The application of SDL to ISDN and OSI

The complex structure of communication protocols in open communicating systems demands powerful structuring and description tools, especially with the aim of specifying behaviour. The development of the ISDN Protocol Reference Model (ISDN PRM) based on the OSI Basic Reference Model (OSI BRM), the conception of suitable test procedures and the use of formal languages to describe the behaviour of protocols and systems are important factors that influence standardization in this area. However, the development of such tools and aids have proceeded independently, leading to difficulties in integrating them into a single concept. The paper deals with these aspects, particularly in connection with the use of the CCITT´s specification language SDL (Specification and Description Language) to model both the architecture and the behaviour of protocols and services within the framework of OSI and the ISDN PRM, the latter especially in connection with the novel ATM (Asynchronous Transfer Mode) concept