Tweaking DSL Speed (MTU Size) Setting in Windows XP

by Eric Geier [Published on 11 June 2008 / Last Updated on 11 June 2008]

How to change the MTU size for PPPoE connections.

The default Maximum Transmission Unit (MTU) size for PPPoE (DSL) connections in Windows XP is typically set to 1,480 or 1,490 bytes. However if find you can’t browse some Web sites or send e-mail messages with attachments, your DSL connection may work better with a slightly lower MTU size setting (somewhere between 1,400 to 1,490). You can refer to another tip on this site for information on how to test out what MTU size is best for your Internet connection.

To edit the MTU size in Windows XP, you must first add the following keys to the Windows Registry:

Key: System\CurrentControlSet\Services\Ndiswan\Parameters\Protocols\

Key: System\CurrentControlSet\Services\Ndiswan\Parameters\Protocols\0

Then add the following entries to the 0 key:

Name: ProtocolType
Value: 0x00000800

Name: PPPProtocolType
Value: 0x00000021

Name: ProtocolMTU
Value: desired MTU size


Eric Geier is an author of many wireless networking and computing books including Home Networking All-in-One Desk Reference For Dummies (Wiley 2008) and 100 Things You Need to Know about Upgrading to Windows Vista (Que 2007).

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The Author — Eric Geier

Eric Geier (Dayton, Ohio) is a Freelance  Tech Writer and Author specializing in computer networking. He's also the Founder and Owner of NoWiresSecurity, which provides a hosted cloud-based RADIUS service to help businesses easily secure their Wi-Fi networks with the Enterprise (802.1X) mode of WPA/WPA2 security. He’s also the Founder and Owner of On Spot Techs, which provides on-site computer and technology services.

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