The OSA Project Design and Formal Specification of an X.25 Based Open Transport Layer and its Protocols

Abstract

The paper presented should be a kind of tutorial for those who have a basic understanding of the open systems interconnections philosophy as well as of software technological problems in developing reliable systems. It mainly consists of four parts, namely

• it explains the requirements for the Transport Layer as given in the Reference Model (of Open Systems Interconnections) document;

• it gives a general design for the RM Transport Layer meeting these requirements; this design is based on simple building blocks that may be easily described and specified;

• it characterizes a subset of the building blocks of the general design suitable for an X.25 based RM Transport Layer (having almost identical services used and provided as those presently discussed in the PIX group);

• it discusses the simplifications obtained from this decomposition of the whole Transport Layer into uniform building blocks and the technique we apply for formally specifying the modules (the building blocks contain) as well as the building blocks, themselves.

• what intentions the Reference Model document associates with its Transport Layer, as well as

The intention of this paper is to provide a sound basis for a common understanding of

• what intentions the Reference Model document associates with its Transport Layer, as well as

• how a layer may be designed such that advanced technologies for producing reliable software may be applied.