How to organize traffic accounting in the network?

Question

Computer networks

Greetings!
We have the following scheme: the Internet comes to Windows Server 2003 with the "Remote Access Server/VPN" role installed, which distributes the Internet directly to other users.
So here's how you can see who eats traffic how much, limit access to speed, etc.

Answer 1

I advise you to look in the direction of Traffic Inspector and the like.

Answer 2

put a proxy on this server - and analyze its logs. users through a proxy can be wrapped with policies or the transparent proxy setting.
squid is also available under Win2003.