A star-shaped ring network with high maintainability

Abstract

Ring networks exhibit a number of desirable properties: they are simple in concept and in implementation; one-way point-to-point signal transmission minimizes analog circuitry and design problems; the cost of a small net is small; and transmission speed is not limited by propagation time. However, there are several potential reliability problems: all repeaters must be powered and operating reliably at all times; cutting of any transmission line in the ring will isrupt the entire network; and trouble-shooting may require visiting each node with test equipment. The advantages of ring networks are sufficiently attractive to merit careful attack onthe reliability and maintainability problems. This paper describes a physical organization of a ring network that we term a “star-shaped ring.” This organization addresses the reliability issues mentioned above by looping all internode links back through a central location so that broken lines or repeaters can be by passed. This approach allows automatic recovery if the ring is accidentally broken. In addition, it simplifies trouble-shooting and, because the lengths of transmission links can be normalized, permits the use of still simpler transmission circuitry. Finally, the “star-shaped ring” appears to be a satisfactory approach to installing a network that can grow to a large number of nodes in a typical office building.