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Connection Admission Control

ATM networks use connection admission control (CAC) to determine whether to accept a connection request, based on whether allocating the connection’s requested bandwidth causes the network to violate the traffic contracts of existing connections. CAC is a set of actions that the network takes during connection setup or renegotiation.

The router supports CAC on PVCs on major ATM interfaces. This implementation of CAC determines available bandwidth based on port subscription bandwidth. The router maintains available bandwidth for each major ATM port. Bandwidth for VP tunnels is included in CAC computations.

Table 5 lists the traffic parameter that the router uses for each service category to compute the bandwidth that the connection requires. For example, the peak cell rate is used to calculate how much bandwidth is required for CBR connections.

Table 5: Traffic Parameters Used to Compute Bandwidth

Service Category	Traffic Parameter Used to Calculate Required Bandwidth
CBR	PCR
VBR-RT	SCR
VBR-NRT	SCR
UBR	UBR bandwidth configured on the ATM major interface
UBR with PCR	UBR bandwidth configured on the ATM major interface

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