Designing and implementing a general purpose OSI stack for the DX 200 switching system using soffware tools

It has been more than ten years since the specification and standardization of OSI Reference Model started, yet rather few implementations have been done. One reason is that such implementation work isa formidable task. In this paper we describe our method designing and implementing a general purpose OSI stack. To begin with we give a short description of our operational environment, the DX 200 switching system. Then we discuss the major problems in implementing OSI stacks. The solutions we propose are based on the software toolbox called CVOPS. CVOPS includes a tool for implementation and testing of portable computer communications software and an ASN.1 to C compiler. In the rest of the paper we describe our OSI architecture which provides two application services, namely FTAM for file transfer and CMISE for networt management. Our implementa tion operates on the X. 25 Packet Switched Public Data Network and an CCITT's Common Channel Signalling System No 7. The implementation architecture is based on the distribution of the OSI layers. We also briefly discuss the background of distribution strategy.