Shared Tree for Application-layer Multi-source Multicast

Group communication is becoming increasingly important with the decreasing cost of broadband access and the growing number of Internet users, which requires efficient multi-source multicast support. This paper targets at addressing two fundamental questions related to application-layer multi-source multicast: how many sources can be simultaneously served and how in reality can such a service be effectively provided. Considering the high bandwidth requirement and potential huge control overhead, in this paper we construct a single distribution tree shared by all the sources. Theoretically, we prove that the optimal single shared tree solution can serve at least m - 1 sources, where m is the maximum number of sources that can be supported in the system with any number of trees. Practically, we propose a distributed protocol for tree construction and tree refinement so as to approach the theoretical optimal. The simulation results manifest that our proposed heuristic protocol significantly increases the number of sources that can be served in multi-source sessions and the result approaches to the optimal solution.