Call Admission Control

The congestion management and avoidance mechanisms discussed in previous sections can be essential in ensuring that voice traffic is protected from (excess) data traffic. But, although congestion management and avoidance mechanisms can protect voice from data, they cannot protect voice traffic from other voice traffic.

The function of CAC is to ensure that too many voice traffic flows are not sent across the network. That is, voice calls are admitted to the network only as long as the network can ensure sufficient quality of service (in terms of delay, jitter, and packet loss) for those voice calls. If the network is unable to ensure sufficient quality for a voice call, that voice call must not be admitted to the network.