Design and implementation of TORNET — A slotted-ring local area network

TORNET is a local area network whose basic design is a variation of the slotted ring where register insertion is used because of its operational advantages. The complete network consists of a number of local rings connected to a central ring. Small computers and the terminals that access them are the normal devices found on a local ring, while expensive shared components, such as large disk files or printers, are attached to the central ring. Two packet lengths are implemented at the ring level. A short packet (one data byte) facilitates interactive communications between terminals and computers. The long packet format (129 data bytes) is used for efficiency in file transfer operations. Two types of units are used to attach devices to a ring. The simpler one, called a character station, is used for simple devices such as teminals, and can only handle short packets. A block station, which can handle both long and short packets, is configured to support multiple virtual connections, and is used for computers. Software is designed using the ISO layered protocol, and has been implemented in the high-level language Concurrent Euclid. A bridge has been implemented for connecting local rings to the central ring, and an initial prototype for an X.25 gateway has been built.