Supervised peer-to-peer overlay networks have many applications such as audio/video streaming, multiplayer online gaming, web crawling, and grid computing. Topology maintenance and security issues are usually much easier to handle with a supervised design. Also, supervised designs can scale to millions of nodes using a relatively moderate supervisor as long as the system does not change too rapidly, the space needed by the supervisor only scales logarithmically with the number of nodes, and the work (i.e. the number of messages) needed by the supervisor to integrate new nodes or remove old nodes is only a small constant. Finally, even peer-to-peer systems that claim to be completely decentralized require servers in practice so that new peers can find out about peers already in the system. Thus, a supervised design may not be that different from other peer-to-peer designs.
The aim of the SPON project is to explore designs of supervised peer-to-peer systems for various applications because we feel that supervised designs allow to combine the advantages of server-based systems and decentralized peer-to-peer systems and are therefore much more useful in practice than the other two designs.