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RE: T is for Transfer

From: Joseph Hui <jhui@digisle.net>
Date: Thu, 28 Mar 2002 11:59:59 -0800
Message-ID: <C153D39717E5F444B81E7B85018A460B081B2796@ex-sj-5.digisle.com>
To: "Mark Baker" <distobj@acm.org>, "Appleton Pete M" <PMAppleton@bemis.com>
Cc: <highland.m.mountain@intel.com>, <xml-dist-app@w3.org>
This is interesting.

Mark's right that HTTP, unlike TCP or UDP, is not a transport
protocol in an OSI or DARPA networking stack.

However, Highland's claim, as far as I can tell from the quoted text
in Mark's message, is only that HTTP can be seen as a transport.
I have no problem with referring to HTTP -- which itself assumes an
underlying reliable transport protocol, say TCP, for transferring
HTTP messages reliably -- as a transport, where HTTP message headers
and bodies are used to carry application-level payloads.
HTTP is not a transport protocol by design; but it doesn't stop people
from seeing it as one creatively, often for its "port-80 firewall
friendliness."  I'd be quite comfortable to design an application
protocol that specifies HTTP as its transport where in-band data
(e.g. HTML content) are carried in HTTP bodies, and out-of-band
data ( e.g. application-specific content signals) are embedded
in HTTP extended headers.

Joe Hui
Exodus, a Cable & Wireless service

> -----Original Message-----
> From: Mark Baker [mailto:distobj@acm.org]
> Sent: Thursday, March 28, 2002 11:15 AM
> To: Appleton Pete M
> Cc: highland.m.mountain@intel.com; xml-dist-app@w3.org
> Subject: T is for Transfer
> > Yes, I do see HTTP as being purely transport.
> With all due respect, it doesn't matter how you see it, it is *not* a
> transport protocol.  You can use it this way, the same way I 
> can use any
> application protocol as a transport protocol by disregarding the task
> that the application protocol is trying to coordinate.  But 
> that doesn't
> make it one.
> http://www.ics.uci.edu/~fielding/pubs/dissertation/evaluation.

Mark Baker, Chief Science Officer, Planetfred, Inc.
Ottawa, Ontario, CANADA.      mbaker@planetfred.com
http://www.markbaker.ca   http://www.planetfred.com
Received on Thursday, 28 March 2002 15:00:00 UTC

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