The authors present a model for specifying real-time protocols that execute on broadcast bus networks. Protocol entities interact by sending and receiving binary signals on buses. The actual propagation of these signals is captured in the proposed model by a set of channel axioms. Protocol entities are specified by sequential programs. The semantics of a set of programming constructs, including two level wait constructs, are defined. To illustrate the model and verification method, the authors present a specification of the Expressnet protocol which was designed for collision-free access to a unidirectional bus. A scenario in which collisions can occur in the original Expressnet was discovered. To guarantee collision-freedom, a modification to the protocol is given. The modified protocol is shown to be collision-free. A bound for its access delay is also derived.>

For high-speed local area networks that offer integrated services for data, voice, and image traffic, a class of demand-assigned multiple-access protocols have been presented in the literature. These protocols exploit the directionality of signal propagation and enforce time constraints to achieve collision-freedom. A correct implementation of such a protocol requires a careful analysis of time-dependent interactions of event occurrences using a formal method. To date, most protocol verification methods are intended for the analysis of asynchronous communication over point-to-point channels.

A class of demand-assigned multiple-access (DAMA) protocols have been proposed for high-speed local area networks (LAN's) that offer integrated services for data, voice, video, and facsimile traffic. These protocols exploit the directionality of signal propagation and implement stringent real-time constraints to achieve collision-freedom. Correct implementation of DAMA protocols will require a very careful analysis of time-dependent interactions using a formal method. To date, most verification methods have been focused on asynchronous communication over point-to-point links.