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Minutes of Hypertext Transfer protocol BOF at 31st IETF

From: Dave Raggett <dsr@hplb.hpl.hp.com>
Date: Tue, 20 Dec 94 12:38:25 GMT
Message-Id: <9412201238.AA00786@dragget.hpl.hp.com>
To: minutes.cnri.reston.us%dragget.hpl.hp.com@hplb.hpl.hp.com, http-wg%cuckoo.hpl.hp.com@hplb.hpl.hp.com
Minutes of the Hypertext Transfer Protocol (HTTP) BOF from
the 31st IETF Meeting (San Jose). Wednesday 7th December 1994.

Chaired by Dave Raggett <dsr@w3.org>

Further info on HTTP is currently available from the URLs

  http://info.cern.ch/hypertext/WWW/Protocols/Overview.html
  http://www.ics.uci.edu/pub/ietf/http/

Mailing list info:

 General Discussion: http-wg@cuckoo.hpl.hp.com
 Archive: http://www.ics.uci.edu/pub/ietf/http/hypermail/
 To subscribe mail http-wg-request@cuckoo.hpl.hp.com
 and include the body:  subscribe http-wg Your Full Name

This BOF followed an earlier one at the World Wide Web Conference at Chicago
in October in which it was decided to pursue setting up a working group for
the World Wide Web hypertext transfer protocol, to standardise existing
practice, and then to work on improved performance, security and payments,
and other improvements such as support for transaction mechanisms for
distributed updates.

The meeting started with a summary by the chair of the steps leading up to
the BOF. HTTP originated as a very simple protocol indeed. This version is now
known as HTTP/0.9. It was soon extended to include a MIME style wrapper to
convey the content type and encoding of the returned document. A number of
RFC 822 style headers are used to support negotiation and convey meta
information, as well as a basic authentication mechanism. This version is
known as HTTP/1.0 and is in very widespread use. The online documentation
at CERN is no longer adequate. Other pressures on HTTP include the need to
improve performance, to avoid the penalties associated with making separate
connections for the document and each of the inlined images. We also need to
standardise ways of adding support for authentication and encryption to support
privacy and commercial services.  Setting up an IETF working group is now a
matter of urgency to ensure the continued health of both HTTP and the Web.

The meeting continued with a presentation by Henrik Frystyk Nielsen and Roy
Fielding on the Internet draft for HTTP/1.0 (draft-fielding-http-spec-00.ps).
together with some ideas for extensions for consideration in HTTP/1.1. The
consensus of the meeting was that the Internet draft for HTTP/1.0 be proposed
for the standards track as soon as possible. Revisions to the HTTP/1.0 draft
specification are being discussed on the http-wg mailing list (see above).

The list of extensions for the 1.1 revision were:

    *  Session method
         o  Intended for short-term session only (~10 sec. request timeout)
            though specialised servers may use longer timeout
         o  Supports multiple transactions over single connection
         o  Allows session-long negotiation of Accept-*, authentication,
            and privacy extensions
         o  More than just an MGET
    *  Packetised Content-Encoding
    *  Better Access Authentication
    *  Base-URL as a New Object header
    *  Allow relative time in Expires header (seconds)
----
Simon Spero talked briefly on the performance problems with HTTP/1.0.
The current protocol uses a separate connection for the document and
each inlined image. Each connection requires at least two round trip times,
and in practice more due to the lengthy accept headers in common use.
Furthermore, tcp/ip uses a slow start mechanism to avoid congestion and
gradually increases the throughput to match the actual bandwidth available. 
As a result, most HTTP transactions operate at a reduced bandwidth. Simon
reported measurements indicating that over a congested link from Bristol,
England to North Carolina for a representative home page, the current
protocol only uses about 10 % of the bandwidth then available (as measured
by a bulk transfer over a single connection). The approach used in the
Netscape browser of opening multiple concurrent tcp/ip connections gives
better performance, but still fails to utilise the full bandwidth. One
explanation, is that most tcp/ip implementations fail to share congestion
information between connections to the same site. The approach also leads
to problems with many more connections left in the time-wait state at the
server.
----
Discussion on HTTP Issues:

Larry Masinter asked whether proposals for extensions such as keep-alive
were based on experience or speculation. He prefers MIME boundary markers
to packetisation schemes for determining message boundaries. Larry also
suggested we should consider richer mechanisms for determining whether
a document has expired. For instance, downloading conditions in SafeTCL
to be evaluated by the client.

Alex Hopmann argued in favor of reusing the connection e.g. for a series of
images, and increasing the use of proxy servers. He has tried out a session
method scheme, and has a written proposal for this and a separate proposal
for a notification proposal (for more info email: alex.hopmann@resnova.com).

Simon Spero described work on log analysis which showed clear groupings of
requests at 3 to 4 images per document. He mentioned problems in analysing
logs due to accesses by netscape browsers which initiate connections for
images concurrently and are then cancelled as the user surfs to the next
document.

Tim Berners-Lee argued that users connecting over phone lines need browsers
that can do things concurrently with dynamic changes in priority as the user
changes his/her actions, e.g. the browser should keep the pipe full by
following links and then abort if the user does something else. He also raised
the issue of abstraction layers for HTTP.

Brian Behlendorf discussed the need for user authentication and realms. He
wants to be able to distinguish accesses to a given machine according to the
alias used for the host name, and advocates using the full URL in the GET
request.

Digital have collected some 9 gigabytes of log data for requested URL and the
duration the connection was kept open. A paper analysing this data was
presented at the World Wide Web Fall Conference held in October 1994, and
can be found in the online proceedings.

Someone asked "what does HTTP do in a couple of words?". It is currently used
for a wide variety of things - should these be unbundled?.  Roy Fielding
answered that HTTP is an extensible protocol used for information transfer.
Tim Berners-Lee replied that this was a good question, and asked is MIME
appropriate for small messages (for online accesses not for email)?

Dave Crocker agreed with the need for performance improvements, and said
that the current problem is in making connections. He argued in favor of
TCPng and other ideas for optimising the underlying protocol rather than
hacking session protocols etc. above tcp. We should feel free to adapt the
MIME syntax to better suit the needs of the Web for online use.

Eric Sink asked when we can start writing code for this (improved
performance). The general reaction was that now was a good time to
try out experiments to feed into the next versions of HTTP.  Alex Hopmann
described his session method for multiple requests.  He was encourage to
carry on with this work and to repost the results so far. Tim asked Alex
why a session method rather than as an attribute of GET (e.g. a keep-alive
pragma). The main thing is to avoid unnecessary round-trip delays.

The question was raised as to the possible impact of keep-alive versus
the session method on the operation of proxies.  The discussion was taken
off-line.
----
HTTP Security Update from Tim Berners-Lee:

Tim reported on the HTTP Security BOF, which had taken place the preceeding
evening. The idea was to split work on security off from the HTTP working
group. This would lessen the workload and make it easier to involve security
experts in a wider context than that of HTTP alone. See the minutes for more
details.
----
Dave Krystal talked about a proposed extension mechanism for HTTP.

As the Web has grown, pressures have mounted to add a variety of facilities
to HTTP. Some of the new features that have been proposed include: keep-alive,
packetized data, compression, security and payment. Dave described an
alternative: well-defined hooks in a slightly modified HTTP framework
that make it possible to add extensions to the basic protocol in a way that
will retain compatible behaviour between clients and servers, yet allow both
clients and servers to discover and use extended capabilities. The proposed
extension mechanism has two fundamental concepts: wrapping and negotiation.
The idea is to avoid a proliferation of new methods and header fields. Instead,
these would be handled through extensions with new stuff passed though to
feature managers. For further information please read the document URL:
http://www.research.att.com/~dmk/extend.txt

Dave also asked whether payments would be covered by the HTTP security
working group.
----
Simon Spero on the HTTPng proposal

Simon raced through the major ideas for HTTPng. A new protcol is needed
which is more efficient; has security built-in from the start; and is caching
and payment aware. HTTPng uses a session protocol above tcp/ip to support
multiple asynchronous transactions interleaved on the same connection.
This allows a browser to send the request for an inlined image before
finishing reading the html document that references it. The approach avoids
the delays associated with starting up new connections and makes better use
of available bandwidth and server resources. The proposal uses a subset of
ASN.1 and the packed encoding rules to formally specify messages. This
simplifies implementations compared to using text based representations.
The lengthy Accept headers in HTTP/1.0 are avoided by using a bit vector for 
common cases with an extension mechanism for the rare occasions when
these are insufficient.  Servers can challenge for payment. A simple
implementation of HTTPng was found to operate approaching an order of
magnitude faster than HTTP/1.0 over an intercontinental link. A transition
strategy was described that allows existing HTTP/1.0 clients and servers
to interoperate with HTTPng via proxy servers supporting both HTTP/1.0 and
HTTPng.
----
Discussion of the charter

A show of hands indicated unanimous support for recommending to the area
directors that a working group be set up for HTTP. We briefly discussed the
draft charter prepared by Roy Fielding. Some minor revisions were agreed.
The meeting expressed confidence in Dave Raggett continuing as chair.
Subsequently, following a suggestion by John Klensin, to co-opt an IETF
oldtimer as co-chair, I bludgeoned Tim Berners-Lee into agreeing to taking
on this role.

Dave Raggett - 19th December 1994
Received on Tuesday, 20 December 1994 04:39:59 EST

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