Experiences with a Layered Approach to Local Area Network Design

The Nestar Plan 4000 network was designed using the ISO Open Systems Interconnection model. The Xerox Network Systems Internet Transport Protocols (XNS) were chosen for the network and transport layers, a token-passing protocol (Arcnet) for the physical and datalink layers, and existing Nestar server software for the highest layers. The physical and datalink layers are supported by a VLSI chip and their implementation was straightforward. In spite of their detailed specification, implementing the network and transport layers presented some unanticipated challenges. This paper discusses details of our experience in implementing the network with emphasis on the problems encountered and how they were solved.