Verifying Maximum Packet Size
At a DOS prompt type:
Ping -f -l nnnn
www.yourisp.com
Replace nnnn with a number that is equal to your MTU setting minus 28 (e.g.: 1454 - 28 = 1426). The ping should not fragment and you should not see the message "Packet needs to be fragmented but DF set" unless nnnn (and thus the value used for your MTU setting) is too high.
Recommended Values for Windows 98 PPPoE Clients
Add or change the MTU value for the NetTrans registry key for the network adapter (or the HSE service adapter for the gateway computer) and values for the MSTCP registry key and delete the Microsoft ICS InternetMTU key, if present, as follows:
HKLM\System\CurrentControlSet\Services\Class\NetTrans\000n
MaxMTU="1454" (string)
HKLM\System\CurrentControlSet\Services\VxD\MSTCP
DefaultRcvWindow="65044" (string)
DefaultTTL="64" (string)
PMTUDiscovery="0" (dword)
PMTUBlackHoleDetect="0" (dword)
Tcp1323Opts="3" (dword)
SackOpts="1" (string)
HKLM\System\CurrentControlSet\Services\VXD\MSTCP\Parameters
MaxDupAcks="3" (dword)
HKLM\System\CurrentControlSet\Services\ICSharing\Settings\General\InternetMTU
[Delete this key as per Microsoft KB Q230/1/16]
Recommended Values for Windows 95 PPPoE Clients
Add or change the MTU value for the NetTrans registry key for the network adapter (or the HSE service adapter for the gateway computer) and values for the MSTCP registry key as follows:
HKLM\System\CurrentControlSet\Services\Class\NetTrans\000n
MaxMTU="1454" (string)
HKLM\System\CurrentControlSet\Services\VxD\MSTCP
DefaultRcvWindow="65044" (string)
DefaultTTL="64" (string)
PMTUDiscovery="0" (dword)
PMTUBlackHoleDetect="0" (dword)
Recommended Values for Windows NT PPPoE Clients
Add or change dword values for registry keys as follows:
HKLM\System\CurrentControlSet\Services\<Adapter>\Parameters\TCPIP
MTU="1454" (dword)
HKLM\System\CurrentControlSet\Services\TCPIP\Parameters
TcpWindowSize="65044" (dword)