Redundancy in communication networks is critical in substation automation, processing, and manufacturing application. Although there are several media redundancy communication protocols, instant switchover to backup or secondary pathways with zero reconfiguration time is required for protection of electrical substation, synchronized drivers, high-power inverters, and printing machines. High-availability Seamless Redundancy (HSR) protocol meets these criteria and is commonly used in substation automation especially for station bus implementation.
- IEC Standard (IEC 62439-3, Clause 5) providing redundancy for standard Ethernet based networks
- Two physical network ports are used for communication, which are connected to a ring network.
- Each Ethernet frame is duplicated and transmitted on both the ports connected to the ring network.
- The receiver discards the duplicate frame and forwards a single copy to the higher layers of network stack.
- The entire process of duplicating on the transmit side and discarding the duplicates on the receiver is done seamlessly and unknown to the application.
- Failure of a network component on a network still ensures that the duplicate is received by the receiver via the other direction in the ring.
- More suitable for simpler (ring) network with limited number of nodes. It has lower cost of deployment when compared to PRP.
We have advanced level expertise with the design and implementation of the HSR on the Texas Instruments Sitara platform with Linux/RTOS running on the ARM core and the firmware running on the Programmable Real-time Unit (PRU) core within the Industrial Communication Sub-System (ICSS). Frame duplication on the transmit side and duplicate discard on the receive side has been offloaded to the firmware to improve the OS performance on the ARM host. The implementation has been tested rigorously under heavy traffic conditions in conjunction with the PTP protocol. Further enhancements in the performance of the driver and the firmware is currently work in progress.