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Hypertext Transfer Protocol Bis (httpbis) (WG)

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Additional information is available at tools.ietf.org/wg/httpbis

Chair(s):

Applications Area Area Director(s):

Applications Area Advisor



Meeting Slides:

Blue Sheets:

Internet-Drafts:

Request for Comments:

Charter (as of 2012-10-02):

This Working Group is charged with maintaining and developing the "core"
specifications for HTTP.

The Working Group's specification deliverables are:
* A document (or set of documents) that is suitable to supersede RFC 2616 as
the definition of HTTP/1.1 and move RFC 2817 to Historic status
* A document cataloguing the security properties of HTTP/1.1
* A document (or set of documents) that specifies HTTP/2.0, an improved
binding of HTTP's semantics to an underlying transport.

HTTP/1.1
--------

HTTP/1.1 is one of the most successful and widely-used protocols on the
Internet today. However, its specification has several editorial issues.
Additionally, after years of implementation and extension, several ambiguities
have become evident, impairing interoperability and the ability to easily
implement and use HTTP.

The working group will refine RFC2616 to:
* Incorporate errata and updates (e.g., references, IANA registries, ABNF)
* Fix editorial problems which have led to misunderstandings of the
specification
* Clarify conformance requirements
* Remove known ambiguities where they affect interoperability
* Clarify existing methods of extensibility
* Remove or deprecate those features that are not widely implemented and
also unduly affect interoperability
* Where necessary, add implementation advice
* Document the security properties of HTTP and its associated mechanisms
(e.g., Basic and Digest authentication, cookies, TLS) for common
applications

It will also incorporate the generic authentication framework from RFC
2617, without obsoleting or updating that specification's definition of
the Basic and Digest schemes.

Finally, it will incorporate relevant portions of RFC 2817 (in
particular, the CONNECT method and advice on the use of Upgrade), so
that that specification can be moved to Historic status.

In doing so, it should consider:
* Implementer experience
* Demonstrated use of HTTP
* Impact on existing implementations and deployments

HTTP/2.0
--------

There is emerging implementation experience and interest in a protocol that
retains the semantics of HTTP without the legacy of HTTP/1.x message
framing and syntax, which have been identified as hampering performance and
encouraging misuse of the underlying transport.

The Working Group will produce a specification of a new expression of HTTP's
current semantics in ordered, bi-directional streams. As with HTTP/1.x,
the primary target transport is TCP, but it should be possible to use
other transports.

Work will begin using draft-mbelshe-httpbis-spdy-00 as a starting point;
proposals are to be expressed in terms of changes to that document. Note that
consensus is required both for changes to the document and anything that
remains in the document. In particular, because something is in the initial
document does not imply that there is consensus around the feature or how
it is specified. The deliverable of the WG is HTTP/2.0, and there is no
consideration of preserving backwards compatibility with the initial starting
point.

As part of the HTTP/2.0 work, the following issues are explicitly called out for
consideration:
* A negotiation mechanism that is capable of not only choosing between
HTTP/1.x and HTTP/2.x, but also for bindings of HTTP URLs to other
transports (for example).
* Header compression (which may encompass header encoding or tokenisation)
* Server push (which may encompass pull or other techniques)

It is expected that HTTP/2.0 will:
* Substantially and measurably improve end-user perceived latency in most
cases, over HTTP/1.1 using TCP.
* Address the "head of line blocking" problem in HTTP.
* Not require multiple connections to a server to enable parallelism, thus
improving its use of TCP, especially regarding congestion control.
* Retain the semantics of HTTP/1.1, leveraging existing documentation (see
above), including (but not limited to) HTTP methods, status codes, URIs, and
where appropriate, header fields.
* Clearly define how HTTP/2.0 interacts with HTTP/1.x, especially in
intermediaries (both 2->1 and 1->2).
* Clearly identify any new extensibility points and policy for their
appropriate use.

The resulting specification(s) are expected to meet these goals for common
existing deployments of HTTP; in particular, Web browsing (desktop and
mobile), non-browsers ("HTTP APIs"), Web serving (at a variety of scales), and
intermediation (by proxies, corporate firewalls, "reverse" proxies and Content
Delivery Networks). Likewise, current and future semantic extensions to
HTTP/1.x (e.g., headers, methods, status codes, cache directives) should be
supported in the new protocol.

Note that this does not include uses of HTTP where non-specified behaviours
are relied upon (e.g., connection state such as timeouts or client affinity,
and "interception" proxies); these uses may or may not be enabled by the final
product.

Explicitly out-of-scope items include:
* Specifying the use of alternate transport-layer protocols. Note that it
is expected that the Working Group will work with the TLS working group
to define how the protocol is used with the TLS Protocol; any revisions to
RFC 2818 will be done in the TLS working group.
* Specifying how the HTTP protocol is to be used or presented in a specific
use case (e.g., in Web browsers).

The Working Group will coordinate this item with:
* The TLS Working Group, regarding use of TLS.
* The Transport Area, regarding impact on and interaction with transport
protocols.
* The HYBI Working Group, regarding the possible future extension of HTTP/2.0
to carry WebSockets semantics.

The Working Group will give priority to HTTP/1.1 work until that work is
complete.

Other HTTP-Related Work
-----------------------

The Working Group may define additional extensions to HTTP as work items,
provided that:
* The Working Group Chairs judge that there is consensus to take on the item
and believe that it will not interfere with the work described above, and
* The Area Directors approve the addition and add corresponding milestones.

Additionally, the Working Group will not start work on any extensions that
are specific to HTTP/2.0 until the HTTP/2.0 work is completed.