A flexible multicast routing protocol for group communication

Multicast routing, once dominated by a single routing protocol, is becoming increasingly diverse. It is generally agreed that at least three routing protocols, PIM, DVMRP, and CBT will be widely deployed and must interoperate. This signals a shift from the Mbone as one large domain to a collection of administrative domains where each domain selects its own multicast routing protocol. This paper proposes another multicast routing protocol, Conference Steiner Multicast (CSM), that is suited for domains that implement OSPF as the unicast routing protocol. CSM is targeted towards (sparse) multicast conferencing and online discussion groups. Characteristics of such discussion groups include any member being a speaker or listener and dynamic changes in the group membership. CSM is futhermore well suited for domains with mobile hosts because its basic architecture can support a mobile environment. CSM is based on the use of a shared, heuristic Steiner minimal tree for interconnecting group members. A key component of the design is that it dynamically and reliably shifts to a di€erent tree as changes warrant. CSM supports rudimentary entry control for security and permits application assistance over routing decisions (termed Application