One document matched: draft-ietf-httpbis-p3-payload-18.xml
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<rfc obsoletes="2616" category="std" ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p3-payload-18">
<front>
<title abbrev="HTTP/1.1, Part 3">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
<author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
<organization abbrev="Adobe">Adobe Systems Incorporated</organization>
<address>
<postal>
<street>345 Park Ave</street>
<city>San Jose</city>
<region>CA</region>
<code>95110</code>
<country>USA</country>
</postal>
<email>fielding@gbiv.com</email>
<uri>http://roy.gbiv.com/</uri>
</address>
</author>
<author initials="J." surname="Gettys" fullname="Jim Gettys">
<organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
<address>
<postal>
<street>21 Oak Knoll Road</street>
<city>Carlisle</city>
<region>MA</region>
<code>01741</code>
<country>USA</country>
</postal>
<email>jg@freedesktop.org</email>
<uri>http://gettys.wordpress.com/</uri>
</address>
</author>
<author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
<organization abbrev="HP">Hewlett-Packard Company</organization>
<address>
<postal>
<street>HP Labs, Large Scale Systems Group</street>
<street>1501 Page Mill Road, MS 1177</street>
<city>Palo Alto</city>
<region>CA</region>
<code>94304</code>
<country>USA</country>
</postal>
<email>JeffMogul@acm.org</email>
</address>
</author>
<author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
<organization abbrev="Microsoft">Microsoft Corporation</organization>
<address>
<postal>
<street>1 Microsoft Way</street>
<city>Redmond</city>
<region>WA</region>
<code>98052</code>
<country>USA</country>
</postal>
<email>henrikn@microsoft.com</email>
</address>
</author>
<author initials="L." surname="Masinter" fullname="Larry Masinter">
<organization abbrev="Adobe">Adobe Systems Incorporated</organization>
<address>
<postal>
<street>345 Park Ave</street>
<city>San Jose</city>
<region>CA</region>
<code>95110</code>
<country>USA</country>
</postal>
<email>LMM@acm.org</email>
<uri>http://larry.masinter.net/</uri>
</address>
</author>
<author initials="P." surname="Leach" fullname="Paul J. Leach">
<organization abbrev="Microsoft">Microsoft Corporation</organization>
<address>
<postal>
<street>1 Microsoft Way</street>
<city>Redmond</city>
<region>WA</region>
<code>98052</code>
</postal>
<email>paulle@microsoft.com</email>
</address>
</author>
<author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
<organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
<address>
<postal>
<street>MIT Computer Science and Artificial Intelligence Laboratory</street>
<street>The Stata Center, Building 32</street>
<street>32 Vassar Street</street>
<city>Cambridge</city>
<region>MA</region>
<code>02139</code>
<country>USA</country>
</postal>
<email>timbl@w3.org</email>
<uri>http://www.w3.org/People/Berners-Lee/</uri>
</address>
</author>
<author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
<organization abbrev="W3C">World Wide Web Consortium</organization>
<address>
<postal>
<street>W3C / ERCIM</street>
<street>2004, rte des Lucioles</street>
<city>Sophia-Antipolis</city>
<region>AM</region>
<code>06902</code>
<country>France</country>
</postal>
<email>ylafon@w3.org</email>
<uri>http://www.raubacapeu.net/people/yves/</uri>
</address>
</author>
<author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
<organization abbrev="greenbytes">greenbytes GmbH</organization>
<address>
<postal>
<street>Hafenweg 16</street>
<city>Muenster</city><region>NW</region><code>48155</code>
<country>Germany</country>
</postal>
<phone>+49 251 2807760</phone>
<facsimile>+49 251 2807761</facsimile>
<email>julian.reschke@greenbytes.de</email>
<uri>http://greenbytes.de/tech/webdav/</uri>
</address>
</author>
<date month="January" year="2012" day="4"/>
<workgroup>HTTPbis Working Group</workgroup>
<abstract>
<t>
The Hypertext Transfer Protocol (HTTP) is an application-level protocol for
distributed, collaborative, hypertext information systems. HTTP has been in
use by the World Wide Web global information initiative since 1990. This
document is Part 3 of the seven-part specification that defines the protocol
referred to as "HTTP/1.1" and, taken together, obsoletes RFC 2616.
</t>
<t>
Part 3 defines HTTP message content, metadata, and content negotiation.
</t>
</abstract>
<note title="Editorial Note (To be removed by RFC Editor)">
<t>
Discussion of this draft should take place on the HTTPBIS working group
mailing list (ietf-http-wg@w3.org), which is archived at
<eref target="http://lists.w3.org/Archives/Public/ietf-http-wg/"/>.
</t>
<t>
The current issues list is at
<eref target="http://tools.ietf.org/wg/httpbis/trac/report/3"/> and related
documents (including fancy diffs) can be found at
<eref target="http://tools.ietf.org/wg/httpbis/"/>.
</t>
<t>
The changes in this draft are summarized in <xref target="changes.since.17"/>.
</t>
</note>
</front>
<middle>
<section title="Introduction" anchor="introduction">
<t>
This document defines HTTP/1.1 message payloads (a.k.a., content), the
associated metadata header fields that define how the payload is intended
to be interpreted by a recipient, the request header fields that
might influence content selection, and the various selection algorithms
that are collectively referred to as HTTP content negotiation.
</t>
<t>
This document is currently disorganized in order to minimize the changes
between drafts and enable reviewers to see the smaller errata changes.
A future draft will reorganize the sections to better reflect the content.
In particular, the sections on entities will be renamed payload and moved
to the first half of the document, while the sections on content negotiation
and associated request header fields will be moved to the second half. The
current mess reflects how widely dispersed these topics and associated
requirements had become in <xref target="RFC2616"/>.
</t>
<section title="Terminology" anchor="terminology">
<t>
This specification uses a number of terms to refer to the roles
played by participants in, and objects of, the HTTP communication.
</t>
<t>
<iref item="content negotiation"/>
<?rfc needLines="4"?>content negotiation
<list>
<t>
The mechanism for selecting the appropriate representation when
servicing a request. The representation in any response
can be negotiated (including error responses).
</t>
</list>
</t>
</section>
<section title="Conformance and Error Handling" anchor="intro.conformance.and.error.handling">
<t>
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in <xref target="RFC2119"/>.
</t>
<t>
This document defines conformance criteria for several roles in HTTP
communication, including Senders, Recipients, Clients, Servers, User-Agents,
Origin Servers, Intermediaries, Proxies and Gateways. See Section 2 of <xref target="Part1"/>
for definitions of these terms.
</t>
<t>
An implementation is considered conformant if it complies with all of the
requirements associated with its role(s). Note that SHOULD-level requirements
are relevant here, unless one of the documented exceptions is applicable.
</t>
<t>
This document also uses ABNF to define valid protocol elements
(<xref target="notation"/>). In addition to the prose requirements placed
upon them, Senders MUST NOT generate protocol elements that are invalid.
</t>
<t>
Unless noted otherwise, Recipients MAY take steps to recover a usable
protocol element from an invalid construct. However, HTTP does not define
specific error handling mechanisms, except in cases where it has direct
impact on security. This is because different uses of the protocol require
different error handling strategies; for example, a Web browser may wish to
transparently recover from a response where the Location header field
doesn't parse according to the ABNF, whereby in a systems control protocol
using HTTP, this type of error recovery could lead to dangerous consequences.
</t>
</section>
<section title="Syntax Notation" anchor="notation">
<t>
This specification uses the ABNF syntax defined in Section 1.2 of <xref target="Part1"/> (which
extends the syntax defined in <xref target="RFC5234"/> with a list rule).
<xref target="collected.abnf"/> shows the collected ABNF, with the list
rule expanded.
</t>
<t>
The following core rules are included by
reference, as defined in <xref target="RFC5234"/>, Appendix B.1:
ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
DIGIT (decimal 0-9), DQUOTE (double quote),
HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
OCTET (any 8-bit sequence of data), SP (space), and
VCHAR (any visible US-ASCII character).
</t>
<section title="Core Rules" anchor="core.rules">
<t>
The core rules below are defined in <xref target="Part1"/>:
</t>
<figure><artwork type="abnf2616"><![CDATA[
OWS = <OWS, defined in [Part1], Section 1.2.2>
token = <token, defined in [Part1], Section 3.2.3>
word = <word, defined in [Part1], Section 3.2.3>
]]></artwork></figure>
</section>
<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
<t>
The ABNF rules below are defined in other parts:
</t>
<figure><artwork type="abnf2616"><![CDATA[
absolute-URI = <absolute-URI, defined in [Part1], Section 2.7>
partial-URI = <partial-URI, defined in [Part1], Section 2.7>
qvalue = <qvalue, defined in [Part1], Section 5.3>
]]></artwork></figure>
</section>
</section>
</section>
<section title="Protocol Parameters" anchor="protocol.parameters">
<section title="Character Encodings (charset)" anchor="character.sets">
<t>
HTTP uses charset names to indicate the character encoding of a
textual representation.
</t>
<t anchor="rule.charset">
A character encoding is identified by a case-insensitive token. The
complete set of tokens is defined by the IANA Character Set registry
(<eref target="http://www.iana.org/assignments/character-sets"/>).
</t>
<figure><iref primary="true" item="Grammar" subitem="charset"/><artwork type="abnf2616"><![CDATA[
charset = token
]]></artwork></figure>
<t>
Although HTTP allows an arbitrary token to be used as a charset
value, any token that has a predefined value within the IANA
Character Set registry MUST represent the character encoding defined
by that registry. Applications SHOULD limit their use of character
encodings to those defined within the IANA registry.
</t>
<t>
HTTP uses charset in two contexts: within an Accept-Charset request
header field (in which the charset value is an unquoted token) and as the
value of a parameter in a Content-Type header field (within a request or
response), in which case the parameter value of the charset parameter
can be quoted.
</t>
<t>
Implementors need to be aware of IETF character set requirements <xref target="RFC3629"/>
<xref target="RFC2277"/>.
</t>
</section>
<section title="Content Codings" anchor="content.codings">
<t>
Content coding values indicate an encoding transformation that has
been or can be applied to a representation. Content codings are primarily
used to allow a representation to be compressed or otherwise usefully
transformed without losing the identity of its underlying media type
and without loss of information. Frequently, the representation is stored in
coded form, transmitted directly, and only decoded by the recipient.
</t>
<figure><iref primary="true" item="Grammar" subitem="content-coding"/><artwork type="abnf2616"><![CDATA[
content-coding = token
]]></artwork></figure>
<t>
All content-coding values are case-insensitive. HTTP/1.1 uses
content-coding values in the Accept-Encoding (<xref target="header.accept-encoding"/>) and
Content-Encoding (<xref target="header.content-encoding"/>) header fields. Although the value
describes the content-coding, what is more important is that it
indicates what decoding mechanism will be required to remove the
encoding.
</t>
<t>
compress<iref item="compress (Coding Format)"/><iref item="Coding Format" subitem="compress"/>
<list>
<t>
See Section 5.1.2.1 of <xref target="Part1"/>.
</t>
</list>
</t>
<t>
deflate<iref item="deflate (Coding Format)"/><iref item="Coding Format" subitem="deflate"/>
<list>
<t>
See Section 5.1.2.2 of <xref target="Part1"/>.
</t>
</list>
</t>
<t>
gzip<iref item="gzip (Coding Format)"/><iref item="Coding Format" subitem="gzip"/>
<list>
<t>
See Section 5.1.2.3 of <xref target="Part1"/>.
</t>
</list>
</t>
<section title="Content Coding Registry" anchor="content.coding.registry">
<t>
The HTTP Content Coding Registry defines the name space for the content
coding names.
</t>
<t>
Registrations MUST include the following fields:
<list style="symbols">
<t>Name</t>
<t>Description</t>
<t>Pointer to specification text</t>
</list>
</t>
<t>
Names of content codings MUST NOT overlap with names of transfer codings
(Section 5.1 of <xref target="Part1"/>), unless the encoding transformation is identical (as it
is the case for the compression codings defined in
Section 5.1.2 of <xref target="Part1"/>).
</t>
<t>
Values to be added to this name space require a specification
(see "Specification Required" in
Section 4.1 of <xref target="RFC5226"/>), and MUST
conform to the purpose of content coding defined in this section.
</t>
<t>
The registry itself is maintained at
<eref target="http://www.iana.org/assignments/http-parameters"/>.
</t>
</section>
</section>
<section title="Media Types" anchor="media.types">
<t>
HTTP uses Internet Media Types <xref target="RFC2046"/> in the Content-Type (<xref target="header.content-type"/>)
and Accept (<xref target="header.accept"/>) header fields in order to provide
open and extensible data typing and type negotiation.
</t>
<figure><iref primary="true" item="Grammar" subitem="media-type"/><iref primary="true" item="Grammar" subitem="type"/><iref primary="true" item="Grammar" subitem="subtype"/><artwork type="abnf2616"><![CDATA[
media-type = type "/" subtype *( OWS ";" OWS parameter )
type = token
subtype = token
]]></artwork></figure>
<t anchor="rule.parameter">
The type/subtype MAY be followed by parameters in the form of
attribute/value pairs.
</t>
<figure><iref primary="true" item="Grammar" subitem="parameter"/><iref primary="true" item="Grammar" subitem="attribute"/><iref primary="true" item="Grammar" subitem="value"/><artwork type="abnf2616"><![CDATA[
parameter = attribute "=" value
attribute = token
value = word
]]></artwork></figure>
<t>
The type, subtype, and parameter attribute names are case-insensitive.
Parameter values might or might not be case-sensitive, depending on the
semantics of the parameter name. The presence or absence of a parameter might
be significant to the processing of a media-type, depending on its
definition within the media type registry.
</t>
<t>
A parameter value that matches the <xref target="core.rules" format="none">token</xref> production can be
transmitted as either a token or within a quoted-string. The quoted and
unquoted values are equivalent.
</t>
<t>
Note that some older HTTP applications do not recognize media type
parameters. When sending data to older HTTP applications,
implementations SHOULD only use media type parameters when they are
required by that type/subtype definition.
</t>
<t>
Media-type values are registered with the Internet Assigned Number
Authority (IANA). The media type registration process is
outlined in <xref target="RFC4288"/>. Use of non-registered media types is
discouraged.
</t>
<section title="Canonicalization and Text Defaults" anchor="canonicalization.and.text.defaults">
<t>
Internet media types are registered with a canonical form. A
representation transferred via HTTP messages MUST be in the
appropriate canonical form prior to its transmission except for
"text" types, as defined in the next paragraph.
</t>
<t>
When in canonical form, media subtypes of the "text" type use CRLF as
the text line break. HTTP relaxes this requirement and allows the
transport of text media with plain CR or LF alone representing a line
break when it is done consistently for an entire representation. HTTP
applications MUST accept CRLF, bare CR, and bare LF as indicating
a line break in text media received via HTTP. In
addition, if the text is in a character encoding that does not
use octets 13 and 10 for CR and LF respectively, as is the case for
some multi-byte character encodings, HTTP allows the use of whatever octet
sequences are defined by that character encoding to represent the
equivalent of CR and LF for line breaks. This flexibility regarding
line breaks applies only to text media in the payload body; a bare CR
or LF MUST NOT be substituted for CRLF within any of the HTTP control
structures (such as header fields and multipart boundaries).
</t>
<t>
If a representation is encoded with a content-coding, the underlying
data MUST be in a form defined above prior to being encoded.
</t>
</section>
<section title="Multipart Types" anchor="multipart.types">
<t>
MIME provides for a number of "multipart" types — encapsulations of
one or more representations within a single message-body. All multipart
types share a common syntax, as defined in Section 5.1.1 of <xref target="RFC2046"/>,
and MUST include a boundary parameter as part of the media type
value. The message body is itself a protocol element and MUST
therefore use only CRLF to represent line breaks between body-parts.
</t>
<t>
In general, HTTP treats a multipart message-body no differently than
any other media type: strictly as payload. HTTP does not use the
multipart boundary as an indicator of message-body length.
<!-- jre: re-insert removed text pointing to caching? -->
In all other respects, an HTTP user agent SHOULD follow the same or similar
behavior as a MIME user agent would upon receipt of a multipart type.
The MIME header fields within each body-part of a multipart message-body
do not have any significance to HTTP beyond that defined by
their MIME semantics.
</t>
<t>
If an application receives an unrecognized multipart subtype, the
application MUST treat it as being equivalent to "multipart/mixed".
</t>
<t><list>
<t>
Note: The "multipart/form-data" type has been specifically defined
for carrying form data suitable for processing via the POST
request method, as described in <xref target="RFC2388"/>.
</t>
</list></t>
</section>
</section>
<section title="Language Tags" anchor="language.tags">
<t>
A language tag, as defined in <xref target="RFC5646"/>, identifies a
natural language spoken, written, or otherwise conveyed by human beings for
communication of information to other human beings. Computer languages are
explicitly excluded. HTTP uses language tags within the Accept-Language and
Content-Language fields.
</t>
<t>
In summary, a language tag is composed of one or more parts: A primary
language subtag followed by a possibly empty series of subtags:
</t>
<figure><iref primary="true" item="Grammar" subitem="language-tag"/><artwork type="abnf2616"><![CDATA[
language-tag = <Language-Tag, defined in [RFC5646], Section 2.1>
]]></artwork></figure>
<t>
White space is not allowed within the tag and all tags are case-insensitive.
The name space of language subtags is administered by the IANA (see
<eref target="http://www.iana.org/assignments/language-subtag-registry"/>).
</t>
<figure>
<preamble>Example tags include:</preamble>
<artwork type="example"><![CDATA[
en, en-US, es-419, az-Arab, x-pig-latin, man-Nkoo-GN
]]></artwork>
</figure>
<t>
See <xref target="RFC5646"/> for further information.
</t>
</section>
</section>
<section title="Payload" anchor="payload">
<t>
HTTP messages MAY transfer a payload if not otherwise restricted by
the request method or response status code. The payload consists of
metadata, in the form of header fields, and data, in the form of the
sequence of octets in the message-body after any transfer-coding has
been decoded.
</t>
<iref item="payload"/>
<t>
A "payload" in HTTP is always a partial or complete
representation of some resource. We use separate terms for payload
and representation because some messages contain only the associated
representation's header fields (e.g., responses to HEAD) or only some
part(s) of the representation (e.g., the 206 status code).
</t>
<section title="Payload Header Fields" anchor="payload.header.fields">
<t>
HTTP header fields that specifically define the payload, rather than the
associated representation, are referred to as "payload header fields".
The following payload header fields are defined by HTTP/1.1:
</t>
<texttable align="left">
<ttcol>Header Field Name</ttcol>
<ttcol>Defined in...</ttcol>
<c>Content-Length</c> <c>Section 8.2 of <xref target="Part1"/></c>
<c>Content-Range</c> <c>Section 5.2 of <xref target="Part5"/></c>
</texttable>
</section>
<section title="Payload Body" anchor="payload.body">
<t>
A payload body is only present in a message when a message-body is
present, as described in Section 3.3 of <xref target="Part1"/>. The payload body is obtained
from the message-body by decoding any Transfer-Encoding that might
have been applied to ensure safe and proper transfer of the message.
</t>
</section>
</section>
<section title="Representation" anchor="representation">
<iref item="representation"/>
<t>
A "representation" is information in a format that can be readily
communicated from one party to another. A resource representation
is information that reflects the state of that resource, as observed
at some point in the past (e.g., in a response to GET) or to be
desired at some point in the future (e.g., in a PUT request).
</t>
<t>
Most, but not all, representations transferred via HTTP are intended
to be a representation of the target resource (the resource identified
by the effective request URI). The precise semantics of a representation
are determined by the type of message (request or response), the request
method, the response status code, and the representation metadata.
For example, the above semantic is true for the representation in any
200 (OK) response to GET and for the representation in any PUT request.
A 200 response to PUT, in contrast, contains either a representation
that describes the successful action or a representation of the target
resource, with the latter indicated by a Content-Location header field
with the same value as the effective request URI. Likewise, response
messages with an error status code usually contain a representation that
describes the error and what next steps are suggested for resolving it.
</t>
<section title="Representation Header Fields" anchor="representation.header.fields">
<t>
Representation header fields define metadata about the representation data
enclosed in the message-body or, if no message-body is present, about
the representation that would have been transferred in a 200 response
to a simultaneous GET request with the same effective request URI.
</t>
<t>
The following header fields are defined as representation metadata:
</t>
<texttable align="left">
<ttcol>Header Field Name</ttcol>
<ttcol>Defined in...</ttcol>
<c>Content-Encoding</c> <c><xref target="header.content-encoding"/></c>
<c>Content-Language</c> <c><xref target="header.content-language"/></c>
<c>Content-Location</c> <c><xref target="header.content-location"/></c>
<c>Content-Type</c> <c><xref target="header.content-type"/></c>
<c>Expires</c> <c>Section 3.3 of <xref target="Part6"/></c>
<c>Last-Modified</c> <c>Section 2.2 of <xref target="Part4"/></c>
</texttable>
</section>
<section title="Representation Data" anchor="representation.data">
<t>
The representation body associated with an HTTP message is
either provided as the payload body of the message or
referred to by the message semantics and the effective request
URI. The representation data is in a format and encoding defined by
the representation metadata header fields.
</t>
<t>
The data type of the representation data
is determined via the header fields Content-Type and Content-Encoding.
These define a two-layer, ordered encoding model:
</t>
<figure><artwork type="example"><![CDATA[
representation-data := Content-Encoding( Content-Type( bits ) )
]]></artwork></figure>
<t>
Content-Type specifies the media type of the underlying data, which
defines both the data format and how that data SHOULD be processed
by the recipient (within the scope of the request method semantics).
Any HTTP/1.1 message containing a payload body SHOULD include a
Content-Type header field defining the media type of the associated
representation unless that metadata is unknown to the sender.
If the Content-Type header field is not present, it indicates that
the sender does not know the media type of the representation;
recipients MAY either assume that the media type is
"application/octet-stream" (<xref target="RFC2046"/>, Section 4.5.1)
or examine the content to determine its type.
</t>
<t>
In practice, resource owners do not always properly configure their origin
server to provide the correct Content-Type for a given representation,
with the result that some clients will examine a response body's content
and override the specified type.
Clients that do so risk drawing incorrect conclusions, which might expose
additional security risks (e.g., "privilege escalation"). Furthermore,
it is impossible to determine the sender's intent by examining the data
format: many data formats match multiple media types that differ only in
processing semantics. Implementers are encouraged to provide a means of
disabling such "content sniffing" when it is used.
</t>
<t>
Content-Encoding is used to indicate any additional content
codings applied to the data, usually for the purpose of data
compression, that are a property of the representation. If
Content-Encoding is not present, then there is no additional
encoding beyond that defined by the Content-Type.
</t>
</section>
</section>
<section title="Content Negotiation" anchor="content.negotiation">
<t>
HTTP responses include a representation which contains information for
interpretation, whether by a human user or for further processing.
Often, the server has different ways of representing the
same information; for example, in different formats, languages,
or using different character encodings.
</t>
<t>
HTTP clients and their users might have different or variable
capabilities, characteristics or preferences which would influence
which representation, among those available from the server,
would be best for the server to deliver. For this reason, HTTP
provides mechanisms for "content negotiation" — a process of
allowing selection of a representation of a given resource,
when more than one is available.
</t>
<t>
This specification defines two patterns of content negotiation;
"server-driven", where the server selects the representation based
upon the client's stated preferences, and "agent-driven" negotiation,
where the server provides a list of representations for the client to
choose from, based upon their metadata. In addition, there are
other patterns: some applications use an "active content" pattern,
where the server returns active content which runs on the client
and, based on client available parameters, selects additional
resources to invoke. "Transparent Content Negotiation" (<xref target="RFC2295"/>)
has also been proposed.
</t>
<t>
These patterns are all widely used, and have trade-offs in applicability
and practicality. In particular, when the number of preferences or
capabilities to be expressed by a client are large (such as when many
different formats are supported by a user-agent), server-driven
negotiation becomes unwieldy, and might not be appropriate. Conversely,
when the number of representations to choose from is very large,
agent-driven negotiation might not be appropriate.
</t>
<t>
Note that in all cases, the supplier of representations has the
responsibility for determining which representations might be
considered to be the "same information".
</t>
<section title="Server-driven Negotiation" anchor="server-driven.negotiation">
<t>
If the selection of the best representation for a response is made by
an algorithm located at the server, it is called server-driven
negotiation. Selection is based on the available representations of
the response (the dimensions over which it can vary; e.g., language,
content-coding, etc.) and the contents of particular header fields in
the request message or on other information pertaining to the request
(such as the network address of the client).
</t>
<t>
Server-driven negotiation is advantageous when the algorithm for
selecting from among the available representations is difficult to
describe to the user agent, or when the server desires to send its
"best guess" to the client along with the first response (hoping to
avoid the round-trip delay of a subsequent request if the "best
guess" is good enough for the user). In order to improve the server's
guess, the user agent MAY include request header fields (Accept,
Accept-Language, Accept-Encoding, etc.) which describe its
preferences for such a response.
</t>
<t>
Server-driven negotiation has disadvantages:
<list style="numbers">
<t>
It is impossible for the server to accurately determine what
might be "best" for any given user, since that would require
complete knowledge of both the capabilities of the user agent
and the intended use for the response (e.g., does the user want
to view it on screen or print it on paper?).
</t>
<t>
Having the user agent describe its capabilities in every
request can be both very inefficient (given that only a small
percentage of responses have multiple representations) and a
potential violation of the user's privacy.
</t>
<t>
It complicates the implementation of an origin server and the
algorithms for generating responses to a request.
</t>
<t>
It might limit a public cache's ability to use the same response
for multiple user's requests.
</t>
</list>
</t>
<t>
Server-driven negotiation allows the user agent to specify its preferences,
but it cannot expect responses to always honour them. For example, the origin
server might not implement server-driven negotiation, or it might decide that
sending a response that doesn't conform to them is better than sending a 406
(Not Acceptable) response.
</t>
<t>
Many of the mechanisms for expressing preferences use quality values to
declare relative preference. See Section 5.3 of <xref target="Part1"/> for more information.
</t>
<t>
HTTP/1.1 includes the following header fields for enabling
server-driven negotiation through description of user agent
capabilities and user preferences: Accept (<xref target="header.accept"/>), Accept-Charset
(<xref target="header.accept-charset"/>), Accept-Encoding (<xref target="header.accept-encoding"/>), Accept-Language
(<xref target="header.accept-language"/>), and User-Agent (Section 9.10 of <xref target="Part2"/>).
However, an origin server is not limited to these dimensions and MAY vary
the response based on any aspect of the request, including aspects
of the connection (e.g., IP address) or information within extension
header fields not defined by this specification.
</t>
<t><list>
<t>
Note: In practice, User-Agent based negotiation is fragile,
because new clients might not be recognized.
</t>
</list></t>
<t>
The Vary header field (Section 3.5 of <xref target="Part6"/>) can be used to express the parameters the
server uses to select a representation that is subject to server-driven
negotiation.
</t>
</section>
<section title="Agent-driven Negotiation" anchor="agent-driven.negotiation">
<t>
With agent-driven negotiation, selection of the best representation
for a response is performed by the user agent after receiving an
initial response from the origin server. Selection is based on a list
of the available representations of the response included within the
header fields or body of the initial response, with each
representation identified by its own URI. Selection from among the
representations can be performed automatically (if the user agent is
capable of doing so) or manually by the user selecting from a
generated (possibly hypertext) menu.
</t>
<t>
Agent-driven negotiation is advantageous when the response would vary
over commonly-used dimensions (such as type, language, or encoding),
when the origin server is unable to determine a user agent's
capabilities from examining the request, and generally when public
caches are used to distribute server load and reduce network usage.
</t>
<t>
Agent-driven negotiation suffers from the disadvantage of needing a
second request to obtain the best alternate representation. This
second request is only efficient when caching is used. In addition,
this specification does not define any mechanism for supporting
automatic selection, though it also does not prevent any such
mechanism from being developed as an extension and used within
HTTP/1.1.
</t>
<t>
This specification defines the 300 (Multiple Choices) and 406 (Not Acceptable)
status codes for enabling agent-driven negotiation when the server is
unwilling or unable to provide a varying response using server-driven
negotiation.
</t>
</section>
</section>
<section title="Header Field Definitions" anchor="header.field.definitions">
<t>
This section defines the syntax and semantics of HTTP/1.1 header fields
related to the payload of messages.
</t>
<section title="Accept" anchor="header.accept">
<iref primary="true" item="Accept header field"/>
<iref primary="true" item="Header Fields" subitem="Accept"/>
<t>
The "Accept" header field can be used by user agents to specify
response media types that are acceptable. Accept header fields can be 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 image.
</t>
<figure><iref primary="true" item="Grammar" subitem="Accept"/><iref primary="true" item="Grammar" subitem="media-range"/><iref primary="true" item="Grammar" subitem="accept-params"/><iref primary="true" item="Grammar" subitem="accept-ext"/><artwork type="abnf2616"><![CDATA[
Accept = #( media-range [ accept-params ] )
media-range = ( "*/*"
/ ( type "/" "*" )
/ ( type "/" subtype )
) *( OWS ";" OWS parameter )
accept-params = OWS ";" OWS "q=" qvalue *( accept-ext )
accept-ext = OWS ";" OWS token [ "=" word ]
]]></artwork></figure>
<t>
The asterisk "*" character is used to group media types into ranges,
with "*/*" indicating all media types and "type/*" indicating all
subtypes of that type. The media-range MAY include media type
parameters that are applicable to that range.
</t>
<t>
Each media-range MAY be followed by one or more accept-params,
beginning with the "q" parameter for indicating a relative quality
factor. The first "q" parameter (if any) separates the media-range
parameter(s) from the accept-params. Quality factors allow the user
or user agent to indicate the relative degree of preference for that
media-range, using the qvalue scale from 0 to 1 (Section 5.3 of <xref target="Part1"/>). The
default value is q=1.
</t>
<t><list>
<t>
Note: Use of the "q" parameter name to separate media type
parameters from Accept extension parameters is due to historical
practice. Although this prevents any media type parameter named
"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
media type registry and the rare usage of any media type
parameters in Accept. Future media types are discouraged from
registering any parameter named "q".
</t>
</list></t>
<t>
The example
</t>
<figure><artwork type="example"><![CDATA[
Accept: audio/*; q=0.2, audio/basic
]]></artwork></figure>
<t>
SHOULD be interpreted as "I prefer audio/basic, but send me any audio
type if it is the best available after an 80% mark-down in quality".
</t>
<t>
A request without any Accept header field implies that the user agent
will accept any media type in response.
If an Accept header field is present in a request and none of the
available representations for the response have a media type that is
listed as acceptable, the origin server MAY either
honor the Accept header field by sending a 406 (Not Acceptable) response
or disregard the Accept header field by treating the response as if
it is not subject to content negotiation.
</t>
<t>
A more elaborate example is
</t>
<figure><artwork type="example"><![CDATA[
Accept: text/plain; q=0.5, text/html,
text/x-dvi; q=0.8, text/x-c
]]></artwork></figure>
<t>
Verbally, this would be interpreted as "text/html and text/x-c are
the preferred media types, but if they do not exist, then send the
text/x-dvi representation, and if that does not exist, send the text/plain
representation".
</t>
<t>
Media ranges can be overridden by more specific media ranges or
specific media types. If more than one media range applies to a given
type, the most specific reference has precedence. For example,
</t>
<figure><artwork type="example"><![CDATA[
Accept: text/*, text/plain, text/plain;format=flowed, */*
]]></artwork></figure>
<t>
have the following precedence:
<list style="numbers">
<t>text/plain;format=flowed</t>
<t>text/plain</t>
<t>text/*</t>
<t>*/*</t>
</list>
</t>
<t>
The media type quality factor associated with a given type is
determined by finding the media range with the highest precedence
which matches that type. For example,
</t>
<figure><artwork type="example"><![CDATA[
Accept: text/*;q=0.3, text/html;q=0.7, text/html;level=1,
text/html;level=2;q=0.4, */*;q=0.5
]]></artwork></figure>
<t>
would cause the following values to be associated:
</t>
<texttable align="left">
<ttcol>Media Type</ttcol><ttcol>Quality Value</ttcol>
<c>text/html;level=1</c> <c>1</c>
<c>text/html</c> <c>0.7</c>
<c>text/plain</c> <c>0.3</c>
<c>image/jpeg</c> <c>0.5</c>
<c>text/html;level=2</c> <c>0.4</c>
<c>text/html;level=3</c> <c>0.7</c>
</texttable>
<t>
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 closed system which cannot interact with other rendering agents,
this default set ought to be configurable by the user.
</t>
</section>
<section title="Accept-Charset" anchor="header.accept-charset">
<iref primary="true" item="Accept-Charset header field"/>
<iref primary="true" item="Header Fields" subitem="Accept-Charset"/>
<t>
The "Accept-Charset" header field can be used by user agents to
indicate what character encodings are acceptable in a response
payload. This field allows
clients capable of understanding more comprehensive or special-purpose
character encodings to signal that capability to a server which is capable of
representing documents in those character encodings.
</t>
<figure><iref primary="true" item="Grammar" subitem="Accept-Charset"/><artwork type="abnf2616"><![CDATA[
Accept-Charset = 1#( ( charset / "*" )
[ OWS ";" OWS "q=" qvalue ] )
]]></artwork></figure>
<t>
Character encoding values (a.k.a., charsets) are described in
<xref target="character.sets"/>. Each charset MAY be given an
associated quality value which represents the user's preference
for that charset. The default value is q=1. An example is
</t>
<figure><artwork type="example"><![CDATA[
Accept-Charset: iso-8859-5, unicode-1-1;q=0.8
]]></artwork></figure>
<t>
The special value "*", if present in the Accept-Charset field,
matches every character encoding which is not mentioned elsewhere in the
Accept-Charset field. If no "*" is present in an Accept-Charset field, then
all character encodings not explicitly mentioned get a quality value of 0.
</t>
<t>
A request without any Accept-Charset header field implies that the user
agent will accept any character encoding in response.
If an Accept-Charset header field is present in a request and none of the
available representations for the response have a character encoding that
is listed as acceptable, the origin server MAY either honor the
Accept-Charset header field by sending a 406 (Not Acceptable) response or
disregard the Accept-Charset header field by treating the response as if
it is not subject to content negotiation.
</t>
</section>
<section title="Accept-Encoding" anchor="header.accept-encoding">
<iref primary="true" item="Accept-Encoding header field"/>
<iref primary="true" item="Header Fields" subitem="Accept-Encoding"/>
<t>
The "Accept-Encoding" header field can be used by user agents to
indicate what response content-codings (<xref target="content.codings"/>)
are acceptable in the response. An "identity" token is used as a synonym
for "no encoding" in order to communicate when no encoding is preferred.
</t>
<figure><iref primary="true" item="Grammar" subitem="Accept-Encoding"/><iref primary="true" item="Grammar" subitem="codings"/><artwork type="abnf2616"><![CDATA[
Accept-Encoding = #( codings [ OWS ";" OWS "q=" qvalue ] )
codings = content-coding / "identity" / "*"
]]></artwork></figure>
<t>
Each codings value MAY be given an associated quality value which
represents the preference for that encoding. The default value is q=1.
</t>
<t>
For example,
</t>
<figure><artwork type="example"><![CDATA[
Accept-Encoding: compress, gzip
Accept-Encoding:
Accept-Encoding: *
Accept-Encoding: compress;q=0.5, gzip;q=1.0
Accept-Encoding: gzip;q=1.0, identity; q=0.5, *;q=0
]]></artwork></figure>
<t>
A server tests whether a content-coding for a given representation is
acceptable, according to an Accept-Encoding field, using these rules:
<list style="numbers">
<t>The special "*" symbol in an Accept-Encoding field matches any
available content-coding not explicitly listed in the header
field.</t>
<t>If the representation has no content-coding, then it is acceptable
by default unless specifically excluded by the Accept-Encoding field
stating either "identity;q=0" or "*;q=0" without a more specific
entry for "identity".</t>
<t>If the representation's content-coding is one of the content-codings
listed in the Accept-Encoding field, then it is acceptable unless
it is accompanied by a qvalue of 0. (As defined in Section 5.3 of <xref target="Part1"/>, a
qvalue of 0 means "not acceptable".)</t>
<t>If multiple content-codings are acceptable, then the acceptable
content-coding with the highest non-zero qvalue is preferred.</t>
</list>
</t>
<t>
An Accept-Encoding header field with a combined field-value that is empty
implies that the user agent does not want any content-coding in response.
If an Accept-Encoding header field is present in a request and none of the
available representations for the response have a content-coding that
is listed as acceptable, the origin server SHOULD send a response
without any content-coding.
</t>
<t>
A request without an Accept-Encoding header field implies that the user
agent will accept any content-coding in response, but a representation
without content-coding is preferred for compatibility with the widest
variety of user agents.
</t>
<t><list>
<t>
Note: Most HTTP/1.0 applications do not recognize or obey qvalues
associated with content-codings. This means that qvalues will not
work and are not permitted with x-gzip or x-compress.
</t>
</list></t>
</section>
<section title="Accept-Language" anchor="header.accept-language">
<iref primary="true" item="Accept-Language header field"/>
<iref primary="true" item="Header Fields" subitem="Accept-Language"/>
<t>
The "Accept-Language" header field can be used by user agents to
indicate the set of natural languages that are preferred in the response.
Language tags are defined in <xref target="language.tags"/>.
</t>
<figure><iref primary="true" item="Grammar" subitem="Accept-Language"/><iref primary="true" item="Grammar" subitem="language-range"/><artwork type="abnf2616"><![CDATA[
Accept-Language =
1#( language-range [ OWS ";" OWS "q=" qvalue ] )
language-range =
<language-range, defined in [RFC4647], Section 2.1>
]]></artwork></figure>
<t>
Each language-range can be given an associated quality value which
represents an estimate of the user's preference for the languages
specified by that range. The quality value defaults to "q=1". For
example,
</t>
<figure><artwork type="example"><![CDATA[
Accept-Language: da, en-gb;q=0.8, en;q=0.7
]]></artwork></figure>
<t>
would mean: "I prefer Danish, but will accept British English and
other types of English".
(see also Section 2.3 of <xref target="RFC4647"/>)
</t>
<t>
For matching, Section 3 of <xref target="RFC4647"/> defines
several matching schemes. Implementations can offer the most appropriate
matching scheme for their requirements.
</t>
<t><list>
<t>
Note: The "Basic Filtering" scheme (<xref target="RFC4647"/>, Section 3.3.1) is identical to the matching scheme that was
previously defined in Section 14.4 of <xref target="RFC2616"/>.
</t>
</list></t>
<t>
It might be contrary to the privacy expectations of the user to send
an Accept-Language header field with the complete linguistic preferences of
the user in every request. For a discussion of this issue, see
<xref target="privacy.issues.connected.to.accept.header.fields"/>.
</t>
<t>
As intelligibility is highly dependent on the individual user, it is
recommended that client applications make the choice of linguistic
preference available to the user. If the choice is not made
available, then the Accept-Language header field MUST NOT be given in
the request.
</t>
<t><list>
<t>
Note: When making the choice of linguistic preference available to
the user, we remind implementors of the fact that users are not
familiar with the details of language matching as described above,
and ought to be provided appropriate guidance. As an example, users
might assume that on selecting "en-gb", they will be served any
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
best matching behavior.
</t>
</list></t>
</section>
<section title="Content-Encoding" anchor="header.content-encoding">
<iref primary="true" item="Content-Encoding header field"/>
<iref primary="true" item="Header Fields" subitem="Content-Encoding"/>
<t>
The "Content-Encoding" header field indicates what content-codings
have been applied to the representation beyond those inherent in the media
type, and thus what decoding mechanisms must be applied in order to obtain
the media-type referenced by the Content-Type header field.
Content-Encoding is primarily used to allow a representation to be
compressed without losing the identity of its underlying media type.
</t>
<figure><iref primary="true" item="Grammar" subitem="Content-Encoding"/><artwork type="abnf2616"><![CDATA[
Content-Encoding = 1#content-coding
]]></artwork></figure>
<t>
Content codings are defined in <xref target="content.codings"/>. An example of its use is
</t>
<figure><artwork type="example"><![CDATA[
Content-Encoding: gzip
]]></artwork></figure>
<t>
The content-coding is a characteristic of the representation.
Typically, the representation body is stored with this
encoding and is only decoded before rendering or analogous usage.
However, a transforming proxy MAY modify the content-coding if the
new coding is known to be acceptable to the recipient, unless the
"no-transform" cache-control directive is present in the message.
</t>
<t>
If the media type includes an inherent encoding, such as a data format
that is always compressed, then that encoding would not be restated as
a Content-Encoding even if it happens to be the same algorithm as one
of the content-codings. Such a content-coding would only be listed if,
for some bizarre reason, it is applied a second time to form the
representation. Likewise, an origin server might choose to publish the
same payload data as multiple representations that differ only in whether
the coding is defined as part of Content-Type or Content-Encoding, since
some user agents will behave differently in their handling of each
response (e.g., open a "Save as ..." dialog instead of automatic
decompression and rendering of content).
</t>
<t>
A representation that has a content-coding applied to it MUST include
a Content-Encoding header field (<xref target="header.content-encoding"/>)
that lists the content-coding(s) applied.
</t>
<t>
If multiple encodings have been applied to a representation, the content
codings MUST be listed in the order in which they were applied.
Additional information about the encoding parameters MAY be provided
by other header fields not defined by this specification.
</t>
<t>
If the content-coding of a representation in a request message is not
acceptable to the origin server, the server SHOULD respond with a
status code of 415 (Unsupported Media Type).
</t>
</section>
<section title="Content-Language" anchor="header.content-language">
<iref primary="true" item="Content-Language header field"/>
<iref primary="true" item="Header Fields" subitem="Content-Language"/>
<t>
The "Content-Language" header field describes the natural
language(s) of the intended audience for the representation. Note that this might
not be equivalent to all the languages used within the representation.
</t>
<figure><iref primary="true" item="Grammar" subitem="Content-Language"/><artwork type="abnf2616"><![CDATA[
Content-Language = 1#language-tag
]]></artwork></figure>
<t>
Language tags are defined in <xref target="language.tags"/>. The primary purpose of
Content-Language is to allow a user to identify and differentiate
representations according to the user's own preferred language. Thus, if the
body content is intended only for a Danish-literate audience, the
appropriate field is
</t>
<figure><artwork type="example"><![CDATA[
Content-Language: da
]]></artwork></figure>
<t>
If no Content-Language is specified, the default is that the content
is intended for all language audiences. This might mean that the
sender does not consider it to be specific to any natural language,
or that the sender does not know for which language it is intended.
</t>
<t>
Multiple languages MAY be listed for content that is intended for
multiple audiences. For example, a rendition of the "Treaty of
Waitangi", presented simultaneously in the original Maori and English
versions, would call for
</t>
<figure><artwork type="example"><![CDATA[
Content-Language: mi, en
]]></artwork></figure>
<t>
However, just because multiple languages are present within a representation
does not mean that it is intended for multiple linguistic audiences.
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-literate audience. In this case, the Content-Language would
properly only include "en".
</t>
<t>
Content-Language MAY be applied to any media type — it is not
limited to textual documents.
</t>
</section>
<section title="Content-Location" anchor="header.content-location">
<iref primary="true" item="Content-Location header field"/>
<iref primary="true" item="Header Fields" subitem="Content-Location"/>
<t>
The "Content-Location" header field supplies a URI that can be used
as a specific identifier for the representation in this message.
In other words, if one were to perform a GET on this URI at the time
of this message's generation, then a 200 response would contain the
same representation that is enclosed as payload in this message.
</t>
<figure><iref primary="true" item="Grammar" subitem="Content-Location"/><artwork type="abnf2616"><![CDATA[
Content-Location = absolute-URI / partial-URI
]]></artwork></figure>
<t>
The Content-Location value is not a replacement for the effective
Request URI (Section 4.3 of <xref target="Part1"/>). It is representation metadata.
It has the same syntax and semantics as the header field of the same name
defined for MIME body parts in Section 4 of <xref target="RFC2557"/>.
However, its appearance in an HTTP message has some special implications
for HTTP recipients.
</t>
<t>
If Content-Location is included in a response message and its value
is the same as the effective request URI, then the response payload
SHOULD be considered the current representation of that resource.
For a GET or HEAD request, this is the same as the default semantics
when no Content-Location is provided by the server. For a state-changing
request like PUT or POST, it implies that the server's response contains
the new representation of that resource, thereby distinguishing it from
representations that might only report about the action (e.g., "It worked!").
This allows authoring applications to update their local copies without
the need for a subsequent GET request.
</t>
<t>
If Content-Location is included in a response message and its value
differs from the effective request URI, then the origin server is
informing recipients that this representation has its own, presumably
more specific, identifier. For a GET or HEAD request, this is an
indication that the effective request URI identifies a resource that
is subject to content negotiation and the representation selected for
this response can also be found at the identified URI. For other
methods, such a Content-Location indicates that this representation
contains a report on the action's status and the same report is
available (for future access with GET) at the given URI. For
example, a purchase transaction made via a POST request might
include a receipt document as the payload of the 200 response;
the Content-Location value provides an identifier for retrieving
a copy of that same receipt in the future.
</t>
<t>
If Content-Location is included in a request message, then it MAY
be interpreted by the origin server as an indication of where the
user agent originally obtained the content of the enclosed
representation (prior to any subsequent modification of the content
by that user agent). In other words, the user agent is providing
the same representation metadata that it received with the original
representation. However, such interpretation MUST NOT be used to
alter the semantics of the method requested by the client. For
example, if a client makes a PUT request on a negotiated resource
and the origin server accepts that PUT (without redirection), then the
new set of values for that resource is expected to be consistent with
the one representation supplied in that PUT; the Content-Location
cannot be used as a form of reverse content selection that
identifies only one of the negotiated representations to be updated.
If the user agent had wanted the latter semantics, it would have applied
the PUT directly to the Content-Location URI.
</t>
<t>
A Content-Location field received in a request message is transitory
information that SHOULD NOT be saved with other representation
metadata for use in later responses. The Content-Location's value
might be saved for use in other contexts, such as within source links
or other metadata.
</t>
<t>
A cache cannot assume that a representation with a Content-Location
different from the URI used to retrieve it can be used to respond to
later requests on that Content-Location URI.
</t>
<t>
If the Content-Location value is a partial URI, the partial URI is
interpreted relative to the effective request URI.
</t>
</section>
<section title="Content-Type" anchor="header.content-type">
<iref primary="true" item="Content-Type header field"/>
<iref primary="true" item="Header Fields" subitem="Content-Type"/>
<t>
The "Content-Type" header field indicates the media type of the
representation. In the case of responses to the HEAD method, the media type is
that which would have been sent had the request been a GET.
</t>
<figure><iref primary="true" item="Grammar" subitem="Content-Type"/><artwork type="abnf2616"><![CDATA[
Content-Type = media-type
]]></artwork></figure>
<t>
Media types are defined in <xref target="media.types"/>. An example of the field is
</t>
<figure><artwork type="example"><![CDATA[
Content-Type: text/html; charset=ISO-8859-4
]]></artwork></figure>
<t>
Further discussion of Content-Type is provided in <xref target="representation.data"/>.
</t>
</section>
</section>
<section title="IANA Considerations" anchor="IANA.considerations">
<section title="Header Field Registration" anchor="header.field.registration">
<t>
The Message Header Field Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> shall be updated
with the permanent registrations below (see <xref target="RFC3864"/>):
</t>
<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
<ttcol>Header Field Name</ttcol>
<ttcol>Protocol</ttcol>
<ttcol>Status</ttcol>
<ttcol>Reference</ttcol>
<c>Accept</c>
<c>http</c>
<c>standard</c>
<c>
<xref target="header.accept"/>
</c>
<c>Accept-Charset</c>
<c>http</c>
<c>standard</c>
<c>
<xref target="header.accept-charset"/>
</c>
<c>Accept-Encoding</c>
<c>http</c>
<c>standard</c>
<c>
<xref target="header.accept-encoding"/>
</c>
<c>Accept-Language</c>
<c>http</c>
<c>standard</c>
<c>
<xref target="header.accept-language"/>
</c>
<c>Content-Encoding</c>
<c>http</c>
<c>standard</c>
<c>
<xref target="header.content-encoding"/>
</c>
<c>Content-Language</c>
<c>http</c>
<c>standard</c>
<c>
<xref target="header.content-language"/>
</c>
<c>Content-Location</c>
<c>http</c>
<c>standard</c>
<c>
<xref target="header.content-location"/>
</c>
<c>Content-Type</c>
<c>http</c>
<c>standard</c>
<c>
<xref target="header.content-type"/>
</c>
<c>MIME-Version</c>
<c>http</c>
<c>standard</c>
<c>
<xref target="mime-version"/>
</c>
</texttable>
<!--(END)-->
<t>
The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
</t>
</section>
<section title="Content Coding Registry" anchor="content.coding.registration">
<t>
The registration procedure for HTTP Content Codings is now defined
by <xref target="content.coding.registry"/> of this document.
</t>
<t>
The HTTP Content Codings Registry located at <eref target="http://www.iana.org/assignments/http-parameters"/>
shall be updated with the registration below:
</t>
<texttable align="left" suppress-title="true" anchor="iana.content.coding.registration.table">
<ttcol>Name</ttcol>
<ttcol>Description</ttcol>
<ttcol>Reference</ttcol>
<c>compress</c>
<c>UNIX "compress" program method</c>
<c>
Section 5.1.2.1 of <xref target="Part1"/>
</c>
<c>deflate</c>
<c>"deflate" compression mechanism (<xref target="RFC1951"/>) used inside
the "zlib" data format (<xref target="RFC1950"/>)
</c>
<c>
Section 5.1.2.2 of <xref target="Part1"/>
</c>
<c>gzip</c>
<c>Same as GNU zip <xref target="RFC1952"/></c>
<c>
Section 5.1.2.3 of <xref target="Part1"/>
</c>
<c>identity</c>
<c>reserved (synonym for "no encoding" in Accept-Encoding header field)</c>
<c>
<xref target="header.accept-encoding"/>
</c>
</texttable>
</section>
</section>
<section title="Security Considerations" anchor="security.considerations">
<t>
This section is meant to inform application developers, information
providers, and users of the security limitations in HTTP/1.1 as
described by this document. The discussion does not include
definitive solutions to the problems revealed, though it does make
some suggestions for reducing security risks.
</t>
<section title="Privacy Issues Connected to Accept Header Fields" anchor="privacy.issues.connected.to.accept.header.fields">
<t>
Accept headers fields can reveal information about the user to all
servers which are accessed. The Accept-Language header field in particular
can reveal information the user would consider to be of a private
nature, because the understanding of particular languages is often
strongly correlated to the membership of a particular ethnic group.
User agents which offer the option to configure the contents of an
Accept-Language header field to be sent in every request are strongly
encouraged to let the configuration process include a message which
makes the user aware of the loss of privacy involved.
</t>
<t>
An approach that limits the loss of privacy would be for a user agent
to omit the sending of Accept-Language header fields by default, and to ask
the user whether or not to start sending Accept-Language header fields to a
server if it detects, by looking for any Vary header fields
generated by the server, that such sending could improve the quality
of service.
</t>
<t>
Elaborate user-customized accept header fields sent in every request,
in particular if these include quality values, can be used by servers
as relatively reliable and long-lived user identifiers. Such user
identifiers would allow content providers to do click-trail tracking,
and would allow collaborating content providers to match cross-server
click-trails or form submissions of individual users. Note that for
many users not behind a proxy, the network address of the host
running the user agent will also serve as a long-lived user
identifier. In environments where proxies are used to enhance
privacy, user agents ought to be conservative in offering accept
header configuration options to end users. As an extreme privacy
measure, proxies could filter the accept header fields in relayed requests.
General purpose user agents which provide a high degree of header
configurability SHOULD warn users about the loss of privacy which can
be involved.
</t>
</section>
</section>
<section title="Acknowledgments" anchor="acks">
<t>
See Section 11 of <xref target="Part1"/>.
</t>
</section>
</middle>
<back>
<references title="Normative References">
<reference anchor="Part1">
<front>
<title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
<author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
<organization abbrev="Adobe">Adobe Systems Incorporated</organization>
<address><email>fielding@gbiv.com</email></address>
</author>
<author initials="J." surname="Gettys" fullname="Jim Gettys">
<organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
<address><email>jg@freedesktop.org</email></address>
</author>
<author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
<organization abbrev="HP">Hewlett-Packard Company</organization>
<address><email>JeffMogul@acm.org</email></address>
</author>
<author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
<organization abbrev="Microsoft">Microsoft Corporation</organization>
<address><email>henrikn@microsoft.com</email></address>
</author>
<author initials="L." surname="Masinter" fullname="Larry Masinter">
<organization abbrev="Adobe">Adobe Systems Incorporated</organization>
<address><email>LMM@acm.org</email></address>
</author>
<author initials="P." surname="Leach" fullname="Paul J. Leach">
<organization abbrev="Microsoft">Microsoft Corporation</organization>
<address><email>paulle@microsoft.com</email></address>
</author>
<author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
<organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
<address><email>timbl@w3.org</email></address>
</author>
<author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
<organization abbrev="W3C">World Wide Web Consortium</organization>
<address><email>ylafon@w3.org</email></address>
</author>
<author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
<organization abbrev="greenbytes">greenbytes GmbH</organization>
<address><email>julian.reschke@greenbytes.de</email></address>
</author>
<date month="January" year="2012"/>
</front>
<seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-18"/>
</reference>
<reference anchor="Part2">
<front>
<title abbrev="HTTP/1.1">HTTP/1.1, part 2: Message Semantics</title>
<author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
<organization abbrev="Adobe">Adobe Systems Incorporated</organization>
<address><email>fielding@gbiv.com</email></address>
</author>
<author initials="J." surname="Gettys" fullname="Jim Gettys">
<organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
<address><email>jg@freedesktop.org</email></address>
</author>
<author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
<organization abbrev="HP">Hewlett-Packard Company</organization>
<address><email>JeffMogul@acm.org</email></address>
</author>
<author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
<organization abbrev="Microsoft">Microsoft Corporation</organization>
<address><email>henrikn@microsoft.com</email></address>
</author>
<author initials="L." surname="Masinter" fullname="Larry Masinter">
<organization abbrev="Adobe">Adobe Systems Incorporated</organization>
<address><email>LMM@acm.org</email></address>
</author>
<author initials="P." surname="Leach" fullname="Paul J. Leach">
<organization abbrev="Microsoft">Microsoft Corporation</organization>
<address><email>paulle@microsoft.com</email></address>
</author>
<author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
<organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
<address><email>timbl@w3.org</email></address>
</author>
<author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
<organization abbrev="W3C">World Wide Web Consortium</organization>
<address><email>ylafon@w3.org</email></address>
</author>
<author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
<organization abbrev="greenbytes">greenbytes GmbH</organization>
<address><email>julian.reschke@greenbytes.de</email></address>
</author>
<date month="January" year="2012"/>
</front>
<seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p2-semantics-18"/>
</reference>
<reference anchor="Part4">
<front>
<title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
<author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
<organization abbrev="Adobe">Adobe Systems Incorporated</organization>
<address><email>fielding@gbiv.com</email></address>
</author>
<author initials="J." surname="Gettys" fullname="Jim Gettys">
<organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
<address><email>jg@freedesktop.org</email></address>
</author>
<author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
<organization abbrev="HP">Hewlett-Packard Company</organization>
<address><email>JeffMogul@acm.org</email></address>
</author>
<author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
<organization abbrev="Microsoft">Microsoft Corporation</organization>
<address><email>henrikn@microsoft.com</email></address>
</author>
<author initials="L." surname="Masinter" fullname="Larry Masinter">
<organization abbrev="Adobe">Adobe Systems Incorporated</organization>
<address><email>LMM@acm.org</email></address>
</author>
<author initials="P." surname="Leach" fullname="Paul J. Leach">
<organization abbrev="Microsoft">Microsoft Corporation</organization>
<address><email>paulle@microsoft.com</email></address>
</author>
<author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
<organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
<address><email>timbl@w3.org</email></address>
</author>
<author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
<organization abbrev="W3C">World Wide Web Consortium</organization>
<address><email>ylafon@w3.org</email></address>
</author>
<author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
<organization abbrev="greenbytes">greenbytes GmbH</organization>
<address><email>julian.reschke@greenbytes.de</email></address>
</author>
<date month="January" year="2012"/>
</front>
<seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-18"/>
</reference>
<reference anchor="Part5">
<front>
<title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
<author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
<organization abbrev="Adobe">Adobe Systems Incorporated</organization>
<address><email>fielding@gbiv.com</email></address>
</author>
<author initials="J." surname="Gettys" fullname="Jim Gettys">
<organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
<address><email>jg@freedesktop.org</email></address>
</author>
<author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
<organization abbrev="HP">Hewlett-Packard Company</organization>
<address><email>JeffMogul@acm.org</email></address>
</author>
<author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
<organization abbrev="Microsoft">Microsoft Corporation</organization>
<address><email>henrikn@microsoft.com</email></address>
</author>
<author initials="L." surname="Masinter" fullname="Larry Masinter">
<organization abbrev="Adobe">Adobe Systems Incorporated</organization>
<address><email>LMM@acm.org</email></address>
</author>
<author initials="P." surname="Leach" fullname="Paul J. Leach">
<organization abbrev="Microsoft">Microsoft Corporation</organization>
<address><email>paulle@microsoft.com</email></address>
</author>
<author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
<organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
<address><email>timbl@w3.org</email></address>
</author>
<author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
<organization abbrev="W3C">World Wide Web Consortium</organization>
<address><email>ylafon@w3.org</email></address>
</author>
<author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
<organization abbrev="greenbytes">greenbytes GmbH</organization>
<address><email>julian.reschke@greenbytes.de</email></address>
</author>
<date month="January" year="2012"/>
</front>
<seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-18"/>
</reference>
<reference anchor="Part6">
<front>
<title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
<author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
<organization abbrev="Adobe">Adobe Systems Incorporated</organization>
<address><email>fielding@gbiv.com</email></address>
</author>
<author initials="J." surname="Gettys" fullname="Jim Gettys">
<organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
<address><email>jg@freedesktop.org</email></address>
</author>
<author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
<organization abbrev="HP">Hewlett-Packard Company</organization>
<address><email>JeffMogul@acm.org</email></address>
</author>
<author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
<organization abbrev="Microsoft">Microsoft Corporation</organization>
<address><email>henrikn@microsoft.com</email></address>
</author>
<author initials="L." surname="Masinter" fullname="Larry Masinter">
<organization abbrev="Adobe">Adobe Systems Incorporated</organization>
<address><email>LMM@acm.org</email></address>
</author>
<author initials="P." surname="Leach" fullname="Paul J. Leach">
<organization abbrev="Microsoft">Microsoft Corporation</organization>
<address><email>paulle@microsoft.com</email></address>
</author>
<author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
<organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
<address><email>timbl@w3.org</email></address>
</author>
<author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
<organization abbrev="W3C">World Wide Web Consortium</organization>
<address><email>ylafon@w3.org</email></address>
</author>
<author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
<organization>Rackspace</organization>
<address><email>mnot@mnot.net</email></address>
</author>
<author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
<organization abbrev="greenbytes">greenbytes GmbH</organization>
<address><email>julian.reschke@greenbytes.de</email></address>
</author>
<date month="January" year="2012"/>
</front>
<seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-18"/>
</reference>
<reference anchor="RFC1950">
<front>
<title>ZLIB Compressed Data Format Specification version 3.3</title>
<author initials="L.P." surname="Deutsch" fullname="L. Peter Deutsch">
<organization>Aladdin Enterprises</organization>
<address><email>ghost@aladdin.com</email></address>
</author>
<author initials="J-L." surname="Gailly" fullname="Jean-Loup Gailly"/>
<date month="May" year="1996"/>
</front>
<seriesInfo name="RFC" value="1950"/>
<!--<annotation>
RFC 1950 is an Informational RFC, thus it might be less stable than
this specification. On the other hand, this downward reference was
present since the publication of <xref target="RFC2068" x:fmt="none">RFC 2068</xref> in 1997,
therefore it is unlikely to cause problems in practice. See also
<xref target="BCP97"/>.
</annotation>-->
</reference>
<reference anchor="RFC1951">
<front>
<title>DEFLATE Compressed Data Format Specification version 1.3</title>
<author initials="P." surname="Deutsch" fullname="L. Peter Deutsch">
<organization>Aladdin Enterprises</organization>
<address><email>ghost@aladdin.com</email></address>
</author>
<date month="May" year="1996"/>
</front>
<seriesInfo name="RFC" value="1951"/>
<!--<annotation>
RFC 1951 is an Informational RFC, thus it might be less stable than
this specification. On the other hand, this downward reference was
present since the publication of <xref target="RFC2068" x:fmt="none">RFC 2068</xref> in 1997,
therefore it is unlikely to cause problems in practice. See also
<xref target="BCP97"/>.
</annotation>-->
</reference>
<reference anchor="RFC1952">
<front>
<title>GZIP file format specification version 4.3</title>
<author initials="P." surname="Deutsch" fullname="L. Peter Deutsch">
<organization>Aladdin Enterprises</organization>
<address><email>ghost@aladdin.com</email></address>
</author>
<author initials="J-L." surname="Gailly" fullname="Jean-Loup Gailly">
<address><email>gzip@prep.ai.mit.edu</email></address>
</author>
<author initials="M." surname="Adler" fullname="Mark Adler">
<address><email>madler@alumni.caltech.edu</email></address>
</author>
<author initials="L.P." surname="Deutsch" fullname="L. Peter Deutsch">
<address><email>ghost@aladdin.com</email></address>
</author>
<author initials="G." surname="Randers-Pehrson" fullname="Glenn Randers-Pehrson">
<address><email>randeg@alumni.rpi.edu</email></address>
</author>
<date month="May" year="1996"/>
</front>
<seriesInfo name="RFC" value="1952"/>
<!--<annotation>
RFC 1952 is an Informational RFC, thus it might be less stable than
this specification. On the other hand, this downward reference was
present since the publication of <xref target="RFC2068" x:fmt="none">RFC 2068</xref> in 1997,
therefore it is unlikely to cause problems in practice. See also
<xref target="BCP97"/>.
</annotation>-->
</reference>
<reference anchor="RFC2045">
<front>
<title abbrev="Internet Message Bodies">Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies</title>
<author initials="N." surname="Freed" fullname="Ned Freed">
<organization>Innosoft International, Inc.</organization>
<address><email>ned@innosoft.com</email></address>
</author>
<author initials="N.S." surname="Borenstein" fullname="Nathaniel S. Borenstein">
<organization>First Virtual Holdings</organization>
<address><email>nsb@nsb.fv.com</email></address>
</author>
<date month="November" year="1996"/>
</front>
<seriesInfo name="RFC" value="2045"/>
</reference>
<reference anchor="RFC2046">
<front>
<title abbrev="Media Types">Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types</title>
<author initials="N." surname="Freed" fullname="Ned Freed">
<organization>Innosoft International, Inc.</organization>
<address><email>ned@innosoft.com</email></address>
</author>
<author initials="N." surname="Borenstein" fullname="Nathaniel S. Borenstein">
<organization>First Virtual Holdings</organization>
<address><email>nsb@nsb.fv.com</email></address>
</author>
<date month="November" year="1996"/>
</front>
<seriesInfo name="RFC" value="2046"/>
</reference>
<reference anchor="RFC2119">
<front>
<title>Key words for use in RFCs to Indicate Requirement Levels</title>
<author initials="S." surname="Bradner" fullname="Scott Bradner">
<organization>Harvard University</organization>
<address><email>sob@harvard.edu</email></address>
</author>
<date month="March" year="1997"/>
</front>
<seriesInfo name="BCP" value="14"/>
<seriesInfo name="RFC" value="2119"/>
</reference>
<reference anchor="RFC4647">
<front>
<title>Matching of Language Tags</title>
<author initials="A." surname="Phillips" fullname="Addison Phillips" role="editor">
<organization>Yahoo! Inc.</organization>
<address><email>addison@inter-locale.com</email></address>
</author>
<author initials="M." surname="Davis" fullname="Mark Davis" role="editor">
<organization>Google</organization>
<address><email>mark.davis@macchiato.com</email></address>
</author>
<date year="2006" month="September"/>
</front>
<seriesInfo name="BCP" value="47"/>
<seriesInfo name="RFC" value="4647"/>
</reference>
<reference anchor="RFC5234">
<front>
<title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
<author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
<organization>Brandenburg InternetWorking</organization>
<address>
<email>dcrocker@bbiw.net</email>
</address>
</author>
<author initials="P." surname="Overell" fullname="Paul Overell">
<organization>THUS plc.</organization>
<address>
<email>paul.overell@thus.net</email>
</address>
</author>
<date month="January" year="2008"/>
</front>
<seriesInfo name="STD" value="68"/>
<seriesInfo name="RFC" value="5234"/>
</reference>
<reference anchor="RFC5646">
<front>
<title>Tags for Identifying Languages</title>
<author initials="A." surname="Phillips" fullname="Addison Phillips" role="editor">
<organization>Lab126</organization>
<address><email>addison@inter-locale.com</email></address>
</author>
<author initials="M." surname="Davis" fullname="Mark Davis" role="editor">
<organization>Google</organization>
<address><email>mark.davis@google.com</email></address>
</author>
<date month="September" year="2009"/>
</front>
<seriesInfo name="BCP" value="47"/>
<seriesInfo name="RFC" value="5646"/>
</reference>
</references>
<references title="Informative References">
<reference anchor="RFC1945">
<front>
<title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
<author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
<organization>MIT, Laboratory for Computer Science</organization>
<address><email>timbl@w3.org</email></address>
</author>
<author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
<organization>University of California, Irvine, Department of Information and Computer Science</organization>
<address><email>fielding@ics.uci.edu</email></address>
</author>
<author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
<organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
<address><email>frystyk@w3.org</email></address>
</author>
<date month="May" year="1996"/>
</front>
<seriesInfo name="RFC" value="1945"/>
</reference>
<reference anchor="RFC2049">
<front>
<title abbrev="MIME Conformance">Multipurpose Internet Mail Extensions (MIME) Part Five: Conformance Criteria and Examples</title>
<author initials="N." surname="Freed" fullname="Ned Freed">
<organization>Innosoft International, Inc.</organization>
<address><email>ned@innosoft.com</email></address>
</author>
<author initials="N.S." surname="Borenstein" fullname="Nathaniel S. Borenstein">
<organization>First Virtual Holdings</organization>
<address><email>nsb@nsb.fv.com</email></address>
</author>
<date month="November" year="1996"/>
</front>
<seriesInfo name="RFC" value="2049"/>
</reference>
<reference anchor="RFC2068">
<front>
<title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
<author initials="R." surname="Fielding" fullname="Roy T. Fielding">
<organization>University of California, Irvine, Department of Information and Computer Science</organization>
<address><email>fielding@ics.uci.edu</email></address>
</author>
<author initials="J." surname="Gettys" fullname="Jim Gettys">
<organization>MIT Laboratory for Computer Science</organization>
<address><email>jg@w3.org</email></address>
</author>
<author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
<organization>Digital Equipment Corporation, Western Research Laboratory</organization>
<address><email>mogul@wrl.dec.com</email></address>
</author>
<author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
<organization>MIT Laboratory for Computer Science</organization>
<address><email>frystyk@w3.org</email></address>
</author>
<author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
<organization>MIT Laboratory for Computer Science</organization>
<address><email>timbl@w3.org</email></address>
</author>
<date month="January" year="1997"/>
</front>
<seriesInfo name="RFC" value="2068"/>
</reference>
<reference anchor="RFC2076">
<front>
<title abbrev="Internet Message Headers">Common Internet Message Headers</title>
<author initials="J." surname="Palme" fullname="Jacob Palme">
<organization>Stockholm University/KTH</organization>
<address><email>jpalme@dsv.su.se</email></address>
</author>
<date month="February" year="1997"/>
</front>
<seriesInfo name="RFC" value="2076"/>
</reference>
<reference anchor="RFC2277">
<front>
<title abbrev="Charset Policy">IETF Policy on Character Sets and Languages</title>
<author initials="H.T." surname="Alvestrand" fullname="Harald Tveit Alvestrand">
<organization>UNINETT</organization>
<address><email>Harald.T.Alvestrand@uninett.no</email></address>
</author>
<date month="January" year="1998"/>
</front>
<seriesInfo name="BCP" value="18"/>
<seriesInfo name="RFC" value="2277"/>
</reference>
<reference anchor="RFC2295">
<front>
<title abbrev="HTTP Content Negotiation">Transparent Content Negotiation in HTTP</title>
<author initials="K." surname="Holtman" fullname="Koen Holtman">
<organization>Technische Universiteit Eindhoven</organization>
<address>
<email>koen@win.tue.nl</email>
</address>
</author>
<author initials="A.H." surname="Mutz" fullname="Andrew H. Mutz">
<organization>Hewlett-Packard Company</organization>
<address>
<email>mutz@hpl.hp.com</email>
</address>
</author>
<date year="1998" month="March"/>
</front>
<seriesInfo name="RFC" value="2295"/>
</reference>
<reference anchor="RFC2388">
<front>
<title abbrev="multipart/form-data">Returning Values from Forms: multipart/form-data</title>
<author initials="L." surname="Masinter" fullname="Larry Masinter">
<organization>Xerox Palo Alto Research Center</organization>
<address><email>masinter@parc.xerox.com</email></address>
</author>
<date year="1998" month="August"/>
</front>
<seriesInfo name="RFC" value="2388"/>
</reference>
<reference anchor="RFC2557">
<front>
<title abbrev="MIME Encapsulation of Aggregate Documents">MIME Encapsulation of Aggregate Documents, such as HTML (MHTML)</title>
<author initials="F." surname="Palme" fullname="Jacob Palme">
<organization>Stockholm University and KTH</organization>
<address><email>jpalme@dsv.su.se</email></address>
</author>
<author initials="A." surname="Hopmann" fullname="Alex Hopmann">
<organization>Microsoft Corporation</organization>
<address><email>alexhop@microsoft.com</email></address>
</author>
<author initials="N." surname="Shelness" fullname="Nick Shelness">
<organization>Lotus Development Corporation</organization>
<address><email>Shelness@lotus.com</email></address>
</author>
<author initials="E." surname="Stefferud" fullname="Einar Stefferud">
<address><email>stef@nma.com</email></address>
</author>
<date year="1999" month="March"/>
</front>
<seriesInfo name="RFC" value="2557"/>
</reference>
<reference anchor="RFC2616">
<front>
<title>Hypertext Transfer Protocol -- HTTP/1.1</title>
<author initials="R." surname="Fielding" fullname="R. Fielding">
<organization>University of California, Irvine</organization>
<address><email>fielding@ics.uci.edu</email></address>
</author>
<author initials="J." surname="Gettys" fullname="J. Gettys">
<organization>W3C</organization>
<address><email>jg@w3.org</email></address>
</author>
<author initials="J." surname="Mogul" fullname="J. Mogul">
<organization>Compaq Computer Corporation</organization>
<address><email>mogul@wrl.dec.com</email></address>
</author>
<author initials="H." surname="Frystyk" fullname="H. Frystyk">
<organization>MIT Laboratory for Computer Science</organization>
<address><email>frystyk@w3.org</email></address>
</author>
<author initials="L." surname="Masinter" fullname="L. Masinter">
<organization>Xerox Corporation</organization>
<address><email>masinter@parc.xerox.com</email></address>
</author>
<author initials="P." surname="Leach" fullname="P. Leach">
<organization>Microsoft Corporation</organization>
<address><email>paulle@microsoft.com</email></address>
</author>
<author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
<organization>W3C</organization>
<address><email>timbl@w3.org</email></address>
</author>
<date month="June" year="1999"/>
</front>
<seriesInfo name="RFC" value="2616"/>
</reference>
<reference anchor="RFC3629">
<front>
<title>UTF-8, a transformation format of ISO 10646</title>
<author initials="F." surname="Yergeau" fullname="F. Yergeau">
<organization>Alis Technologies</organization>
<address><email>fyergeau@alis.com</email></address>
</author>
<date month="November" year="2003"/>
</front>
<seriesInfo name="STD" value="63"/>
<seriesInfo name="RFC" value="3629"/>
</reference>
<reference anchor="RFC3864">
<front>
<title>Registration Procedures for Message Header Fields</title>
<author initials="G." surname="Klyne" fullname="G. Klyne">
<organization>Nine by Nine</organization>
<address><email>GK-IETF@ninebynine.org</email></address>
</author>
<author initials="M." surname="Nottingham" fullname="M. Nottingham">
<organization>BEA Systems</organization>
<address><email>mnot@pobox.com</email></address>
</author>
<author initials="J." surname="Mogul" fullname="J. Mogul">
<organization>HP Labs</organization>
<address><email>JeffMogul@acm.org</email></address>
</author>
<date year="2004" month="September"/>
</front>
<seriesInfo name="BCP" value="90"/>
<seriesInfo name="RFC" value="3864"/>
</reference>
<reference anchor="RFC4288">
<front>
<title>Media Type Specifications and Registration Procedures</title>
<author initials="N." surname="Freed" fullname="N. Freed">
<organization>Sun Microsystems</organization>
<address>
<email>ned.freed@mrochek.com</email>
</address>
</author>
<author initials="J." surname="Klensin" fullname="J. Klensin">
<address>
<email>klensin+ietf@jck.com</email>
</address>
</author>
<date year="2005" month="December"/>
</front>
<seriesInfo name="BCP" value="13"/>
<seriesInfo name="RFC" value="4288"/>
</reference>
<reference anchor="RFC5226">
<front>
<title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
<author initials="T." surname="Narten" fullname="T. Narten">
<organization>IBM</organization>
<address><email>narten@us.ibm.com</email></address>
</author>
<author initials="H." surname="Alvestrand" fullname="H. Alvestrand">
<organization>Google</organization>
<address><email>Harald@Alvestrand.no</email></address>
</author>
<date year="2008" month="May"/>
</front>
<seriesInfo name="BCP" value="26"/>
<seriesInfo name="RFC" value="5226"/>
</reference>
<reference anchor="RFC5322">
<front>
<title>Internet Message Format</title>
<author initials="P." surname="Resnick" fullname="P. Resnick">
<organization>Qualcomm Incorporated</organization>
</author>
<date year="2008" month="October"/>
</front>
<seriesInfo name="RFC" value="5322"/>
</reference>
<reference anchor="RFC6151">
<front>
<title>Updated Security Considerations for the MD5 Message-Digest and the HMAC-MD5 Algorithms</title>
<author initials="S." surname="Turner" fullname="S. Turner"/>
<author initials="L." surname="Chen" fullname="L. Chen"/>
<date year="2011" month="March"/>
</front>
<seriesInfo name="RFC" value="6151"/>
</reference>
<!--<reference anchor='BCP97'>
<front>
<title>Handling Normative References to Standards-Track Documents</title>
<author initials='J.' surname='Klensin' fullname='J. Klensin'>
<address>
<email>klensin+ietf@jck.com</email>
</address>
</author>
<author initials='S.' surname='Hartman' fullname='S. Hartman'>
<organization>MIT</organization>
<address>
<email>hartmans-ietf@mit.edu</email>
</address>
</author>
<date year='2007' month='June' />
</front>
<seriesInfo name='BCP' value='97' />
<seriesInfo name='RFC' value='4897' />
</reference>-->
<reference anchor="RFC6266">
<front>
<title abbrev="Content-Disposition in HTTP">Use of the Content-Disposition Header Field
in the Hypertext Transfer Protocol (HTTP)</title>
<author initials="J. F." surname="Reschke" fullname="Julian F. Reschke">
<organization abbrev="greenbytes">greenbytes GmbH</organization>
<address>
<email>julian.reschke@greenbytes.de</email>
</address>
</author>
<date month="June" year="2011"/>
</front>
<seriesInfo name="RFC" value="6266"/>
</reference>
</references>
<section title="Differences between HTTP and MIME" anchor="differences.between.http.and.mime">
<t>
HTTP/1.1 uses many of the constructs defined for Internet Mail (<xref target="RFC5322"/>) and the Multipurpose Internet Mail Extensions (MIME <xref target="RFC2045"/>) to
allow a message-body to be transmitted in an open variety of
representations and with extensible mechanisms. However, RFC 2045
discusses mail, and HTTP has a few features that are different from
those described in MIME. These differences were carefully chosen
to optimize performance over binary connections, to allow greater
freedom in the use of new media types, to make date comparisons
easier, and to acknowledge the practice of some early HTTP servers
and clients.
</t>
<t>
This appendix describes specific areas where HTTP differs from MIME.
Proxies and gateways to strict MIME environments SHOULD be
aware of these differences and provide the appropriate conversions
where necessary. Proxies and gateways from MIME environments to HTTP
also need to be aware of the differences because some conversions
might be required.
</t>
<section title="MIME-Version" anchor="mime-version">
<iref primary="true" item="MIME-Version header field"/>
<iref primary="true" item="Header Fields" subitem="MIME-Version"/>
<t>
HTTP is not a MIME-compliant protocol. However, HTTP/1.1 messages MAY
include a single MIME-Version header field to indicate what
version of the MIME protocol was used to construct the message. Use
of the MIME-Version header field indicates that the message is in
full compliance with the MIME protocol (as defined in <xref target="RFC2045"/>).
Proxies/gateways are responsible for ensuring full compliance (where
possible) when exporting HTTP messages to strict MIME environments.
</t>
<figure><iref primary="true" item="Grammar" subitem="MIME-Version"/><artwork type="abnf2616"><![CDATA[
MIME-Version = 1*DIGIT "." 1*DIGIT
]]></artwork></figure>
<t>
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
and not the MIME specification.
</t>
</section>
<section title="Conversion to Canonical Form" anchor="conversion.to.canonical.form">
<t>
MIME requires that an Internet mail body-part be converted to
canonical form prior to being transferred, as described in Section 4 of <xref target="RFC2049"/>.
<xref target="canonicalization.and.text.defaults"/> of this document describes the forms
allowed for subtypes of the "text" media type when transmitted over
HTTP. <xref target="RFC2046"/> requires that content with a type of "text" 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 indicate a
line break within text content when a message is transmitted over
HTTP.
</t>
<t>
Where it is possible, a proxy or gateway from HTTP to a strict MIME
environment SHOULD translate all line breaks within the text media
types described in <xref target="canonicalization.and.text.defaults"/>
of this document to the RFC 2049
canonical form of CRLF. Note, however, that this might be complicated
by the presence of a Content-Encoding and by the fact that HTTP
allows the use of some character encodings which do not use octets 13 and
10 to represent CR and LF, respectively, as is the case for some multi-byte
character encodings.
</t>
<t>
Conversion will break any cryptographic
checksums applied to the original content unless the original content
is already in canonical form. Therefore, the canonical form is
recommended for any content that uses such checksums in HTTP.
</t>
</section>
<section title="Conversion of Date Formats" anchor="conversion.of.date.formats">
<t>
HTTP/1.1 uses a restricted set of date formats (Section 8 of <xref target="Part2"/>) to
simplify the process of date comparison. Proxies and gateways from
other protocols SHOULD ensure that any Date header field present in a
message conforms to one of the HTTP/1.1 formats and rewrite the date
if necessary.
</t>
</section>
<section title="Introduction of Content-Encoding" anchor="introduction.of.content-encoding">
<t>
MIME does not include any concept equivalent to HTTP/1.1's
Content-Encoding header field. Since this acts as a modifier on the
media type, proxies and gateways from HTTP to MIME-compliant
protocols MUST either change the value of the Content-Type header
field or decode the representation before forwarding the message. (Some
experimental applications of Content-Type for Internet mail have used
a media-type parameter of ";conversions=<content-coding>" to perform
a function equivalent to Content-Encoding. However, this parameter is
not part of the MIME standards).
</t>
</section>
<section title="No Content-Transfer-Encoding" anchor="no.content-transfer-encoding">
<t>
HTTP does not use the Content-Transfer-Encoding field of MIME.
Proxies and gateways from MIME-compliant protocols to HTTP MUST
remove any Content-Transfer-Encoding
prior to delivering the response message to an HTTP client.
</t>
<t>
Proxies and gateways from HTTP to MIME-compliant protocols are
responsible for ensuring that the message is in the correct format
and encoding for safe transport on that protocol, where "safe
transport" is defined by the limitations of the protocol being used.
Such a proxy or gateway SHOULD label the data with an appropriate
Content-Transfer-Encoding if doing so will improve the likelihood of
safe transport over the destination protocol.
</t>
</section>
<section title="Introduction of Transfer-Encoding" anchor="introduction.of.transfer-encoding">
<t>
HTTP/1.1 introduces the Transfer-Encoding header field (Section 8.6 of <xref target="Part1"/>).
Proxies/gateways MUST remove any transfer-coding prior to
forwarding a message via a MIME-compliant protocol.
</t>
</section>
<section title="MHTML and Line Length Limitations" anchor="mhtml.line.length">
<t>
HTTP implementations which share code with MHTML <xref target="RFC2557"/> implementations
need to be aware of MIME line length limitations. Since HTTP does not
have this limitation, HTTP does not fold long lines. MHTML messages
being transported by HTTP follow all conventions of MHTML, including
line length limitations and folding, canonicalization, etc., since
HTTP transports all message-bodies as payload (see <xref target="multipart.types"/>) and
does not interpret the content or any MIME header lines that might be
contained therein.
</t>
</section>
</section>
<section title="Additional Features" anchor="additional.features">
<t>
<xref target="RFC1945"/> and <xref target="RFC2068"/> document protocol elements used by some
existing HTTP implementations, but not consistently and correctly
across most HTTP/1.1 applications. Implementors are advised to be
aware of these features, but cannot rely upon their presence in, or
interoperability with, other HTTP/1.1 applications. Some of these
describe proposed experimental features, and some describe features
that experimental deployment found lacking that are now addressed in
the base HTTP/1.1 specification.
</t>
<t>
A number of other header fields, such as Content-Disposition and Title,
from SMTP and MIME are also often implemented (see <xref target="RFC6266"/>
and <xref target="RFC2076"/>).
</t>
</section>
<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
<t>
Clarify contexts that charset is used in.
(<xref target="character.sets"/>)
</t>
<t>
Remove the default character encoding for text media types; the default
now is whatever the media type definition says.
(<xref target="canonicalization.and.text.defaults"/>)
</t>
<t>
Change ABNF productions for header fields to only define the field value.
(<xref target="header.field.definitions"/>)
</t>
<t>
Remove definition of Content-MD5 header field because it was inconsistently
implemented with respect to partial responses, and also because of known
deficiencies in the hash algorithm itself (see <xref target="RFC6151"/> for details).
(<xref target="header.field.definitions"/>)
</t>
<t>
Remove ISO-8859-1 special-casing in Accept-Charset.
(<xref target="header.accept-charset"/>)
</t>
<t>
Remove base URI setting semantics for Content-Location due to poor
implementation support, which was caused by too many broken servers emitting
bogus Content-Location header fields, and also the potentially undesirable effect
of potentially breaking relative links in content-negotiated resources.
(<xref target="header.content-location"/>)
</t>
<t>
Remove discussion of Content-Disposition header field, it is now defined
by <xref target="RFC6266"/>.
(<xref target="additional.features"/>)
</t>
<t>
Remove reference to non-existant identity transfer-coding value tokens.
(<xref target="no.content-transfer-encoding"/>)
</t>
</section>
<section title="Collected ABNF" anchor="collected.abnf">
<figure>
<artwork type="abnf" name="p3-payload.parsed-abnf"><![CDATA[
Accept = [ ( "," / ( media-range [ accept-params ] ) ) *( OWS "," [
OWS media-range [ accept-params ] ] ) ]
Accept-Charset = *( "," OWS ) ( charset / "*" ) [ OWS ";" OWS "q="
qvalue ] *( OWS "," [ OWS ( charset / "*" ) [ OWS ";" OWS "q="
qvalue ] ] )
Accept-Encoding = [ ( "," / ( codings [ OWS ";" OWS "q=" qvalue ] ) )
*( OWS "," [ OWS codings [ OWS ";" OWS "q=" qvalue ] ] ) ]
Accept-Language = *( "," OWS ) language-range [ OWS ";" OWS "q="
qvalue ] *( OWS "," [ OWS language-range [ OWS ";" OWS "q=" qvalue ]
] )
Content-Encoding = *( "," OWS ) content-coding *( OWS "," [ OWS
content-coding ] )
Content-Language = *( "," OWS ) language-tag *( OWS "," [ OWS
language-tag ] )
Content-Location = absolute-URI / partial-URI
Content-Type = media-type
MIME-Version = 1*DIGIT "." 1*DIGIT
OWS = <OWS, defined in [Part1], Section 1.2.2>
absolute-URI = <absolute-URI, defined in [Part1], Section 2.7>
accept-ext = OWS ";" OWS token [ "=" word ]
accept-params = OWS ";" OWS "q=" qvalue *accept-ext
attribute = token
charset = token
codings = content-coding / "identity" / "*"
content-coding = token
language-range = <language-range, defined in [RFC4647], Section 2.1>
language-tag = <Language-Tag, defined in [RFC5646], Section 2.1>
media-range = ( "*/*" / ( type "/*" ) / ( type "/" subtype ) ) *( OWS
";" OWS parameter )
media-type = type "/" subtype *( OWS ";" OWS parameter )
parameter = attribute "=" value
partial-URI = <partial-URI, defined in [Part1], Section 2.7>
qvalue = <qvalue, defined in [Part1], Section 5.3>
subtype = token
token = <token, defined in [Part1], Section 3.2.3>
type = token
value = word
word = <word, defined in [Part1], Section 3.2.3>
]]></artwork>
</figure>
<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline"><![CDATA[
; Accept defined but not used
; Accept-Charset defined but not used
; Accept-Encoding defined but not used
; Accept-Language defined but not used
; Content-Encoding defined but not used
; Content-Language defined but not used
; Content-Location defined but not used
; Content-Type defined but not used
; MIME-Version defined but not used
]]></artwork></figure></section>
<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
<section title="Since RFC 2616">
<t>
Extracted relevant partitions from <xref target="RFC2616"/>.
</t>
</section>
<section title="Since draft-ietf-httpbis-p3-payload-00">
<t>
Closed issues:
<list style="symbols">
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/8"/>:
"Media Type Registrations"
(<eref target="http://purl.org/NET/http-errata#media-reg"/>)
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/14"/>:
"Clarification regarding quoting of charset values"
(<eref target="http://purl.org/NET/http-errata#charactersets"/>)
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/16"/>:
"Remove 'identity' token references"
(<eref target="http://purl.org/NET/http-errata#identity"/>)
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/25"/>:
"Accept-Encoding BNF"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
"Normative and Informative references"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/46"/>:
"RFC1700 references"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/55"/>:
"Updating to RFC4288"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
"Informative references"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/66"/>:
"ISO-8859-1 Reference"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/68"/>:
"Encoding References Normative"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/86"/>:
"Normative up-to-date references"
</t>
</list>
</t>
</section>
<section title="Since draft-ietf-httpbis-p3-payload-01">
<t>
Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
<list style="symbols">
<t>
Add explicit references to BNF syntax and rules imported from other parts of the specification.
</t>
</list>
</t>
</section>
<section title="Since draft-ietf-httpbis-p3-payload-02" anchor="changes.since.02">
<t>
Closed issues:
<list style="symbols">
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/67"/>:
"Quoting Charsets"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
"Classification for Allow header"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/115"/>:
"missing default for qvalue in description of Accept-Encoding"
</t>
</list>
</t>
<t>
Ongoing work on IANA Message Header Field Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
<list style="symbols">
<t>
Reference RFC 3984, and update header field registrations for headers defined
in this document.
</t>
</list>
</t>
</section>
<section title="Since draft-ietf-httpbis-p3-payload-03" anchor="changes.since.03">
<t>
Closed issues:
<list style="symbols">
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/67"/>:
"Quoting Charsets"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/113"/>:
"language tag matching (Accept-Language) vs RFC4647"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/121"/>:
"RFC 1806 has been replaced by RFC2183"
</t>
</list>
</t>
<t>
Other changes:
<list style="symbols">
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/68"/>:
"Encoding References Normative" — rephrase the annotation and reference
BCP97.
</t>
</list>
</t>
</section>
<section title="Since draft-ietf-httpbis-p3-payload-04" anchor="changes.since.04">
<t>
Closed issues:
<list style="symbols">
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
"RFC 2822 is updated by RFC 5322"
</t>
</list>
</t>
<t>
Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
<list style="symbols">
<t>
Use "/" instead of "|" for alternatives.
</t>
<t>
Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
whitespace ("OWS") and required whitespace ("RWS").
</t>
<t>
Rewrite ABNFs to spell out whitespace rules, factor out
header field value format definitions.
</t>
</list>
</t>
</section>
<section title="Since draft-ietf-httpbis-p3-payload-05" anchor="changes.since.05">
<t>
Closed issues:
<list style="symbols">
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/118"/>:
"Join "Differences Between HTTP Entities and RFC 2045 Entities"?"
</t>
</list>
</t>
<t>
Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
<list style="symbols">
<t>
Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
</t>
</list>
</t>
<t>
Other changes:
<list style="symbols">
<t>
Move definition of quality values into Part 1.
</t>
</list>
</t>
</section>
<section title="Since draft-ietf-httpbis-p3-payload-06" anchor="changes.since.06">
<t>
Closed issues:
<list style="symbols">
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/80"/>:
"Content-Location isn't special"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/155"/>:
"Content Sniffing"
</t>
</list>
</t>
</section>
<section title="Since draft-ietf-httpbis-p3-payload-07" anchor="changes.since.07">
<t>
Closed issues:
<list style="symbols">
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/13"/>:
"Updated reference for language tags"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
"Clarify rules for determining what entities a response carries"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/154"/>:
"Content-Location base-setting problems"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/155"/>:
"Content Sniffing"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/188"/>:
"pick IANA policy (RFC5226) for Transfer Coding / Content Coding"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/189"/>:
"move definitions of gzip/deflate/compress to part 1"
</t>
</list>
</t>
<t>
Partly resolved issues:
<list style="symbols">
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/148"/>:
"update IANA requirements wrt Transfer-Coding values" (add the
IANA Considerations subsection)
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/149"/>:
"update IANA requirements wrt Content-Coding values" (add the
IANA Considerations subsection)
</t>
</list>
</t>
</section>
<section title="Since draft-ietf-httpbis-p3-payload-08" anchor="changes.since.08">
<t>
Closed issues:
<list style="symbols">
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/81"/>:
"Content Negotiation for media types"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/181"/>:
"Accept-Language: which RFC4647 filtering?"
</t>
</list>
</t>
</section>
<section title="Since draft-ietf-httpbis-p3-payload-09" anchor="changes.since.09">
<t>
Closed issues:
<list style="symbols">
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/122"/>:
"MIME-Version not listed in P1, general header fields"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/143"/>:
"IANA registry for content/transfer encodings"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/155"/>:
"Content Sniffing"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/200"/>:
"use of term "word" when talking about header structure"
</t>
</list>
</t>
<t>
Partly resolved issues:
<list style="symbols">
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196"/>:
"Term for the requested resource's URI"
</t>
</list>
</t>
</section>
<section title="Since draft-ietf-httpbis-p3-payload-10" anchor="changes.since.10">
<t>
Closed issues:
<list style="symbols">
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/69"/>:
"Clarify 'Requested Variant'"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/80"/>:
"Content-Location isn't special"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/90"/>:
"Delimiting messages with multipart/byteranges"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/109"/>:
"Clarify entity / representation / variant terminology"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/136"/>:
"confusing req. language for Content-Location"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/167"/>:
"Content-Location on 304 responses"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/183"/>:
"'requested resource' in content-encoding definition"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/220"/>:
"consider removing the 'changes from 2068' sections"
</t>
</list>
</t>
<t>
Partly resolved issues:
<list style="symbols">
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/178"/>:
"Content-MD5 and partial responses"
</t>
</list>
</t>
</section>
<section title="Since draft-ietf-httpbis-p3-payload-11" anchor="changes.since.11">
<t>
Closed issues:
<list style="symbols">
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/123"/>:
"Factor out Content-Disposition"
</t>
</list>
</t>
</section>
<section title="Since draft-ietf-httpbis-p3-payload-12" anchor="changes.since.12">
<t>
Closed issues:
<list style="symbols">
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/224"/>:
"Header Classification"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
"untangle ABNFs for header fields"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/277"/>:
"potentially misleading MAY in media-type def"
</t>
</list>
</t>
</section>
<section title="Since draft-ietf-httpbis-p3-payload-13" anchor="changes.since.13">
<t>
Closed issues:
<list style="symbols">
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/20"/>:
"Default charsets for text media types"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/178"/>:
"Content-MD5 and partial responses"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
"untangle ABNFs for header fields"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/281"/>:
"confusing undefined parameter in media range example"
</t>
</list>
</t>
</section>
<section title="Since draft-ietf-httpbis-p3-payload-14" anchor="changes.since.14">
<t>
None.
</t>
</section>
<section title="Since draft-ietf-httpbis-p3-payload-15" anchor="changes.since.15">
<t>
Closed issues:
<list style="symbols">
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/285"/>:
"Strength of requirements on Accept re: 406"
</t>
</list>
</t>
</section>
<section title="Since draft-ietf-httpbis-p3-payload-16" anchor="changes.since.16">
<t>
Closed issues:
<list style="symbols">
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/186"/>:
"Document HTTP's error-handling philosophy"
</t>
</list>
</t>
</section>
<section title="Since draft-ietf-httpbis-p3-payload-17" anchor="changes.since.17">
<t>
Closed issues:
<list style="symbols">
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/323"/>:
"intended maturity level vs normative references"
</t>
</list>
</t>
</section>
</section>
</back>
</rfc>| PAFTECH AB 2003-2026 | 2026-04-23 20:34:53 |