Design and Implementation of an ISO/OSI Session Layer for a Microprocessor-Based LAN

This paper deals with the design and implementation of an ISO/OSI session layer carried out at the Dipartimento di Automatica e Informatica of the Politecnico of Turin for the MODIAC local area network. A detailed analysis of the application task requirements is introduced in order to explain the functional features selected for the layer. A Datagram service, not foreseen by the standard specifications, has been added to the session functional units, not foreseen by the standard specifications, to efficiently support time critical applications such as very high priority message handling. Performance data concerning memory occupancy and response times measured in a MODIAC prototype for the main session services are also reported.