An efficient distributed QoS based multicast routing algorithm

This paper proposes an efficient distributed multicast routing algorithm that provides quality of service (QoS) guarantees for real-time applications. It focuses on the delay-constrained minimum cost tree (or constrained Steiner tree) problem; that is, it constructs a multicast tree that not only meets the constrained end-to-end delay requirements but also is the minimum cost multicast tree. Two representative algorithms DKPP and DSPH are MST and SP based heuristics, respectively. The MST based algorithms like DKPP run with a high message and time complexity of O(n/sup 3/). Furthermore, the MST based algorithms have a very low success rate in constructing a constrained multicast tree especially under tight delay constraints. On the other hand, the SP based algorithms like DSPH have a fatal deficiency; that is, these algorithms will not be able to find a solution if the delay constraint is less than the maximum delay of a cost based shortest path tree. Both types of algorithms try to construct the multicast tree sequentially without taking advantage of the concurrency in a distributed algorithm. This paper proposes an efficient distributed multicast routing algorithm which builds the multicast tree in a concurrent manner rather than in a sequential manner. As a result, the proposed algorithm runs with a very low message and time complexity and has a near zero failure rate in constructing a multicast tree even under tight delay constraints without any limitation on the value of delay constraints.