Is any-one familiar with how radius works?

I have a client that gets 718's on a regular basis.
The funky thing about it is: He has a Cisco AS5400 that requires you to disable software compression and Use ip header compression in order to get Dataflow once connected.

I am trying to figure out if the PPP Timeout (error 718) is coming from the router or if the Radius server is causing the issue when negotiating the packets??

any ideas??

It could be that the RADIUS server is not responding within quick enough. Although, it's possible that the RADIUS server is not properly configured, e.g. the router isn't listed as a client/NAS, so it won't authenticate the user.

If it doesn't happen all the time, then here's something to check. Make sure the RADIUS server is bound to the IP that the router is sending the authentication packets to.