THE PIM ARCHITECTURE FOR WIDE-AREA MULTICAST ROUTING

The purpose of multicast routing is to reduce the communication costs for applications that send the same data to multiple recipients, Exist ing multicast routing mechanisms were intended for use within regions where a group is widely represented or bandwidth is universally plenti ful, When group members, and senders to those group members, are distr ibuted sparsely across a wide area, these schemes are not efficient; d ata packets or membership report information are occasionally sent ove r many links that do not lead to receivers or senders, respectively, W e have developed a multicast routing architecture that efficiently est ablishes distribution trees across wide area internets, where many gro ups will be sparsely represented, Efficiency is measured in terms of t he router state, control message processing, and data packet processin g, required across the entire network in order to deliver data packets to the members of the group, Our protocol independent multicast (PIM) architecture: a) maintains the traditional IP multicast service model of receiver-initiated membership, b) supports both shared and source- specific (shortest-path) distribution trees, c) is not dependent on a specific unicast routing protocol, and d) uses soft-state mechanisms t o adapt to underlying network conditions and group dynamics, The robus tness, flexibility, and scaling properties of this architecture make i t well-suited to large heterogeneous internetworks.