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Re: Proposal for #486: Requiring proxies to process warn-date

From: Julian Reschke <julian.reschke@gmx.de>
Date: Tue, 03 Sep 2013 09:40:59 +0200
Message-ID: <5225928B.5040102@gmx.de>
To: Mark Nottingham <mnot@mnot.net>
CC: "ietf-http-wg@w3.org Group" <ietf-http-wg@w3.org>
On 2013-09-03 09:23, Mark Nottingham wrote:
>
> On 03/09/2013, at 4:46 PM, Julian Reschke <julian.reschke@gmx.de> wrote:
>
>> RFC 2616 was the first spec to define "Warning" -- what is the backwards compat story here? After all, an 1.0 intermediary will not even know what "Warning" is.
>>
>> What am I missing here?
>
> The actions of a HTTP/1.0 cache can affect the validity of a warning. For example, if a response has the warning "This response is stale" and a HTTP/1.0 cache revalidates it, the response is no longer stale, but the 1.0 cache will not have removed the warning.
>
> Warn-date is a mechanism to detect this situation; if warn-date is different to Date, we know that the warning is no longer valid.

But it seems we lost the description of that mechanism; in 
<http://greenbytes.de/tech/webdav/rfc2616.html#warnings> I see:

"HTTP/1.0 caches will cache all Warnings in responses, without deleting 
the ones in the first category. Warnings in responses that are passed to 
HTTP/1.0 caches carry an extra warning-date field, which prevents a 
future HTTP/1.1 recipient from believing an erroneously cached Warning."

Maybe it would be good to re-add something like that because it explains 
what the date actually is for.

> ...

Best regards, Julian
Received on Tuesday, 3 September 2013 07:41:29 UTC

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