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Subject Re: mod_cache, mod_deflate and Vary: User-Agent
Date Fri, 28 Aug 2009 05:13:48 GMT

> Brian Akins of Turner Broadcasting, Inc. wrote...
> We are moving towards the 'if you say you support gzip,
> then you get gzip' attitude.

There isn't a browser in the world that can 'Accept Encoding'
successfully for ALL mime types.

Some are better than others but there are always certain
mime types that should never be returned with any
'Content Encoding' regardless of what the browser
is saying.

In that sense, you can never really trust the 
'Accept-encoding: gzip, deflate' header at all.

There is (currently) no mechanism in the HTTP protocol
for a client to specify WHICH mime types it can
successfully decode.

It was supposed to be an 'all or nothing' DEVCAP
indicator but that's not how things have evolved in
the real world.

There are really only 3 choices...

1. Stick with the original spec and continue to treat
'Accept-encoding: whatever' as an 'all or nothing' indicator
with regards to possible mime types and treat every 
complaint of breakage as 'it's not our problem, your 
browser is non-compliant'.

2. Change the original spec and add a way for clients 
to indicate which mime types can be successfully
decoded and then wait for all the resulting support code 
to be added to all Servers and Proxies.

3. Do nothing, and let every individual Server owner
continue to find their own solution(s) to the problem(s).

Kevin Kiley


-----Original Message-----
From: Akins, Brian <>
To: <>
Sent: Thu, Aug 27, 2009 9:42 am
Subject: Re: mod_cache, mod_deflate and Vary: User-Agent

On 8/26/09 3:20 PM, "Paul Querna" <> wrote:

> I would write little lua scriptlets that map user agents to two
> buckets: supports gzip, doesnt support gzip.  store the thing in
> mod_cache only twice, instead of once for every user agent.

We do the same basic thing.  We are moving towards the "if you say you
support gzip, then you get gzip" attitude.  I think less than 1% of our
clients would be affected, and I think a lot of those are fake agents

Brian Akins


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