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


  • 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,"","")) return "DIRECT";
      else return "PROXY";

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

    If I re-enable IPv6 part, then speed isn't so bad.  FYI, Firefox v13 also had the same PAC slow network speed problem with system settings, so it is not just Vista's IE7 and W7's IE8.

    Is there a way to improve this? This proxy server is just for internal. Nothing fancy. I am just a network newbie. ;) Thank you in advance.

    Ant @ Ant's Quality Foraged Links ( and The Ant Farm (

    • Edited by Ant Dude Friday, June 15, 2012 6:24 PM
    Friday, June 15, 2012 5:11 PM


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