A simple method for implementing PIM to ATM based MPLS networks

A simple method for providing multicast service in ATM based multi-protocol label switching (MPLS) networks using PIM-SM is presented. This method does not require establishing dedicated multicast routes, but it uses point-to-point LSPs that were established for delivering best-effort traffic in the MPLS network. As a result, this method reduces the signaling overhead associated with establishing multicast trees and enhances scalability by sharing LSPs with multiple groups. The tradeoff is bandwidth inefficiency compared to the optimized tree, however the inefficiency is acceptable compared to the optimal shortest-path tree, and it grows slowly as the size of a group increase. This method is appropriate as the initial implementation scheme for protocol independent multicast-sparse mode (PIM-SM) in an ATM based MPLS network where only a few of switches have the capability of the multicast function.