[Mod_gzip] Gzip encoding, IE 5 & 6, proxy caches, NetCache

[Kieran Topping]

I am getting some very strange results when trying to gzip-encode content.

I'm not specifically using mod_gzip; however the problems I'm experiencing
appear to be concerned more with browser versions and with proxy servers
than they are to do with the webserver compression code.

The problems I'm experiencing have already been documented in previous
posts: mainly pages in IE (5 & 6) either not loading, partially loading, or
loading with garbled content (truncated at the beginning or end).

There is a lot more evidence I have amassed about the specific circumstances
in which this occurs, which I can provide either on or off-list, if
requested. However, one *big* factor, that occurs time and time again, is
that IE (5 & 6) appear to specifically dislike dealing with gzip-encoded,
chunked content served via the (very common) "NetCache" web-proxy
(http://www.netapp.com/products/netcache/). All experiments I have conducted
*have* worked with Netscape 6.2, and Mozilla, which would tend to suggest to
me that this is an Internet Explorer bug.

Generally, the first time a page is downloaded, it works fine, but
subsequent downloads appear to exhibit the problems.

Simple example
==============

One simple test, repeatable time and time again on my PC (running Win 2000,
using IE 5 & 6), and others, is to:

* Ensure that IE's HTTP content is downloaded via a "NetCache" proxy cache
  How?
  Either:
     Transparently, for instance by connecting to a Freeserve dial-up
account
     (Freeserve, and many other ISPs, use NetCache as a proxy cache)
  or
     Explicitly, by manually setting IE to use a NetCache proxy cache
     (Tools->Internet Options->Connection->LAN Settings)
     An open cache you can use is www-cache.demon.co.uk (port 8080)
     If you do it this way, you must also configure IE to use
     HTTP/1.1 via proxies (in Tools->Options->Advanced)

* Go to Google (http://www.google.com) in IE
  Google uses gzip compression. Generally, the first download works fine.

* Hit "Refresh".
  For me, this refresh renders the same page but with the first couple of
thousand bytes missing.

Subsequent refreshes yield the same result, despite the fact that - as found
out by sniffing the network - exactly the same response is being served each
time!

I would be intrigued to know whether anyone else has experienced similar
problems as this has been driving me to near distraction.

NB The above example isn't valid for IE for the Mac, as it doesn't support
gzip-encoded content.
Furthermore, if relevent, the versions of IE that I've been using are 5.5.40
and 6.026.

I would be delighted to enter into a dialogue either on or off-list with
anyone who has experienced similar frustration, might want some further
information, or might have any solutions!

Kind regards,
Kieran
kieran@kitsite.com