The protocol specification language ESTELLE

Abstract

ESTELLE is being developed by the International Standards Organisation (ISO), Technical Committee (TC) 97, Sub-committee (SC) 21, Working Group (WG) 1, Formal Definition Technique (FDT) Subgroup B to fulfil the need for a protocol specification language. FDT Subgroup C is working on LOTOS as an alternative protocol specification language and the International Telegraph and Telephone Consultative Committee (CCITT) has developed SDL for the same purpose. The purpose of this paper is to briefly introduce the language ESTELLE and to discuss the following: - The characteristics of the language. • The finite state machine orientation of the language. • The formal semantics of the language constructs. • The levels of abstraction provided by the language. • Features enhancing protocol specification and verification. - The current level of maturity of the language. Some indications of the limitations of the language are given and the appendix contains a very simple skeleton example of an ESTELLE specification.