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Re: Does no-store in request imply no-cache?

From: Mark Nottingham <mnot@mnot.net>
Date: Mon, 18 Oct 2010 15:30:27 +1100
Cc: Adrien de Croy <adrien@qbik.com>, HTTP Working Group <ietf-http-wg@w3.org>, David Morris <dwm@xpasc.com>
Message-Id: <9D10B0A5-3578-482A-B1DE-A1F2AC1C8634@mnot.net>
To: Eric J. Bowman <eric@bisonsystems.net>
It looks like we're getting off-track here; can we focus on the issue at hand, please?


On 18/10/2010, at 3:24 PM, Eric J. Bowman wrote:

> Adrien de Croy wrote:
>> 
>> talking about IP and tracerts is a complete red herring.  These
>> agents are the parties in TCP connections.  Sure, the IP packets may
>> go via different routers between the endpoints, but the endpoints are
>> the endpoints.
>> 
> 
> Exactly, which is why this is no red herring...
> 
> A = user-agent
> B = origin server
> C = cache
> 
> The route from A to B passes through C, the route from B to A passes
> through D.  User-agent A sends a GET request to the origin server B.
> The request is a hit on cache C, so the response goes from C to A.
> 
> In the event of a cache miss it is not A, but C, making the request to
> B -- but only for safe methods, otherwise C is not an endpoint.
> 
> The user at A changes the representation and makes a PUT request to B.
> Cache C intercepts this request, and *routes* it to B.  B then sends a
> 200 OK response to A, which does not pass through C.
> 
> This is because caches are stand-ins for origin servers, not user-agent
> proxies.  B knows nothing of C, because A made the PUT request.
> 
> So, C only knows the status of the response to the PUT if the route
> from B to A is the same as the route from A to B.  When dealing with
> unsafe request methods, intermediaries are not participants, only the
> user-agent and origin server are endpoints.
> 
> -Eric
> 

--
Mark Nottingham   http://www.mnot.net/
Received on Monday, 18 October 2010 04:30:59 GMT

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