Call Admission Control of Bandwidth Management is a function that admits or rejects incoming calls between zones based on availability of bandwidth.
If a call cannot reach the destination because it encounters a managed point between ICPs in the network that have reached maximum bandwidth, the call follows network congestion handling, allowing alternate routing, for example, over TDM.
If a call reaches the destination ICP, but cannot get to the IP Phone because there isn't enough bandwidth, the call is handled as if the user is busy, for example, the call may go to voice mail.
Note: Error messages may differ for congested calls on an out-of-service trunk, indicating "Out of Service" or "Xnet Busy". This is due to the behavior of Call Admission Control, which is performed prior to seizing an outgoing trunk. If the Zone Access Point (ZAP) is blocked, the user receives the message "Xnet Busy". If the ZAP is not blocked, the call passes Call Admission Control, and attempts to go out and returns the message "Out of Service".
