Research And Implementation Of PIM-DM Multicast Routing Protocol

As one of the hotspots in the field of computer communication, multicast is a very important research area. Because there are lots of applications, such as videoconference, video on demand, large-scale coordinated computation, white board, all depend on the capability that one host or multi-hosts could send the same packet to multi-hosts. This leads to the need of much more bandwidth wich goes beyond the limitation of the unicast. As one of the solutions to this problem is the multicast technology which bas been paied attention from both reseach and industrial department.In this paper, we study some key techniques for the implementation of the multicast routing protocol, the generation and the optimization of the high performance multicast shortest path tree, the high performance optimization interface with IP layer and operating system, and the high performance interactive operation among mulitcast routing protocols.Concentrating on the high performance multicast shortest path tree generation and its optimization, an optimized algorithm FLSPT (fast low-cost shortest path tree) is presented. FLSPT adapts the path increasing idea of Dijkstra's shortest path algorithm, and combines with the node share path method of the DDMC algorithm, can always choose the shortest path from the shared paths to the destination node if there are multipaths, so the total consumption of the generation of the SPT is reduced. If a node is selected as the current for computation, its parent node needs not to be recomputed, so the total computation is reduced greatly. The length of the shortest path of the neighbor node and the distance for the nearest goal node are updated according to the current node, so it is the same that the parent node is updated at the time or recomputed later by the vector value. Therefor, the performance of the shortest path tree generated by FLSPT or the DDSP is same, but the efficiency of FLSPT is better than DDSP.Considering that multi multicast protocol can run and be used in an application at the same time, we proposed a co-operation module of multi multicast protocol according to Dave. Thale's Multicast Border Router model. The model is extended as the driver model in the multicast routing protocol implementation. The router's performance of the muticast routing protocol is improved.The kernel code is added and updated in IP level in order to perform the switch of muticast data stream efficiently. By theory and experiment studies,the multicast routing protocols present in this paper are of good performance.