A simple high-performance priority scheme for ATM switching systems

Cell loss priority schemes in the ATM switches are studied. We propose a simple priority scheme called separate logic queues with complete buffer sharing (SQCS). In the SQCS scheme, buffers are shared for the two priority classes; however, two logic queues are required for a high-priority class and a low-priority class, respectively. High-priority cells are placed away from the head of the list of buffers, whereas low-priority cells are placed away from the tail of the list of buffers. When buffers are full and new high-priority cells arrive, the low-priority cells that have just entered the low-priority queue are replaced with these new high-priority cells. Also, we investigate two service strategies, first-come-first-service (FCFS) and absolute service (ABS). Next, our proposed scheme is applied in output-buffering and completely shared-buffering ATM switches. Finally, the performance of our proposed scheme is evaluated and a comparison is made with those of other priority schemes. The results indicate that our proposed scheme obtains a very high performance. Also, the buffer replacement strategy and service strategies in our proposed priority scheme are simple. Hence, the SQCS scheme is an efficient priority scheme for an ATM switching system.