No abstract

No abstract

No abstract

The call establishment procedure of the X.2l interface recommended by the International Telegraph and Telephone Consultative Committee (CCITT) has been validated as a test of a recently developed theory and of an implemented system for automated communications protocol validation. The test demonstrated the applicability of the validation technique and identified a number of points where the interface state diagram does not completely define the interface behavior. IntroductionA recent theory due to Zafiropulo [1] has shown that it is possible to validate the syntax of a communications protocol between two processes that can be represented as a pair of directed graphs. A reformulated version of the theory has been programmed in a system that enables errors in protocols to be automatically identified [2].The work described in this paper was undertaken in order to test the above theory and validation system in a real environment, by validating a reasonably complex protocol.The X.21 interface has been chosen as a test case because of its current interest and also because it is formally defined in state diagram form and so can be readily validated.In this paper we first briefly describe the X.21 interface and how its specification was interpreted for the purpose of validation. The results of the validation are then presented and their significance discussed.

No abstract