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Re: HTTP Partial Download Query

From: Alex Rousskov <rousskov@measurement-factory.com>
Date: Tue, 10 Dec 2002 09:10:27 -0700 (MST)
To: Scott Lawrence <lawrence@world.std.com>
cc: Yogesh Bang <Y.Bang@zensar.com>, <ietf-http-wg@w3.org>
Message-ID: <Pine.BSF.4.44.0212100900010.8496-100000@measurement-factory.com>

On 10 Dec 2002, Scott Lawrence wrote:

> B) Express the limitation using HTTP Range (your choice 1).  I have
>    seen this done in exactly this application.  See Alexs comments on
>    the possible problems with proxies that don't honor Range (is there
>    any emperical data about how deployed proxies respond to this?).

IIRC, a popular open-source Squid proxy would do one of the following,
depending on the Squid version, hit/miss status, and complexity of the
Range expression:

	- tunnel the Range transaction through
	- respond with entire [cached] entity
	- convert Range request to a regular GET,
	  possibly cache the entire response, and
	  extract requested range(s) to be sent the
	  the client
	- respond with requested [cached] range(s)

I bet that other deployed proxies use a combination of the above
techniques as well. Keep in mind that some proxies are "transparent"
and some are "reversed", making a naive client unaware of the proxy
presence. This makes it difficult, if not impractical, to auto-adjust
client behavior depending on the environment.

Alex.

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Received on Tuesday, 10 December 2002 11:10:35 GMT

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