network performance

[ihateusernames]

I recently got cable broadband hooked up (15Mbit/s). I've found that with a computer connected directly to the modem I achieve the rated speed. Currently I have a mini-ITX Pentium M board with dual Intel PRO100 NICs connected to the modem and LAN with internet connection sharing on Windows 2000. Sadly, in this configuration the other PCs on the LAN don't seem to be getting the full speed when downloading from websites. Are there any tricks to improve this? It should be no problem to pass 15Mbit/s over 100mbit ethernet, but I guess there is some kind of latency issue. I have a router I could use instead, but if I move it to where the modem is then I would need to buy another switch or some long cables to keep everything connected...

[ihateusernames]

OK, did some more research. I added these settings to the registry on both Win2K machines (needs a reboot to take effect)

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters

EnablePMTUDiscovery (DWORD) = 1

GlobalMaxTcpWindowSize (DWORD) = 128480 (decimal)

Tcp1323Opts (DWORD) = 1

TcpWindowSize (DWORD) = 128480 (decimal)

This doubled my throughput!

Edited February 7, 2016 by ihateusernames

[jumper]

Unless your Internet+ICS latency is rarely over 70ms, you'll probably want to increase your window size again.

I suggest using the SpeedGuide.net TCP Optimizer to measure and optimize your settings. There you will also find:

sguide_tweak_2k.zip

Description: Generic patch for Windows XP and Windows 2000 (all versions). This patch will optimize your TCP/IP Registry settings for high speed Internet connections. To install, extract the .inf file first, then double-click (or right-click on filename and choose install from the pull-down menu) and reboot for changes to take effect.

OS: Windows 2K/XP/2k3 | version: 1.0 | date: 12/18/01 | filesize: 1 KB