An Experimental Interconnection of Computers Through a Loop Transmission System

J. R. Pierce has described a digital communications system in which addressed messages are transmitted through a hierarchy of interconnecting loops or rings. 1 Components for one ring have been implemented by W. J. Kropfl. 2 We have used the ring to interconnect two laboratory computers. l.i User's View of the Ring To the user, the system resembles a high-speed telegraph service. A message, headed by a destination address, can be "put on the wire," and a moment later, it will be delivered to the addressee. Inside the network, the message is multiplexed onto a loop of circulating message blocks. If the addressee is on the same loop as the sender, the message travels around until it reaches him. If the addressee is on another ring, the message is passed from ring to ring, up and down the hierarchy, until it reaches him. Thereupon it is removed and its place on the loop marked "empty." But these internal details are invisible to the user. From his viewpoint, he can transmit directly to anyone he designates-without prior negotiation with the network to place a call, without worries of maintaining the connection for possible further communication, or of breaking it when finished. 1167