Making RADIUS work with Layer 3

Hi all,

I am trying to find a way to make RADIUS work with layer 3. We have quite a few connections coming in through a VPN connection and our provider does not pass layer 2 at all. We really need to get bandwidth quotas setup for all the users but I have yet to find a way to do this using only IP addresses. Is there any way to do this? I am currently messing around with DMASoftlabs Radius Manager but am willing to use any other solution as well as possibly having a custom solution developed.

Thanks for any help!