Inter-domain multicast routing protocol for forwarding state reduction

Abstract

Reducing the amount of routing information is a critical issue for scalable multicast. A multicast router has a routing table and a forwarding table to maintain the routing information. BGMP is an inter-domain multicast routing protocol intended to limit the size of routing table to a manageable degree. Dynamic Tunnel Multicast has been proposed to reduce the size of forwarding table for intra-domain multicast. In this thesis, we propose an approach to reduce the amount of the routing information by combining BGMP and Dynamic Tunnel Multicast. By dynamically setting up a tunnel between two domains, the domains in between can be relieved from the overhead to maintain forwarding table entries for all the groups whose traffic just transits. We propose the structure of border routers for our approach and a tunnel end point detection algorithm to determine which domains need to be connected with tunnels. Tunnel end point detection uses domain status information distributed using intra-domain multicast trees. We also modify the existing Dynamic Tunnel Multicast to be compatible with BGMP and to make border routers in a domain cooperate with each other. We perform simulations with focus on the size of forwarding table. Analysis and simulation results show a great reduction in the size of the forwarding table when the group members are sparsely distributed. By reducing the size of forwarding table, a multicast router can scale to a large number of groups. The proposed system can improve the forwarding performance because it saves time to look up the forwarding table.