Cell Loss Priority Control with Dynamic Threshold Buffer Management Scheme : A Simulation Study

We study the dynamic threshold buffer management scheme applied to a hierarchical shared memory ATM switch which consists of three modules:multiplexer, switching fabric and demultiplexer. Traffic flow between neighboring modules are controlled by the dynamic threshold scheme which is based on a backpressure mechanism. With multiple loss priority traffic within the system, we focus on the usage of controllable parameters, so-called sharing factors, towards prioritized loss control. We show the superiority of the backpressure mechanism enabled system in view of system throughput and prioritized loss control capability. We reach a conclusion that the prioritized buffer management capability is achievable by imposing traffic flow restriction at the entrance of the system, and restrictions within the system have no effect other than degrading the system throughput. Additionally, we realize that the backpressure mechanism enhances buffer utilization as well. Comparing with the delayed pushout scheme which allows full occupancy of buffer space, we observe that the dynamic threshold scheme is more flexible in loss control capability and has a simple process for implementation.