A decomposition method for the analysis and design of finite state protocols

Abstract

Finite state automata have been applied with success to the modeling of Computer Network Protocols. The interaction of finite state machines can be very complex especially if the protocol involves a large number of states. To counteract the complexity of analysis and design, we propose an approach of decomposition. Through this approach, the protocol graph can be partitioned into subgraphs each having a unique entry node and zero or more exit nodes. The exit nodes of one subgraph can be connected only to the entry nodes of other subgraphs. From the standpoint of protocol analysis, the correctness of the entire protocol graph can be inferred from the correctness of individual protocol subgraphs. From the standpoint of protocol design, the individual protocol subgraphs can be designed to correspond to different phases of the protocol. If the individual protocol subgraphs are designed correctly and the connections between subgraphs conform to the structure discussed above, then we show that the entire protocol graph will operate correctly.