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Re: 13.1.2 Warnings

From: Ari Luotonen <luotonen@netscape.com>
Date: Thu, 17 Oct 1996 18:49:39 -0700 (PDT)
Message-Id: <199610180149.SAA06781@step.mcom.com>
To: "Roy T. Fielding" <fielding@liege.ICS.UCI.EDU>
Cc: mogul@pa.dec.com, http-wg%cuckoo.hpl.hp.com@hplb.hpl.hp.com

> Ummm, is there some reason why an HTTP/1.1 user agent cannot tell
> for itself whether or not a message is stale?  After all, the
> same information that made the proxy decide to add the Warning
> header is still present in the cached message, and that information
> can be interpreted by the HTTP/1.1 user agent just as easily as the
> HTTP/1.1 proxy.

Only the proxy knows its own configuration, which contributes to the
decision of whether or not the proxy does an up-to-date check or not.
The Warning header is the only means of telling the client of that
fact.

> BTW, that begs the question of why the client is being warned about
> something that should be obvious from the Date, Age, and Expires/max-age?

See above.  The proxy has config parameters only known to itself,
which affect the cache control policy.

> As a separate issue, Warning is one of the headers that should be
> listed as MUST be sent in a 304 response, with the lack of such a header
> meaning remove any existing Warning messages from the cached entity.
> That would settle the problem entirely, I think.

Not, because HTTP/1.0 doesn't do any of that header wiggling stuff in
the cache.

Cheers,
--
Ari Luotonen	* * * Opinions my own, not Netscape's * * *
Netscape Communications Corp.		ari@netscape.com
501 East Middlefield Road		http://home.netscape.com/people/ari/
Mountain View, CA 94043, USA		Netscape Proxy Server Development
Received on Thursday, 17 October 1996 18:55:15 EDT

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