So I've installed VPN service that comes with Windows Server 2008. Works perfectly, etc.

When a client remote desktops to one of the private servers at the office, via VPN .. it's pretty slow.

Now - how long is a piece of string?

So before I get all the obligatory checks, I'll list the things from Mr. Obvious:

• Our modem/router (fritz!box) has a data/graph that shows incoming and outbound bandwidth. Both directions are barely getting used when a client has RDP'd via VPN.
• Our office internet connection is running at 21,9 Mbit/s download 1,3 Mbit/s upload.

I feel like it's maxing at .. modem speeds ??

Is there any tricks I can do to confirm this and possibly even fix this?