Abstract: A communications system and method is provided in which data is transmitted between a plurality of nodes (A, B, C, D) in a network comprising a closed loop configuration of one or more pairs of unidirectional transmission rings (1, 2) arranged to transmit data in opposite directions around the rings. Each node includes a respective message processor (5, 6) for each of the transmission rings (1, 2) and a host processor (60) linked to the message processors (5, 6). The traffic of data in each ring is dynamically monitored to obtain traffic information which is utilized by the message processors in accordance with a traffic control process to select one of the rings to transmit data from an originating node to a destination node. In the event of a fault in one of the rings, the other ring is utilized to transmit data at a reduced performance level while repairs are made to the faulty ring.