Coming Broadband Integrated Services Digital Networks (B-ISDNs) will be required to carry a broad range of traffic classes ranging from bursty, variable-rate sources, such as voice and variable-rate coded video, to smooth constant bit rate sources. Moreover, these networks will have to do so while providing a guaranteed quality-of-service (QoS) to these traffic classes. The problem of characterizing the performance of such networks is thus particularly important since this must be done, not only during the network design (in an off-line manner) but also for on-line control purposes such as call admission control. In this proposal we describe a novel technique for evaluating network performance based on the use of Global Rational Approximations (GRA) which has the potential of providing accurate estimates for a variety of performance measures such as packet loss probability in a wide variety of network settings. We outline research on GRAs whose aim is to develop a solid theoretical foundation on which the proposed algorithms can rest and to develop practical techniques for estimating network performance both during the design phase and in a real-time setting. Specifically, we propose to develop a complete theoretical foundation on which to develop algorithms for obtaining accurate global rational approximations for a variety of quality-of-service (QoS) metrics such as packet loss probability and probability that packet delay exceeds a particular value and to develop practical algorithms which can be used to evaluate large B ISDNs.
