MTU, TTL & others

Windows 2000, much like Windows NT4 previously, is superior to Windows9x is many respects. The TCP/IP stack is better & you should be quite happy to let Windows 2000 self-determine these settings. The same can't be said of Windows9x however. You may still configure some of these settings yourself if you wish. Its not  necessary to do this though.

If you don't feel comfortable with manually editing the registry I'd recommend using Net Optimizer, which is designed for Windows 2000 internet optimization. It uses a GUI based interface for configuration options.

Click on Start, Run. Type regedit & hit enter. Open this key [HKEY_LOCAL_MACHINE\CurrentControlSet\Services\Tcpip\Paramters].

Add/edit the following New DWORD values as you see fit.

DefaultTTL, enter a (Decimal) value for this. I'd recommend a setting of 32 or 64.

 EnablePMTUDiscovery, a value of 1 enables MTU autodetection, leave this enabled.

 EnablePMTUBHDetect, a value of 0 disables Black hole detection, make sure it is set to 0 for best results. Only set it to 1 (enabled)if you have a very bad ISP, in which case you should change provider.

Now go to [HKEY_LOCAL_MACHINE\CurrentControlSet\Services\Tcpip\Paramters\Interfaces]. Add/edit the following New DWORD value.

 MTU, enter a (Decimal) value for this. To find you MTU use the following procedure.

1.    First set the MTU to 1500. Restart your PC.

2.    Upon connecting to the Internet click on Start, Programs, Accessories, Command prompt. Type in ping –f –l xxxx www.yourisp.com. –f means Set Don’t Fragment flag in packet. –l xxxx means Send buffer size xxxx. Replace yourisp with whatever address your ISP’s is. Replace xxxx with numeric values until you get the message Packet needs to be fragmented by DF set. Use whatever the largest value is before the error message & add 28 to it to find your MTU.

3.    E.g. If 1472 is the highest value you can use, then 1500 would be your MTU (1472+28).

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