Newly emerging applications in distributed multimedia and distributed simulation are increasingly expected to support a multiparty environment, in which connections are set up between a sender and multiple receivers (point-to-multipoint) or multiple senders and multiple receivers (multipoint-to-multipoint) [7]. In order to conserve resources, the underlying network service must be able to support a point-to-multipoint connection abstraction (e.g, hostgroups in multicast IP [6] or target sets in Tenet Scheme 2 [12, 13]) and an appropriate mechanism to support multicasting at network level.