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Re: Session-ID proposal

From: Jim Seidman <jim@spyglass.com>
Date: Mon, 14 Aug 95 09:40:35 -0500
Message-Id: <9508141440.AA12117@hook.spyglass.com>
To: dmk@allegra.att.com (Dave Kristol)
Cc: www-talk@www10.w3.org, http-wg@cuckoo.hpl.hp.com
At 05:48 PM 8/10/95 EDT, Dave Kristol writes:
>I have assumed (erroneously?) that a caching proxy must send
>conditional GETs to the origin server.  If so, there's already the cost
>of a connection.  The State-Info (previously "Session-ID") can ride the
>request almost for free.

This isn't necessarily true.  If the server sends "Expires" headers, then
the proxy can pretty safely avoid sending if-modified-since requests, for

Even without "Expires" headers, some caching proxies just use simple
algorithms to avoid doing a GET on each request, e.g. only re-requesting
text/* files if they're at least an hour old.  This applies not only to
proxies, but also to clients with persistent caches such, if I have a
document still cached on my hard-drive from an access yesterday.

Given these considerations, and the slowly increasing use of "Expires"
headers, State-Info could be expensive indeed.

Jim Seidman, Senior Software Engineer
Spyglass Inc., 1230 E. Diehl Road, Naperville IL 60563
Received on Monday, 14 August 1995 10:40:49 UTC

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