This paper describes the NICE (NICE is the Internet Cooperative Environment) multicast protocol. Like SRM, NICE is implemented at the application layer so as not to require changes to the underlying network. NICE uses hierarchical layers to group nodes into clusters and in doing so, reduce stretch, or unnecessarily increased path length from the unicast path.
When new hosts attempt to join, they first communicate with a Rendezvous Point (RP) node, which then directs them to high-tiered nodes, which subsequently direct the host to lower-level nodes close to them. Higher-level nodes are cluster leaders, responsible for keeping the size of their associated cluster between a certain threshold and splitting or merging the cluster group when the max or min threshold is passed. Members of a cluster alert each other to their presence throughput periodic heartbeat messages.
The authors simulate NICE and compare their results to Narada, an existing multicast protocol. They find that it performs comparably, but with less control overhead and less stress (total messages sent over a link) on links. The hierarachical structure of NICE seems to be the main reason that it has such low control overhead and hence can be used (at least in simulation) for groups of large sizes, say, greater than 1024 hosts, which Narada cannot do. The paper references another paper about Narada, but I wished they would have given a succint, organized comparison of the two protocols.
This paper went much more into detail about the underlying workings of the multicast groups, while the other paper offered a more concrete example of when this multicast framework would be used and how to detect and deal with losses.
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