Providing Call Admission Control Overview
With the call admission contol (CAC) feature you can prevent voice traffic congestion and ensure that there is enough bandwidth for authorized media sessions by limiting the calls on a connection or link. The BSG applies CAC during call setup to limit the initiation of dialogs and transactions. Dialogs are call attempts or INVITE messages. Transactions are out-of-dialog request messages, including REGISTER, OPTIONS, MESSAGE, and INVITE (INVITE messages that open a dialog).
To use CAC, you configure CAC criteria and then apply the criteria using new transaction policy actions. The policy action verifies whether a new event is permitted or not. If it is not permitted, the BSG rejects the dialog or out-of-dialog transaction by sending 403 FORBIDDEN message.
Table 1 lists the configurable CAC criteria and their maximum values. These maximum values are used by default.
Table 1: CAC Parameters
CAC Parameter | Maximum (Default) Value |
|---|---|
Maximum concurrent dialogs | 100,000 |
Maximum dialog attempts per second | 100 |
Maximum dialog attempts burst size | 200 |
Maximum concurrent transactions | 50,000 |
Maximum transaction attempts per second | 1500 |
Maximum transaction attempts burst size | 3000 |
