Scalability issues in multicast ATM switching architectures. Problems and solutions

Most of the services that an ATM broadband integrated services digital network (B-ISDN) has to offer have a multicast nature. For this type of services, a source of traffic transmits information to multiple destinations. In consequence, the ATM switching nodes have to support multi-point connections and they require some mechanisms to allow the replication of ATM multicast cells to subsequently route them. In this paper, we investigate some of the troubles along with their solutions found in a large ATM switch to provide multicast. Large switches apply in wide area network (WAN) environments where the number of multiplexed connections is often large as well as the number of necessary ports in the switching architecture. First, we describe the multicast switching technologies for local area networks (LANs). In this case, the number of ports is normally quite small (8 up to 32). Then, two common approaches to increase the switch size are outlined: one based on a Clos-like network and the other employing the knockout effect. Our contributions in this work are both the evaluation of the knockout effect in a multicast scenario and the evaluation of several routing algorithms in a three stage Clos-like network. The results obtained by computer simulation are presented and the most relevant conclusions addressed.