Very slow network speeds with proxy.pac scripts with a(n) internal/local proxy server.

[Ant]

Hi!

I am trying to figure out why using simple/basic proxy.pac files with
two different Intranet computer, acting as temporary web and proxy
servers, make network speeds very slow for web even if the web sites are
internal on LAN (Intranet). Web pages pause/hang and download speed is
horrible like 300-2400 dial-up modems! If I don't use proxy.pac and just
connect directly to the proxies, then they are fast but I want to use
the PAC scripts.

My proxy.pac files hosted on two different separate small Windows web
servers on Windows XP (Pro.'s IIS[web for proxy.pac file]+Squid[proxy]
and Apache [both proxy and web with proxy.pac]. An example of a
proxy.pac file from Squid+IIS:

function FindProxyForURL(url,host)
{ if(isPlainHostName(host)||
isInNet(host,"192.168.0.0","255.255.0.0")) return "DIRECT";
else return "PROXY 10.147.30.159:3128";
}

I want all network traffics go through the proxy server. Nothing go in
and out around it. Hence 192.168.0.0 part.

I also noticed Windows XP clients are faster in terms of download and
shorter hangs/pauses. Vista and Windows 7 are way worse and sometiems
forever like overnight! I also found out that disabling Vista and W7's
IPv6 network make them faster like XP. XP doesn't come with IPv6 by
default. Also, I don't use or need IPv6 at this time.

Is there a way to improve this? This proxy server is just for internal.
Nothing fancy. Thank you in advance. :)
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