Extension to OSPF for scalable multicasting through recursive unicast

IP multicast suffers from the forwarding state scalability issue when the number of simultaneously on-going multicast sessions is very large, since traditional multicast routing protocols require each router to maintain a forwarding entry for each multicast session whose distribution tree passes through the router. We introduce the idea of recursive unicast into the existing MOSPF (multicast extension to open shortest path first) routing protocol to improve its scalability. Simulation results show that the designed protocol can significantly reduce multicast forwarding state and computational overhead at routers without hurting the per-destination shortest path characteristic of a resulting tree.