Seam: Scalable and Eecient Atm Multipoint-to-multipoint Multicasting Extended Abstract]

Human collaboration applications and distributed systems are expected to beneet from a group multicast service, both in terms of performance and design simm plicity. We argue that such a service must be scalable both in the number of potential senders and receivers. The success of ATM will in part depend on the availl ability of an eecient group multicast service. We provide a brief description of the requirements for a general multicast service, and then present SEAM, a proposal for scalable and eecient multicast in ATM. SEAM relies on an additional switching feaa ture we call cut-through forwarding, which enables the mapping of several incoming Virtual Channels into one or several outgoing Virtual Channels. SEAM ree lies on a shared tree spanning all senders and receivers of the group. It allows for centrally initiated group setup as well as dynamic group membership changes. An additional feature, short-cuttingg, allows for the transmission of a packet to follow the shortest path along this shared tree. We believe that SEAM is both an important and necessary step in the evolution of ATM. It will enable a class of applications relying on group multicast to beneet directly from ATM's quality of service support and scalable bandwidth and the resulting performance advantages.