Call authorization and authentication When an endpoint attempts
to make a call, it will place the request with the gatekeeper.The gatekeeper
can authenticate the endpoint (user) with Terminal Access
Controller Access Control System Plus (TACACS+) or Remote Dial-In
User Service (RADIUS).The gatekeeper can authorize or reject the call
based on the user ID alone or in conjunction with parameters such as
time of day, the number being called, and so on.