Re: Antwort: Re: Antwort: Re: Antwort: Re: Antwort: [Mod_gzip] Vary: header and mod_gzip

On Wed, 28 Aug 2002 Michael.Schroepl@telekurs.de wrote:

> If Squid 2.4 _did_ treat Accept-Encoding as something
> special, it would be able to prevent M$IE running in
> HTTP/1.0 from unexpectedly receiving gzipped content,
> thus "questioning" the "obviously" missing "Vary:"
> header.
> (If encoded content is there, it _should_ at least de-
> pend on the "Accept-Encoding" header - Squid could be
> suspicious about this combination and rather not use
> the cache content in this case, but "punish the server"
> by forwarding the request. Isn't this an option?)

Sure, it is an option, but outside of the HTTP specification.

Content-Encoding is end-to-end, and semantically transparent proxies is
not allowed to decide on end-to-end features. (non-transparent proxies are
allowed to do pretty much everyting)

> Of course this would not help in the Netscape 4 issue,
> but the M$IE issue seems to be ten times as important,
> given the current market shares of both.

So give me a clear description of the MSIE issue and I'll try to comment
on what I think is the correct approach. So far in this thread I have
received conflicting indications on the nature of this problem.

> This will likely result in a very long "Vary:" list.

True, but in real life not likely.

If there is any kind of structure in your rule engine processor then
detecting shortcuts should be pretty easy once you get access to the
needed data.

> > Meaning: If your server is configured for this URL to respond with
> > gzipped replies to all "Accept-encoding: gzip" requests except for
> > Netscape-4 User-agents then it should respond with "Vary:
> > Accept-encoding, User-agent". At a minimum on all gzipped replies, but
> > preferably on all.
>
> Even on those where a "mod_gzip_item_exclude uri" rule
> will definitely prevent compression? Or in a lot of
> other situations mod_gzip _could_ be able to detect,
> given an enhanced rules checking mechanism?

No. I only care about the rules that may vary for the same URI. A rule
that is always same for the same URI (with the same content) is
irrelevant in terms of HTTP and caching.

Regards
Henrik
Received on Tue Aug 27 2002 - 21:43:08 MDT