A Dynamic Bootstrap Mechanism for Rendezvous-based Multicast Routing

Current multicast routing protocols can be classi ed into three types according to how the multicast tree is established broadcast and prune e g DVMRP PIM DM membership ad vertisement e g MOSPF and rendezvous based e g CBT PIM SM Rendezvous based protocols associate with each logical multicast group address a physical unicast address re ferred to as the core or rendezvous point RP Members rst join a multicast tree rooted at this rendezvous point in order to receive data packets sent to the group Rendezvous mech anisms are well suited to large wide area networks because they distribute group speci c data and membership information only to those routers that are on the multicast distribution tree However rendezvous protocols require a bootstrap mechanism to map each logical multicast address to its current physical rendezvous point address The bootstrap mechanism must adapt to network and router failures but should minimize unnecessary changes in the group to RP mapping In addition the bootstrap mechanism should be transparent to the hosts This paper describes and analyzes the bootstrap mechanism developed for PIM SM The mechanism employs an algorithmic mapping of multicast group to rendezvous point address based on a set of available RPs distributed throughout a multicast domain The primary eval uation measures are convergence time message distribution overhead balanced assignment of groups to RPs and host impact The mechanism as a whole and the design lessons in particular are applicable to other rendezvous based multicast routing protocols as well