Dynamic thresholds for multiple loss priorities

Buffer management schemes are needed in shared-memory ATM switches to regulate the sharing of memory among different output port queues and among traffic classes with different loss priorities. Earlier we proposed a single-priority scheme called dynamic threshold, in which the maximum permissible queue length is proportional to the unused buffering in the switch. In this paper, we propose, analyze and simulate nine different ways of incorporating loss priorities into the dynamic threshold scheme. We determine how each scheme allocates buffers among the competing ports and loss priority classes, and we also note how this buffer allocation induces an allocation of bandwidth among the loss priority classes at each port. We find that minor variations in the dynamic threshold control law can produce dramatically different resource allocations.