Core-manager based scalable multicast routing

With the growing interests in distributed applications, efficient and scalable multicast routing is of great concern. Source-based tree multicast routing protocols, however, become very inefficient when used with large number of sources over large scale internetworks. Shared-tree based multicast routing protocols like PIM and CBT being developed by the IDMR working group of the IETF, trade efficiency of multicast delivery trees with scalability, but there are some issues open to further study. The work presented in this paper, the core-manager based multicast routing (CMMR) architecture, adopts shared-tree based techniques to achieve good scalability. It worked out an innovative approach to issues like core selection and multicast delivery tree management. The basic idea behind CMMR is that the core-manager (CM) keeps tracking cores of each multicast delivery tree in order to maintain a brief image of the tree. Consequently, new members will almost always be directed to a nearby core so that tree cost is well confined. However, not every new member has to actually consult the CM thanks to a self-growing scheme, maintaining control overhead low. Simulations show that the CMMR outperforms other existing shared-tree based multicast routing protocols like PIM, and can do as well as expensive near-optimal Steiner tree heuristics when average costs of multicast delivery trees are compared. Further improving on scalability is sought by using a hierarchical architecture, which requires the multicast addresses be administratively scoped in accordance with the hierarchy. Management of candidate cores are restricted within individual hierarchical regions. In addition, the CMMR scheme is recursive, meaning that all routers run the same algorithm regardless of their hierarchical levels.