Sender-initiated multicast for small group communications

Sender-Initiated Multicast for small group communications Vasaka Visoottiviseth Current IP multicast offers efficient multipoint-to-multipoint data delivery for large group communications. Nevertheless, it suffers from deployment issues such as configuration complexity, lack of sufficient group management, and global address allocation. IP multicast also suffers from a scalability problem because the router has to maintain forwarding states for all multicast distribution trees passing through it. Thus, the number of forwarding entries increases with the number of groups. While IP multicast was designed for large group communications, we can learn from various statistical studies on how multicast communications are under way, which are publicly available on many web pages, that most multicast sessions presently are relatively small and consist less than 50 receivers. Therefore, supporting small multicast group should be appropriate for the present applications. In this dissertation, we propose Sender-Initiated Multicast (SIM) as an alternative multicast forwarding scheme for small group communications such as teleconferencing and file distribution. SIM eliminates the cost of allocating global multicast address, by routing packets according to receiver unicast addresses attached to packet headers. The key feature of SIM is in its Preset mode, which can lessen the costs of route lookups and provides cost-efficient packet forwarding by using a SIM Forwarding Information Base (FIB) maintained on routers. Moreover, a SIM tunnel will be automatically created between two routers that act as multicast branching points. Thus, SIM can gain scalability by maintaining FIB entries only on the branching routers. Furthermore, all multicast applications today use the connectionless and unreliable protocol such as the User Datagram Protocol (UDP) to achieve multicast communications. However, developing a reliable protocol over UDP is as complicated as developing TCP. Moreover, the existing reliable multicast protocols have been designed for general proposes, while different levels of reliability are required by multicast applications.