VPN Problems with Vista and Windows Server 2008? Could be "DisableTaskOffload"

Having problems connecting via VPN using RRAS on Windows Server 2008? It might be a problem with the "DisableTaskOffload" setting in the registry.

DisableTaskOffload is a setting that has been around since Windows Server 2000. Essentially it was designed to allow intelligent network adapters to manage network transfers instead of the server CPU - notably TCP checksum calculations and IPSec encryption - thus freeing CPU bandwidth for other tasks .

Well Microsoft Support Esclation Engineer Aydin Aslaner just published in the Routing and Remote Access Blog their discovery that Windows Vista and Windows Server 2008's TCP/IP stacks do not configure DisableTaskOffload properly. It should either be set to 0 (allow offload) or 1 (disable offload). Vista and WS set this value to 255, which stops aplications that depend on this flag. Aslaner suggests modifying the registry entry for DisableTaskOffload to enable it.

Of course, this makes me wonder why turn it off? Why not turn it on since most network adapters in today's servers are intelligent and can easily handle these tasks.