EFFECTIVE BANDWIDTHS WITH PRIORITIES

The notion of effective bandwidths has provided a useful practical fra mework far connection admission control and capacity planning in high- speed communication networks. The associated admissible set with a sin gle linear boundary makes it possible to apply stochastic-loss-network (generalized-Erlang) models for capacity planning, In this paper we c onsider the case of network nodes that use a priority-service discipli ne to support multiple classes of service, and we wish to determine an appropriate notion of effective bandwidths. Just as was done previous ly for the first-in first-out (FIFO) discipline, we use large-buffer a symptotics (large deviations principles) for workload tail probabiliti es as a theoretical basis, We let each priority class have its own buf fer and its own constraint on the probability of buffer overflow, Unfo rtunately, however, this leads to a constraint for each priority class , Moreover, the large-buffer asymptotic theory with priority classes d oes not produce an admissible set with linear boundaries, but we show that it nearly does and that a natural bound on the admissible set doe s have this property, We propose it as an approximation for priority c lasses; then there is one linear constraint for each priority class. T his linear-admissible-set structure implies a new notion of effective bandwidths, where a given connection is associated with multiple effec tive bandwidths: one for the priority level of the given connection an d one for each lower priority level. This structure can be used regard less of whether the individual effective bandwidths are determined by large-buffer asymptotics or by some other method.