Abstract: The reliability of a distributed processing system is enhanced through the use of a highly reliable data communication system. Each node of such a system is connected to the other nodes by a local data network, including duplicated data network media, such as coaxial cables. Each node includes a maintenance processor for controlling which of the duplicate network media is active and which is standby. Regular inter-node data packets are transmitted over the active network medium. Control data packets to the maintenance processor are sent from a control node over the standby network medium. The maintenance processor can also totally stop transmission of data from the associated node to both data network media.

Abstract: A method and apparatus for flexibly interconnecting the nodes of a local data network to achieve reliable internodal data transmission while minimizing the extra data processing load on the host processors of each node. An interface processor is provided at each node which controls transmission and reception of data packets and the communication of data from and to the location in node storage associated with the program processes which generate and receive the data. Different protocols are provided for different types of messages and are controlled by the interface processor in order to provide high reliability data transmission where needed. Destination addresses are associated with each data packet to provide flexible routing of data.