If your 100MB EtherNet TCP/IP network performs poorly, it could be due to ACK collisions. You can contact your NIC manufacturer to see if there is a way to increase the interframe gap.
The Intel EtherExpress 100B adapters have a registry parameter:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\e100bx\Parameters
where
If you have a different NIC, edit:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters
and add Value name TcpWindowSize as type REG_DWORD and set it to 2920 (decimal).
Note: This tip is for 100MB EtherNet TCP/IP networks only. Using this parameter on a 10MB network, or on a WAN or FDDI, or Token Ring, or anything else, will impact performance.