Abstract: A method is described for ordering a plurality of messages from a plurality of sources wherein, in order for all the application processes to receive the messages in the same order, a single relay process common to all the sources is selected from the application processes, the other application processes constituting slave processes. All messages broadcast by the sources are rebroadcast from the relay process to all the application processes, including the relay process. The relay process processes data from all messages that it rebroadcasts. The slave process processes only data from messages received via the relay process, data from messages received directly from the sources not being processed. Applications include data processing systems, in particular where part of the software is replicated.

Abstract: A method of transmitting data between a set of data processing nodes interconnected by a communications network. Each node broadcasts data to the other nodes by causing a train of such data to travel over the network around a looped circuit or "ring" passing through each of said nodes, each node in the ring having a predecessor and a successor. A counter is provided in the data train, and on receiving a data train sent by its predecessor, each node recovers the counter from the received data train, increments the counter, and dispatches to its successor a new data train including the counter as incremented. It also stores the new data train with the incremented counter in its memory so that it is possible to implement a simple fault recovery procedure in the event of one of the nodes becoming faulty.