draft-ietf-httpbis-p3-payload-01.txt   draft-ietf-httpbis-p3-payload-02.txt 
Network Working Group R. Fielding, Ed. Network Working Group R. Fielding, Ed.
Internet-Draft Day Software Internet-Draft Day Software
Obsoletes: 2616 (if approved) J. Gettys Obsoletes: 2616 (if approved) J. Gettys
Intended status: Standards Track One Laptop per Child Intended status: Standards Track One Laptop per Child
Expires: July 15, 2008 J. Mogul Expires: August 27, 2008 J. Mogul
HP HP
H. Frystyk H. Frystyk
Microsoft Microsoft
L. Masinter L. Masinter
Adobe Systems Adobe Systems
P. Leach P. Leach
Microsoft Microsoft
T. Berners-Lee T. Berners-Lee
W3C/MIT W3C/MIT
Y. Lafon, Ed. Y. Lafon, Ed.
W3C W3C
J. Reschke, Ed. J. Reschke, Ed.
greenbytes greenbytes
January 12, 2008 February 24, 2008
HTTP/1.1, part 3: Message Payload and Content Negotiation HTTP/1.1, part 3: Message Payload and Content Negotiation
draft-ietf-httpbis-p3-payload-01 draft-ietf-httpbis-p3-payload-02
Status of this Memo Status of this Memo
By submitting this Internet-Draft, each author represents that any By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79. aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
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and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
This Internet-Draft will expire on July 15, 2008. This Internet-Draft will expire on August 27, 2008.
Copyright Notice Copyright Notice
Copyright (C) The IETF Trust (2008). Copyright (C) The IETF Trust (2008).
Abstract Abstract
The Hypertext Transfer Protocol (HTTP) is an application-level The Hypertext Transfer Protocol (HTTP) is an application-level
protocol for distributed, collaborative, hypermedia information protocol for distributed, collaborative, hypermedia information
systems. HTTP has been in use by the World Wide Web global systems. HTTP has been in use by the World Wide Web global
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This draft incorporates those issue resolutions that were either This draft incorporates those issue resolutions that were either
collected in the original RFC2616 errata list collected in the original RFC2616 errata list
(<http://purl.org/NET/http-errata>), or which were agreed upon on the (<http://purl.org/NET/http-errata>), or which were agreed upon on the
mailing list between October 2006 and November 2007 (as published in mailing list between October 2006 and November 2007 (as published in
"draft-lafon-rfc2616bis-03"). "draft-lafon-rfc2616bis-03").
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1. Requirements . . . . . . . . . . . . . . . . . . . . . . . 5 1.1. Requirements . . . . . . . . . . . . . . . . . . . . . . . 5
2. Protocol Parameters . . . . . . . . . . . . . . . . . . . . . 5 2. Notational Conventions and Generic Grammar . . . . . . . . . . 5
2.1. Character Sets . . . . . . . . . . . . . . . . . . . . . . 5 3. Protocol Parameters . . . . . . . . . . . . . . . . . . . . . 6
2.1.1. Missing Charset . . . . . . . . . . . . . . . . . . . 6 3.1. Character Sets . . . . . . . . . . . . . . . . . . . . . . 6
2.2. Content Codings . . . . . . . . . . . . . . . . . . . . . 7 3.1.1. Missing Charset . . . . . . . . . . . . . . . . . . . 7
2.3. Media Types . . . . . . . . . . . . . . . . . . . . . . . 8 3.2. Content Codings . . . . . . . . . . . . . . . . . . . . . 7
2.3.1. Canonicalization and Text Defaults . . . . . . . . . . 9 3.3. Media Types . . . . . . . . . . . . . . . . . . . . . . . 9
2.3.2. Multipart Types . . . . . . . . . . . . . . . . . . . 9 3.3.1. Canonicalization and Text Defaults . . . . . . . . . . 9
2.4. Quality Values . . . . . . . . . . . . . . . . . . . . . . 10 3.3.2. Multipart Types . . . . . . . . . . . . . . . . . . . 10
2.5. Language Tags . . . . . . . . . . . . . . . . . . . . . . 10 3.4. Quality Values . . . . . . . . . . . . . . . . . . . . . . 11
3. Entity . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 3.5. Language Tags . . . . . . . . . . . . . . . . . . . . . . 11
3.1. Entity Header Fields . . . . . . . . . . . . . . . . . . . 11 4. Entity . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.2. Entity Body . . . . . . . . . . . . . . . . . . . . . . . 12 4.1. Entity Header Fields . . . . . . . . . . . . . . . . . . . 12
3.2.1. Type . . . . . . . . . . . . . . . . . . . . . . . . . 12 4.2. Entity Body . . . . . . . . . . . . . . . . . . . . . . . 12
3.2.2. Entity Length . . . . . . . . . . . . . . . . . . . . 12 4.2.1. Type . . . . . . . . . . . . . . . . . . . . . . . . . 13
4. Content Negotiation . . . . . . . . . . . . . . . . . . . . . 13 4.2.2. Entity Length . . . . . . . . . . . . . . . . . . . . 13
4.1. Server-driven Negotiation . . . . . . . . . . . . . . . . 13 5. Content Negotiation . . . . . . . . . . . . . . . . . . . . . 13
4.2. Agent-driven Negotiation . . . . . . . . . . . . . . . . . 14 5.1. Server-driven Negotiation . . . . . . . . . . . . . . . . 14
4.3. Transparent Negotiation . . . . . . . . . . . . . . . . . 15 5.2. Agent-driven Negotiation . . . . . . . . . . . . . . . . . 15
5. Header Field Definitions . . . . . . . . . . . . . . . . . . . 15 5.3. Transparent Negotiation . . . . . . . . . . . . . . . . . 16
5.1. Accept . . . . . . . . . . . . . . . . . . . . . . . . . . 16 6. Header Field Definitions . . . . . . . . . . . . . . . . . . . 16
5.2. Accept-Charset . . . . . . . . . . . . . . . . . . . . . . 18 6.1. Accept . . . . . . . . . . . . . . . . . . . . . . . . . . 16
5.3. Accept-Encoding . . . . . . . . . . . . . . . . . . . . . 18 6.2. Accept-Charset . . . . . . . . . . . . . . . . . . . . . . 18
5.4. Accept-Language . . . . . . . . . . . . . . . . . . . . . 20 6.3. Accept-Encoding . . . . . . . . . . . . . . . . . . . . . 19
5.5. Content-Encoding . . . . . . . . . . . . . . . . . . . . . 21 6.4. Accept-Language . . . . . . . . . . . . . . . . . . . . . 20
5.6. Content-Language . . . . . . . . . . . . . . . . . . . . . 22 6.5. Content-Encoding . . . . . . . . . . . . . . . . . . . . . 22
5.7. Content-Location . . . . . . . . . . . . . . . . . . . . . 22 6.6. Content-Language . . . . . . . . . . . . . . . . . . . . . 22
5.8. Content-MD5 . . . . . . . . . . . . . . . . . . . . . . . 23 6.7. Content-Location . . . . . . . . . . . . . . . . . . . . . 23
5.9. Content-Type . . . . . . . . . . . . . . . . . . . . . . . 24 6.8. Content-MD5 . . . . . . . . . . . . . . . . . . . . . . . 24
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25 6.9. Content-Type . . . . . . . . . . . . . . . . . . . . . . . 25
7. Security Considerations . . . . . . . . . . . . . . . . . . . 25 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26
7.1. Privacy Issues Connected to Accept Headers . . . . . . . . 25 8. Security Considerations . . . . . . . . . . . . . . . . . . . 26
7.2. Content-Disposition Issues . . . . . . . . . . . . . . . . 26 8.1. Privacy Issues Connected to Accept Headers . . . . . . . . 26
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 26 8.2. Content-Disposition Issues . . . . . . . . . . . . . . . . 27
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 26 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 27
9.1. Normative References . . . . . . . . . . . . . . . . . . . 26 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 27
9.2. Informative References . . . . . . . . . . . . . . . . . . 28 10.1. Normative References . . . . . . . . . . . . . . . . . . . 27
10.2. Informative References . . . . . . . . . . . . . . . . . . 29
Appendix A. Differences Between HTTP Entities and RFC 2045 Appendix A. Differences Between HTTP Entities and RFC 2045
Entities . . . . . . . . . . . . . . . . . . . . . . 29 Entities . . . . . . . . . . . . . . . . . . . . . . 30
A.1. MIME-Version . . . . . . . . . . . . . . . . . . . . . . . 29 A.1. MIME-Version . . . . . . . . . . . . . . . . . . . . . . . 30
A.2. Conversion to Canonical Form . . . . . . . . . . . . . . . 30 A.2. Conversion to Canonical Form . . . . . . . . . . . . . . . 30
A.3. Introduction of Content-Encoding . . . . . . . . . . . . . 30 A.3. Introduction of Content-Encoding . . . . . . . . . . . . . 31
A.4. No Content-Transfer-Encoding . . . . . . . . . . . . . . . 30 A.4. No Content-Transfer-Encoding . . . . . . . . . . . . . . . 31
A.5. Introduction of Transfer-Encoding . . . . . . . . . . . . 31 A.5. Introduction of Transfer-Encoding . . . . . . . . . . . . 31
A.6. MHTML and Line Length Limitations . . . . . . . . . . . . 31 A.6. MHTML and Line Length Limitations . . . . . . . . . . . . 32
Appendix B. Additional Features . . . . . . . . . . . . . . . . . 31 Appendix B. Additional Features . . . . . . . . . . . . . . . . . 32
B.1. Content-Disposition . . . . . . . . . . . . . . . . . . . 31 B.1. Content-Disposition . . . . . . . . . . . . . . . . . . . 32
Appendix C. Compatibility with Previous Versions . . . . . . . . 32 Appendix C. Compatibility with Previous Versions . . . . . . . . 33
C.1. Changes from RFC 2068 . . . . . . . . . . . . . . . . . . 32 C.1. Changes from RFC 2068 . . . . . . . . . . . . . . . . . . 33
C.2. Changes from RFC 2616 . . . . . . . . . . . . . . . . . . 33 C.2. Changes from RFC 2616 . . . . . . . . . . . . . . . . . . 33
Appendix D. Change Log (to be removed by RFC Editor before Appendix D. Change Log (to be removed by RFC Editor before
publication) . . . . . . . . . . . . . . . . . . . . 33 publication) . . . . . . . . . . . . . . . . . . . . 34
D.1. Since RFC2616 . . . . . . . . . . . . . . . . . . . . . . 33 D.1. Since RFC2616 . . . . . . . . . . . . . . . . . . . . . . 34
D.2. Since draft-ietf-httpbis-p3-payload-00 . . . . . . . . . . 33 D.2. Since draft-ietf-httpbis-p3-payload-00 . . . . . . . . . . 34
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 D.3. Since draft-ietf-httpbis-p3-payload-01 . . . . . . . . . . 35
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 36 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Intellectual Property and Copyright Statements . . . . . . . . . . 39 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 37
Intellectual Property and Copyright Statements . . . . . . . . . . 40
1. Introduction 1. Introduction
This document defines HTTP/1.1 message payloads (a.k.a., content), This document defines HTTP/1.1 message payloads (a.k.a., content),
the associated metadata header fields that define how the payload is the associated metadata header fields that define how the payload is
intended to be interpreted by a recipient, the request header fields intended to be interpreted by a recipient, the request header fields
that may influence content selection, and the various selection that may influence content selection, and the various selection
algorithms that are collectively referred to as HTTP content algorithms that are collectively referred to as HTTP content
negotiation. negotiation.
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An implementation is not compliant if it fails to satisfy one or more An implementation is not compliant if it fails to satisfy one or more
of the MUST or REQUIRED level requirements for the protocols it of the MUST or REQUIRED level requirements for the protocols it
implements. An implementation that satisfies all the MUST or implements. An implementation that satisfies all the MUST or
REQUIRED level and all the SHOULD level requirements for its REQUIRED level and all the SHOULD level requirements for its
protocols is said to be "unconditionally compliant"; one that protocols is said to be "unconditionally compliant"; one that
satisfies all the MUST level requirements but not all the SHOULD satisfies all the MUST level requirements but not all the SHOULD
level requirements for its protocols is said to be "conditionally level requirements for its protocols is said to be "conditionally
compliant." compliant."
2. Protocol Parameters 2. Notational Conventions and Generic Grammar
2.1. Character Sets This specification uses the ABNF syntax defined in Section 2.1 of
[Part1] and the core rules defined in Section 2.2 of [Part1]:
[[abnf.dep: ABNF syntax and basic rules will be adopted from RFC
5234, see <http://tools.ietf.org/wg/httpbis/trac/ticket/36>.]]
ALPHA = <ALPHA, defined in [Part1], Section 2.2>
DIGIT = <DIGIT, defined in [Part1], Section 2.2>
OCTET = <OCTET, defined in [Part1], Section 2.2>
quoted-string = <quoted-string, defined in [Part1], Section 2.2>
token = <token, defined in [Part1], Section 2.2>
The ABNF rules below are defined in other parts:
absoluteURI = <absoluteURI, defined in [Part1], Section 3.2.1>
Content-Length = <Content-Length, defined in [Part1], Section 8.2>
relativeURI = <relativeURI, defined in [Part1], Section 3.2.1>
message-header = <message-header, defined in [Part1], Section 4.2>
Allow = <Allow, defined in [Part2], Section 10.1>
Last-Modified = <Last-Modified, defined in [Part4], Section 7.6>
Content-Range = <Content-Range, defined in [Part5], Section 6.2>
Expires = <Expires, defined in [Part6], Section 16.3>
3. Protocol Parameters
3.1. Character Sets
HTTP uses the same definition of the term "character set" as that HTTP uses the same definition of the term "character set" as that
described for MIME: described for MIME:
The term "character set" is used in this document to refer to a The term "character set" is used in this document to refer to a
method used with one or more tables to convert a sequence of octets method used with one or more tables to convert a sequence of octets
into a sequence of characters. Note that unconditional conversion in into a sequence of characters. Note that unconditional conversion in
the other direction is not required, in that not all characters may the other direction is not required, in that not all characters may
be available in a given character set and a character set may provide be available in a given character set and a character set may provide
more than one sequence of octets to represent a particular character. more than one sequence of octets to represent a particular character.
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HTTP uses charset in two contexts: within an Accept-Charset request HTTP uses charset in two contexts: within an Accept-Charset request
header (in which the charset value is an unquoted token) and as the header (in which the charset value is an unquoted token) and as the
value of a parameter in a Content-Type header (within a request or value of a parameter in a Content-Type header (within a request or
response), in which case the parameter value of the charset parameter response), in which case the parameter value of the charset parameter
may be quoted. may be quoted.
Implementors should be aware of IETF character set requirements Implementors should be aware of IETF character set requirements
[RFC3629] [RFC2277]. [RFC3629] [RFC2277].
2.1.1. Missing Charset 3.1.1. Missing Charset
Some HTTP/1.0 software has interpreted a Content-Type header without Some HTTP/1.0 software has interpreted a Content-Type header without
charset parameter incorrectly to mean "recipient should guess." charset parameter incorrectly to mean "recipient should guess."
Senders wishing to defeat this behavior MAY include a charset Senders wishing to defeat this behavior MAY include a charset
parameter even when the charset is ISO-8859-1 ([ISO-8859-1]) and parameter even when the charset is ISO-8859-1 ([ISO-8859-1]) and
SHOULD do so when it is known that it will not confuse the recipient. SHOULD do so when it is known that it will not confuse the recipient.
Unfortunately, some older HTTP/1.0 clients did not deal properly with Unfortunately, some older HTTP/1.0 clients did not deal properly with
an explicit charset parameter. HTTP/1.1 recipients MUST respect the an explicit charset parameter. HTTP/1.1 recipients MUST respect the
charset label provided by the sender; and those user agents that have charset label provided by the sender; and those user agents that have
a provision to "guess" a charset MUST use the charset from the a provision to "guess" a charset MUST use the charset from the
content-type field if they support that charset, rather than the content-type field if they support that charset, rather than the
recipient's preference, when initially displaying a document. See recipient's preference, when initially displaying a document. See
Section 2.3.1. Section 3.3.1.
2.2. Content Codings 3.2. Content Codings
Content coding values indicate an encoding transformation that has Content coding values indicate an encoding transformation that has
been or can be applied to an entity. Content codings are primarily been or can be applied to an entity. Content codings are primarily
used to allow a document to be compressed or otherwise usefully used to allow a document to be compressed or otherwise usefully
transformed without losing the identity of its underlying media type transformed without losing the identity of its underlying media type
and without loss of information. Frequently, the entity is stored in and without loss of information. Frequently, the entity is stored in
coded form, transmitted directly, and only decoded by the recipient. coded form, transmitted directly, and only decoded by the recipient.
content-coding = token content-coding = token
All content-coding values are case-insensitive. HTTP/1.1 uses All content-coding values are case-insensitive. HTTP/1.1 uses
content-coding values in the Accept-Encoding (Section 5.3) and content-coding values in the Accept-Encoding (Section 6.3) and
Content-Encoding (Section 5.5) header fields. Although the value Content-Encoding (Section 6.5) header fields. Although the value
describes the content-coding, what is more important is that it describes the content-coding, what is more important is that it
indicates what decoding mechanism will be required to remove the indicates what decoding mechanism will be required to remove the
encoding. encoding.
The Internet Assigned Numbers Authority (IANA) acts as a registry for The Internet Assigned Numbers Authority (IANA) acts as a registry for
content-coding value tokens. Initially, the registry contains the content-coding value tokens. Initially, the registry contains the
following tokens: following tokens:
gzip gzip
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whatsoever. This content-coding is used only in the Accept- whatsoever. This content-coding is used only in the Accept-
Encoding header, and SHOULD NOT be used in the Content-Encoding Encoding header, and SHOULD NOT be used in the Content-Encoding
header. header.
New content-coding value tokens SHOULD be registered; to allow New content-coding value tokens SHOULD be registered; to allow
interoperability between clients and servers, specifications of the interoperability between clients and servers, specifications of the
content coding algorithms needed to implement a new value SHOULD be content coding algorithms needed to implement a new value SHOULD be
publicly available and adequate for independent implementation, and publicly available and adequate for independent implementation, and
conform to the purpose of content coding defined in this section. conform to the purpose of content coding defined in this section.
2.3. Media Types 3.3. Media Types
HTTP uses Internet Media Types [RFC2046] in the Content-Type HTTP uses Internet Media Types [RFC2046] in the Content-Type
(Section 5.9) and Accept (Section 5.1) header fields in order to (Section 6.9) and Accept (Section 6.1) header fields in order to
provide open and extensible data typing and type negotiation. provide open and extensible data typing and type negotiation.
media-type = type "/" subtype *( ";" parameter ) media-type = type "/" subtype *( ";" parameter )
type = token type = token
subtype = token subtype = token
Parameters MAY follow the type/subtype in the form of attribute/value Parameters MAY follow the type/subtype in the form of attribute/value
pairs. pairs.
parameter = attribute "=" value parameter = attribute "=" value
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Note that some older HTTP applications do not recognize media type Note that some older HTTP applications do not recognize media type
parameters. When sending data to older HTTP applications, parameters. When sending data to older HTTP applications,
implementations SHOULD only use media type parameters when they are implementations SHOULD only use media type parameters when they are
required by that type/subtype definition. required by that type/subtype definition.
Media-type values are registered with the Internet Assigned Number Media-type values are registered with the Internet Assigned Number
Authority (IANA). The media type registration process is outlined in Authority (IANA). The media type registration process is outlined in
[RFC4288]. Use of non-registered media types is discouraged. [RFC4288]. Use of non-registered media types is discouraged.
2.3.1. Canonicalization and Text Defaults 3.3.1. Canonicalization and Text Defaults
Internet media types are registered with a canonical form. An Internet media types are registered with a canonical form. An
entity-body transferred via HTTP messages MUST be represented in the entity-body transferred via HTTP messages MUST be represented in the
appropriate canonical form prior to its transmission except for appropriate canonical form prior to its transmission except for
"text" types, as defined in the next paragraph. "text" types, as defined in the next paragraph.
When in canonical form, media subtypes of the "text" type use CRLF as When in canonical form, media subtypes of the "text" type use CRLF as
the text line break. HTTP relaxes this requirement and allows the the text line break. HTTP relaxes this requirement and allows the
transport of text media with plain CR or LF alone representing a line transport of text media with plain CR or LF alone representing a line
break when it is done consistently for an entire entity-body. HTTP break when it is done consistently for an entire entity-body. HTTP
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sequences are defined by that character set to represent the sequences are defined by that character set to represent the
equivalent of CR and LF for line breaks. This flexibility regarding equivalent of CR and LF for line breaks. This flexibility regarding
line breaks applies only to text media in the entity-body; a bare CR line breaks applies only to text media in the entity-body; a bare CR
or LF MUST NOT be substituted for CRLF within any of the HTTP control or LF MUST NOT be substituted for CRLF within any of the HTTP control
structures (such as header fields and multipart boundaries). structures (such as header fields and multipart boundaries).
If an entity-body is encoded with a content-coding, the underlying If an entity-body is encoded with a content-coding, the underlying
data MUST be in a form defined above prior to being encoded. data MUST be in a form defined above prior to being encoded.
The "charset" parameter is used with some media types to define the The "charset" parameter is used with some media types to define the
character set (Section 2.1) of the data. When no explicit charset character set (Section 3.1) of the data. When no explicit charset
parameter is provided by the sender, media subtypes of the "text" parameter is provided by the sender, media subtypes of the "text"
type are defined to have a default charset value of "ISO-8859-1" when type are defined to have a default charset value of "ISO-8859-1" when
received via HTTP. Data in character sets other than "ISO-8859-1" or received via HTTP. Data in character sets other than "ISO-8859-1" or
its subsets MUST be labeled with an appropriate charset value. See its subsets MUST be labeled with an appropriate charset value. See
Section 2.1.1 for compatibility problems. Section 3.1.1 for compatibility problems.
2.3.2. Multipart Types 3.3.2. Multipart Types
MIME provides for a number of "multipart" types -- encapsulations of MIME provides for a number of "multipart" types -- encapsulations of
one or more entities within a single message-body. All multipart one or more entities within a single message-body. All multipart
types share a common syntax, as defined in Section 5.1.1 of types share a common syntax, as defined in Section 5.1.1 of
[RFC2046], and MUST include a boundary parameter as part of the media [RFC2046], and MUST include a boundary parameter as part of the media
type value. The message body is itself a protocol element and MUST type value. The message body is itself a protocol element and MUST
therefore use only CRLF to represent line breaks between body-parts. therefore use only CRLF to represent line breaks between body-parts.
Unlike in RFC 2046, the epilogue of any multipart message MUST be Unlike in RFC 2046, the epilogue of any multipart message MUST be
empty; HTTP applications MUST NOT transmit the epilogue (even if the empty; HTTP applications MUST NOT transmit the epilogue (even if the
original multipart contains an epilogue). These restrictions exist original multipart contains an epilogue). These restrictions exist
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In general, an HTTP user agent SHOULD follow the same or similar In general, an HTTP user agent SHOULD follow the same or similar
behavior as a MIME user agent would upon receipt of a multipart type. behavior as a MIME user agent would upon receipt of a multipart type.
If an application receives an unrecognized multipart subtype, the If an application receives an unrecognized multipart subtype, the
application MUST treat it as being equivalent to "multipart/mixed". application MUST treat it as being equivalent to "multipart/mixed".
Note: The "multipart/form-data" type has been specifically defined Note: The "multipart/form-data" type has been specifically defined
for carrying form data suitable for processing via the POST for carrying form data suitable for processing via the POST
request method, as described in [RFC2388]. request method, as described in [RFC2388].
2.4. Quality Values 3.4. Quality Values
HTTP content negotiation (Section 4) uses short "floating point" HTTP content negotiation (Section 5) uses short "floating point"
numbers to indicate the relative importance ("weight") of various numbers to indicate the relative importance ("weight") of various
negotiable parameters. A weight is normalized to a real number in negotiable parameters. A weight is normalized to a real number in
the range 0 through 1, where 0 is the minimum and 1 the maximum the range 0 through 1, where 0 is the minimum and 1 the maximum
value. If a parameter has a quality value of 0, then content with value. If a parameter has a quality value of 0, then content with
this parameter is `not acceptable' for the client. HTTP/1.1 this parameter is `not acceptable' for the client. HTTP/1.1
applications MUST NOT generate more than three digits after the applications MUST NOT generate more than three digits after the
decimal point. User configuration of these values SHOULD also be decimal point. User configuration of these values SHOULD also be
limited in this fashion. limited in this fashion.
qvalue = ( "0" [ "." 0*3DIGIT ] ) qvalue = ( "0" [ "." 0*3DIGIT ] )
| ( "1" [ "." 0*3("0") ] ) | ( "1" [ "." 0*3("0") ] )
"Quality values" is a misnomer, since these values merely represent "Quality values" is a misnomer, since these values merely represent
relative degradation in desired quality. relative degradation in desired quality.
2.5. Language Tags 3.5. Language Tags
A language tag identifies a natural language spoken, written, or A language tag identifies a natural language spoken, written, or
otherwise conveyed by human beings for communication of information otherwise conveyed by human beings for communication of information
to other human beings. Computer languages are explicitly excluded. to other human beings. Computer languages are explicitly excluded.
HTTP uses language tags within the Accept-Language and Content- HTTP uses language tags within the Accept-Language and Content-
Language fields. Language fields.
The syntax and registry of HTTP language tags is the same as that The syntax and registry of HTTP language tags is the same as that
defined by [RFC1766]. In summary, a language tag is composed of 1 or defined by [RFC1766]. In summary, a language tag is composed of 1 or
more parts: A primary language tag and a possibly empty series of more parts: A primary language tag and a possibly empty series of
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insensitive. The name space of language tags is administered by the insensitive. The name space of language tags is administered by the
IANA. Example tags include: IANA. Example tags include:
en, en-US, en-cockney, i-cherokee, x-pig-latin en, en-US, en-cockney, i-cherokee, x-pig-latin
where any two-letter primary-tag is an ISO-639 language abbreviation where any two-letter primary-tag is an ISO-639 language abbreviation
and any two-letter initial subtag is an ISO-3166 country code. (The and any two-letter initial subtag is an ISO-3166 country code. (The
last three tags above are not registered tags; all but the last are last three tags above are not registered tags; all but the last are
examples of tags which could be registered in future.) examples of tags which could be registered in future.)
3. Entity 4. Entity
Request and Response messages MAY transfer an entity if not otherwise Request and Response messages MAY transfer an entity if not otherwise
restricted by the request method or response status code. An entity restricted by the request method or response status code. An entity
consists of entity-header fields and an entity-body, although some consists of entity-header fields and an entity-body, although some
responses will only include the entity-headers. responses will only include the entity-headers.
In this section, both sender and recipient refer to either the client In this section, both sender and recipient refer to either the client
or the server, depending on who sends and who receives the entity. or the server, depending on who sends and who receives the entity.
3.1. Entity Header Fields 4.1. Entity Header Fields
Entity-header fields define metainformation about the entity-body or, Entity-header fields define metainformation about the entity-body or,
if no body is present, about the resource identified by the request. if no body is present, about the resource identified by the request.
entity-header = Allow ; [Part2], Section 10.1 entity-header = Allow ; [Part2], Section 10.1
| Content-Encoding ; Section 5.5 | Content-Encoding ; Section 6.5
| Content-Language ; Section 5.6 | Content-Language ; Section 6.6
| Content-Length ; [Part1], Section 8.2 | Content-Length ; [Part1], Section 8.2
| Content-Location ; Section 5.7 | Content-Location ; Section 6.7
| Content-MD5 ; Section 5.8 | Content-MD5 ; Section 6.8
| Content-Range ; [Part5], Section 5.2 | Content-Range ; [Part5], Section 6.2
| Content-Type ; Section 5.9 | Content-Type ; Section 6.9
| Expires ; [Part6], Section 15.3 | Expires ; [Part6], Section 16.3
| Last-Modified ; [Part4], Section 6.6 | Last-Modified ; [Part4], Section 7.6
| extension-header | extension-header
extension-header = message-header extension-header = message-header
The extension-header mechanism allows additional entity-header fields The extension-header mechanism allows additional entity-header fields
to be defined without changing the protocol, but these fields cannot to be defined without changing the protocol, but these fields cannot
be assumed to be recognizable by the recipient. Unrecognized header be assumed to be recognizable by the recipient. Unrecognized header
fields SHOULD be ignored by the recipient and MUST be forwarded by fields SHOULD be ignored by the recipient and MUST be forwarded by
transparent proxies. transparent proxies.
3.2. Entity Body 4.2. Entity Body
The entity-body (if any) sent with an HTTP request or response is in The entity-body (if any) sent with an HTTP request or response is in
a format and encoding defined by the entity-header fields. a format and encoding defined by the entity-header fields.
entity-body = *OCTET entity-body = *OCTET
An entity-body is only present in a message when a message-body is An entity-body is only present in a message when a message-body is
present, as described in Section 4.3 of [Part1]. The entity-body is present, as described in Section 4.3 of [Part1]. The entity-body is
obtained from the message-body by decoding any Transfer-Encoding that obtained from the message-body by decoding any Transfer-Encoding that
might have been applied to ensure safe and proper transfer of the might have been applied to ensure safe and proper transfer of the
message. message.
3.2.1. Type 4.2.1. Type
When an entity-body is included with a message, the data type of that When an entity-body is included with a message, the data type of that
body is determined via the header fields Content-Type and Content- body is determined via the header fields Content-Type and Content-
Encoding. These define a two-layer, ordered encoding model: Encoding. These define a two-layer, ordered encoding model:
entity-body := Content-Encoding( Content-Type( data ) ) entity-body := Content-Encoding( Content-Type( data ) )
Content-Type specifies the media type of the underlying data. Content-Type specifies the media type of the underlying data.
Content-Encoding may be used to indicate any additional content Content-Encoding may be used to indicate any additional content
codings applied to the data, usually for the purpose of data codings applied to the data, usually for the purpose of data
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no default encoding. no default encoding.
Any HTTP/1.1 message containing an entity-body SHOULD include a Any HTTP/1.1 message containing an entity-body SHOULD include a
Content-Type header field defining the media type of that body. If Content-Type header field defining the media type of that body. If
and only if the media type is not given by a Content-Type field, the and only if the media type is not given by a Content-Type field, the
recipient MAY attempt to guess the media type via inspection of its recipient MAY attempt to guess the media type via inspection of its
content and/or the name extension(s) of the URI used to identify the content and/or the name extension(s) of the URI used to identify the
resource. If the media type remains unknown, the recipient SHOULD resource. If the media type remains unknown, the recipient SHOULD
treat it as type "application/octet-stream". treat it as type "application/octet-stream".
3.2.2. Entity Length 4.2.2. Entity Length
The entity-length of a message is the length of the message-body The entity-length of a message is the length of the message-body
before any transfer-codings have been applied. Section 4.4 of before any transfer-codings have been applied. Section 4.4 of
[Part1] defines how the transfer-length of a message-body is [Part1] defines how the transfer-length of a message-body is
determined. determined.
4. Content Negotiation 5. Content Negotiation
Most HTTP responses include an entity which contains information for Most HTTP responses include an entity which contains information for
interpretation by a human user. Naturally, it is desirable to supply interpretation by a human user. Naturally, it is desirable to supply
the user with the "best available" entity corresponding to the the user with the "best available" entity corresponding to the
request. Unfortunately for servers and caches, not all users have request. Unfortunately for servers and caches, not all users have
the same preferences for what is "best," and not all user agents are the same preferences for what is "best," and not all user agents are
equally capable of rendering all entity types. For that reason, HTTP equally capable of rendering all entity types. For that reason, HTTP
has provisions for several mechanisms for "content negotiation" -- has provisions for several mechanisms for "content negotiation" --
the process of selecting the best representation for a given response the process of selecting the best representation for a given response
when there are multiple representations available. when there are multiple representations available.
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including error responses. including error responses.
There are two kinds of content negotiation which are possible in There are two kinds of content negotiation which are possible in
HTTP: server-driven and agent-driven negotiation. These two kinds of HTTP: server-driven and agent-driven negotiation. These two kinds of
negotiation are orthogonal and thus may be used separately or in negotiation are orthogonal and thus may be used separately or in
combination. One method of combination, referred to as transparent combination. One method of combination, referred to as transparent
negotiation, occurs when a cache uses the agent-driven negotiation negotiation, occurs when a cache uses the agent-driven negotiation
information provided by the origin server in order to provide server- information provided by the origin server in order to provide server-
driven negotiation for subsequent requests. driven negotiation for subsequent requests.
4.1. Server-driven Negotiation 5.1. Server-driven Negotiation
If the selection of the best representation for a response is made by If the selection of the best representation for a response is made by
an algorithm located at the server, it is called server-driven an algorithm located at the server, it is called server-driven
negotiation. Selection is based on the available representations of negotiation. Selection is based on the available representations of
the response (the dimensions over which it can vary; e.g. language, the response (the dimensions over which it can vary; e.g. language,
content-coding, etc.) and the contents of particular header fields in content-coding, etc.) and the contents of particular header fields in
the request message or on other information pertaining to the request the request message or on other information pertaining to the request
(such as the network address of the client). (such as the network address of the client).
Server-driven negotiation is advantageous when the algorithm for Server-driven negotiation is advantageous when the algorithm for
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violation of the user's privacy. violation of the user's privacy.
3. It complicates the implementation of an origin server and the 3. It complicates the implementation of an origin server and the
algorithms for generating responses to a request. algorithms for generating responses to a request.
4. It may limit a public cache's ability to use the same response 4. It may limit a public cache's ability to use the same response
for multiple user's requests. for multiple user's requests.
HTTP/1.1 includes the following request-header fields for enabling HTTP/1.1 includes the following request-header fields for enabling
server-driven negotiation through description of user agent server-driven negotiation through description of user agent
capabilities and user preferences: Accept (Section 5.1), Accept- capabilities and user preferences: Accept (Section 6.1), Accept-
Charset (Section 5.2), Accept-Encoding (Section 5.3), Accept-Language Charset (Section 6.2), Accept-Encoding (Section 6.3), Accept-Language
(Section 5.4), and User-Agent (Section 10.9 of [Part2]). However, an (Section 6.4), and User-Agent (Section 10.9 of [Part2]). However, an
origin server is not limited to these dimensions and MAY vary the origin server is not limited to these dimensions and MAY vary the
response based on any aspect of the request, including information response based on any aspect of the request, including information
outside the request-header fields or within extension header fields outside the request-header fields or within extension header fields
not defined by this specification. not defined by this specification.
The Vary header field (Section 15.5 of [Part6]) can be used to The Vary header field (Section 16.5 of [Part6]) can be used to
express the parameters the server uses to select a representation express the parameters the server uses to select a representation
that is subject to server-driven negotiation. that is subject to server-driven negotiation.
4.2. Agent-driven Negotiation 5.2. Agent-driven Negotiation
With agent-driven negotiation, selection of the best representation With agent-driven negotiation, selection of the best representation
for a response is performed by the user agent after receiving an for a response is performed by the user agent after receiving an
initial response from the origin server. Selection is based on a initial response from the origin server. Selection is based on a
list of the available representations of the response included within list of the available representations of the response included within
the header fields or entity-body of the initial response, with each the header fields or entity-body of the initial response, with each
representation identified by its own URI. Selection from among the representation identified by its own URI. Selection from among the
representations may be performed automatically (if the user agent is representations may be performed automatically (if the user agent is
capable of doing so) or manually by the user selecting from a capable of doing so) or manually by the user selecting from a
generated (possibly hypertext) menu. generated (possibly hypertext) menu.
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this specification does not define any mechanism for supporting this specification does not define any mechanism for supporting
automatic selection, though it also does not prevent any such automatic selection, though it also does not prevent any such
mechanism from being developed as an extension and used within mechanism from being developed as an extension and used within
HTTP/1.1. HTTP/1.1.
HTTP/1.1 defines the 300 (Multiple Choices) and 406 (Not Acceptable) HTTP/1.1 defines the 300 (Multiple Choices) and 406 (Not Acceptable)
status codes for enabling agent-driven negotiation when the server is status codes for enabling agent-driven negotiation when the server is
unwilling or unable to provide a varying response using server-driven unwilling or unable to provide a varying response using server-driven
negotiation. negotiation.
4.3. Transparent Negotiation 5.3. Transparent Negotiation
Transparent negotiation is a combination of both server-driven and Transparent negotiation is a combination of both server-driven and
agent-driven negotiation. When a cache is supplied with a form of agent-driven negotiation. When a cache is supplied with a form of
the list of available representations of the response (as in agent- the list of available representations of the response (as in agent-
driven negotiation) and the dimensions of variance are completely driven negotiation) and the dimensions of variance are completely
understood by the cache, then the cache becomes capable of performing understood by the cache, then the cache becomes capable of performing
server-driven negotiation on behalf of the origin server for server-driven negotiation on behalf of the origin server for
subsequent requests on that resource. subsequent requests on that resource.
Transparent negotiation has the advantage of distributing the Transparent negotiation has the advantage of distributing the
negotiation work that would otherwise be required of the origin negotiation work that would otherwise be required of the origin
server and also removing the second request delay of agent-driven server and also removing the second request delay of agent-driven
negotiation when the cache is able to correctly guess the right negotiation when the cache is able to correctly guess the right
response. response.
This specification does not define any mechanism for transparent This specification does not define any mechanism for transparent
negotiation, though it also does not prevent any such mechanism from negotiation, though it also does not prevent any such mechanism from
being developed as an extension that could be used within HTTP/1.1. being developed as an extension that could be used within HTTP/1.1.
5. Header Field Definitions 6. Header Field Definitions
This section defines the syntax and semantics of HTTP/1.1 header This section defines the syntax and semantics of HTTP/1.1 header
fields related to the payload of messages. fields related to the payload of messages.
For entity-header fields, both sender and recipient refer to either For entity-header fields, both sender and recipient refer to either
the client or the server, depending on who sends and who receives the the client or the server, depending on who sends and who receives the
entity. entity.
5.1. Accept 6.1. Accept
The Accept request-header field can be used to specify certain media The Accept request-header field can be used to specify certain media
types which are acceptable for the response. Accept headers can be types which are acceptable for the response. Accept headers can be
used to indicate that the request is specifically limited to a small used to indicate that the request is specifically limited to a small
set of desired types, as in the case of a request for an in-line set of desired types, as in the case of a request for an in-line
image. image.
Accept = "Accept" ":" Accept = "Accept" ":"
#( media-range [ accept-params ] ) #( media-range [ accept-params ] )
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The asterisk "*" character is used to group media types into ranges, The asterisk "*" character is used to group media types into ranges,
with "*/*" indicating all media types and "type/*" indicating all with "*/*" indicating all media types and "type/*" indicating all
subtypes of that type. The media-range MAY include media type subtypes of that type. The media-range MAY include media type
parameters that are applicable to that range. parameters that are applicable to that range.
Each media-range MAY be followed by one or more accept-params, Each media-range MAY be followed by one or more accept-params,
beginning with the "q" parameter for indicating a relative quality beginning with the "q" parameter for indicating a relative quality
factor. The first "q" parameter (if any) separates the media-range factor. The first "q" parameter (if any) separates the media-range
parameter(s) from the accept-params. Quality factors allow the user parameter(s) from the accept-params. Quality factors allow the user
or user agent to indicate the relative degree of preference for that or user agent to indicate the relative degree of preference for that
media-range, using the qvalue scale from 0 to 1 (Section 2.4). The media-range, using the qvalue scale from 0 to 1 (Section 3.4). The
default value is q=1. default value is q=1.
Note: Use of the "q" parameter name to separate media type Note: Use of the "q" parameter name to separate media type
parameters from Accept extension parameters is due to historical parameters from Accept extension parameters is due to historical
practice. Although this prevents any media type parameter named practice. Although this prevents any media type parameter named
"q" from being used with a media range, such an event is believed "q" from being used with a media range, such an event is believed
to be unlikely given the lack of any "q" parameters in the IANA to be unlikely given the lack of any "q" parameters in the IANA
media type registry and the rare usage of any media type media type registry and the rare usage of any media type
parameters in Accept. Future media types are discouraged from parameters in Accept. Future media types are discouraged from
registering any parameter named "q". registering any parameter named "q".
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text/plain = 0.3 text/plain = 0.3
image/jpeg = 0.5 image/jpeg = 0.5
text/html;level=2 = 0.4 text/html;level=2 = 0.4
text/html;level=3 = 0.7 text/html;level=3 = 0.7
Note: A user agent might be provided with a default set of quality Note: A user agent might be provided with a default set of quality
values for certain media ranges. However, unless the user agent is a values for certain media ranges. However, unless the user agent is a
closed system which cannot interact with other rendering agents, this closed system which cannot interact with other rendering agents, this
default set ought to be configurable by the user. default set ought to be configurable by the user.
5.2. Accept-Charset 6.2. Accept-Charset
The Accept-Charset request-header field can be used to indicate what The Accept-Charset request-header field can be used to indicate what
character sets are acceptable for the response. This field allows character sets are acceptable for the response. This field allows
clients capable of understanding more comprehensive or special- clients capable of understanding more comprehensive or special-
purpose character sets to signal that capability to a server which is purpose character sets to signal that capability to a server which is
capable of representing documents in those character sets. capable of representing documents in those character sets.
Accept-Charset = "Accept-Charset" ":" Accept-Charset = "Accept-Charset" ":"
1#( ( charset | "*" ) [ ";" "q" "=" qvalue ] ) 1#( ( charset | "*" ) [ ";" "q" "=" qvalue ] )
Character set values are described in Section 2.1. Each charset MAY Character set values are described in Section 3.1. Each charset MAY
be given an associated quality value which represents the user's be given an associated quality value which represents the user's
preference for that charset. The default value is q=1. An example preference for that charset. The default value is q=1. An example
is is
Accept-Charset: iso-8859-5, unicode-1-1;q=0.8 Accept-Charset: iso-8859-5, unicode-1-1;q=0.8
The special value "*", if present in the Accept-Charset field, The special value "*", if present in the Accept-Charset field,
matches every character set (including ISO-8859-1) which is not matches every character set (including ISO-8859-1) which is not
mentioned elsewhere in the Accept-Charset field. If no "*" is mentioned elsewhere in the Accept-Charset field. If no "*" is
present in an Accept-Charset field, then all character sets not present in an Accept-Charset field, then all character sets not
explicitly mentioned get a quality value of 0, except for ISO-8859-1, explicitly mentioned get a quality value of 0, except for ISO-8859-1,
which gets a quality value of 1 if not explicitly mentioned. which gets a quality value of 1 if not explicitly mentioned.
If no Accept-Charset header is present, the default is that any If no Accept-Charset header is present, the default is that any
character set is acceptable. If an Accept-Charset header is present, character set is acceptable. If an Accept-Charset header is present,
and if the server cannot send a response which is acceptable and if the server cannot send a response which is acceptable
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explicitly mentioned get a quality value of 0, except for ISO-8859-1, explicitly mentioned get a quality value of 0, except for ISO-8859-1,
which gets a quality value of 1 if not explicitly mentioned. which gets a quality value of 1 if not explicitly mentioned.
If no Accept-Charset header is present, the default is that any If no Accept-Charset header is present, the default is that any
character set is acceptable. If an Accept-Charset header is present, character set is acceptable. If an Accept-Charset header is present,
and if the server cannot send a response which is acceptable and if the server cannot send a response which is acceptable
according to the Accept-Charset header, then the server SHOULD send according to the Accept-Charset header, then the server SHOULD send
an error response with the 406 (Not Acceptable) status code, though an error response with the 406 (Not Acceptable) status code, though
the sending of an unacceptable response is also allowed. the sending of an unacceptable response is also allowed.
5.3. Accept-Encoding 6.3. Accept-Encoding
The Accept-Encoding request-header field is similar to Accept, but The Accept-Encoding request-header field is similar to Accept, but
restricts the content-codings (Section 2.2) that are acceptable in restricts the content-codings (Section 3.2) that are acceptable in
the response. the response.
Accept-Encoding = "Accept-Encoding" ":" Accept-Encoding = "Accept-Encoding" ":"
#( codings [ ";" "q" "=" qvalue ] ) #( codings [ ";" "q" "=" qvalue ] )
codings = ( content-coding | "*" ) codings = ( content-coding | "*" )
Examples of its use are: Examples of its use are:
Accept-Encoding: compress, gzip Accept-Encoding: compress, gzip
Accept-Encoding: Accept-Encoding:
Accept-Encoding: * Accept-Encoding: *
Accept-Encoding: compress;q=0.5, gzip;q=1.0 Accept-Encoding: compress;q=0.5, gzip;q=1.0
Accept-Encoding: gzip;q=1.0, identity; q=0.5, *;q=0 Accept-Encoding: gzip;q=1.0, identity; q=0.5, *;q=0
A server tests whether a content-coding is acceptable, according to A server tests whether a content-coding is acceptable, according to
an Accept-Encoding field, using these rules: an Accept-Encoding field, using these rules:
1. If the content-coding is one of the content-codings listed in the 1. If the content-coding is one of the content-codings listed in the
Accept-Encoding field, then it is acceptable, unless it is Accept-Encoding field, then it is acceptable, unless it is
accompanied by a qvalue of 0. (As defined in Section 2.4, a accompanied by a qvalue of 0. (As defined in Section 3.4, a
qvalue of 0 means "not acceptable.") qvalue of 0 means "not acceptable.")
2. The special "*" symbol in an Accept-Encoding field matches any 2. The special "*" symbol in an Accept-Encoding field matches any
available content-coding not explicitly listed in the header available content-coding not explicitly listed in the header
field. field.
3. If multiple content-codings are acceptable, then the acceptable 3. If multiple content-codings are acceptable, then the acceptable
content-coding with the highest non-zero qvalue is preferred. content-coding with the highest non-zero qvalue is preferred.
4. The "identity" content-coding is always acceptable, unless 4. The "identity" content-coding is always acceptable, unless
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codings commonly understood by HTTP/1.0 clients (i.e., "gzip" and codings commonly understood by HTTP/1.0 clients (i.e., "gzip" and
"compress") are preferred; some older clients improperly display "compress") are preferred; some older clients improperly display
messages sent with other content-codings. The server might also messages sent with other content-codings. The server might also
make this decision based on information about the particular user- make this decision based on information about the particular user-
agent or client. agent or client.
Note: Most HTTP/1.0 applications do not recognize or obey qvalues Note: Most HTTP/1.0 applications do not recognize or obey qvalues
associated with content-codings. This means that qvalues will not associated with content-codings. This means that qvalues will not
work and are not permitted with x-gzip or x-compress. work and are not permitted with x-gzip or x-compress.
5.4. Accept-Language 6.4. Accept-Language
The Accept-Language request-header field is similar to Accept, but The Accept-Language request-header field is similar to Accept, but
restricts the set of natural languages that are preferred as a restricts the set of natural languages that are preferred as a
response to the request. Language tags are defined in Section 2.5. response to the request. Language tags are defined in Section 3.5.
Accept-Language = "Accept-Language" ":" Accept-Language = "Accept-Language" ":"
1#( language-range [ ";" "q" "=" qvalue ] ) 1#( language-range [ ";" "q" "=" qvalue ] )
language-range = ( ( 1*8ALPHA *( "-" 1*8ALPHA ) ) | "*" ) language-range = ( ( 1*8ALPHA *( "-" 1*8ALPHA ) ) | "*" )
Each language-range MAY be given an associated quality value which Each language-range MAY be given an associated quality value which
represents an estimate of the user's preference for the languages represents an estimate of the user's preference for the languages
specified by that range. The quality value defaults to "q=1". For specified by that range. The quality value defaults to "q=1". For
example, example,
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the field that matches the language-tag. If no language-range in the the field that matches the language-tag. If no language-range in the
field matches the tag, the language quality factor assigned is 0. If field matches the tag, the language quality factor assigned is 0. If
no Accept-Language header is present in the request, the server no Accept-Language header is present in the request, the server
SHOULD assume that all languages are equally acceptable. If an SHOULD assume that all languages are equally acceptable. If an
Accept-Language header is present, then all languages which are Accept-Language header is present, then all languages which are
assigned a quality factor greater than 0 are acceptable. assigned a quality factor greater than 0 are acceptable.
It might be contrary to the privacy expectations of the user to send It might be contrary to the privacy expectations of the user to send
an Accept-Language header with the complete linguistic preferences of an Accept-Language header with the complete linguistic preferences of
the user in every request. For a discussion of this issue, see the user in every request. For a discussion of this issue, see
Section 7.1. Section 8.1.
As intelligibility is highly dependent on the individual user, it is As intelligibility is highly dependent on the individual user, it is
recommended that client applications make the choice of linguistic recommended that client applications make the choice of linguistic
preference available to the user. If the choice is not made preference available to the user. If the choice is not made
available, then the Accept-Language header field MUST NOT be given in available, then the Accept-Language header field MUST NOT be given in
the request. the request.
Note: When making the choice of linguistic preference available to Note: When making the choice of linguistic preference available to
the user, we remind implementors of the fact that users are not the user, we remind implementors of the fact that users are not
familiar with the details of language matching as described above, familiar with the details of language matching as described above,
and should provide appropriate guidance. As an example, users and should provide appropriate guidance. As an example, users
might assume that on selecting "en-gb", they will be served any might assume that on selecting "en-gb", they will be served any
kind of English document if British English is not available. A kind of English document if British English is not available. A
user agent might suggest in such a case to add "en" to get the user agent might suggest in such a case to add "en" to get the
best matching behavior. best matching behavior.
5.5. Content-Encoding 6.5. Content-Encoding
The Content-Encoding entity-header field is used as a modifier to the The Content-Encoding entity-header field is used as a modifier to the
media-type. When present, its value indicates what additional media-type. When present, its value indicates what additional
content codings have been applied to the entity-body, and thus what content codings have been applied to the entity-body, and thus what
decoding mechanisms must be applied in order to obtain the media-type decoding mechanisms must be applied in order to obtain the media-type
referenced by the Content-Type header field. Content-Encoding is referenced by the Content-Type header field. Content-Encoding is
primarily used to allow a document to be compressed without losing primarily used to allow a document to be compressed without losing
the identity of its underlying media type. the identity of its underlying media type.
Content-Encoding = "Content-Encoding" ":" 1#content-coding Content-Encoding = "Content-Encoding" ":" 1#content-coding
Content codings are defined in Section 2.2. An example of its use is Content codings are defined in Section 3.2. An example of its use is
Content-Encoding: gzip Content-Encoding: gzip
The content-coding is a characteristic of the entity identified by The content-coding is a characteristic of the entity identified by
the Request-URI. Typically, the entity-body is stored with this the Request-URI. Typically, the entity-body is stored with this
encoding and is only decoded before rendering or analogous usage. encoding and is only decoded before rendering or analogous usage.
However, a non-transparent proxy MAY modify the content-coding if the However, a non-transparent proxy MAY modify the content-coding if the
new coding is known to be acceptable to the recipient, unless the new coding is known to be acceptable to the recipient, unless the
"no-transform" cache-control directive is present in the message. "no-transform" cache-control directive is present in the message.
If the content-coding of an entity is not "identity", then the If the content-coding of an entity is not "identity", then the
response MUST include a Content-Encoding entity-header (Section 5.5) response MUST include a Content-Encoding entity-header (Section 6.5)
that lists the non-identity content-coding(s) used. that lists the non-identity content-coding(s) used.
If the content-coding of an entity in a request message is not If the content-coding of an entity in a request message is not
acceptable to the origin server, the server SHOULD respond with a acceptable to the origin server, the server SHOULD respond with a
status code of 415 (Unsupported Media Type). status code of 415 (Unsupported Media Type).
If multiple encodings have been applied to an entity, the content If multiple encodings have been applied to an entity, the content
codings MUST be listed in the order in which they were applied. codings MUST be listed in the order in which they were applied.
Additional information about the encoding parameters MAY be provided Additional information about the encoding parameters MAY be provided
by other entity-header fields not defined by this specification. by other entity-header fields not defined by this specification.
5.6. Content-Language 6.6. Content-Language
The Content-Language entity-header field describes the natural The Content-Language entity-header field describes the natural
language(s) of the intended audience for the enclosed entity. Note language(s) of the intended audience for the enclosed entity. Note
that this might not be equivalent to all the languages used within that this might not be equivalent to all the languages used within
the entity-body. the entity-body.
Content-Language = "Content-Language" ":" 1#language-tag Content-Language = "Content-Language" ":" 1#language-tag
Language tags are defined in Section 2.5. The primary purpose of Language tags are defined in Section 3.5. The primary purpose of
Content-Language is to allow a user to identify and differentiate Content-Language is to allow a user to identify and differentiate
entities according to the user's own preferred language. Thus, if entities according to the user's own preferred language. Thus, if
the body content is intended only for a Danish-literate audience, the the body content is intended only for a Danish-literate audience, the
appropriate field is appropriate field is
Content-Language: da Content-Language: da
If no Content-Language is specified, the default is that the content If no Content-Language is specified, the default is that the content
is intended for all language audiences. This might mean that the is intended for all language audiences. This might mean that the
sender does not consider it to be specific to any natural language, sender does not consider it to be specific to any natural language,
skipping to change at page 22, line 44 skipping to change at page 23, line 31
However, just because multiple languages are present within an entity However, just because multiple languages are present within an entity
does not mean that it is intended for multiple linguistic audiences. does not mean that it is intended for multiple linguistic audiences.
An example would be a beginner's language primer, such as "A First An example would be a beginner's language primer, such as "A First
Lesson in Latin," which is clearly intended to be used by an English- Lesson in Latin," which is clearly intended to be used by an English-
literate audience. In this case, the Content-Language would properly literate audience. In this case, the Content-Language would properly
only include "en". only include "en".
Content-Language MAY be applied to any media type -- it is not Content-Language MAY be applied to any media type -- it is not
limited to textual documents. limited to textual documents.
5.7. Content-Location 6.7. Content-Location
The Content-Location entity-header field MAY be used to supply the The Content-Location entity-header field MAY be used to supply the
resource location for the entity enclosed in the message when that resource location for the entity enclosed in the message when that
entity is accessible from a location separate from the requested entity is accessible from a location separate from the requested
resource's URI. A server SHOULD provide a Content-Location for the resource's URI. A server SHOULD provide a Content-Location for the
variant corresponding to the response entity; especially in the case variant corresponding to the response entity; especially in the case
where a resource has multiple entities associated with it, and those where a resource has multiple entities associated with it, and those
entities actually have separate locations by which they might be entities actually have separate locations by which they might be
individually accessed, the server SHOULD provide a Content-Location individually accessed, the server SHOULD provide a Content-Location
for the particular variant which is returned. for the particular variant which is returned.
skipping to change at page 23, line 16 skipping to change at page 24, line 4
Content-Location = "Content-Location" ":" Content-Location = "Content-Location" ":"
( absoluteURI | relativeURI ) ( absoluteURI | relativeURI )
The value of Content-Location also defines the base URI for the The value of Content-Location also defines the base URI for the
entity. entity.
The Content-Location value is not a replacement for the original The Content-Location value is not a replacement for the original
requested URI; it is only a statement of the location of the resource requested URI; it is only a statement of the location of the resource
corresponding to this particular entity at the time of the request. corresponding to this particular entity at the time of the request.
Future requests MAY specify the Content-Location URI as the request- Future requests MAY specify the Content-Location URI as the request-
URI if the desire is to identify the source of that particular URI if the desire is to identify the source of that particular
entity. entity.
A cache cannot assume that an entity with a Content-Location A cache cannot assume that an entity with a Content-Location
different from the URI used to retrieve it can be used to respond to different from the URI used to retrieve it can be used to respond to
later requests on that Content-Location URI. However, the Content- later requests on that Content-Location URI. However, the Content-
Location can be used to differentiate between multiple entities Location can be used to differentiate between multiple entities
retrieved from a single requested resource, as described in Section 7 retrieved from a single requested resource, as described in Section 8
of [Part6]. of [Part6].
If the Content-Location is a relative URI, the relative URI is If the Content-Location is a relative URI, the relative URI is
interpreted relative to the Request-URI. interpreted relative to the Request-URI.
The meaning of the Content-Location header in PUT or POST requests is The meaning of the Content-Location header in PUT or POST requests is
undefined; servers are free to ignore it in those cases. undefined; servers are free to ignore it in those cases.
5.8. Content-MD5 6.8. Content-MD5
The Content-MD5 entity-header field, as defined in [RFC1864], is an The Content-MD5 entity-header field, as defined in [RFC1864], is an
MD5 digest of the entity-body for the purpose of providing an end-to- MD5 digest of the entity-body for the purpose of providing an end-to-
end message integrity check (MIC) of the entity-body. (Note: a MIC end message integrity check (MIC) of the entity-body. (Note: a MIC
is good for detecting accidental modification of the entity-body in is good for detecting accidental modification of the entity-body in
transit, but is not proof against malicious attacks.) transit, but is not proof against malicious attacks.)
Content-MD5 = "Content-MD5" ":" md5-digest Content-MD5 = "Content-MD5" ":" md5-digest
md5-digest = <base64 of 128 bit MD5 digest as per [RFC1864]> md5-digest = <base64 of 128 bit MD5 digest as per [RFC1864]>
skipping to change at page 24, line 47 skipping to change at page 25, line 34
in which the application of Content-MD5 to HTTP entity-bodies in which the application of Content-MD5 to HTTP entity-bodies
differs from its application to MIME entity-bodies. One is that differs from its application to MIME entity-bodies. One is that
HTTP, unlike MIME, does not use Content-Transfer-Encoding, and HTTP, unlike MIME, does not use Content-Transfer-Encoding, and
does use Transfer-Encoding and Content-Encoding. Another is that does use Transfer-Encoding and Content-Encoding. Another is that
HTTP more frequently uses binary content types than MIME, so it is HTTP more frequently uses binary content types than MIME, so it is
worth noting that, in such cases, the byte order used to compute worth noting that, in such cases, the byte order used to compute
the digest is the transmission byte order defined for the type. the digest is the transmission byte order defined for the type.
Lastly, HTTP allows transmission of text types with any of several Lastly, HTTP allows transmission of text types with any of several
line break conventions and not just the canonical form using CRLF. line break conventions and not just the canonical form using CRLF.
5.9. Content-Type 6.9. Content-Type
The Content-Type entity-header field indicates the media type of the The Content-Type entity-header field indicates the media type of the
entity-body sent to the recipient or, in the case of the HEAD method, entity-body sent to the recipient or, in the case of the HEAD method,
the media type that would have been sent had the request been a GET. the media type that would have been sent had the request been a GET.
Content-Type = "Content-Type" ":" media-type Content-Type = "Content-Type" ":" media-type
Media types are defined in Section 2.3. An example of the field is Media types are defined in Section 3.3. An example of the field is
Content-Type: text/html; charset=ISO-8859-4 Content-Type: text/html; charset=ISO-8859-4
Further discussion of methods for identifying the media type of an Further discussion of methods for identifying the media type of an
entity is provided in Section 3.2.1. entity is provided in Section 4.2.1.
6. IANA Considerations 7. IANA Considerations
TBD. [[anchor1: TBD.]]
7. Security Considerations 8. Security Considerations
This section is meant to inform application developers, information This section is meant to inform application developers, information
providers, and users of the security limitations in HTTP/1.1 as providers, and users of the security limitations in HTTP/1.1 as
described by this document. The discussion does not include described by this document. The discussion does not include
definitive solutions to the problems revealed, though it does make definitive solutions to the problems revealed, though it does make
some suggestions for reducing security risks. some suggestions for reducing security risks.
7.1. Privacy Issues Connected to Accept Headers 8.1. Privacy Issues Connected to Accept Headers
Accept request-headers can reveal information about the user to all Accept request-headers can reveal information about the user to all
servers which are accessed. The Accept-Language header in particular servers which are accessed. The Accept-Language header in particular
can reveal information the user would consider to be of a private can reveal information the user would consider to be of a private
nature, because the understanding of particular languages is often nature, because the understanding of particular languages is often
strongly correlated to the membership of a particular ethnic group. strongly correlated to the membership of a particular ethnic group.
User agents which offer the option to configure the contents of an User agents which offer the option to configure the contents of an
Accept-Language header to be sent in every request are strongly Accept-Language header to be sent in every request are strongly
encouraged to let the configuration process include a message which encouraged to let the configuration process include a message which
makes the user aware of the loss of privacy involved. makes the user aware of the loss of privacy involved.
skipping to change at page 26, line 14 skipping to change at page 27, line 5
many users not behind a proxy, the network address of the host many users not behind a proxy, the network address of the host
running the user agent will also serve as a long-lived user running the user agent will also serve as a long-lived user
identifier. In environments where proxies are used to enhance identifier. In environments where proxies are used to enhance
privacy, user agents ought to be conservative in offering accept privacy, user agents ought to be conservative in offering accept
header configuration options to end users. As an extreme privacy header configuration options to end users. As an extreme privacy
measure, proxies could filter the accept headers in relayed requests. measure, proxies could filter the accept headers in relayed requests.
General purpose user agents which provide a high degree of header General purpose user agents which provide a high degree of header
configurability SHOULD warn users about the loss of privacy which can configurability SHOULD warn users about the loss of privacy which can
be involved. be involved.
7.2. Content-Disposition Issues 8.2. Content-Disposition Issues
[RFC1806], from which the often implemented Content-Disposition (see [RFC1806], from which the often implemented Content-Disposition (see
Appendix B.1) header in HTTP is derived, has a number of very serious Appendix B.1) header in HTTP is derived, has a number of very serious
security considerations. Content-Disposition is not part of the HTTP security considerations. Content-Disposition is not part of the HTTP
standard, but since it is widely implemented, we are documenting its standard, but since it is widely implemented, we are documenting its
use and risks for implementors. See [RFC2183] (which updates use and risks for implementors. See [RFC2183] (which updates
[RFC1806]) for details. [RFC1806]) for details.
8. Acknowledgments 9. Acknowledgments
9. References 10. References
9.1. Normative References 10.1. Normative References
[ISO-8859-1] [ISO-8859-1]
International Organization for Standardization, International Organization for Standardization,
"Information technology -- 8-bit single-byte coded graphic "Information technology -- 8-bit single-byte coded graphic
character sets -- Part 1: Latin alphabet No. 1", ISO/ character sets -- Part 1: Latin alphabet No. 1", ISO/
IEC 8859-1:1998, 1998. IEC 8859-1:1998, 1998.
[Part1] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H., [Part1] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed., Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed.,
and J. Reschke, Ed., "HTTP/1.1, part 1: URIs, Connections, and J. Reschke, Ed., "HTTP/1.1, part 1: URIs, Connections,
and Message Parsing", draft-ietf-httpbis-p1-messaging-01 and Message Parsing", draft-ietf-httpbis-p1-messaging-02
(work in progress), January 2008. (work in progress), February 2008.
[Part2] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H., [Part2] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed., Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed.,
and J. Reschke, Ed., "HTTP/1.1, part 2: Message and J. Reschke, Ed., "HTTP/1.1, part 2: Message
Semantics", draft-ietf-httpbis-p2-semantics-01 (work in Semantics", draft-ietf-httpbis-p2-semantics-02 (work in
progress), January 2008. progress), February 2008.
[Part4] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H., [Part4] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed., Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed.,
and J. Reschke, Ed., "HTTP/1.1, part 4: Conditional and J. Reschke, Ed., "HTTP/1.1, part 4: Conditional
Requests", draft-ietf-httpbis-p4-conditional-01 (work in Requests", draft-ietf-httpbis-p4-conditional-02 (work in
progress), January 2008. progress), February 2008.
[Part5] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H., [Part5] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed., Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed.,
and J. Reschke, Ed., "HTTP/1.1, part 5: Range Requests and and J. Reschke, Ed., "HTTP/1.1, part 5: Range Requests and
Partial Responses", draft-ietf-httpbis-p5-range-01 (work Partial Responses", draft-ietf-httpbis-p5-range-02 (work
in progress), January 2008. in progress), February 2008.
[Part6] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H., [Part6] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed., Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed.,
and J. Reschke, Ed., "HTTP/1.1, part 6: Caching", and J. Reschke, Ed., "HTTP/1.1, part 6: Caching",
draft-ietf-httpbis-p6-cache-01 (work in progress), draft-ietf-httpbis-p6-cache-02 (work in progress),
January 2008. February 2008.
[RFC1766] Alvestrand, H., "Tags for the Identification of [RFC1766] Alvestrand, H., "Tags for the Identification of
Languages", RFC 1766, March 1995. Languages", RFC 1766, March 1995.
[RFC1864] Myers, J. and M. Rose, "The Content-MD5 Header Field", [RFC1864] Myers, J. and M. Rose, "The Content-MD5 Header Field",
RFC 1864, October 1995. RFC 1864, October 1995.
[RFC1950] Deutsch, L. and J-L. Gailly, "ZLIB Compressed Data Format [RFC1950] Deutsch, L. and J-L. Gailly, "ZLIB Compressed Data Format
Specification version 3.3", RFC 1950, May 1996. Specification version 3.3", RFC 1950, May 1996.
skipping to change at page 28, line 16 skipping to change at page 29, line 6
Extensions (MIME) Part One: Format of Internet Message Extensions (MIME) Part One: Format of Internet Message
Bodies", RFC 2045, November 1996. Bodies", RFC 2045, November 1996.
[RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail [RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part Two: Media Types", RFC 2046, Extensions (MIME) Part Two: Media Types", RFC 2046,
November 1996. November 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4288] Freed, N. and J. Klensin, "Media Type Specifications and 10.2. Informative References
Registration Procedures", BCP 13, RFC 4288, December 2005.
9.2. Informative References
[RFC1806] Troost, R. and S. Dorner, "Communicating Presentation [RFC1806] Troost, R. and S. Dorner, "Communicating Presentation
Information in Internet Messages: The Content-Disposition Information in Internet Messages: The Content-Disposition
Header", RFC 1806, June 1995. Header", RFC 1806, June 1995.
[RFC1945] Berners-Lee, T., Fielding, R., and H. Nielsen, "Hypertext [RFC1945] Berners-Lee, T., Fielding, R., and H. Nielsen, "Hypertext
Transfer Protocol -- HTTP/1.0", RFC 1945, May 1996. Transfer Protocol -- HTTP/1.0", RFC 1945, May 1996.
[RFC2049] Freed, N. and N. Borenstein, "Multipurpose Internet Mail [RFC2049] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part Five: Conformance Criteria and Extensions (MIME) Part Five: Conformance Criteria and
skipping to change at page 29, line 15 skipping to change at page 29, line 50
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., [RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999. Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
[RFC2822] Resnick, P., "Internet Message Format", RFC 2822, [RFC2822] Resnick, P., "Internet Message Format", RFC 2822,
April 2001. April 2001.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", RFC 3629, STD 63, November 2003. 10646", RFC 3629, STD 63, November 2003.
[RFC4288] Freed, N. and J. Klensin, "Media Type Specifications and
Registration Procedures", BCP 13, RFC 4288, December 2005.
Appendix A. Differences Between HTTP Entities and RFC 2045 Entities Appendix A. Differences Between HTTP Entities and RFC 2045 Entities
HTTP/1.1 uses many of the constructs defined for Internet Mail HTTP/1.1 uses many of the constructs defined for Internet Mail
([RFC2822]) and the Multipurpose Internet Mail Extensions (MIME ([RFC2822]) and the Multipurpose Internet Mail Extensions (MIME
[RFC2045]) to allow entities to be transmitted in an open variety of [RFC2045]) to allow entities to be transmitted in an open variety of
representations and with extensible mechanisms. However, RFC 2045 representations and with extensible mechanisms. However, RFC 2045
discusses mail, and HTTP has a few features that are different from discusses mail, and HTTP has a few features that are different from
those described in RFC 2045. These differences were carefully chosen those described in RFC 2045. These differences were carefully chosen
to optimize performance over binary connections, to allow greater to optimize performance over binary connections, to allow greater
freedom in the use of new media types, to make date comparisons freedom in the use of new media types, to make date comparisons
skipping to change at page 30, line 9 skipping to change at page 30, line 45
MIME-Version = "MIME-Version" ":" 1*DIGIT "." 1*DIGIT MIME-Version = "MIME-Version" ":" 1*DIGIT "." 1*DIGIT
MIME version "1.0" is the default for use in HTTP/1.1. However, MIME version "1.0" is the default for use in HTTP/1.1. However,
HTTP/1.1 message parsing and semantics are defined by this document HTTP/1.1 message parsing and semantics are defined by this document
and not the MIME specification. and not the MIME specification.
A.2. Conversion to Canonical Form A.2. Conversion to Canonical Form
[RFC2045] requires that an Internet mail entity be converted to [RFC2045] requires that an Internet mail entity be converted to
canonical form prior to being transferred, as described in Section 4 canonical form prior to being transferred, as described in Section 4
of [RFC2049]. Section 2.3.1 of this document describes the forms of [RFC2049]. Section 3.3.1 of this document describes the forms
allowed for subtypes of the "text" media type when transmitted over allowed for subtypes of the "text" media type when transmitted over
HTTP. [RFC2046] requires that content with a type of "text" HTTP. [RFC2046] requires that content with a type of "text"
represent line breaks as CRLF and forbids the use of CR or LF outside represent line breaks as CRLF and forbids the use of CR or LF outside
of line break sequences. HTTP allows CRLF, bare CR, and bare LF to of line break sequences. HTTP allows CRLF, bare CR, and bare LF to
indicate a line break within text content when a message is indicate a line break within text content when a message is
transmitted over HTTP. transmitted over HTTP.
Where it is possible, a proxy or gateway from HTTP to a strict MIME Where it is possible, a proxy or gateway from HTTP to a strict MIME
environment SHOULD translate all line breaks within the text media environment SHOULD translate all line breaks within the text media
types described in Section 2.3.1 of this document to the RFC 2049 types described in Section 3.3.1 of this document to the RFC 2049
canonical form of CRLF. Note, however, that this might be canonical form of CRLF. Note, however, that this might be
complicated by the presence of a Content-Encoding and by the fact complicated by the presence of a Content-Encoding and by the fact
that HTTP allows the use of some character sets which do not use that HTTP allows the use of some character sets which do not use
octets 13 and 10 to represent CR and LF, as is the case for some octets 13 and 10 to represent CR and LF, as is the case for some
multi-byte character sets. multi-byte character sets.
Implementors should note that conversion will break any cryptographic Implementors should note that conversion will break any cryptographic
checksums applied to the original content unless the original content checksums applied to the original content unless the original content
is already in canonical form. Therefore, the canonical form is is already in canonical form. Therefore, the canonical form is
recommended for any content that uses such checksums in HTTP. recommended for any content that uses such checksums in HTTP.
skipping to change at page 31, line 23 skipping to change at page 32, line 13
to forwarding a message via a MIME-compliant protocol. to forwarding a message via a MIME-compliant protocol.
A.6. MHTML and Line Length Limitations A.6. MHTML and Line Length Limitations
HTTP implementations which share code with MHTML [RFC2557] HTTP implementations which share code with MHTML [RFC2557]
implementations need to be aware of MIME line length limitations. implementations need to be aware of MIME line length limitations.
Since HTTP does not have this limitation, HTTP does not fold long Since HTTP does not have this limitation, HTTP does not fold long
lines. MHTML messages being transported by HTTP follow all lines. MHTML messages being transported by HTTP follow all
conventions of MHTML, including line length limitations and folding, conventions of MHTML, including line length limitations and folding,
canonicalization, etc., since HTTP transports all message-bodies as canonicalization, etc., since HTTP transports all message-bodies as
payload (see Section 2.3.2) and does not interpret the content or any payload (see Section 3.3.2) and does not interpret the content or any
MIME header lines that might be contained therein. MIME header lines that might be contained therein.
Appendix B. Additional Features Appendix B. Additional Features
[RFC1945] and [RFC2068] document protocol elements used by some [RFC1945] and [RFC2068] document protocol elements used by some
existing HTTP implementations, but not consistently and correctly existing HTTP implementations, but not consistently and correctly
across most HTTP/1.1 applications. Implementors are advised to be across most HTTP/1.1 applications. Implementors are advised to be
aware of these features, but cannot rely upon their presence in, or aware of these features, but cannot rely upon their presence in, or
interoperability with, other HTTP/1.1 applications. Some of these interoperability with, other HTTP/1.1 applications. Some of these
describe proposed experimental features, and some describe features describe proposed experimental features, and some describe features
skipping to change at page 32, line 20 skipping to change at page 33, line 4
disp-extension-token = token disp-extension-token = token
disp-extension-parm = token "=" ( token | quoted-string ) disp-extension-parm = token "=" ( token | quoted-string )
An example is An example is
Content-Disposition: attachment; filename="fname.ext" Content-Disposition: attachment; filename="fname.ext"
The receiving user agent SHOULD NOT respect any directory path The receiving user agent SHOULD NOT respect any directory path
information present in the filename-parm parameter, which is the only information present in the filename-parm parameter, which is the only
parameter believed to apply to HTTP implementations at this time. parameter believed to apply to HTTP implementations at this time.
The filename SHOULD be treated as a terminal component only. The filename SHOULD be treated as a terminal component only.
If this header is used in a response with the application/ If this header is used in a response with the application/
octet-stream content-type, the implied suggestion is that the user octet-stream content-type, the implied suggestion is that the user
agent should not display the response, but directly enter a `save agent should not display the response, but directly enter a `save
response as...' dialog. response as...' dialog.
See Section 7.2 for Content-Disposition security issues. See Section 8.2 for Content-Disposition security issues.
Appendix C. Compatibility with Previous Versions Appendix C. Compatibility with Previous Versions
C.1. Changes from RFC 2068 C.1. Changes from RFC 2068
Transfer-coding and message lengths all interact in ways that Transfer-coding and message lengths all interact in ways that
required fixing exactly when chunked encoding is used (to allow for required fixing exactly when chunked encoding is used (to allow for
transfer encoding that may not be self delimiting); it was important transfer encoding that may not be self delimiting); it was important
to straighten out exactly how message lengths are computed. to straighten out exactly how message lengths are computed.
(Section 3.2.2, see also [Part1], [Part5] and [Part6]). (Section 4.2.2, see also [Part1], [Part5] and [Part6]).
Charset wildcarding is introduced to avoid explosion of character set Charset wildcarding is introduced to avoid explosion of character set
names in accept headers. (Section 5.2) names in accept headers. (Section 6.2)
Content-Base was deleted from the specification: it was not Content-Base was deleted from the specification: it was not
implemented widely, and there is no simple, safe way to introduce it implemented widely, and there is no simple, safe way to introduce it
without a robust extension mechanism. In addition, it is used in a without a robust extension mechanism. In addition, it is used in a
similar, but not identical fashion in MHTML [RFC2557]. similar, but not identical fashion in MHTML [RFC2557].
A content-coding of "identity" was introduced, to solve problems A content-coding of "identity" was introduced, to solve problems
discovered in caching. (Section 2.2) discovered in caching. (Section 3.2)
Quality Values of zero should indicate that "I don't want something" Quality Values of zero should indicate that "I don't want something"
to allow clients to refuse a representation. (Section 2.4) to allow clients to refuse a representation. (Section 3.4)
The Alternates, Content-Version, Derived-From, Link, URI, Public and The Alternates, Content-Version, Derived-From, Link, URI, Public and
Content-Base header fields were defined in previous versions of this Content-Base header fields were defined in previous versions of this
specification, but not commonly implemented. See [RFC2068]. specification, but not commonly implemented. See [RFC2068].
C.2. Changes from RFC 2616 C.2. Changes from RFC 2616
Clarify contexts that charset is used in. (Section 2.1) Clarify contexts that charset is used in. (Section 3.1)
Remove reference to non-existant identity transfer-coding value Remove reference to non-existant identity transfer-coding value
tokens. (Appendix A.4) tokens. (Appendix A.4)
Appendix D. Change Log (to be removed by RFC Editor before publication) Appendix D. Change Log (to be removed by RFC Editor before publication)
D.1. Since RFC2616 D.1. Since RFC2616
Extracted relevant partitions from [RFC2616]. Extracted relevant partitions from [RFC2616].
skipping to change at page 33, line 45 skipping to change at page 34, line 35
o <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/25>: "Accept- o <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/25>: "Accept-
Encoding BNF" Encoding BNF"
o <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/35>: "Normative o <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/35>: "Normative
and Informative references" and Informative references"
o <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/46>: "RFC1700 o <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/46>: "RFC1700
references" references"
o <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/55>: "Updating
to RFC4288"
o <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/65>: o <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/65>:
"Informative references" "Informative references"
o <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/66>: o <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/66>:
"ISO-8859-1 Reference" "ISO-8859-1 Reference"
o <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/68>: "Encoding o <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/68>: "Encoding
References Normative" References Normative"
o <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/86>: "Normative o <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/86>: "Normative
up-to-date references" up-to-date references"
D.3. Since draft-ietf-httpbis-p3-payload-01
Ongoing work on ABNF conversion
(<http://www3.tools.ietf.org/wg/httpbis/trac/ticket/36>):
o Add explicit references to BNF syntax and rules imported from
other parts of the specification.
Index Index
A A
Accept header 16 Accept header 16
Accept-Charset header 18 Accept-Charset header 18
Accept-Encoding header 18 Accept-Encoding header 19
Accept-Language header 20 Accept-Language header 20
Alternates header 33 Alternates header 33
C C
compress 7 compress 8
Content-Base header 33 Content-Base header 33
Content-Disposition header 31 Content-Disposition header 32
Content-Encoding header 21 Content-Encoding header 22
Content-Language header 22 Content-Language header 22
Content-Location header 22 Content-Location header 23
Content-MD5 header 23 Content-MD5 header 24
Content-Type header 24 Content-Type header 25
Content-Version header 33 Content-Version header 33
D D
deflate 7 deflate 8
Derived-From header 33 Derived-From header 33
G G
Grammar Grammar
Accept 16 Accept 16
Accept-Charset 18 Accept-Charset 18
Accept-Encoding 18 Accept-Encoding 19
accept-extension 16 accept-extension 16
Accept-Language 20 Accept-Language 20
accept-params 16 accept-params 16
attribute 8 attribute 9
charset 6 charset 7
codings 18 codings 19
content-coding 7 content-coding 7
content-disposition 32 content-disposition 32
Content-Encoding 21 Content-Encoding 22
Content-Language 22 Content-Language 22
Content-Location 23 Content-Location 23
Content-MD5 23 Content-MD5 24
Content-Type 24 Content-Type 25
disp-extension-parm 32 disp-extension-parm 32
disp-extension-token 32 disp-extension-token 32
disposition-parm 32 disposition-parm 32
disposition-type 32 disposition-type 32
entity-body 12 entity-body 12
entity-header 11 entity-header 12
extension-header 11 extension-header 12
filename-parm 32 filename-parm 32
language-range 20 language-range 20
language-tag 11 language-tag 11
md5-digest 23 md5-digest 24
media-range 16 media-range 16
media-type 8 media-type 9
MIME-Version 29 MIME-Version 30
parameter 8 parameter 9
primary-tag 11 primary-tag 11
qvalue 10 qvalue 11
subtag 11 subtag 11
subtype 8 subtype 9
type 8 type 9
value 8 value 9
gzip 7 gzip 8
H H
Headers Headers
Accept 16 Accept 16
Accept-Charset 18 Accept-Charset 18
Accept-Encoding 18 Accept-Encoding 19
Accept-Language 20 Accept-Language 20
Alternate 33 Alternate 33
Content-Base 33 Content-Base 33
Content-Disposition 31 Content-Disposition 32
Content-Encoding 21 Content-Encoding 22
Content-Language 22 Content-Language 22
Content-Location 22 Content-Location 23
Content-MD5 23 Content-MD5 24
Content-Type 24 Content-Type 25
Content-Version 33 Content-Version 33
Derived-From 33 Derived-From 33
Link 33 Link 33
Public 33 Public 33
URI 33 URI 33
I I
identity 8 identity 8
L L
Link header 33 Link header 33
P P
Public header 33 Public header 33
U U
URI header 33 URI header 33
Authors' Addresses Authors' Addresses
 End of changes. 108 change blocks. 
180 lines changed or deleted 223 lines changed or added

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