Estelle specification of MIL-STD 188-220 datalink layer interoperability standard for digital message transfer device subsystems

This paper presents the results of a contract between ARL and the University of Delaware to develop a formal specification of the link layer of 188-220 using the ISO International Standard Formal Description Technique Estelle. This formal specification aims at discovering and resolving ambiguities in the original English document that would cause interpretation problems for implementers. The specification considers Type 1 connectionless (CL) operation of the link layer. It contains the complete set of command and response PDUs for the CL mode (UI, XID, URR, URNR, TEST). The paper discusses state diagrams and state transition tables needed for the Estelle specification. It also summarizes several ambiguities that were discovered in developing the Estelle specification