Cac Overview; Measurement Based Cac; Resource Based Cac - Alcatel-Lucent OmniAccess 700 Cli Configuration Manual

Release versions: 2.2, 2.2-r02, 2.3

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Call Admission Controller

In a typical deployment, QoS provides priority to certain type of traffic including

voice. But to have effective voice communication, QoS alone may not be

Consider an outgoing WAN interface that is capable of providing bandwidth for

two voice calls and a third call comes in. Instead of rejecting the request, if

allowed, it might affect all the existing as well as the new calls, with poor voice

quality (like jitter) and delay would be observed everywhere. Few reasons for the

poor voice quality can be network congestion and delay or overloaded gateways.

CAC avoids network congestion by dropping connection requests that cannot be

serviced with the requested QoS parameters.

Since voice is very stringent on its QoS requirement and sensitive to latency and

packet loss, CAC is required for such traffic. CAC is therefore a deterministic and

informed decision that is made before a voice call is established. It is based on the

availability of the network resources that are required to provide suitable QoS for

There are different mechanisms, which can be used to provide CAC functionality.

This mechanism probes the network to find out the delay and congestion even

before the call is established. Based on the result, decision will be made whether

to allow the call or not.

There are multiple resources, which can contribute to the decision for allowing/

controlling new calls in Resource Based CAC. CPU, Memory, Link Bandwidth,

etc., can be used to calculate the resource availability.

Resources like CPU, memory availability can be used to make decision but

cannot reserve. Link bandwidth can be reserved for specific calls and released

when the call ends.

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