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Re: Clarification on cacheability

From: Koen Holtman <koen@win.tue.nl>
Date: Thu, 23 Dec 1999 13:44:12 +0100 (MET)
Message-Id: <199912231244.NAA00813@wsooti28.win.tue.nl>
To: "Josh Cohen (Exchange)" <joshco@exchange.microsoft.com>
Cc: fielding@kiwi.ICS.UCI.EDU, joshco@exchange.microsoft.com, http-wg@hplb.hpl.hp.com
X-Mailing-List: <http-wg@cuckoo.hpl.hp.com> archive/latest/654
Josh Cohen:
>I guess if there is any chance that the response could be different,
>based on client auth, client type, or whatever, then it is not safe to

It _is_ safe to make the response cacheable as long as you use Vary
correctly, this is what Vary was invented for.

>(especially since caches dont filter based on accept before
>returning responses)

As Roy said, most (all?) 1.1 caches don't actually implement the
refined filtering made possible by Vary.  They implement the Vary
requirements in 1.1 by treating 'Vary: anything' as equivalent to

But you can still use Vary if you want to help possible future caches:
I would consider this to be good protocol design.  You can find some
examples of the use of Vary+Expires in RFC2295.

Received on Thursday, 23 December 1999 04:52:11 UTC

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