Dynamic Thresholds for Multiple Loss Priorities

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