| The Protocol Independent Multicast-Sparse Mode (PIM-SM) protocol establishes a core-based tree to forward multicast datagrams in a network. In the previous works on the RP selection, an artificial cost function was always used to calculate the cost of the multicasting tree [10]. It can just get an approximate result comparing with the real tree cost. Consequently, it affected the accuracy of the RP selection obviously. Moreover, PIM-SM provisionally uses administrative selection or simple heuristics for locating the center of a group, but doesn't preclude the use of other methods that provide an ordered list of centers. As the sources and receivers in the multicast group join and leave the group, a bad result may occur in terms of high cost, delay, and overhead. In this report we investigate the problem of finding a good center in centralized fashion, propose a new algorithm for the real tree cost calculation function and a new algorithm for RP selection in PIM-SM Multicast Routing, and examine them in a virtual network environment. We also present simulation results to show that our new algorithms can provide better results than other algorithms. |
