Designing reliable ATM networks for multimedia interactive IP applications

This paper mainly concerns with the design and the performance evaluation of network systems offering a high quality, high reliable videoconferencing service to a community of users dispersed on a metropolitan area. A network topology has been considered in which Ethernet technology based LAN segments are interconnected by a triangular ATM backbone. The main issues of interest in the paper are: the selection and the evaluation of meaningful indices of user satisfaction; the efficiency of Ethernet technology based LAN segments in supporting the real time transmission of multimedia flows; the dimensioning of ATM virtual channels established on a single link; the potentiality of IP and ATM integrated architectures in maintaining the quality of multimedia interactive services in the presence of link fault conditions. Several series of simulations have been performed dealing with different topological configurations, numbers of simultaneously active videoconference sessions, users locations and temporal sequences of activation of the traffic generators. The quality of the user perception has been evaluated with respect to different simulation scenarios. The simulation results show that the ATM technology is a very satisfactory solution to legacy LANs internetworking. ATM link fault tolerance is reached, in a transparent way, simply rerouting ATM switched virtual channels on the available links.