An Iterative Algorithm in Building Delay-constrained Multicast Trees over VPLS Domain

VPLS has gained worldwide recognition in recent years. However, deploying VPLS in metro is confronted with one complicated issue: the multicast problem. Instead of solving the NP-complete Steiner tree problem, we devote our attention to emphasize more on the experimental and implementary aspect of multicast in VPLS network. We begin our proposal with the minimal spanning tree (referred as default data tree in [10][11]) and minimal delay tree. Between them we find out the edge difference and check if delay-constrained requirements could be satisfied. Through the iteration process we try to construct all the delay-constrained candidates, among them the one with the least cost is selected. To avoid unwanted traffic sent to PE devices, we propose the pruning mechanism. Compared with Steiner heuristic solutions, the algorithm proposed in this paper can be easily implemented as the time complexity is only O(n2). Simulation result shows that the algorithm is suitable for building delay-constrained multicast trees over VPLS domain.