1.  Entity Header Fields
634
635   Entity-header fields define metainformation about the entity-body or,
636   if no body is present, about the resource identified by the request.
637
638     entity-header  = Allow                    ; [Part2], Section 10.1
639                    | Content-Encoding         ; Section 6.5
640                    | Content-Language         ; Section 6.6
641                    | Content-Length           ; [Part1], Section 8.2
642                    | Content-Location         ; Section 6.7
643                    | Content-MD5              ; Section 6.8
644                    | Content-Range            ; [Part5], Section 6.2
645                    | Content-Type             ; Section 6.9
646                    | Expires                  ; [Part6], Section 16.3
647                    | Last-Modified            ; [Part4], Section 7.6
648                    | extension-header
649
650     extension-header = message-header
651
652   The extension-header mechanism allows additional entity-header fields
653   to be defined without changing the protocol, but these fields cannot
654   be assumed to be recognizable by the recipient.  Unrecognized header
655   fields SHOULD be ignored by the recipient and MUST be forwarded by
656   transparent proxies.
657
6584.2.  Entity Body
659
660   The entity-body (if any) sent with an HTTP request or response is in
661   a format and encoding defined by the entity-header fields.
662
663     entity-body    = *OCTET
664
665   An entity-body is only present in a message when a message-body is
666   present, as described in Section 4.3 of [Part1].  The entity-body is
667   obtained from the message-body by decoding any Transfer-Encoding that
668
669
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675
676   might have been applied to ensure safe and proper transfer of the
677   message.
678
6794.2.1.  Type
680
681   When an entity-body is included with a message, the data type of that
682   body is determined via the header fields Content-Type and Content-
683   Encoding.  These define a two-layer, ordered encoding model:
684
685       entity-body := Content-Encoding( Content-Type( data ) )
686
687   Content-Type specifies the media type of the underlying data.
688   Content-Encoding may be used to indicate any additional content
689   codings applied to the data, usually for the purpose of data
690   compression, that are a property of the requested resource.  There is
691   no default encoding.
692
693   Any HTTP/1.1 message containing an entity-body SHOULD include a
694   Content-Type header field defining the media type of that body.  If
695   and only if the media type is not given by a Content-Type field, the
696   recipient MAY attempt to guess the media type via inspection of its
697   content and/or the name extension(s) of the URI used to identify the
698   resource.  If the media type remains unknown, the recipient SHOULD
699   treat it as type "application/octet-stream".
700
7014.2.2.  Entity Length
702
703   The entity-length of a message is the length of the message-body
704   before any transfer-codings have been applied.  Section 4.4 of
705   [Part1] defines how the transfer-length of a message-body is
706   determined.
707
708
7095.  Content Negotiation
710
711   Most HTTP responses include an entity which contains information for
712   interpretation by a human user.  Naturally, it is desirable to supply
713   the user with the "best available" entity corresponding to the
714   request.  Unfortunately for servers and caches, not all users have
715   the same preferences for what is "best," and not all user agents are
716   equally capable of rendering all entity types.  For that reason, HTTP
717   has provisions for several mechanisms for "content negotiation" --
718   the process of selecting the best representation for a given response
719   when there are multiple representations available.
720
721      Note: This is not called "format negotiation" because the
722      alternate representations may be of the same media type, but use
723      different capabilities of that type, be in different languages,
724
725
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731
732      etc.
733
734   Any response containing an entity-body MAY be subject to negotiation,
735   including error responses.
736
737   There are two kinds of content negotiation which are possible in
738   HTTP: server-driven and agent-driven negotiation.  These two kinds of
739   negotiation are orthogonal and thus may be used separately or in
740   combination.  One method of combination, referred to as transparent
741   negotiation, occurs when a cache uses the agent-driven negotiation
742   information provided by the origin server in order to provide server-
743   driven negotiation for subsequent requests.
744
7455.1.  Server-driven Negotiation
746
747   If the selection of the best representation for a response is made by
748   an algorithm located at the server, it is called server-driven
749   negotiation.  Selection is based on the available representations of
750   the response (the dimensions over which it can vary; e.g. language,
751   content-coding, etc.) and the contents of particular header fields in
752   the request message or on other information pertaining to the request
753   (such as the network address of the client).
754
755   Server-driven negotiation is advantageous when the algorithm for
756   selecting from among the available representations is difficult to
757   describe to the user agent, or when the server desires to send its
758   "best guess" to the client along with the first response (hoping to
759   avoid the round-trip delay of a subsequent request if the "best
760   guess" is good enough for the user).  In order to improve the
761   server's guess, the user agent MAY include request header fields
762   (Accept, Accept-Language, Accept-Encoding, etc.) which describe its
763   preferences for such a response.
764
765   Server-driven negotiation has disadvantages:
766
767   1.  It is impossible for the server to accurately determine what
768       might be "best" for any given user, since that would require
769       complete knowledge of both the capabilities of the user agent and
770       the intended use for the response (e.g., does the user want to
771       view it on screen or print it on paper?).
772
773   2.  Having the user agent describe its capabilities in every request
774       can be both very inefficient (given that only a small percentage
775       of responses have multiple representations) and a potential
776       violation of the user's privacy.
777
778   3.  It complicates the implementation of an origin server and the
779       algorithms for generating responses to a request.
780
781
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787
788   4.  It may limit a public cache's ability to use the same response
789       for multiple user's requests.
790
791   HTTP/1.1 includes the following request-header fields for enabling
792   server-driven negotiation through description of user agent
793   capabilities and user preferences: Accept (Section 6.1), Accept-
794   Charset (Section 6.2), Accept-Encoding (Section 6.3), Accept-Language
795   (Section 6.4), and User-Agent (Section 10.9 of [Part2]).  However, an
796   origin server is not limited to these dimensions and MAY vary the
797   response based on any aspect of the request, including information
798   outside the request-header fields or within extension header fields
799   not defined by this specification.
800
801   The Vary header field (Section 16.5 of [Part6]) can be used to
802   express the parameters the server uses to select a representation
803   that is subject to server-driven negotiation.
804
8055.2.  Agent-driven Negotiation
806
807   With agent-driven negotiation, selection of the best representation
808   for a response is performed by the user agent after receiving an
809   initial response from the origin server.  Selection is based on a
810   list of the available representations of the response included within
811   the header fields or entity-body of the initial response, with each
812   representation identified by its own URI.  Selection from among the
813   representations may be performed automatically (if the user agent is
814   capable of doing so) or manually by the user selecting from a
815   generated (possibly hypertext) menu.
816
817   Agent-driven negotiation is advantageous when the response would vary
818   over commonly-used dimensions (such as type, language, or encoding),
819   when the origin server is unable to determine a user agent's
820   capabilities from examining the request, and generally when public
821   caches are used to distribute server load and reduce network usage.
822
823   Agent-driven negotiation suffers from the disadvantage of needing a
824   second request to obtain the best alternate representation.  This
825   second request is only efficient when caching is used.  In addition,
826   this specification does not define any mechanism for supporting
827   automatic selection, though it also does not prevent any such
828   mechanism from being developed as an extension and used within
829   HTTP/1.1.
830
831   HTTP/1.1 defines the 300 (Multiple Choices) and 406 (Not Acceptable)
832   status codes for enabling agent-driven negotiation when the server is
833   unwilling or unable to provide a varying response using server-driven
834   negotiation.
835
836
837
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843
8445.3.  Transparent Negotiation
845
846   Transparent negotiation is a combination of both server-driven and
847   agent-driven negotiation.  When a cache is supplied with a form of
848   the list of available representations of the response (as in agent-
849   driven negotiation) and the dimensions of variance are completely
850   understood by the cache, then the cache becomes capable of performing
851   server-driven negotiation on behalf of the origin server for
852   subsequent requests on that resource.
853
854   Transparent negotiation has the advantage of distributing the
855   negotiation work that would otherwise be required of the origin
856   server and also removing the second request delay of agent-driven
857   negotiation when the cache is able to correctly guess the right
858   response.
859
860   This specification does not define any mechanism for transparent
861   negotiation, though it also does not prevent any such mechanism from
862   being developed as an extension that could be used within HTTP/1.1.
863
864
8656.  Header Field Definitions
866
867   This section defines the syntax and semantics of HTTP/1.1 header
868   fields related to the payload of messages.
869
870   For entity-header fields, both sender and recipient refer to either
871   the client or the server, depending on who sends and who receives the
872   entity.
873
8746.1.  Accept
875
876   The Accept request-header field can be used to specify certain media
877   types which are acceptable for the response.  Accept headers can be
878   used to indicate that the request is specifically limited to a small
879   set of desired types, as in the case of a request for an in-line
880   image.
881
882     Accept         = "Accept" ":"
883                      #( media-range [ accept-params ] )
884
885     media-range    = ( "*/*"
886                      | ( type "/" "*" )
887                      | ( type "/" subtype )
888                      ) *( ";" parameter )
889     accept-params  = ";" "q" "=" qvalue *( accept-extension )
890     accept-extension = ";" token [ "=" ( token | quoted-string ) ]
891
892
893
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899
900   The asterisk "*" character is used to group media types into ranges,
901   with "*/*" indicating all media types and "type/*" indicating all
902   subtypes of that type.  The media-range MAY include media type
903   parameters that are applicable to that range.
904
905   Each media-range MAY be followed by one or more accept-params,
906   beginning with the "q" parameter for indicating a relative quality
907   factor.  The first "q" parameter (if any) separates the media-range
908   parameter(s) from the accept-params.  Quality factors allow the user
909   or user agent to indicate the relative degree of preference for that
910   media-range, using the qvalue scale from 0 to 1 (Section 3.4).  The
911   default value is q=1.
912
913      Note: Use of the "q" parameter name to separate media type
914      parameters from Accept extension parameters is due to historical
915      practice.  Although this prevents any media type parameter named
916      "q" from being used with a media range, such an event is believed
917      to be unlikely given the lack of any "q" parameters in the IANA
918      media type registry and the rare usage of any media type
919      parameters in Accept.  Future media types are discouraged from
920      registering any parameter named "q".
921
922   The example
923
924       Accept: audio/*; q=0.2, audio/basic
925
926   SHOULD be interpreted as "I prefer audio/basic, but send me any audio
927   type if it is the best available after an 80% mark-down in quality."
928
929   If no Accept header field is present, then it is assumed that the
930   client accepts all media types.  If an Accept header field is
931   present, and if the server cannot send a response which is acceptable
932   according to the combined Accept field value, then the server SHOULD
933   send a 406 (Not Acceptable) response.
934
935   A more elaborate example is
936
937       Accept: text/plain; q=0.5, text/html,
938               text/x-dvi; q=0.8, text/x-c
939
940   Verbally, this would be interpreted as "text/html and text/x-c are
941   the preferred media types, but if they do not exist, then send the
942   text/x-dvi entity, and if that does not exist, send the text/plain
943   entity."
944
945   Media ranges can be overridden by more specific media ranges or
946   specific media types.  If more than one media range applies to a
947   given type, the most specific reference has precedence.  For example,
948
949
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955
956       Accept: text/*, text/html, text/html;level=1, */*
957
958   have the following precedence:
959
960       1) text/html;level=1
961       2) text/html
962       3) text/*
963       4) */*
964
965   The media type quality factor associated with a given type is
966   determined by finding the media range with the highest precedence
967   which matches that type.  For example,
968
969       Accept: text/*;q=0.3, text/html;q=0.7, text/html;level=1,
970               text/html;level=2;q=0.4, */*;q=0.5
971
972   would cause the following values to be associated:
973
974       text/html;level=1         = 1
975       text/html                 = 0.7
976       text/plain                = 0.3
977       image/jpeg                = 0.5
978       text/html;level=2         = 0.4
979       text/html;level=3         = 0.7
980
981   Note: A user agent might be provided with a default set of quality
982   values for certain media ranges.  However, unless the user agent is a
983   closed system which cannot interact with other rendering agents, this
984   default set ought to be configurable by the user.
985
9866.2.  Accept-Charset
987
988   The Accept-Charset request-header field can be used to indicate what
989   character sets are acceptable for the response.  This field allows
990   clients capable of understanding more comprehensive or special-
991   purpose character sets to signal that capability to a server which is
992   capable of representing documents in those character sets.
993
994     Accept-Charset = "Accept-Charset" ":"
995             1#( ( charset | "*" ) [ ";" "q" "=" qvalue ] )
996
997   Character set values are described in Section 3.1.  Each charset MAY
998   be given an associated quality value which represents the user's
999   preference for that charset.  The default value is q=1.  An example
1000   is
1001
1002      Accept-Charset: iso-8859-5, unicode-1-1;q=0.8
1003
1004
1005
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1011
1012   The special value "*", if present in the Accept-Charset field,
1013   matches every character set (including ISO-8859-1) which is not
1014   mentioned elsewhere in the Accept-Charset field.  If no "*" is
1015   present in an Accept-Charset field, then all character sets not
1016   explicitly mentioned get a quality value of 0, except for ISO-8859-1,
1017   which gets a quality value of 1 if not explicitly mentioned.
1018
1019   If no Accept-Charset header is present, the default is that any
1020   character set is acceptable.  If an Accept-Charset header is present,
1021   and if the server cannot send a response which is acceptable
1022   according to the Accept-Charset header, then the server SHOULD send
1023   an error response with the 406 (Not Acceptable) status code, though
1024   the sending of an unacceptable response is also allowed.
1025
10266.3.  Accept-Encoding
1027
1028   The Accept-Encoding request-header field is similar to Accept, but
1029   restricts the content-codings (Section 3.2) that are acceptable in
1030   the response.
1031
1032     Accept-Encoding  = "Accept-Encoding" ":"
1033                        #( codings [ ";" "q" "=" qvalue ] )
1034     codings          = ( content-coding | "*" )
1035
1036   Examples of its use are:
1037
1038       Accept-Encoding: compress, gzip
1039       Accept-Encoding:
1040       Accept-Encoding: *
1041       Accept-Encoding: compress;q=0.5, gzip;q=1.0
1042       Accept-Encoding: gzip;q=1.0, identity; q=0.5, *;q=0
1043
1044   A server tests whether a content-coding is acceptable, according to
1045   an Accept-Encoding field, using these rules:
1046
1047   1.  If the content-coding is one of the content-codings listed in the
1048       Accept-Encoding field, then it is acceptable, unless it is
1049       accompanied by a qvalue of 0.  (As defined in Section 3.4, a
1050       qvalue of 0 means "not acceptable.")
1051
1052   2.  The special "*" symbol in an Accept-Encoding field matches any
1053       available content-coding not explicitly listed in the header
1054       field.
1055
1056   3.  If multiple content-codings are acceptable, then the acceptable
1057       content-coding with the highest non-zero qvalue is preferred.
1058
1059
1060
1061
1062
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1066
1067
1068   4.  The "identity" content-coding is always acceptable, unless
1069       specifically refused because the Accept-Encoding field includes
1070       "identity;q=0", or because the field includes "*;q=0" and does
1071       not explicitly include the "identity" content-coding.  If the
1072       Accept-Encoding field-value is empty, then only the "identity"
1073       encoding is acceptable.
1074
1075   If an Accept-Encoding field is present in a request, and if the
1076   server cannot send a response which is acceptable according to the
1077   Accept-Encoding header, then the server SHOULD send an error response
1078   with the 406 (Not Acceptable) status code.
1079
1080   If no Accept-Encoding field is present in a request, the server MAY
1081   assume that the client will accept any content coding.  In this case,
1082   if "identity" is one of the available content-codings, then the
1083   server SHOULD use the "identity" content-coding, unless it has
1084   additional information that a different content-coding is meaningful
1085   to the client.
1086
1087      Note: If the request does not include an Accept-Encoding field,
1088      and if the "identity" content-coding is unavailable, then content-
1089      codings commonly understood by HTTP/1.0 clients (i.e., "gzip" and
1090      "compress") are preferred; some older clients improperly display
1091      messages sent with other content-codings.  The server might also
1092      make this decision based on information about the particular user-
1093      agent or client.
1094
1095      Note: Most HTTP/1.0 applications do not recognize or obey qvalues
1096      associated with content-codings.  This means that qvalues will not
1097      work and are not permitted with x-gzip or x-compress.
1098
10996.4.  Accept-Language
1100
1101   The Accept-Language request-header field is similar to Accept, but
1102   restricts the set of natural languages that are preferred as a
1103   response to the request.  Language tags are defined in Section 3.5.
1104
1105     Accept-Language = "Accept-Language" ":"
1106                       1#( language-range [ ";" "q" "=" qvalue ] )
1107     language-range  = ( ( 1*8ALPHA *( "-" 1*8ALPHA ) ) | "*" )
1108
1109   Each language-range MAY be given an associated quality value which
1110   represents an estimate of the user's preference for the languages
1111   specified by that range.  The quality value defaults to "q=1".  For
1112   example,
1113
1114       Accept-Language: da, en-gb;q=0.8, en;q=0.7
1115
1116
1117
1118
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1122
1123
1124   would mean: "I prefer Danish, but will accept British English and
1125   other types of English."  A language-range matches a language-tag if
1126   it exactly equals the tag, or if it exactly equals a prefix of the
1127   tag such that the first tag character following the prefix is "-".
1128   The special range "*", if present in the Accept-Language field,
1129   matches every tag not matched by any other range present in the
1130   Accept-Language field.
1131
1132      Note: This use of a prefix matching rule does not imply that
1133      language tags are assigned to languages in such a way that it is
1134      always true that if a user understands a language with a certain
1135      tag, then this user will also understand all languages with tags
1136      for which this tag is a prefix.  The prefix rule simply allows the
1137      use of prefix tags if this is the case.
1138
1139   The language quality factor assigned to a language-tag by the Accept-
1140   Language field is the quality value of the longest language-range in
1141   the field that matches the language-tag.  If no language-range in the
1142   field matches the tag, the language quality factor assigned is 0.  If
1143   no Accept-Language header is present in the request, the server
1144   SHOULD assume that all languages are equally acceptable.  If an
1145   Accept-Language header is present, then all languages which are
1146   assigned a quality factor greater than 0 are acceptable.
1147
1148   It might be contrary to the privacy expectations of the user to send
1149   an Accept-Language header with the complete linguistic preferences of
1150   the user in every request.  For a discussion of this issue, see
1151   Section 8.1.
1152
1153   As intelligibility is highly dependent on the individual user, it is
1154   recommended that client applications make the choice of linguistic
1155   preference available to the user.  If the choice is not made
1156   available, then the Accept-Language header field MUST NOT be given in
1157   the request.
1158
1159      Note: When making the choice of linguistic preference available to
1160      the user, we remind implementors of the fact that users are not
1161      familiar with the details of language matching as described above,
1162      and should provide appropriate guidance.  As an example, users
1163      might assume that on selecting "en-gb", they will be served any
1164      kind of English document if British English is not available.  A
1165      user agent might suggest in such a case to add "en" to get the
1166      best matching behavior.
1167
1168
1169
1170
1171
1172
1173
1174
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1178
1179
11806.5.  Content-Encoding
1181
1182   The Content-Encoding entity-header field is used as a modifier to the
1183   media-type.  When present, its value indicates what additional
1184   content codings have been applied to the entity-body, and thus what
1185   decoding mechanisms must be applied in order to obtain the media-type
1186   referenced by the Content-Type header field.  Content-Encoding is
1187   primarily used to allow a document to be compressed without losing
1188   the identity of its underlying media type.
1189
1190     Content-Encoding  = "Content-Encoding" ":" 1#content-coding
1191
1192   Content codings are defined in Section 3.2.  An example of its use is
1193
1194       Content-Encoding: gzip
1195
1196   The content-coding is a characteristic of the entity identified by
1197   the Request-URI.  Typically, the entity-body is stored with this
1198   encoding and is only decoded before rendering or analogous usage.
1199   However, a non-transparent proxy MAY modify the content-coding if the
1200   new coding is known to be acceptable to the recipient, unless the
1201   "no-transform" cache-control directive is present in the message.
1202
1203   If the content-coding of an entity is not "identity", then the
1204   response MUST include a Content-Encoding entity-header (Section 6.5)
1205   that lists the non-identity content-coding(s) used.
1206
1207   If the content-coding of an entity in a request message is not
1208   acceptable to the origin server, the server SHOULD respond with a
1209   status code of 415 (Unsupported Media Type).
1210
1211   If multiple encodings have been applied to an entity, the content
1212   codings MUST be listed in the order in which they were applied.
1213   Additional information about the encoding parameters MAY be provided
1214   by other entity-header fields not defined by this specification.
1215
12166.6.  Content-Language
1217
1218   The Content-Language entity-header field describes the natural
1219   language(s) of the intended audience for the enclosed entity.  Note
1220   that this might not be equivalent to all the languages used within
1221   the entity-body.
1222
1223     Content-Language  = "Content-Language" ":" 1#language-tag
1224
1225   Language tags are defined in Section 3.5.  The primary purpose of
1226   Content-Language is to allow a user to identify and differentiate
1227   entities according to the user's own preferred language.  Thus, if
1228
1229
1230
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1234
1235
1236   the body content is intended only for a Danish-literate audience, the
1237   appropriate field is
1238
1239       Content-Language: da
1240
1241   If no Content-Language is specified, the default is that the content
1242   is intended for all language audiences.  This might mean that the
1243   sender does not consider it to be specific to any natural language,
1244   or that the sender does not know for which language it is intended.
1245
1246   Multiple languages MAY be listed for content that is intended for
1247   multiple audiences.  For example, a rendition of the "Treaty of
1248   Waitangi," presented simultaneously in the original Maori and English
1249   versions, would call for
1250
1251       Content-Language: mi, en
1252
1253   However, just because multiple languages are present within an entity
1254   does not mean that it is intended for multiple linguistic audiences.
1255   An example would be a beginner's language primer, such as "A First
1256   Lesson in Latin," which is clearly intended to be used by an English-
1257   literate audience.  In this case, the Content-Language would properly
1258   only include "en".
1259
1260   Content-Language MAY be applied to any media type -- it is not
1261   limited to textual documents.
1262
12636.7.  Content-Location
1264
1265   The Content-Location entity-header field MAY be used to supply the
1266   resource location for the entity enclosed in the message when that
1267   entity is accessible from a location separate from the requested
1268   resource's URI.  A server SHOULD provide a Content-Location for the
1269   variant corresponding to the response entity; especially in the case
1270   where a resource has multiple entities associated with it, and those
1271   entities actually have separate locations by which they might be
1272   individually accessed, the server SHOULD provide a Content-Location
1273   for the particular variant which is returned.
1274
1275     Content-Location = "Content-Location" ":"
1276                       ( absoluteURI | relativeURI )
1277
1278   The value of Content-Location also defines the base URI for the
1279   entity.
1280
1281   The Content-Location value is not a replacement for the original
1282   requested URI; it is only a statement of the location of the resource
1283   corresponding to this particular entity at the time of the request.
1284
1285
1286
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1290
1291
1292   Future requests MAY specify the Content-Location URI as the request-
1293   URI if the desire is to identify the source of that particular
1294   entity.
1295
1296   A cache cannot assume that an entity with a Content-Location
1297   different from the URI used to retrieve it can be used to respond to
1298   later requests on that Content-Location URI.  However, the Content-
1299   Location can be used to differentiate between multiple entities
1300   retrieved from a single requested resource, as described in Section 8
1301   of [Part6].
1302
1303   If the Content-Location is a relative URI, the relative URI is
1304   interpreted relative to the Request-URI.
1305
1306   The meaning of the Content-Location header in PUT or POST requests is
1307   undefined; servers are free to ignore it in those cases.
1308
13096.8.  Content-MD5
1310
1311   The Content-MD5 entity-header field, as defined in [RFC1864], is an
1312   MD5 digest of the entity-body for the purpose of providing an end-to-
1313   end message integrity check (MIC) of the entity-body.  (Note: a MIC
1314   is good for detecting accidental modification of the entity-body in
1315   transit, but is not proof against malicious attacks.)
1316
1317     Content-MD5   = "Content-MD5" ":" md5-digest
1318     md5-digest    = <base64 of 128 bit MD5 digest as per [RFC1864]>
1319
1320   The Content-MD5 header field MAY be generated by an origin server or
1321   client to function as an integrity check of the entity-body.  Only
1322   origin servers or clients MAY generate the Content-MD5 header field;
1323   proxies and gateways MUST NOT generate it, as this would defeat its
1324   value as an end-to-end integrity check.  Any recipient of the entity-
1325   body, including gateways and proxies, MAY check that the digest value
1326   in this header field matches that of the entity-body as received.
1327
1328   The MD5 digest is computed based on the content of the entity-body,
1329   including any content-coding that has been applied, but not including
1330   any transfer-encoding applied to the message-body.  If the message is
1331   received with a transfer-encoding, that encoding MUST be removed
1332   prior to checking the Content-MD5 value against the received entity.
1333
1334   This has the result that the digest is computed on the octets of the
1335   entity-body exactly as, and in the order that, they would be sent if
1336   no transfer-encoding were being applied.
1337
1338   HTTP extends RFC 1864 to permit the digest to be computed for MIME
1339   composite media-types (e.g., multipart/* and message/rfc822), but
1340
1341
1342
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1346
1347
1348   this does not change how the digest is computed as defined in the
1349   preceding paragraph.
1350
1351   There are several consequences of this.  The entity-body for
1352   composite types MAY contain many body-parts, each with its own MIME
1353   and HTTP headers (including Content-MD5, Content-Transfer-Encoding,
1354   and Content-Encoding headers).  If a body-part has a Content-
1355   Transfer-Encoding or Content-Encoding header, it is assumed that the
1356   content of the body-part has had the encoding applied, and the body-
1357   part is included in the Content-MD5 digest as is -- i.e., after the
1358   application.  The Transfer-Encoding header field is not allowed
1359   within body-parts.
1360
1361   Conversion of all line breaks to CRLF MUST NOT be done before
1362   computing or checking the digest: the line break convention used in
1363   the text actually transmitted MUST be left unaltered when computing
1364   the digest.
1365
1366      Note: while the definition of Content-MD5 is exactly the same for
1367      HTTP as in RFC 1864 for MIME entity-bodies, there are several ways
1368      in which the application of Content-MD5 to HTTP entity-bodies
1369      differs from its application to MIME entity-bodies.  One is that
1370      HTTP, unlike MIME, does not use Content-Transfer-Encoding, and
1371      does use Transfer-Encoding and Content-Encoding.  Another is that
1372      HTTP more frequently uses binary content types than MIME, so it is
1373      worth noting that, in such cases, the byte order used to compute
1374      the digest is the transmission byte order defined for the type.
1375      Lastly, HTTP allows transmission of text types with any of several
1376      line break conventions and not just the canonical form using CRLF.
1377
13786.9.  Content-Type
1379
1380   The Content-Type entity-header field indicates the media type of the
1381   entity-body sent to the recipient or, in the case of the HEAD method,
1382   the media type that would have been sent had the request been a GET.
1383
1384     Content-Type   = "Content-Type" ":" media-type
1385
1386   Media types are defined in Section 3.3.  An example of the field is
1387
1388       Content-Type: text/html; charset=ISO-8859-4
1389
1390   Further discussion of methods for identifying the media type of an
1391   entity is provided in Section 4.2.1.
1392
1393
1394
1395
1396
1397
1398
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1402
1403
14047.  IANA Considerations
1405
1406   [[anchor1: TBD.]]
1407
1408
14098.  Security Considerations
1410
1411   This section is meant to inform application developers, information
1412   providers, and users of the security limitations in HTTP/1.1 as
1413   described by this document.  The discussion does not include
1414   definitive solutions to the problems revealed, though it does make
1415   some suggestions for reducing security risks.
1416
14178.1.  Privacy Issues Connected to Accept Headers
1418
1419   Accept request-headers can reveal information about the user to all
1420   servers which are accessed.  The Accept-Language header in particular
1421   can reveal information the user would consider to be of a private
1422   nature, because the understanding of particular languages is often
1423   strongly correlated to the membership of a particular ethnic group.
1424   User agents which offer the option to configure the contents of an
1425   Accept-Language header to be sent in every request are strongly
1426   encouraged to let the configuration process include a message which
1427   makes the user aware of the loss of privacy involved.
1428
1429   An approach that limits the loss of privacy would be for a user agent
1430   to omit the sending of Accept-Language headers by default, and to ask
1431   the user whether or not to start sending Accept-Language headers to a
1432   server if it detects, by looking for any Vary response-header fields
1433   generated by the server, that such sending could improve the quality
1434   of service.
1435
1436   Elaborate user-customized accept header fields sent in every request,
1437   in particular if these include quality values, can be used by servers
1438   as relatively reliable and long-lived user identifiers.  Such user
1439   identifiers would allow content providers to do click-trail tracking,
1440   and would allow collaborating content providers to match cross-server
1441   click-trails or form submissions of individual users.  Note that for
1442   many users not behind a proxy, the network address of the host
1443   running the user agent will also serve as a long-lived user
1444   identifier.  In environments where proxies are used to enhance
1445   privacy, user agents ought to be conservative in offering accept
1446   header configuration options to end users.  As an extreme privacy
1447   measure, proxies could filter the accept headers in relayed requests.
1448   General purpose user agents which provide a high degree of header
1449   configurability SHOULD warn users about the loss of privacy which can
1450   be involved.
1451
1452
1453
1454
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1458
1459
14608.2.  Content-Disposition Issues
1461
1462   [RFC1806], from which the often implemented Content-Disposition (see
1463   Appendix B.1) header in HTTP is derived, has a number of very serious
1464   security considerations.  Content-Disposition is not part of the HTTP
1465   standard, but since it is widely implemented, we are documenting its
1466   use and risks for implementors.  See [RFC2183] (which updates
1467   [RFC1806]) for details.
1468
1469
14709.  Acknowledgments
1471
1472
147310.  References
1474
147510.1.  Normative References
1476
1477   [ISO-8859-1]
1478              International Organization for Standardization,
1479              "Information technology -- 8-bit single-byte coded graphic
1480              character sets -- Part 1: Latin alphabet No. 1", ISO/
1481              IEC 8859-1:1998, 1998.
1482
1483   [Part1]    Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
1484              Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed.,
1485              and J. Reschke, Ed., "HTTP/1.1, part 1: URIs, Connections,
1486              and Message Parsing", draft-ietf-httpbis-p1-messaging-02
1487              (work in progress), February 2008.
1488
1489   [Part2]    Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
1490              Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed.,
1491              and J. Reschke, Ed., "HTTP/1.1, part 2: Message
1492              Semantics", draft-ietf-httpbis-p2-semantics-02 (work in
1493              progress), February 2008.
1494
1495   [Part4]    Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
1496              Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed.,
1497              and J. Reschke, Ed., "HTTP/1.1, part 4: Conditional
1498              Requests", draft-ietf-httpbis-p4-conditional-02 (work in
1499              progress), February 2008.
1500
1501   [Part5]    Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
1502              Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed.,
1503              and J. Reschke, Ed., "HTTP/1.1, part 5: Range Requests and
1504              Partial Responses", draft-ietf-httpbis-p5-range-02 (work
1505              in progress), February 2008.
1506
1507   [Part6]    Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
1508
1509
1510
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1514
1515
1516              Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed.,
1517              and J. Reschke, Ed., "HTTP/1.1, part 6: Caching",
1518              draft-ietf-httpbis-p6-cache-02 (work in progress),
1519              February 2008.
1520
1521   [RFC1766]  Alvestrand, H., "Tags for the Identification of
1522              Languages", RFC 1766, March 1995.
1523
1524   [RFC1864]  Myers, J. and M. Rose, "The Content-MD5 Header Field",
1525              RFC 1864, October 1995.
1526
1527   [RFC1950]  Deutsch, L. and J-L. Gailly, "ZLIB Compressed Data Format
1528              Specification version 3.3", RFC 1950, May 1996.
1529
1530              RFC1950 is an Informational RFC, thus it may be less
1531              stable than this specification.  On the other hand, this
1532              downward reference was present since [RFC2068] (published
1533              in 1997), therefore it is unlikely to cause problems in
1534              practice.
1535
1536   [RFC1951]  Deutsch, P., "DEFLATE Compressed Data Format Specification
1537              version 1.3", RFC 1951, May 1996.
1538
1539              RFC1951 is an Informational RFC, thus it may be less
1540              stable than this specification.  On the other hand, this
1541              downward reference was present since [RFC2068] (published
1542              in 1997), therefore it is unlikely to cause problems in
1543              practice.
1544
1545   [RFC1952]  Deutsch, P., Gailly, J-L., Adler, M., Deutsch, L., and G.
1546              Randers-Pehrson, "GZIP file format specification version
1547              4.3", RFC 1952, May 1996.
1548
1549              RFC1952 is an Informational RFC, thus it may be less
1550              stable than this specification.  On the other hand, this
1551              downward reference was present since [RFC2068] (published
1552              in 1997), therefore it is unlikely to cause problems in
1553              practice.
1554
1555   [RFC2045]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
1556              Extensions (MIME) Part One: Format of Internet Message
1557              Bodies", RFC 2045, November 1996.
1558
1559   [RFC2046]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
1560              Extensions (MIME) Part Two: Media Types", RFC 2046,
1561              November 1996.
1562
1563   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
1564
1565
1566
1567Fielding, et al.         Expires August 27, 2008               [Page 28]
1568
1569Internet-Draft              HTTP/1.1, Part 3               February 2008
1570
1571
1572              Requirement Levels", BCP 14, RFC 2119, March 1997.
1573
157410.2.  Informative References
1575
1576   [RFC1806]  Troost, R. and S. Dorner, "Communicating Presentation
1577              Information in Internet Messages: The Content-Disposition
1578              Header", RFC 1806, June 1995.
1579
1580   [RFC1945]  Berners-Lee, T., Fielding, R., and H. Nielsen, "Hypertext
1581              Transfer Protocol -- HTTP/1.0", RFC 1945, May 1996.
1582
1583   [RFC2049]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
1584              Extensions (MIME) Part Five: Conformance Criteria and
1585              Examples", RFC 2049, November 1996.
1586
1587   [RFC2068]  Fielding, R., Gettys, J., Mogul, J., Nielsen, H., and T.
1588              Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1",
1589              RFC 2068, January 1997.
1590
1591   [RFC2076]  Palme, J., "Common Internet Message Headers", RFC 2076,
1592              February 1997.
1593
1594   [RFC2183]  Troost, R., Dorner, S., and K. Moore, "Communicating
1595              Presentation Information in Internet Messages: The
1596              Content-Disposition Header Field", RFC 2183, August 1997.
1597
1598   [RFC2277]  Alvestrand, H., "IETF Policy on Character Sets and
1599              Languages", BCP 18, RFC 2277, January 1998.
1600
1601   [RFC2388]  Masinter, L., "Returning Values from Forms:  multipart/
1602              form-data", RFC 2388, August 1998.
1603
1604   [RFC2557]  Palme, F., Hopmann, A., Shelness, N., and E. Stefferud,
1605              "MIME Encapsulation of Aggregate Documents, such as HTML
1606              (MHTML)", RFC 2557, March 1999.
1607
1608   [RFC2616]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
1609              Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
1610              Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
1611
1612   [RFC2822]  Resnick, P., "Internet Message Format", RFC 2822,
1613              April 2001.
1614
1615   [RFC3629]  Yergeau, F., "UTF-8, a transformation format of ISO
1616              10646", RFC 3629, STD 63, November 2003.
1617
1618   [RFC4288]  Freed, N. and J. Klensin, "Media Type Specifications and
1619              Registration Procedures", BCP 13, RFC 4288, December 2005.
1620
1621
1622
1623Fielding, et al.         Expires August 27, 2008               [Page 29]
1624
1625Internet-Draft              HTTP/1.1, Part 3               February 2008
1626
1627
1628Appendix A.  Differences Between HTTP Entities and RFC 2045 Entities
1629
1630   HTTP/1.1 uses many of the constructs defined for Internet Mail
1631   ([RFC2822]) and the Multipurpose Internet Mail Extensions (MIME
1632   [RFC2045]) to allow entities to be transmitted in an open variety of
1633   representations and with extensible mechanisms.  However, RFC 2045
1634   discusses mail, and HTTP has a few features that are different from
1635   those described in RFC 2045.  These differences were carefully chosen
1636   to optimize performance over binary connections, to allow greater
1637   freedom in the use of new media types, to make date comparisons
1638   easier, and to acknowledge the practice of some early HTTP servers
1639   and clients.
1640
1641   This appendix describes specific areas where HTTP differs from RFC
1642   2045.  Proxies and gateways to strict MIME environments SHOULD be
1643   aware of these differences and provide the appropriate conversions
1644   where necessary.  Proxies and gateways from MIME environments to HTTP
1645   also need to be aware of the differences because some conversions
1646   might be required.
1647
1648A.1.  MIME-Version
1649
1650   HTTP is not a MIME-compliant protocol.  However, HTTP/1.1 messages
1651   MAY include a single MIME-Version general-header field to indicate
1652   what version of the MIME protocol was used to construct the message.
1653   Use of the MIME-Version header field indicates that the message is in
1654   full compliance with the MIME protocol (as defined in [RFC2045]).
1655   Proxies/gateways are responsible for ensuring full compliance (where
1656   possible) when exporting HTTP messages to strict MIME environments.
1657
1658     MIME-Version   = "MIME-Version" ":" 1*DIGIT "." 1*DIGIT
1659
1660   MIME version "1.0" is the default for use in HTTP/1.1.  However,
1661   HTTP/1.1 message parsing and semantics are defined by this document
1662   and not the MIME specification.
1663
1664A.2.  Conversion to Canonical Form
1665
1666   [RFC2045] requires that an Internet mail entity be converted to
1667   canonical form prior to being transferred, as described in Section 4
1668   of [RFC2049].  Section 3.3.1 of this document describes the forms
1669   allowed for subtypes of the "text" media type when transmitted over
1670   HTTP.  [RFC2046] requires that content with a type of "text"
1671   represent line breaks as CRLF and forbids the use of CR or LF outside
1672   of line break sequences.  HTTP allows CRLF, bare CR, and bare LF to
1673   indicate a line break within text content when a message is
1674   transmitted over HTTP.
1675
1676
1677
1678
1679Fielding, et al.         Expires August 27, 2008               [Page 30]
1680
1681Internet-Draft              HTTP/1.1, Part 3               February 2008
1682
1683
1684   Where it is possible, a proxy or gateway from HTTP to a strict MIME
1685   environment SHOULD translate all line breaks within the text media
1686   types described in Section 3.3.1 of this document to the RFC 2049
1687   canonical form of CRLF.  Note, however, that this might be
1688   complicated by the presence of a Content-Encoding and by the fact
1689   that HTTP allows the use of some character sets which do not use
1690   octets 13 and 10 to represent CR and LF, as is the case for some
1691   multi-byte character sets.
1692
1693   Implementors should note that conversion will break any cryptographic
1694   checksums applied to the original content unless the original content
1695   is already in canonical form.  Therefore, the canonical form is
1696   recommended for any content that uses such checksums in HTTP.
1697
1698A.3.  Introduction of Content-Encoding
1699
1700   RFC 2045 does not include any concept equivalent to HTTP/1.1's
1701   Content-Encoding header field.  Since this acts as a modifier on the
1702   media type, proxies and gateways from HTTP to MIME-compliant
1703   protocols MUST either change the value of the Content-Type header
1704   field or decode the entity-body before forwarding the message.  (Some
1705   experimental applications of Content-Type for Internet mail have used
1706   a media-type parameter of ";conversions=<content-coding>" to perform
1707   a function equivalent to Content-Encoding.  However, this parameter
1708   is not part of RFC 2045).
1709
1710A.4.  No Content-Transfer-Encoding
1711
1712   HTTP does not use the Content-Transfer-Encoding field of RFC 2045.
1713   Proxies and gateways from MIME-compliant protocols to HTTP MUST
1714   remove any Content-Transfer-Encoding prior to delivering the response
1715   message to an HTTP client.
1716
1717   Proxies and gateways from HTTP to MIME-compliant protocols are
1718   responsible for ensuring that the message is in the correct format
1719   and encoding for safe transport on that protocol, where "safe
1720   transport" is defined by the limitations of the protocol being used.
1721   Such a proxy or gateway SHOULD label the data with an appropriate
1722   Content-Transfer-Encoding if doing so will improve the likelihood of
1723   safe transport over the destination protocol.
1724
1725A.5.  Introduction of Transfer-Encoding
1726
1727   HTTP/1.1 introduces the Transfer-Encoding header field (Section 8.7
1728   of [Part1]).  Proxies/gateways MUST remove any transfer-coding prior
1729   to forwarding a message via a MIME-compliant protocol.
1730
1731
1732
1733
1734
1735Fielding, et al.         Expires August 27, 2008               [Page 31]
1736
1737Internet-Draft              HTTP/1.1, Part 3               February 2008
1738
1739
1740A.6.  MHTML and Line Length Limitations
1741
1742   HTTP implementations which share code with MHTML [RFC2557]
1743   implementations need to be aware of MIME line length limitations.
1744   Since HTTP does not have this limitation, HTTP does not fold long
1745   lines.  MHTML messages being transported by HTTP follow all
1746   conventions of MHTML, including line length limitations and folding,
1747   canonicalization, etc., since HTTP transports all message-bodies as
1748   payload (see Section 3.3.2) and does not interpret the content or any
1749   MIME header lines that might be contained therein.
1750
1751
1752Appendix B.  Additional Features
1753
1754   [RFC1945] and [RFC2068] document protocol elements used by some
1755   existing HTTP implementations, but not consistently and correctly
1756   across most HTTP/1.1 applications.  Implementors are advised to be
1757   aware of these features, but cannot rely upon their presence in, or
1758   interoperability with, other HTTP/1.1 applications.  Some of these
1759   describe proposed experimental features, and some describe features
1760   that experimental deployment found lacking that are now addressed in
1761   the base HTTP/1.1 specification.
1762
1763   A number of other headers, such as Content-Disposition and Title,
1764   from SMTP and MIME are also often implemented (see [RFC2076]).
1765
1766B.1.  Content-Disposition
1767
1768   The Content-Disposition response-header field has been proposed as a
1769   means for the origin server to suggest a default filename if the user
1770   requests that the content is saved to a file.  This usage is derived
1771   from the definition of Content-Disposition in [RFC1806].
1772
1773     content-disposition = "Content-Disposition" ":"
1774                           disposition-type *( ";" disposition-parm )
1775     disposition-type = "attachment" | disp-extension-token
1776     disposition-parm = filename-parm | disp-extension-parm
1777     filename-parm = "filename" "=" quoted-string
1778     disp-extension-token = token
1779     disp-extension-parm = token "=" ( token | quoted-string )
1780
1781   An example is
1782
1783        Content-Disposition: attachment; filename="fname.ext"
1784
1785   The receiving user agent SHOULD NOT respect any directory path
1786   information present in the filename-parm parameter, which is the only
1787   parameter believed to apply to HTTP implementations at this time.
1788
1789
1790
1791Fielding, et al.         Expires August 27, 2008               [Page 32]
1792
1793Internet-Draft              HTTP/1.1, Part 3               February 2008
1794
1795
1796   The filename SHOULD be treated as a terminal component only.
1797
1798   If this header is used in a response with the application/
1799   octet-stream content-type, the implied suggestion is that the user
1800   agent should not display the response, but directly enter a `save
1801   response as...' dialog.
1802
1803   See Section 8.2 for Content-Disposition security issues.
1804
1805
1806Appendix C.  Compatibility with Previous Versions
1807
1808C.1.  Changes from RFC 2068
1809
1810   Transfer-coding and message lengths all interact in ways that
1811   required fixing exactly when chunked encoding is used (to allow for
1812   transfer encoding that may not be self delimiting); it was important
1813   to straighten out exactly how message lengths are computed.
1814   (Section 4.2.2, see also [Part1], [Part5] and [Part6]).
1815
1816   Charset wildcarding is introduced to avoid explosion of character set
1817   names in accept headers.  (Section 6.2)
1818
1819   Content-Base was deleted from the specification: it was not
1820   implemented widely, and there is no simple, safe way to introduce it
1821   without a robust extension mechanism.  In addition, it is used in a
1822   similar, but not identical fashion in MHTML [RFC2557].
1823
1824   A content-coding of "identity" was introduced, to solve problems
1825   discovered in caching.  (Section 3.2)
1826
1827   Quality Values of zero should indicate that "I don't want something"
1828   to allow clients to refuse a representation.  (Section 3.4)
1829
1830   The Alternates, Content-Version, Derived-From, Link, URI, Public and
1831   Content-Base header fields were defined in previous versions of this
1832   specification, but not commonly implemented.  See [RFC2068].
1833
1834C.2.  Changes from RFC 2616
1835
1836   Clarify contexts that charset is used in.  (Section 3.1)
1837
1838   Remove reference to non-existant identity transfer-coding value
1839   tokens.  (Appendix A.4)
1840
1841
1842
1843
1844
1845
1846
1847Fielding, et al.         Expires August 27, 2008               [Page 33]
1848
1849Internet-Draft              HTTP/1.1, Part 3               February 2008
1850
1851
1852Appendix D.  Change Log (to be removed by RFC Editor before publication)
1853
1854D.1.  Since RFC2616
1855
1856   Extracted relevant partitions from [RFC2616].
1857
1858D.2.  Since draft-ietf-httpbis-p3-payload-00
1859
1860   Closed issues:
1861
1862   o  <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/8>: "Media Type
1863      Registrations" (<http://purl.org/NET/http-errata#media-reg>)
1864
1865   o  <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/14>:
1866      "Clarification regarding quoting of charset values"
1867      (<http://purl.org/NET/http-errata#charactersets>)
1868
1869   o  <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/16>: "Remove
1870      'identity' token references"
1871      (<http://purl.org/NET/http-errata#identity>)
1872
1873   o  <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/25>: "Accept-
1874      Encoding BNF"
1875
1876   o  <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/35>: "Normative
1877      and Informative references"
1878
1879   o  <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/46>: "RFC1700
1880      references"
1881
1882   o  <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/55>: "Updating
1883      to RFC4288"
1884
1885   o  <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/65>:
1886      "Informative references"
1887
1888   o  <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/66>:
1889      "ISO-8859-1 Reference"
1890
1891   o  <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/68>: "Encoding
1892      References Normative"
1893
1894   o  <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/86>: "Normative
1895      up-to-date references"
1896
1897
1898
1899
1900
1901
1902
1903Fielding, et al.         Expires August 27, 2008               [Page 34]
1904
1905Internet-Draft              HTTP/1.1, Part 3               February 2008
1906
1907
1908D.3.  Since draft-ietf-httpbis-p3-payload-01
1909
1910   Ongoing work on ABNF conversion
1911   (<http://www3.tools.ietf.org/wg/httpbis/trac/ticket/36>):
1912
1913   o  Add explicit references to BNF syntax and rules imported from
1914      other parts of the specification.
1915
1916
1917Index
1918
1919   A
1920      Accept header  16
1921      Accept-Charset header  18
1922      Accept-Encoding header  19
1923      Accept-Language header  20
1924      Alternates header  33
1925
1926   C
1927      compress  8
1928      Content-Base header  33
1929      Content-Disposition header  32
1930      Content-Encoding header  22
1931      Content-Language header  22
1932      Content-Location header  23
1933      Content-MD5 header  24
1934      Content-Type header  25
1935      Content-Version header  33
1936
1937   D
1938      deflate  8
1939      Derived-From header  33
1940
1941   G
1942      Grammar
1943         Accept  16
1944         Accept-Charset  18
1945         Accept-Encoding  19
1946         accept-extension  16
1947         Accept-Language  20
1948         accept-params  16
1949         attribute  9
1950         charset  7
1951         codings  19
1952         content-coding  7
1953         content-disposition  32
1954         Content-Encoding  22
1955         Content-Language  22
1956
1957
1958
1959Fielding, et al.         Expires August 27, 2008               [Page 35]
1960
1961Internet-Draft              HTTP/1.1, Part 3               February 2008
1962
1963
1964         Content-Location  23
1965         Content-MD5  24
1966         Content-Type  25
1967         disp-extension-parm  32
1968         disp-extension-token  32
1969         disposition-parm  32
1970         disposition-type  32
1971         entity-body  12
1972         entity-header  12
1973         extension-header  12
1974         filename-parm  32
1975         language-range  20
1976         language-tag  11
1977         md5-digest  24
1978         media-range  16
1979         media-type  9
1980         MIME-Version  30
1981         parameter  9
1982         primary-tag  11
1983         qvalue  11
1984         subtag  11
1985         subtype  9
1986         type  9
1987         value  9
1988      gzip  8
1989
1990   H
1991      Headers
1992         Accept  16
1993         Accept-Charset  18
1994         Accept-Encoding  19
1995         Accept-Language  20
1996         Alternate  33
1997         Content-Base  33
1998         Content-Disposition  32
1999         Content-Encoding  22
2000         Content-Language  22
2001         Content-Location  23
2002         Content-MD5  24
2003         Content-Type  25
2004         Content-Version  33
2005         Derived-From  33
2006         Link  33
2007         Public  33
2008         URI  33
2009
2010   I
2011      identity  8
2012
2013
2014
2015Fielding, et al.         Expires August 27, 2008               [Page 36]
2016
2017Internet-Draft              HTTP/1.1, Part 3               February 2008
2018
2019
2020   L
2021      Link header  33
2022
2023   P
2024      Public header  33
2025
2026   U
2027      URI header  33
2028
2029
2030Authors' Addresses
2031
2032   Roy T. Fielding (editor)
2033   Day Software
2034   23 Corporate Plaza DR, Suite 280
2035   Newport Beach, CA  92660
2036   USA
2037
2038   Phone: +1-949-706-5300
2039   Fax:   +1-949-706-5305
2040   Email: fielding@gbiv.com
2041   URI:   http://roy.gbiv.com/
2042
2043
2044   Jim Gettys
2045   One Laptop per Child
2046   21 Oak Knoll Road
2047   Carlisle, MA  01741
2048   USA
2049
2050   Email: jg@laptop.org
2051   URI:   http://www.laptop.org/
2052
2053
2054   Jeffrey C. Mogul
2055   Hewlett-Packard Company
2056   HP Labs, Large Scale Systems Group
2057   1501 Page Mill Road, MS 1177
2058   Palo Alto, CA  94304
2059   USA
2060
2061   Email: JeffMogul@acm.org
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071Fielding, et al.         Expires August 27, 2008               [Page 37]
2072
2073Internet-Draft              HTTP/1.1, Part 3               February 2008
2074
2075
2076   Henrik Frystyk Nielsen
2077   Microsoft Corporation
2078   1 Microsoft Way
2079   Redmond, WA  98052
2080   USA
2081
2082   Email: henrikn@microsoft.com
2083
2084
2085   Larry Masinter
2086   Adobe Systems, Incorporated
2087   345 Park Ave
2088   San Jose, CA  95110
2089   USA
2090
2091   Email: LMM@acm.org
2092   URI:   http://larry.masinter.net/
2093
2094
2095   Paul J. Leach
2096   Microsoft Corporation
2097   1 Microsoft Way
2098   Redmond, WA  98052
2099
2100   Email: paulle@microsoft.com
2101
2102
2103   Tim Berners-Lee
2104   World Wide Web Consortium
2105   MIT Computer Science and Artificial Intelligence Laboratory
2106   The Stata Center, Building 32
2107   32 Vassar Street
2108   Cambridge, MA  02139
2109   USA
2110
2111   Email: timbl@w3.org
2112   URI:   http://www.w3.org/People/Berners-Lee/
2113
2114
2115
2116
2117
2118
2119
2120
2121
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2127Fielding, et al.         Expires August 27, 2008               [Page 38]
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2129Internet-Draft              HTTP/1.1, Part 3               February 2008
2130
2131
2132   Yves Lafon (editor)
2133   World Wide Web Consortium
2134   W3C / ERCIM
2135   2004, rte des Lucioles
2136   Sophia-Antipolis, AM  06902
2137   France
2138
2139   Email: ylafon@w3.org
2140   URI:   http://www.raubacapeu.net/people/yves/
2141
2142
2143   Julian F. Reschke (editor)
2144   greenbytes GmbH
2145   Hafenweg 16
2146   Muenster, NW  48155
2147   Germany
2148
2149   Phone: +49 251 2807760
2150   Fax:   +49 251 2807761
2151   Email: julian.reschke@greenbytes.de
2152   URI:   http://greenbytes.de/tech/webdav/
2153
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2183Fielding, et al.         Expires August 27, 2008               [Page 39]
2184
2185Internet-Draft              HTTP/1.1, Part 3               February 2008
2186
2187
2188Full Copyright Statement
2189
2190   Copyright (C) The IETF Trust (2008).
2191
2192   This document is subject to the rights, licenses and restrictions
2193   contained in BCP 78, and except as set forth therein, the authors
2194   retain all their rights.
2195
2196   This document and the information contained herein are provided on an
2197   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
2198   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
2199   THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
2200   OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
2201   THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
2202   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
2203
2204
2205Intellectual Property
2206
2207   The IETF takes no position regarding the validity or scope of any
2208   Intellectual Property Rights or other rights that might be claimed to
2209   pertain to the implementation or use of the technology described in
2210   this document or the extent to which any license under such rights
2211   might or might not be available; nor does it represent that it has
2212   made any independent effort to identify any such rights.  Information
2213   on the procedures with respect to rights in RFC documents can be
2214   found in BCP 78 and BCP 79.
2215
2216   Copies of IPR disclosures made to the IETF Secretariat and any
2217   assurances of licenses to be made available, or the result of an
2218   attempt made to obtain a general license or permission for the use of
2219   such proprietary rights by implementers or users of this
2220   specification can be obtained from the IETF on-line IPR repository at
2221   http://www.ietf.org/ipr.
2222
2223   The IETF invites any interested party to bring to its attention any
2224   copyrights, patents or patent applications, or other proprietary
2225   rights that may cover technology that may be required to implement
2226   this standard.  Please address the information to the IETF at
2227   ietf-ipr@ietf.org.
2228
2229
2230Acknowledgment
2231
2232   Funding for the RFC Editor function is provided by the IETF
2233   Administrative Support Activity (IASA).
2234
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2239Fielding, et al.         Expires August 27, 2008               [Page 40]
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