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Re: Confusion about Age: accuracy vs. safety

From: Koen Holtman <koen@win.tue.nl>
Date: Mon, 26 Aug 1996 19:48:53 +0200 (MET DST)
Message-Id: <199608261748.TAA18444@wsooti04.win.tue.nl>
To: Jeffrey Mogul <mogul@pa.dec.com>
Cc: koen@win.tue.nl, http-wg%cuckoo.hpl.hp.com@hplb.hpl.hp.com
X-Mailing-List: <http-wg@cuckoo.hpl.hp.com> archive/latest/1465
Jeffrey Mogul:
>If people are confused by this, then maybe we need to add some
>clarifying language that makes it explict: a proxy SHOULD NOT
>(or perhaps MUST NOT) retry a request that completed with
>a successful transmission of a response, whether or not that
>response is acceptable to the requesting client.

Clarifying language like this is already in the draft, see the end of
Section 13.1.1.  The start of 13.1.2 could be interpreted to
contradict the clarification as far as the Warning header is
concerned, though.  My concerns are mainly about cache implementers
who just get it wrong, and add a Warning:stale when they should not.
Like I said, `obvious' mechanisms added for robustness could easily
cause catastrophic failure when deployed in a chain of proxies.

>After thinking about the possible failure modes, I believe that Koen's
>proposal would be acceptable to me, but only with the following
>     - MUST add Age when serving from cache memory
>     - MUST add Age when relaying a response from a pre-1.1 source
>     - SHOULD NOT add Age when relaying a response from a 1.1 or
>       higher source

That would be acceptable to me.  I don't see the need to add Age when
you get something directly from a pre-1.1 _origin_ server, but I could
live with this requirement.


Received on Monday, 26 August 1996 10:53:19 UTC

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