A phase connection method for communication protocols

As one of the methods to define a large-scale protocol by combining multiple subprotocols, Chow et al. proposed a method in which protocols satisfying a certain condition called phase are serially connected. In their method of connection, however, two conditions for connection are imposed: 1) the protocol machine should be modeled as a finite-state machine; and 2) the two-way channels should both be empty at the termination of the phase. This paper relaxes those two constraints, and proposes a more general method of phase connection. Using the method proposed in this paper, it is made possible, for example, to define the protocol containing the token passing control by connecting two phases, where the token is fixed in one of the protocol machines.