The protocols used in today's Internet do not support large scale broadcasting. Traditional unicast does not scale. IP multicast will not happen for a number of reasons. The papers in this group explore an alternative strategy called a multicast overlay. An overlay approach shares the basic spirit of IP multicast, in that distribution uses a tree topology. The tree makes more efficient use of bandwidth, and prevents any one node from having to do work for all clients. However, the overlay approach differs significantly from IP multicast in its details.
The papers in this group use distinct styles of multicast overlay. The papers from Berkeley [1] and CMU [4,5] use a two-level overlay, where the lower level is a routing mesh, and the higher level are the multicast trees. The paper from CISCO [3] uses a one-level overlay. All of these overlays are designed to automatically form tree topologies. The Inktomi broadcast architecture [2] differs, assuming statically configured distribution trees. The Inktomi approach is more geared towards providing network management tools for the network operations centers of content distribution networks.
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