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Re: The problem with proxy-revalidate, and a proposed solution

From: Koen Holtman <koen@win.tue.nl>
Date: Fri, 27 Dec 1996 21:04:56 +0100 (MET)
Message-Id: <199612272004.VAA12811@wsooti04.win.tue.nl>
To: Jeffrey Mogul <mogul@pa.dec.com>
Cc: http-wg%cuckoo.hpl.hp.com@hplb.hpl.hp.com
Jeffrey Mogul:
>
>The other approach, which Paul favors (and I think I do, too) is
>define something like
>        Cache-control: proxy-maxage=NNN
>which supplies a separate age limit that applies only to shared
>caches.  For example, a server doing authentication or hit-metering
>might send:
>        Cache-control: max-age=30, proxy-maxage=0

I think you have a good case for adding a directive to get these
semantics.  However, I'm not very happy with proxy-maxage.  I prefer
to add an agent-max-age directive, which will (generally) _weaken_ the
age limit for user agents, like this:

        Cache-control: max-age=0, agent-max-age=30

I prefer agent-max-age because, unlike proxy-maxage, it is a `safe'
extension of the current set of directives.  With `safe', I mean that
a client which ignores the new directive, because it does not (yet)
know about it, would err on the safe side: this client would
revalidate earlier, not later.

We would have no choice but to go for a safe extension if process or
smooth deployment were issues, but it seems that they are not.  Still,
I prefer a safe extension, because it is better engineering practice.

Koen.
Received on Friday, 3 January 1997 15:20:40 EST

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