Distributed quality of service multicast routing with multiple metrics for receiver initiated joins

This paper describes a novel method of building multicast trees for real time traffic with quality of service constraints. There is a wide range of heuristics to calculate the optimal multicast distribution trees with bounds on the maximum delay from the source to all members. However these heuristics require all the members to be known in advance and assume the existence of a centralized service. We present a heuristic-best cost individual join (BCIJ)-that joins members one by one, randomly to the existing tree. The method does not need previous knowledge of the group members. Trees are dynamically built when each member arrives in the group. A distributed method-multiple metric broadcast (MMB)-for nodes to obtain the best valid path to the existing tree is also presented. MMB is inspired by reverse path forwarding and broadcasts queries to the network that reach existing on-tree members. These reply with the best valid paths to the joining member. The member then selects the best path. This avoids the use of any centralized service and the need for link-state information to be available in any node. The evaluation presented shows that the BCIJ produces trees with better cost than existing centralized heuristics and that MMB does not have a major effect on the network if the group participation is sufficiently large.