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Re: Warnings and SHOULD

From: Mark Nottingham <mnot@mnot.net>
Date: Sun, 17 Jul 2011 12:54:50 +1000
Cc: HTTP Working Group <ietf-http-wg@w3.org>
Message-Id: <5E0FCE7F-EB54-4C8A-8A7C-4B9DC7459C17@mnot.net>
To: Robert Collins <robertc@squid-cache.org>

On 17/07/2011, at 12:49 PM, Robert Collins wrote:

> I don't see how they are redundant:
> 110 depends on cache heuristics
>   stale
>      A response is stale if its age has passed its freshness lifetime.
> ->
> freshness lifetime
>      The length of time between the generation of a response and its
>      expiration time.
> ->
>   heuristic expiration time
>      An expiration time assigned by a cache when no explicit expiration
>      time is available.
> 113 likewise: if squid determines that a not-modified-for-3-weeks file
> does not need refreshing for 30 hours, 25 hours later a client can
> determine that the age is (say) 25 hours, but not why - was it due to
> disconnected operation? was it a heuristic?
> (squid implements 113 FWIW).

If a heuristic was applied, there won't be any headers for explicit freshness.

The semantics of 112 can't be determined solely by looking at the response (although if it had explicit freshness and was served stale, it's a big hint). I just don't think we need a SHOULD enforcing something that's advisory (and not implemented).

Mark Nottingham   http://www.mnot.net/
Received on Sunday, 17 July 2011 02:55:16 UTC

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