Distributed center location algorithm for fault-tolerant multicast in wide-area networks

Group shared trees form a major component of most multicast routing protocols (e.g. PIM-SMv2, CBTv3). The shared trees are built by choosing one node as the center of the tree. The optimal location of a center under the constraints of minimal tree cost and delay for a particular group is an NP-complete problem. Current implementations of protocols decide on the location of these centers administratively, an attractive choice given that the solution is obviously sub-optimal and does not lend itself to dynamic reconfiguration of centers. We present a scalable heuristic to find a near-optimal solution to the center location problem. Our solution is easily amenable to distributed implementation and provides the protocol with a list of possible centers ranked in the order of their optimality, therefore providing fault tolerance and reducing the chances of a single point of failure at the center.