Architectural Choices in Large ScaleATM

The rapid development of Asynchronous Transfer Mode technology in the last 10-15 years has stimulated renewed interest in the design and analysis of switching systems, leading to new ideas for system designs and new insights into the performance and evaluation of such systems. As ATM moves closer to realizing the vision of ubiquitous broadband ISDN services, the design of switching systems takes on growing importance. This paper seeks to clarify the key architectural issues for ATM switching system design and provides a survey of the current state-of-the-art. 1. Intoduction Switching systems are central components in communications networks and serve two key purposes. First, they allow a reduction in overall network costs by reducing the number and/or cost of the transmission links required to enable a given population of users to communicate. Second, they enable heterogeneity among terminals and transmission links, by providing a variety of interface types. ATM networks have introduced a range of new issues into switching system design, but the principal ones arise from two key features of ATM. The rst is its support of multi-rate virtual circuits with statistical multiplexingfor eecient transmission of mul-timedia and data traac. The second is its support for multicast virtual circuits which enable eecient transmission of information from a source to many receivers. At the same time, switching systems for ATM, must address the fundamental issues of scalability, reliability and cost-eeectiveness. The pressure of the competing requirements on switching systems, together with new opportunities created by advances in underlying technologies , have helped to spark a remarkable period of creativity in switching system design. As the title of the paper suggests, we attach considerable importance to the issue of scalability in ATM switch design. While one can build communication networks of arbitrary size using switching systems of limited capacity, it turns out to be far more cost-eeective to use switching systems that have suucient capacity to handle traac from tens or hundreds of thousands of individual users. As ATM networks are more widely deployed and approach the sort of ubiquitous usage that telephone networks enjoy, there will be a compelling need for high capacity systems. Just as telephone switches require capacities of 1-10 Gb/s to provide cost/eeective service to large user populations, ATM switches supporting applications using thousands of times the bandwidth of traditional voice services, will need terabit per second capacities. This in turn demands switch architectures with linear or near-linear …