Receiver-based multicast scoping: a new cost-conscious join/leave paradigm

In Internet multicast, the set of receivers can be dynamic with receivers joining and leaving a group asynchronously and without the knowledge of the source(s). The Internet today uses source-based scoping by which the source determines how far its multicast transmissions will propagate. This mechanism, however, does not allow a receiver to bound the number of hops added to a multicast routing tree as a result of its join request or its continued membership. In this paper we explore the use of receiver-based scoping, in which a receiver's join request is augmented with one or more scope values. By use of these values, the receiver specifies its wish to join and remain in the multicast group as long as the number of additional hops its membership incurs is within its declared scope. In environments where a multicast receiver incurs a cost in relation to its incremental resource usage, this scoping technique can be used to give the receiver direct control over this cost. The paper is concerned with discussion of the design of the receiver-based scoping mechanism and its possible use within multicast applications. We also consider the implementation of the mechanism as an extension to the existing Internet multicast infrastructure in a manner that is independent of the multicast routing protocol in use.