Hierarchical Approach to Multicast in a Datagram Internetwork

摘要

Multicasting in datagram internetworks enables multi-party interactions amongusers distributed over wide areas by eliminating duplicate packets in one-to-many and many-to-many communication. It requires formation of a tree to distribute multicast data to the communicating group of members. Present multicast techniques need improvement in scope control, resource discovery mechanisms, and tree construction to efficiently support a large number of global groups with dense as well as sparse membership. We deploy a hierarchy of clustered routers with the following features to make these improvements. Each group is assigned a scope level enabling access to resources at that level when members join and permits well-defined boundaries for scope control. The list of border routers and presence of groups at any level is maintained and supplied to members by a level-specific resource discovery mechanism called a registrar. To make tree construction scalable, the border routers determine the shortest inter-cluster paths to source clusters using the available unicast routing information, facilitator aggregation of router state for all senders in a cluster. Unlike the existing approaches, administrative configuration of the hierarchy eliminates the need for locating distribution centers dynamically.