Modeling and Verification of Communication Protocols in Sara: The X.21 Interface

This paper models the CCITT X.21 interface specification using a graph model and verifies the behavior of the interface using analysis tools accessible through UCLA's SARA (System Architects' Apprentice) design aid system. Behavior of the interface is modeled in three domains: control flow, data flow, and interpretation. Explicit models of assumed behavior for the environment and for the system under study are incorporated in a SARA world view such that systematic analysis and simulation can be applied.