Application-layer group communication server for extending reliable multicast protocols services

Reliable multicast protocols are becoming an essential element in distributed applications such as interactive distance learning applications. However, the existing implementations of reliable multicast protocols are not sufficient to satisfy the group communications requirements of some distributed applications. Our experience of using number of multicast protocols in IRI distance learning applications shows the necessity of providing an application-layer Reliable Multicast Server (RMS) to extend the primitive group communication services provided by such multicast protocols. Examples of such services include handling heterogeneous environments (such as LAN vs. WAN networks and different reliable multicast protocols), automatic fault recovery and simple application interface. In this paper, we motivate and describe the design and the implementation of RMS architecture which has been used in IRI learning sessions for two semesters. We also show how RMS improves the reliability, performance and flexibility of IRI sessions via supporting extended group communication services.