Cabletron Systems 04-0053-01 Call Admission Control Policy, SmartSwitch # add trafficdescriptor

Traffic Management Traffic Management Capabilities

A user-defined PVC must have user-defined traffic descriptors. For instance, if a video link over a PVC requires a peak cell rate of 8000 kb/s, create a traffic descriptor for CBR traffic that specifies 8000 as the peak cell rate.

SmartSwitch # add trafficdescriptor
TrafficType(UBR)	: cbr
TrafficDescriptorType(2)	:3
PCRCLP01(100)	:8000
QOSCLASS(1)	:
AalType(5)	:
SmartSwitch #

Each traffic descriptor is identified by a unique index number. Use the index number to specify which traffic descriptor to use when setting up a PVC. For example, the add pvc command prompts you for the traffic descriptor index.

SmartSwitch # add pvc
ConnType(PTP)	:
Port-1-Number()	: 7a1
Port-1-VPCI()	: 0
Port-1-VCI()	: 100
Port-2-Number()	: 7b2
Port-2-VPCI()	: 0
Port-2-VCI()	: 100
Port1-to-Port2TrafficDescriptorIndex()	: 3	— Forward traffic descriptor
Port2-to-Port1TrafficDescriptorIndex()	: 2	— Backward traffic descriptor

SmartSwitch #

Notice in the example above that you can use different traffic descriptors for forward and backward traffic provided that both traffic descriptors used belong to the same service category.

6.1.2Call Admission Control Policy

Call Admission Control (CAC) policy defines the bandwidth allocation scheme used by the CAC when setting up connections. ATM SmartSwitches offer three schemes that can be set on a per-port, per-service class basis,

•Conservative

•Moderate

•Liberal

Under conservative policy, the CAC allocates bandwidth closest to the requested bandwidth and QoS parameters. Conversely, liberal policy causes the CAC to allocate the least amount of bandwidth. And the CAC under moderate policy allocates intermediate amounts of bandwidth.

Depending on the type of traffic on your network, each of these CAC policies has its advantages. For instance, liberal policy allows a larger number of connections over that of the conservative or moderate policy. Liberal policy assumes that the traffic pattern of individual VCs does not overlap most of the time. For example, if VC1 and VC2 are created under the liberal CAC policy, it’s assumed that the probability of both VCs sending large bursts of cells at the same time is relatively low. On the other hand, conservative policy assumes that there might be a larger overlap of traffic from different VCs, and provides each VC with bandwidth closer to the requested bandwidth. This higher bandwidth provides a guarantee of quality for each VC.

SmartSwitch ATM User Guide 6-3