Scalable Application Layer Multicast

This paper again is on multicast at the application layer. This paper focuses on a protocol to maintain an overlay topology for efficient delivery of multicast data. The paper introduces NICE trees, which is the topology of the overlay network. The idea uses the location of the nodes to form several clusters with nodes that are close. The center node of the cluster is the cluster leader which contacts other cluster leaders. The whole NICE tree is hierarchical with different layers. All nodes are in the lowest layer, the node leaders are also at a higher layer with the other node leaders, so communication goes by passing data first to the highest layer possible, then going down the tree. Since the nodes and clusters are allocated by their geographic location, so the different clusters can communicate within cluster faster, and across cluster, the cluster leader talks to another cluster leader on the same layer. It's kind of like routing within AS and outside of ASes.

With a protocol like this, the most important thing to notice is how nodes join and leave and how the hierarchy is continuously maintained. The NICE tress has a Rendezvous point that is in charge of telling the new nodes where to look and where to join, which also traverses down the hierarchy and finds its spot. Other important situations include when cluster leaders leave the network or are down, then a new leader must be selected. This process is summarized in another paper, but is not really mentioned in this one. The topology of this network definitely seems like it could work, and simulation results weren't bad either. Seemed like a great paper.