Termination when there is no traffic

[Johnny]

Hi there,

I've got a little proiblem with my radius server. I use it for dial-in accounts via ISDN. I've the problem that connections are terminated automatically when no traffic is on the line. The authentification works without problems, but I do not know which parameter I have to change so that connections wont be terminated automatically anymore. Could anyone help me with this? Thank you!

Regards, John