On-demand multicast routing scheme and its algorithms

Multicast communication is one of the major techniques to share the transmission cost. However, in the typical multicast service, all destinations are expected to receive the same multicast stream from the source at the same time. Unfortunately, this is a severe restriction for some on-demand multimedia applications, such as video-on-demand (VOD), in which customers´ requests are expected at various time. Therefore, only few customers can be served in the same multicast group; thus additional bandwidth is required. In this paper we propose a new multicast communication scheme to allow the destinations accessing the same multicast stream at different time by buffering technique and hence tremendously reduce the communication bandwidth. We call this type of communications as the on-demand multicast communications. We also define the optimization problems of the on-demand multicast routing and give a theoretical analysis. A greedy algorithm for this problem is also presented and had been implemented on our VOD systems