A Formal Specification of Signalling System Number 7 Link Layer
P.W. King · Australian Software Engineering Conference · 1989
The Link Layer Services of CCITT's Signalling System Number 7 are specified from two points of view using the Z specification language. The Service Specification describes the service properties observable by the Network Layer. These externally visible properties are described in terms of a timed service-primitive history. Various periods of operation in the history are distinguished. Allowable times for each service primitive are described in terms of these periods. Time constraints between particular service primitives are also specified. The Protocol Specification describes the underlying protocol used to provide the services in terms of internal functions. Internal timing constraints and the allowable concurrency among these functions are specified in terms of a timed function history.