Verification and Validation of a Reliable Multicast Protocol

This paper describes the methods used to specify and implement a complex communications protocol that provides reliable delivery of data in multicast-capable, packet-switching telecommunication networks. The protocol, called the Reliable Multicasting Protocol (RMP), was developed incrementally by two complementary teams using a combination of formal and informal techniques in an attempt to ensure the correctness of the protocol implementation. The first team, called the Design team, initially specified protocol requirements using a variant of SCH requirements tables and implemented a prototype solution. The second team, called die V&V team, developed a state model based on die requirements tables and derived test cases from these tables to exercise the implementation. In a series of iterative steps, the Design team added new functionality to the implementation while the V&V team kept the state model in fidelity with the implementation through testing. Test cases derived from state transition paths hi the formal model formed the dialogue between teams during development and served as the vehicles for keeping die model and implementation in fidelity with each other. This paper describes our experiences hi developing our process model, details of our approach, and some example problems found during die development of RMP.