A minimal duplex connection capability in the top three layers of the OSI reference model

A minimal duplex connection capability is described as the ability to open, close, abort, and transfer data through a duplex connection between two application processes. The goal of this paper is to describe a minimal duplex connection capability for the top three layers of the Open Systems Interconnection (OSI) Reference Model that will be appropriate for use by very small Open Systems such as home computers. Such a connection capability would allow these small systems to interconnect with machines of arbitrary size. The approach taken is to use only the parameters on service primitives that are absolutely required to accomplish this connection service. The protocol and services necessary to accomplish such a minimal connection are described for the application, presentation, and session layers of the OSI Reference Model. The existing draft proposals for services and protocol for the session layer provide a basis for this duplex connection service. A minor modification to the session draft proposals is suggested. The services for the presentation and application layer are defined in terms of the tentative service primitives being considered in the international standards efforts. The transparent initial context defined for the presentation layer is used to minimize the work of that layer. The benefits of this minimal duplex connection capability are then discussed from the point of view of very small Open Systems.