The Maximum Transmission Unit which is the largest possible packet size in bytes that can be sent or received over the network connection in a single physical frame.
This is one of the more popular parameters to change in the TCP/IP stack. A condition called fragmentation will occur if a frame is received that has an MTU smaller than the frame length. Because fragments need to be reassembled it can reduce the overall performance of the connection. When two hosts negotiate a connection the MTU size is determined by using the smallest of the two during the negotiation process. Problem is that if this number is still higher than one of the routers between the connection fragmentation will occur such that the router can handle the packet. In theory, if the MTU size can be adjusted optimally for the MTU size of the ISP router you can cut down fragmentation at one point where your data much always pass therefore cutting down on overall connection time as well. The default MTU is set to 1500 bytes in windows because that is the default size for a LAN (local area network) because generally, they are running much faster wire speeds than WAN (wide area network) like 1000Gbps,100Mbps and 10Mbps. Internet connections generally aren't nearly this speed and therefore will use a smaller MTU size on the WAN connections.
Common recommendations for dial-up MTU size is 576 bytes, a setting between 1400 to 1480 is recommended for DSL users running PPPoE and 1500 for all others.
Because changing the MTU size requires adding multiple keys and DWORD values I will offer only manual instructions for changing the MTU values to optimize PPPoE connections on Windows XP and 2000.
NOTE:
If you're not an experienced user it is never a good idea to manually edit your registry. Always perform a backup prior to any edit.
In Windows XP and Windows 2000 go to the start menu and click on run and type in "regedit" at the prompt, then press ok.
NDIS
In the registry editor click on the + next to HKEY_LOCAL_MACHINE to expand.
HKEY
Then click the + next to SYSTEM and then click the + next to CurrentControlSet to expand these.
Control
Then click the + next to Services to expand a long list, you will be looking for NDIS, when you find it click the + next to it.
NDIS
Now click on the word Parameters and you will see a list of settings appear to the right.
Protocols
Click Edit from the top menu, click New from the drop-down menu, and click Key from the side menu. Type in 0 and press enter.
0
Click Edit from the top menu, click New from the drop-down menu, and click DWORD value from the side menu. A new setting will appear at the bottom of the list on the right with the name "New Value #1" in the field, change this value to "ProtocolType".
Protocol Type
Now, double-click on the Parameter ProtocolType and it will pop up an edit window, change the value to 800 and press ok.
800
Click Edit from the top menu, click New from the drop-down menu, and click DWORD value from the side menu. A new setting will appear at the bottom of the list on the right with the name "New Value #1" in the field, change this value to "PPProtocolType".
PPP Protocol Type
Now, double-click on the Parameter PPProtocolType and it will pop up an edit window, change the value to 21 and press ok.
21
Click Edit from the top menu, click New from the drop-down menu, and click DWORD value from the side menu. A new setting will appear at the bottom of the list on the right with the name "New Value #1" in the field, change this value to "ProtocolMTU".
Protocol MTU
Now, double-click on the Parameter ProtocolMTU and it will pop up an edit window, change the value to the decimal value you wish to change the parameter to (In this example we used 1450) and press ok.
1450
You should benchmark your speed before changing the setting and then benchmark the speed again trying different settings. If you have any problems or it just doesn't benefit you the new keys and DWORD values that you added can simply be deleted.
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