What is Internet Connection Booster?
Internet Connection Booster 2000 is a utility that can improve the speed at which you browse, send and receive email, and download files from the Internet. Internet Connection Booster 2000 adjusts and modifies the various "hidden" configuration parameters used by the Internet protocol (TCP/IP) under Windows 95 and 98. By default, the Internet settings in both Windows 95 and 98 do not come optimized for people accessing the Internet with a Dial-Up or Modem connection, but instead come optimized for In-House Networks (LAN's). By adjusting and optimizing these settings, Internet Connection Booster 2000 can improve the performance of all your Internet-related software.
This can turn MTU value from 1500 to 576 easily.
Link:
http://toshi.50megs.com/icb2000/
You can download it from there. Freeware.