An Efficient Delay Sensitive Multicast Routing Algorithm

As a key issue in multicast routing with quality of service (QoS) support, constrained minimum Steiner tree (CMST) problem has been a research focus for more than a decade, and tens of heuristics have been developed to solve this NP-complete problem. Among all the previously proposed algorithms, the bounded shortest path algorithm (BSMA) [15] have proved to be capable of producing a multicast tree that has on average the lowest cost. However, such an excellent cost performance is accompanied with an extremely high time complexity. In this paper, we propose a brand new heuristic TCF, which is based on an idea called “tightest constraint first.” TCF runs a DCLC (delay-constrained least cost) heuristic only once for each destination and therefore has a provably low time complexity. We further propose an iterative heuristic ITCF, which uses TCF to obtain an initial tree and then gradually refines it. Extensive simulations demonstrate that, in the average sense, TCF can achieve a cost performance comparable to or even better (for networks of large size) than that of BSMA, the cost performance of ITCF is even better than that of TCF, TCF runs twice as fast as ITCF, and ITCF runs 2 ∼ 5 times as fast as the best implementation of BSMA.