Practical multicasting on a nonbroadcast subnetwork

LAN multicast is now an essential service for users of the MBone and other IP multicast tools. Traditional IP multicast has travelled over two types of subnetwork: point-to-point links and subnetworks with inherent multicast capability, such as Ethernet and token ring. More recent LANs may be arbitrary mesh networks with no built-in, efficient, multicast capability. The authors describe a successful implementation of multicasting over a 640 Mbit/s, wormhole-routing LAN. The implementation is integrated with the wider-area multicast IP service. Consideration is given to practical issues such as interoperation with existing multicast routing protocols and software, and multicast-group setup latencies.