David Yerka asked what can cause really slow network performance in Windows 95/98. I mailed him, suggesting maybe someone had run MTUSpeed or some similar utility on the machine to optimize dialup performance. LAN performance tends to go into the toilet after doing that. (Voice of experience speaking… My Win95 box was a real dog until that light went off–long after my book was on store shelves, of course.) He responded with some useful information.
From: David M. Yerka
Subject: Re: Slow Win9x network performance
To: Dave FarquharHi Dave:
Thanks for the reply you win the big bucks! That is exactly what is going on. Apparently Win9x only sets the MaxMTU in one place:
HKey_local machine\system\currentcontrolset\services\class\nettrans000
and while additional information makes this key appear to belong only to dialup networking apparently it is the place where Win9x picks up the settings for the network also. You were right also I remembered (actually, before I got your email) that someone had used MTUSpeed on this machine to optimize dialup before I convinced my clients to get a “webramp appliance” to do sharing. Unfortunately, it appears that even if you tell MTUSpeed to “remove all settings” it leaves the MaxMTU setting at say 576 (which is usually the best for dialup ISP’s). You must explicitly change the settings in MTUSpeed to 1500 and reboot BEFORE have MTUSpeed “remove all settings.”
Interestingly, I found that you could sort of hack the registry with a combination of stuff and seemingly get both optimizations: stick a string in the key below of MaxMTU=”1500″
HKey_local machine\system\currentcontrolset\services\class\nettrans\netservice000
Use MTUSpeed to set the MTU to 1500 reboot
edit the first key …\nettrans000 to MaxMTU=”576″ and reboot.
checking with MTUspeed (and don’t under any circumstance change anything) shows the MTU to be 576 while network performance approaches 950K for a 10T UTP network.
Isn’t Window just wonderful and weird.. or something!!
Thanks again David Yerka
David Farquhar is a computer security professional, entrepreneur, and author. He started his career as a part-time computer technician in 1994, worked his way up to system administrator by 1997, and has specialized in vulnerability management since 2013. He invests in real estate on the side and his hobbies include O gauge trains, baseball cards, and retro computers and video games. A University of Missouri graduate, he holds CISSP and Security+ certifications. He lives in St. Louis with his family.