Extension of RP relocation to PIM-SM multicast routing

Abstract

The Protocol Independent Multicast-Sparse Mode (PIM-SM) protocol establishes core-base tree to forward multicast datagrams in a network. In PIM-SM, the core or Rendezvous Point (RP) of a group is determined at each multicast router by hashing a group address, i.e., a class-D IP address, to one of the candidate RPs. The hash function is characterized by its ability to evenly and uniquely choose the core for a group and remains insensitive to the geographic distribution of the group members and the sources. However, it may result in a multicast tree with high cost. This study presents a relocation mechanism which is extension to PIM-SM, in which RP could be relocated periodically. When a new RP is found, the original RP informs all members to re-join to the new RP, Simulation results indicate that the extended version, RPIM-SM, reduces about 20% tree cost than PIM-SM when the group size is medium. Moreover, comparing RPIM-SM with the optimal core-based tree reveals that they have less than 5% difference in tree cost. Furthermore, an increase of the number of candidate RPs brings RPIM-SM even closer to the optimal core-based tree. Results in this study demonstrate that relocation improves the performance of PIM-SM.