Protocol Verification by Simultaneous Reachability Graph

Non-executable transitions, deadlock states, and livelock cycles are typical errors in communication protocols. Reachability analysis is a direct method to detect these errors, while the state-space explosion is the most severe limitation to such a method. In this letter, a relief strategy is proposed by using the simultaneous reachability graph-a simple graph generated by the simultaneous execution of transitions that are executable on a global state. It is found out that both the correctness and types of errors of a protocol can be detected from the structure of such a graph. An algorithm for plotting the simultaneous reachability graph is developed and its complexity is considered. A numerical example about the handshake protocol is used to illustrate how the method works in practical applications.