Much research has been done on supporting real-time IP multicast applications with dynamic group member joining and QoS requirements. Various existing greedy QoS-aware routing protocols, such as YAM and QoSMIC have been shown to outperform shortest-path heuristics, such as PIM and DVMRP. However they still suffer from the problem of poor scalability resulting from high control overhead, un-robustness for centralized group manager, and longer than necessary join latency. In addition, most existing dynamic join protocols perform best when group members are either densely populated or sparsely populated, but not both. In this paper, we introduce a distributed candidates selection protocol, named DSDMR, that is capable of self-adaptation depending on sensed group densities by ways of an adaptive two-direction join mechanism. We evaluate our scheme using extensive simulations and found that DSDMR can create low cost tree close to optimal greedy strategy with very low control overhead and join latency.
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