Abstract: A local network, particularly an Ethernet network having redundancy properties, in which coupling devices (K1, K2, K3) and a redundancy manager (RM) are interconnected in a ring-shaped topology. The redundancy manager opens the ring to create a linear topology if test messages (T11, T12) emitted by the redundancy manager (RM) are received at the other port (P42, P41) within a given period of time, otherwise the redundancy manager (RM) closes the connection. As a so-called redundancy manager observer, at least one of the coupling devices (K3) is configured such that it evaluates messages received at the port (P32) thereof, the port (P32) being connected to the redundancy manager, opens the ring to create a linear topology, and signals an error if more than initial test messages (T11) have been received at this port (P32) and if the status “ring opened” has been indicated by the redundancy manager (RM) in the last-received initial test message (T11), whereby messages are prevented from circulating on the ring.

Abstract: A distributed automation communication system, in particular a real-time critical, cyclic, real-time Ethernet system, which has a plurality of users. Each user has at least one diagnostic unit (7, 8, 15) for the diagnosis and recording of data concerning the data exchange between users. In addition, the communication system (1) has a further user embodied as a central diagnostic terminal (13). The central diagnostic terminal (13) carries out a central diagnosis of the whole communication system (1) by configuration of the diagnostic units (7, 8, 15) of the users and calling up and analyzing the diagnostic data recorded by the diagnostic units (7, 8, 15) of the users.

Abstract: A local network, particularly an Ethernet network having redundancy properties, in which coupling devices (K1, K2, K3) and a redundancy manager (RM) are interconnected in a ring-shaped topology. The redundancy manager opens the ring to create a linear topology if test messages (T11, T12) emitted by the redundancy manager (RM) are received at the other port (P42, P41) within a given period of time, otherwise the redundancy manager (RM) closes the connection. As a so-called redundancy manager observer, at least one of the coupling devices (K3) is configured such that it evaluates messages received at the port (P32) thereof, the port (P32) being connected to the redundancy manager, opens the ring to create a linear topology, and signals an error if more than initial test messages (T11) have been received at this port (P32) and if the status “ring opened” has been indicated by the redundancy manager (RM) in the last-received initial test message (T11), whereby messages are prevented from circulating on the ring.