A comparison of application-level and router-assisted hierarchical schemes for reliable multicast

One possible approach to achieve scalability in reliable multicast is to use a hierarchy. A hierarchy can be established at the application level, or by using router assistance. Because the routers have more detailed knowledge about the underlying network topology, intuitively a hierarchy produced by router assistance is expected to improve performance. In this paper we test this assumption by comparing two schemes, one that uses an Application-Level Hierarchy (ALH) and another that uses Router-Assisted Hierarchy (RAH). Contrary to our expectations, we find that the qualitative performance of ALH is comparable to RAH when a good technique is used to build the hierarchy. We do not model the overhead of creating the hierarchy nor the cost of adding router-assistance to the network. Therefore, our conclusions inform rather than close the debate of which approach is better