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The MaxMTU Fix

So how can you avoid fragmentation during TCP data transfers? Very simple... you can limit the MTU of your TCP/IP request to a smaller or optimum size. Most people using Windows 95 are using the built-in Win95 Dialup Adapter. Indeed, some experts, like John Navas of The Navas Group, say Win95 really only works well with the Win95 adapter. Other experts, however, like Albert Belle Isle say they prefer to stay with a 32-bit version of Trumpet Winsock when connecting to the Internet.

If you are like most Win95 users, though, you are using the Win95 Dialup Adapter which employs the winsock.dll in C:\windows and wsock32.dll file in C:\windows\system (wsock32n.dll belongs to MSIE) and you have a PPP dialup connection (which most ISP's use these days). Windows 95 is set up by default to request a maximum MTU of 1500. You can, however, change that default setting. And, it turns out, depending on how your ISP and other routers encountered on the Internet handle your TCP/IP requests, that a MaxMTU setting of 576 will in many cases avoid the fragmentation of packets of data and the slow transfer speeds which result. (The numbers are reportedly lower for the less efficient SLIP connection, so check with your ISP if that's what you are using.)

How can you change your MTU setting, you ask? Fortunately John Navas of The Navas Group has come up with a handy, free little utility for Windows 95 called TCPIPCFG. This utility will install an "applet" in your Control Panel which allows you to change that pesky little MaxMTU setting to the magical 576. It will only work with the earlier build of Windows 95. If you have a relatively new computer with the newer build of Windows 95, OEM Service Release [OSR] 2, you will have to follow the manual procedure for editing your registry. It seems that this utility may only work with English language versions of Windows 95. If this seems to be your experience as well, or if you find a workaround for this, we would appreciate some feedback.

Whether you use this little utility, TCPIPCFG, or the manual procedure, you will be changing Windows 95's MaxMTU setting by entering the string value MaxMTU=576 to your registry where previously there was no entry at all...
(Windows was using a default value of 1500). TCPIPCFG just makes it easy by making this entry for you automatically.Manual Procedure for the MaxMTU Fix You will probably want to print this file to refer to as you undertake this procedure.

If you don't already have a shortcut to the Registry Editor, regedit.exe, do this:Open Windows Explorer and go to your windows directory and find regedit.exe. Right-click on the file and choose "Create Shortcut" which will create an entry at the end of the list in the directory called "shortcut to regedit.exe". Drag this shortcut to desktop or any folder of your choice. You can also add it C:\windows\start menu\Programs\Accessories which will add it to that collection of utilities accessible from the Start Menu on your taskbar.Once again, be sure you have backed up your registry first.

  1. Now double-click on the shortcut and open the Registry Editor.
  2. You will see a list of folders under "My Computer".
  3. Click on the "+" sign in front of HKEY_LOCAL_MACHINE to expand that folder.
  4. Click on the "+" sign in front of "Enum", and then "Root" and then "Net".
  5. The "Net" subkey will have one or more subkeys under it with names like "0000", "0001", and so on.
  6. Click on each key, starting with the first (not the "+" sign) and it will list the string values contained therein in the window on the right. Find the one with the name "DeviceDesc" with the value of "Dial-Up Adapter" listed in the "Data" column.
  7. Now go back and click on the "+" sign in front of this key (with DeviceDesc in it) and click on the "bindings" subkey. In the righthand window you will see a string name listed like "MSTCP\0000". Use that 4-digit number after MSTCP\ ("0000" in this example) for the next step.
  8. Proceed to the "Network" key under "Enum", expand that and then expand the "MSTCP" key. Click on the 4-digit key with the same number determined in step 7.
  9. In that key, in the window on the right, you will see a string name "Driver" with a value something like "NetTrans\0002". Use that 4-digit number for the next step.
  10. Go all the way back to the "HKEY_LOCAL_MACHINE" key and go down to "System". Click on the "+" sign to expand that folder, then on "CurrentControlSet", then on "Services", then on "Class", then on "NetTrans".
  11. Click on the 4-digit number from step 9 (not on the "+" sign). You will see a list of string values with names like "IP address" and "DriverDesc".
  12. With the 4-digit number still hightlighted, go to the Edit Menu and select New/String Value. A new one will appear on the list with a cursor blinking in it which will allow you to name it "MaxMTU". Hit "Enter" tofinish.
  13. Right-click on the new string name "MaxMTU" and choose "modify" then in the "value data" field type the number..... 576
  14. Whew! That wasn't so bad! With a little practice, like anything else with computers, editing the registry becomes almost second nature.

OK! Close the Registry Editor. Exit your programs and reboot windows (Tip: If you hold down the shift key while clicking on "Restart Computer" in the Shutdown menu, you can reboot only Windows 95 rather than the whole machine.)