It is well known that IP multicast suffers from deployment issues. The problem mainly originates from the multicast routing complexities in the inter-domain level and state-full nature of current solutions. To cope with the problem, many alternative group communication methods have been proposed. Among them, branching point (BP) based approaches have promising features like incremental deployment, high tree availability, low memory requirement and, hence, high scalability. However, current BP-based methods suffer from two major inefficiencies namely the tree construction difficulties and presence of excessive lookups in the forwarding process of unicast and multicast data packets. We propose a new BP-based protocol named NBM (Next Branch Multicast) to avoid the existing drawbacks. NBM constructs the multicast distribution tree in the forward direction and has a fault-detection and repair mechanism which protects the tree against BPs failures. NBM detects the failure of a higher level BP in the tree sooner than a lower level BP. NBM does not maintain any type of control state in non-branching routers. Our simulation results show that NBM memory requirement for maintaining multicast forwarding states is approximately less than half when compared to the traditional approach. In addition, the NBM tree is more available than the traditional one at least by a factor of 2.
