A distributed approach to the interconnection of heterogeneous computer networks

This paper describes a distributed architecture for the flexible interconnection of heterogeneous networks with a number of mini- and micro computers, in a research environment. The interconnected networks include the DARPA Internet, which uses the DoD protocols, and the X25-based networks PSS and SERCNET. The approach described here distributes the network access into a set of microcomputers acting as network frontends ("network access machines"), with a local area network (Cambridge Ring) as a common bus. Communication between the hosts and the network access machines uses an interprocessor communication mechanism with a standard transport-level virtualcall interface, which is described. This arrangement provides local hosts with flexible access to any of the networks, and supports a relay system which allows users on one network to access hosts and facilities on any of the other networks.