IP multicasting allows a source to define a multicast group address and receivers can dynamically join and leave this group. Currently the propagation of multicast packets is controlled by two scoping methods: TTL scoping and administrative scoping. Both of these approaches require the source to control the scope of the multicast. Receiver-based scoping allows a receiver to place conditions on its multicast join that must be met in order to join successfully and remain a member of the multicast group. Such a scoping mechanism would be useful in environments where the receiver incurs a cost for its membership of the multicast group. We describe two receiver-based scoping approaches: router-supported and end-to-end. The router-supported approach requires state to be maintained in routers while the end-to-end approach uses the multicast traceroute tool and does not require state maintenance by the routers. We evaluate the performance of these approaches in terms of their accuracy, bandwidth overhead and state requirements.

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.