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Can I optimize the same computer for both a Cable or DSL connection as well as Dialup?

TweakMASTER Knowledge Base article KB0022

If you are using both a broadband connection like Cable/DSL and a dialup connection at times as well from the same computer with older Windows operating systems, then it may be necessary to change settings (which requires a system reboot) when switching from one to the other. With Windows XP, this is no longer needed and TweakMASTER will allow you to set different MTU and TCP Receive Window values for both broadband and dialup connections. With older Windows OS, you can experiment as follows:

MTU is set individually for each type of interface (or adapter). On the "Internet Optimization" screen in TweakMASTER simply use the drop down arrow at the right of the field to select each adapter individually. Set all dialup adapters the same: 576 is often a good choice there although you may wish to experiment with some other numbers as suggested in the TCP/IP Parameters Tweaking Tips section of "Getting Started" in the TweakMASTER helpfile.

As for your broadband connection, you should have an interface on the list which is used for that, typically some kind of Network card. Select that one and set MTU to 1500 as a first step. There are some special circumstances where this may not apply (please see the section near the bottom of this email on that.)

Thus MTU may be set differently for your different adapters... and except in the case of certain AOL users, these settings will be retained (AOL has a nasty habit of reverting to its own settings for the occasional user.)

RWIN however is set globally in older Windows OS. In Windows XP this is called TCP Receive Window and may be set to different values for different network interfaces. With older Windows OS, there is only one place in the registry where RWIN is set and it applies to ALL MTU settings for all adapters. Normally a broadband connection wants a very large RWIN while dialup connections prefer a smaller one. For older Windows and for XP, you can experiment here. Use the drop down list the in box labelled "Set to:" and try some of the higher ones and see how your connection works. Try this first with your Network card's MTU selected. If this doesn't work well under all circumstances, try lowering the MTU.

In the alternative, with older Windows OS, you may want to try setting ALL your adapters to the same MTU (the one best for your broadband connection) and then set RWIN to that and experiment with that. The other option to try would be setting RWIN to "Windows default" which allows Windows to adjust it automatically. Windows doesn't do a terribly good job with this, but in certain circumstances it may be the best alternative with older Windows OS.

This will take a little patience, but the results may be well worth it in the long run. And we would GREATLY appreciate your feedback on what worked best for you. We are trying to make TweakMASTER the best it can be and with so many different kinds of Internet access out there, it's a tricky task. You input will help a lot!

Special circumstances

There are certain special circumstances where a standard combination of settings will not work. If yours is one of them, please read below about various situations which require special settings.

On an ADSL connection, for example, an MTU of 1500 may result in no connection at all. It must be set it to 1456 or lower because of NAT and PPTP.

Anyone who wants to have decent performance with NT Terminal Services will have to set MTU to somewhere around 1000.

Anyone on cable/DSL with PPPoE will want to set MTU to a value lower then 1500. Since all the users over the Ethernet share a common connection, the Ethernet principles supporting multiple users in a LAN combine with the principles of PPP, which apply to connections. 1492 is one number to experiment with here. Or with it set to 1500 try the MTU probe to your ISP and see what number is returned and try that.

Dialing up with a Linux box (using it as gateway) you would want to try running the TweakMASTER wizard on a Windows machine, and use "dial-up" with "network adapter" (set 576 MTU to the network card). This has resulted in considerable speedup for some users.

We hope some of these hints help you.