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DrTCP TCP/IP Registry Entries Adjustment Utility

If you are having problems browsing to certain websites on the internet, you may consider using this utility to adjust your PC's MTU setting.  *Some* Windows 2000 computers dialing into *certain* KansasNet local access numbers may not be able to retrieve *some* sites on the internet.  We provide this utility ONLY as a method of helping to correct this problem for KansasNet Dial-up subscribers with Windows 2000 who are having this problem.  Ordinarily, it is NOT necessary to adjust your TCP/IP registry entries using this utility, and doing so would be considered uncommon.  It is highly recommended that you DO NOT use this utility to adjust anything without talking to our tech support staff.  Please note, we will only provide tech support to active KansasNet subscribers.

Our intentions are that this utility is to be used ONLY to change the Dialup MTU setting on Windows 2000 computers as discussed above.  Changing any other settings other than the Dialup MTU using this utility could result in unpredictable behavior with your computer.

What is MTU?
MTU stands for Maximum Transmittable Unit and this setting specifies the maximum size datagram IP that can pass to a media driver. SNAP and source routing headers (if used on the media) are not included in this value. For example, on an Ethernet network, MaxMTU will default to 1500. The actual value used will be the minimum of the value specified with this parameter and the size reported by the media driver. The default is the size reported by the media driver and is usually 1500.  The MaxMTU setting can be adjusted via the Windows Registry key:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Class\netTrans\000n

where n represents the particular TCP/IP-to-network adapter binding.  By default Windows 95/98 do not have the MaxMTU setting in the system registry, so most of the time the MTU will default to 1500.  Because it is often not easy to determine which of the 000n keys (mentioned above) in the system registry is the correct key for the particular adapter of which you want to change the MTU (that's a mouthful), the DrTcp utility provides an easy means of adjusting the MTU.

DrTCP version 020 for Windows 95/98/NT/Me/2000/XP -- Download Now

How do I use DrTCP?
Click on the link above to download DrTCP and you will be presented with another window.  You need to choose the "Save this program to disk" or other similar option and then click OK.  Then you will be presented with another window like the one below.  From the list at the top, choose Desktop as the location to save and make sure drtcp019.exe appears in the filename box, then click Save.  The file will download and save to your Windows desktop.

Once the file has been saved to your desktop, you can execute the program by double-clicking on the DRTCP.EXE icon.

 Once you have executed the program, you will see one of the DrTCP windows shown below, depending on which version of Windows you are using.

Windows 95/98/NT/Me Screenshot

Windows 2000/XP Screenshot

If you have Windows 95/98/Me, in the box labeled Adapter Settings, make sure you have selected Dial-Up Adapter.  Then in the box labeled MaxMTU enter the number 1006.  Next you will need to click in the box at the top labeled Tcp Receive Window to make the Apply button light up.  Do not enter anything in the Tcp Receive Window box, just press Apply.  Then press Exit.

If instead you have Windows 2000/XP, in the box labeled Dial Up (RAS) MTU enter the number 1006.  Then click Save, and then click Exit.

Finally, you MUST reboot your computer for the changes to take effect, by choosing Start-->Shutdown-->Restart the Computer.

NOTE:  You can remove the MaxMTU setting from your computer by running the DrTCP utility again later.  Follow the same steps above, but erase the 1006 number instead of typing it in.  Remember to reboot after you make the change.


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Last modified: April 17, 2007