High-availability Seamless Redundancy (HSR) is a network protocol for Ethernet that provides seamless failover against failure of any single network component. This redundancy is invisible to the application. HSR nodes have two ports and act as a switch (bridge), which allows arranging them into a ring or meshed structure without dedicated switches. This is in contrast to the companion standard Parallel Redundancy Protocol (IEC 62439-3 Clause 4), with which HSR shares the operating principle. PRP and HSR are standardized by the IEC 62439-3:2016). PRP and HSR are independent of the application-protocol and can be used by most Industrial Ethernet protocols in the IEC 61784 suite. It has been adopted for substation automation in the framework of IEC 61850. PRP and HSR are suited for applications that request high availability and short switchover time,such as: protection for electrical substation, synchronized drives (e.g. in printing machines) or high power inverters. For such applications, the recovery time of commonly used protocols such as the Rapid Spanning Tree Protocol (RSTP) is too long. The cost of HSR is that nodes require hardware support (FPGA or ASIC) to forward or discard frames within microseconds. This cost is compensated because no Ethernet switches are required. Hardware support is anyhow needed when the node supports clock synchronization or security. HSR does not cover the failure of end nodes, but redundant nodes can be connected via HSR.
High-availability Seamless Redundancy (HSR) is a network protocol for Ethernet that provides seamless failover against failure of any single network component. This redundancy is invisible to the application. HSR nodes have two ports and act as a switch (bridge), which allows arranging them into a ring or meshed structure without dedicated switches. This is in contrast to the companion standard Parallel Redundancy Protocol (IEC 62439-3 Clause 4), with which HSR shares the operating principle. HSR does not cover the failure of end nodes, but redundant nodes can be connected via HSR.