ATM Traffic Descriptors

The ability of a network to guarantee QoS depends on the way in which the source generates cells (Uniformly or in a bursty way) and also on the availability of network resources for e.g. buffers and bandwidth. The connection contract between user and network will thus contain information about the way in which traffic will be generated by the source. A set of traffic descriptors is specified for this purpose. Policing algorithms check to see if the source abides by the traffic contract. The network only provide the QoS for the cells that do not violate these specifications.

The following are traffic descriptors specified for an ATM network.

· Peak Cell Rate (PCR):

The maximum instantaneous rate at which the user will transmit.

· Sustained Cell Rate (SCR):

The average rate as measured over a long interval.

· Burst Tolerance (BT):

The maximum burst size that can be sent at the peak rate.

· Maximum Burst Size (MBS):

The maximum number of back-to-back cells that can be sent at the peak cell rate.

· Minimum Cell Rate (MCR):

The minimum cell rate desired by a user.