Antwort: [Mod_gzip] About 'Vary' header insertion

[mod_gzip@lists.over.net]

Hi Sara,


> 2. Adding 'Vary: user-agent, Accept-Encoding' header to it,
> so that if any caches if they capable, they server the gzipped
> content correctly based on the user-agent/Accept-Encoding.

If you _want_ the content to be cached, you should encourage
the client to not ask for revalidations.
"Expires" and "Cache-Control" are your friends here.

>  Now, the problem, what if the cache does not know about Vary header
> and discards the header?. Will it end up caching the content?.

You could have asked as well "what if the client doesn't
know "Pragma". If you assume that any one player in the game
is broken, then you will be in trouble when predicting the
behaviour of the whole system.

> But when I use <BACK/FORWARD> button in Netscape 4.7, it re-fetches
> the page instead of display the previously fetched page

Which caching strategy did you configure in Netscape 4.7?
And you should know that Netscape believes _very_much_ in
Expires headers ... sometimes even more than in "Pragma:
no-cache" for the same response ... ;-)

> and sometime it displays 'Data not found' error.

Which method are you talking about? GET or POST?

> Now, whats the safer method, to make sure the browser receives
> compressed response without any hiccups if there are some shared
> caches on the way.

This depends on numerous aspects you didn't even mention.
After all, you cannot do more than guess who you will have
to deal with and how this one will comply to the standards-

Regards, Michael