The ADNET Communications System: Inter-Process Communication in a Fault Tolerant Local Area Network

Abstract An experimental local area network (ADNET) has been developed at the Admiralty Surface Weapons Establishment (ASWE) to investigate the use of a distributed computer architecture for shipborne command and control systems. The ADNET Communications System provides the means by which software processes distributed throughout the network can communicate. At the hardware level it uses the ASWE Serial Highway. This is a polled multi-drop bus which employs hardware redundancy to achieve high reliability. Both broadcast and point-to-point intercomputer message transfers are supported and a high level of error detection and correction is provided. The software of the communications system provides protocols which eliminate the need for a fixed connectively within the network. This allows the applications software to be dynamically reconfigurable and leads to the provision of fault tolerant functions for the network. The ASWE Serial Highway is described together with the software and protocols of the communications system. In addition, the use of the protocols by fault tolerant functions is illustrated by examining the operation of the ASWE Distributed Database Management System (ADDAM).