For Fast Ethernet and Gigabit Ethernet interfaces, ISDN BRI interfaces, and serial interfaces with PPP or Frame Relay encapsulation on J4350 and J6350 Services Routers supporting VoIP through the TGM550 media gateway module, you can configure dynamic call admission control (CAC). Dynamic CAC provides enhanced control over WAN bandwidth. When dynamic CAC is configured on an interface responsible for providing call bandwidth, the TGM550 informs the Media Gateway Controller (MGC) of the bandwidth limit available for voice packets on the interface and requests the MGC to block new calls when the bandwidth is exhausted.
Dynamic CAC is useful in situations where a primary link becomes unavailable and a backup link with less bandwidth takes its place. Without dynamic CAC, the MGC cannot detect the switchover to the backup link or the resulting changes in network topology and available bandwidth. The MGC would continue to admit calls at the bandwidth of the primary link, causing network congestion and possible jitter, delay, and loss of calls.
To configure dynamic CAC, you define the bearer bandwidth limit (BBL) and activation priority on each WAN interface responsible for providing call bandwidth.
The Gigabit Ethernet interface is used as the primary link for providing call bandwidth because it has the highest activation priority value. When the Gigabit Ethernet interface is active, the TGM550 reports its BBL value of 3000 Kbps to the MGC. If the Gigabit Ethernet interface fails, the TGM550 automatically switches over to the T1 interface because it has the next highest activation priority. The TGM550 now reports the BBL value of the T1 interface to the MGC. If the T1 interface also fails, the TGM550 switches over to the ISDN BRI interface and reports the BBL value of the ISDN BRI interface to the MGC. Configuring dynamic CAC on multiple WAN interfaces allows the MGC to automatically control the call bandwidth when interfaces responsible for providing call bandwidth are unavailable.
To configure dynamic CAC, include the following configuration statements:
- unit 0 {
-
-
dynamic-call-admission-control {
-
activation-priority value;
-
bearer-bandwidth-limit value;
- }
- }
You must configure dynamic CAC on logical unit 0. You can include this statement at the following hierarchy levels:
kilobits-per-second is the dynamic CAC BBL—the maximum bandwidth available for voice traffic on the interface. The TGM550 reports the BBL to the MGC. When the call bandwidth exceeds the BBL, the MGC blocks new calls and alerts the user with a busy tone. The default BBL is –1, which indicates that the complete interface bandwidth is available for voice traffic. Configure bbl 0 to report zero bandwidth for bearer traffic to the MGC or to use the interface for signaling purposes only. The range is from 0 through 9999 Kbps.
priority is the dynamic CAC activation priority value that specifies the order in which interfaces are used for providing call bandwidth. The interface with the highest activation priority value is used as the primary link for providing call bandwidth. If the primary link becomes unavailable, the TGM550 switches over to the next active interface with the highest activation priority value, and so on. The activation priority value range is 0 through 255. The default is 50.
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Note: Dynamic CAC works in conjunction with the Avaya Communication Manager (CM) Call Admission Control: Bandwidth Limitation (CAC-BL) feature. If you configure dynamic CAC on WAN interfaces, you must also configure CAC-BL on the Avaya CM. For more information about configuring CAC-BL, see the Administrator Guide for Avaya Communication Manager. |
The following is a configuration example:
- interfaces ge-0/0/3 {
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- unit 0 {
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- dynamic-call-admission-control {
- activation-priority 150;
- bearer-bandwidth-limit 1000;
- }
- }
- }