Ethernet ring redundancy is becoming a commodity in Industrial Ethernet environments. There are many ring redundancy protocols in existence, both standardized and proprietary. They all share the common disadvantage, that they can sustain only one fault in the network structure. A second fault results in parts of the network being unavailable. In this paper, we propose a mechanism which enhances well-known ring redundancy protocols with the capability of tolerating more than a single fault. This is achieved by installing secondary network paths and adding health monitoring to the ring clients. Protocol operation has been tested through simulation and prototypical implementation and is intended to be part of a future major software release of Hirschmann switches. A main advantage of this new protocol is the straightforward network design approach that enables to specifically protect vulnerable ring segments, based on availability calculations.
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