Analysis of Ethernet-based safe automation networks according to IEC 61508

Most applications in industrial automation could be hazardous for people, plant and environment. Therefore it is necessary for related distributed control systems, implementing safety functions for such applications, to rely on a real-time and fault tolerant communication among all connected stations. To realise this objective, safety related networks should be realised using Ethernet-based protocols with additional layers involved to fulfill safety requisites. The paper investigates the state of art technology of Ethernet-based safe communication systems with special attention to functional safety network requirements defined by the IEC 61508, pointing out the problems and examining how these communication protocols satisfy the defined requirements.