Dimensioning of play-out buffers for real time services in a B-ISDN

A large fraction of traffic that the future B-ISDN will probably transport is made up of real-time services with stringent delay and delay jitter requirements. Since ATM networks do not provide time transparent links, a delay equalisation has to be provided in the adaptation layer or in user equipment. In this paper we first propose an analytical model that allows the evaluation of the end-to-end delay and of the relevant jitter (the delay that we consider is the one suffered in the network queueing systems plus the time needed to transmit a cell but not the propagation delay; the latter can be trivially added to the former); then we focus on the dimensioning of play-out buffers. The proposed model is validated with simulation results and we found a good agreement between analytical and simulation results. To make the study analytically tractable we use rather simple traffic source models and we make suitable simplifying assumptions. These assumptions are fairly general but the source models are still far from representing accurately certain kinds of real traffic. For this reason we carry out also an additional simulation study (supported by some analytical arguments), by using real experimental MPEG, LAN and Internet traffic traces, to assess the system performance in real scenarios.