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Re: p6: Returning the freshest response

Ken Murchison <murch@andrew.cmu.edu> Fri, 29 March 2013 16:04 UTC

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Date: Fri, 29 Mar 2013 12:02:36 -0400
From: Ken Murchison <murch@andrew.cmu.edu>
Organization: Carnegie Mellon University
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To: Martin Thomson <martin.thomson@gmail.com>
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Subject: Re: p6: Returning the freshest response
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Martin Thomson wrote:
> On 29 March 2013 08:24, Ken Murchison <murch@andrew.cmu.edu> wrote:
>   
>> So the (my) question is, what can/should a cache do with multiple stored
>> responses in the absence of any Vary headers, as in your example above?  Can
>> the cache use proactive content negotiation headers provided in the request
>> to select the stored response that the client would prefer?  Or should the
>> cache not select a response and punt it to the origin server per Section
>> 4.2?
>>     
>
> An origin server is required to include a Vary header if conneg is
> possible, even if conneg isn't used.
>   
Hi Martin,

The current language in 
https://svn.tools.ietf.org/svn/wg/httpbis/draft-ietf-httpbis/latest/p2-semantics.html#proactive.negotiation 
(MAY) and 
https://svn.tools.ietf.org/svn/wg/httpbis/draft-ietf-httpbis/latest/p2-semantics.html#header.vary 
(SHOULD)
don't seem to make it a requirement.  However, the SHOULD certainly 
suggests best practice.

That notwithstanding, unless Mark's example omitted the Vary headers for 
brevity, my question still stands.

-- 
Kenneth Murchison
Principal Systems Software Engineer
Carnegie Mellon University

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