A new local area network architecture using a centralized bus

LOCAL AREA NETWORKS are currently enjoying tremendous popularity as a means for providing wideband interconnection and communications among data terminals, host computers and other types of digital equipment located throughout a single building or a campus of buildings. Such networks are typically based on bus, ring, or star architectures, each of which manifests its own set of advantages and disadvantages. In this paper, an architectural approach is described that draws upon and integrates the advantages found separately in these three different architectures, while avoiding the major disadvantages found in any one. This new architecture employs a centrally located short bus that provides an extremely efficient packet-switching service to the devices attached to the network. Bandwidth on the short bus is dynamically allocated in response to instantaneous demands by means of a highly efficient but flexible prioritybased bus contention scheme. The approach permits multiple priority classes with fair allocation of bandwidth within each class, along with a capability for integrated circuit and packet switching. The architecture can also make use of existing twisted-pair building wiring, and at the same time take advantage of emerging optical-fiber technology. In addition, the architecture provides a means to expand the network beyond a local area, resulting in a wide-area network capability.