High availability is crucial for industrial Ethernet networks and Ethernet-based control systems, such as automation networks and substation automation systems. Because the standard Ethernet does not support fault tolerance capability, the high availability of Ethernet networks can be increased by using redundancy protocols. Various redundancy protocols for Ethernet networks have been developed and standardized, such as rapid spanning tree protocol (RSTP), media redundancy protocol (MRP), parallel redundancy protocol (PRP), high-availability seamless redundancy (HSR), and others. RSTP and MRP provide redundancy in the network, whereas PRP and HSR provide redundancy in the end nodes. RSTP and MRP have a disadvantage in switchover delay. PRP and HSR provide zero recovery time, but PRP requires a duplicate network infrastructure, and HSR is mainly used in ring-based topologies. Additionally, PRP and HSR provide seamless redundancy in the end nodes and are applied in dedicated HSR networks with dedicated HSR nodes. In this paper, we present a novel seamless redundancy protocol for Ethernet networks, which is called the Redundancy Protocol for Ethernet (RPE). The RPE provides seamless redundancy in the network. This protocol not only provides seamless communications with zero switchover time in case of failure but also supports all topologies. The RPE is transparent and compatible with standard Ethernet nodes. These features make the RPE very useful in time-critical and mission-critical systems, such as substation automation systems, automation networks, and other industrial Ethernet networks.

In this paper, we present a new fault-tolerant, large-scale star network scheme called Scalable Autonomous Fault-tolerant Ethernet (SAFE). The primary goal of a SAFE scheme is to provide network scalability and autonomous fault detection and recovery. SAFE divides a large-scale, mission-critical network, such as the naval combatant network, into several subnets by limiting the number of nodes in each subnet. This network can be easily configured as a star network in order to meet fault recovery time requirements. For SAFE, we developed a novel mechanism for inter-subnet fault detection and recovery; a conventional Ethernet-based heartbeat mechanism is used in each subnet. Theoretical and experimental performance analyses of SAFE in terms of fail-over time were conducted under various network failure scenarios. The results validate our scheme.