Cost-based scheduling and dropping algorithms to support integrated services

Applications with diverse performance objectives must be supported on a single packet-switched network. The e ciency of such networks can be greatly improved through use of sophisticated scheduling and dropping algorithms within the queues that form at the network access points and in switches throughout the network. In our approach, arbitrary performance objectives are expressed in the form of cost functions, which map the queueing delay experienced by each packet to a cost incurred. Our heuristic algorithms, cost-based scheduling (CBS) and cost-based dropping (CBD), then attempt to optimize network performance as perceived by the applications by minimizing the total cost incurred by all packets. Appropriate cost functions are presented for common applications. Scheduling and dropping algorithms are de ned from these cost functions. It is demonstrated that network performance is better when these algorithms are used as opposed to the common alternatives. Also, contrary to conventional wisdom, some evidence is presented that sophisticated scheduling may be preferable to sophisticated dropping as a means of adjusting loss rates.