Tweaking Your Broadband Connection

While there are a wide variety of cable modem tweaks, I believe the TCP (packet based protocol) RWIN (receive window) registry setting is by far the best tweak you can perform manually. The bad news is you will have to edit the registry which can be a dangerous venture. Below is the simple information on performing this registry tweak, *WARNING* Always backup your registry prior to making any changes!

Cable Modem Tweaks - TCP RWIN Setting

The TCP RWIN registry setting controls the receive window size which will impact your cable modem speed. Generally speaking, the TCP RWIN setting controls how large a window is set to pick up transmitted packets, these data packets need to have delivery confirmed before more data is sent. Therefore if the window is too small, there will be a delay if the new incoming packets have to wait for their predecessors to be confirmed delivered.

A larger receive window allows a continuous flow of data packets. It's a sensitive adjustment because an over sized receive window may result in reloading of unnecessary data packets when there is a transmission error. So the TCP RWIN setting needs to be large enough to allow continuous data flow, but not overly large to hinder performance with the transmission errors that constantly occur.

Backup Your Registry

You should always backup your registry before attempting any kind of registry manipulation.

For Windows 98 & ME click here to learn how to back up the registry.

For Windows 2000 click here.

For Window XP click here.

For Windows 95 click here.

To start the registry editor (REGEDIT), which should already be on your system, simply click Start, then click Run. Type in REGEDIT and click OK. This should popup the registry editor.

Finding the Proper Registry

In your left window pane, you'll need to open the following folders by clicking on them...

HKEY_LOCAL_MACHINE

System

CurrentControlSet

Services

VxD

MSTCP

Changing the RWIN Value

Make sure the MSTCP folder is highlighted so as to display the key values in the right panel. Double-click to open the DefaultRcvWindow key. Now the moment of truth, the value to put here is the subject of much debate... some suggest a value between 32120 to 32760. Some believe it should be set much higher. You could start with 32120 and if there's no speed increase, just experiment a little until you zero in on the optimal setting. After typing in the new value, simply click OK. BUT don't close the editor, there's one more key you may wish to change in this folder.

Some believe setting the DefaultTTL key to 128 may help performance. Others prefer 64. Since this folder is open, you could try to adjusting this setting to 128 now.

Close the Registry and reboot for changes to take effect.