Optimal multiplexing on a single link: delay and buffer requirements

This paper is motivated by the need to provide per-session quality of service guarantees in fast packet-switched networks. We address the problem of characterizing and designing scheduling policies that are optimal in the sense of minimizing buffer and/or delay requirements under the assumption of commonly accepted traffic constraints. We investigate buffer requirements under three typical memory allocation mechanisms which represent tradeoffs between efficiency and complexity. For traffic with delay constraints we provide policies that are optimal in the sense of satisfying the constraints if they are satisfiable by any policy. We also investigate the tradeoff between delay and buffer optimality, and design policies that are "good" (optimal or close to) for both. Finally, we extend our results to the case of "soft" delay constraints and address the issue of designing policies that satisfy such constraints in a fair manner. Given our focus on packet switching, we mainly concern ourselves with nonpreemptive policies, but one class of nonpreemptive policies which we consider is based on tracking preemptive policies. This class is introduced and may be of interest in other applications as well.