A Hybrid Approach to Quality of Service Multicast Routing
John Crawford, A. Gill Waters · Kent Academic Repository (University of Kent) · 1997
Several multicast routing heuristics have been proposed to support multimedia services, both interactive and distribution, in high speed networks such as B-ISDN/ATM. Since such services may have large numbers of members and have real-time constraints, the objective of the heuristics is to minimise the multicast tree cost while maintaining a bound on delay. Previous evaluation work has compared the relative average performance of some of these heuristics and concludes that they are generally ecient, although some perform better for small multicast groups and others perform better for larger groups. We present a detailed analysis and evaluation of some of these heuristics which illustrate that in some situations their average performance is reversed; a heuristic that in general produces ecient solutions for small multicasts may sometimes produce a more ecient solution for a particular large multicast/network combination. Also, in a limited number of cases using Dijkstra's algorithm produces the best result. We conclude that the specic eciency of a heuristics solution depends on the topology of both the network and the multicast, and that it is dicult to predict. Because of this unpredictability we propose the integration of two heuristics with Dijk-stra's shortest path tree algorithm to produce a hybrid that consistently generates ecient multicast solutions for all possible multicast groups in any network. These heuristics are based on Dijkstra's algorithm which maintains acceptable time complexity for the hybrid, and they rarely produce inecient solutions for the same network/multicast. The resulting performance attained is generally good and in the rare worst cases is that of the shortest path tree. The performance of our proposal is supported by our evaluation results. We conclude by discussing the types of networks for which this method is most appro-priate and identifying further work. 1