HSR & PRP Redundancy

In the high stakes world of industrial automation, standard Ethernet protocols originally designed for office environments proved inadequate for mission critical operations. The primary technical hurdle was convergence time, the delay required for a network to reroute data after a link or node failure. Traditional redundancy protocols, such as Spanning Tree Protocol (STP) and even its Rapid variant (RSTP), operate reactively; they detect a break and then reconfigure the path. This reactive nature creates a period of network silence while the topology resets.

In a high-speed manufacturing line or a power substation, a recovery delay of even a few milliseconds can be catastrophic. Such micro-blackouts in data transmission can trigger emergency equipment shutdowns, cause synchronized robotic arms to lose timing, or lead to massive financial losses due to production downtime. This vulnerability necessitated a proactive rather than reactive approach. Consequently, High-availability Seamless Redundancy (HSR) and Parallel Redundancy Protocol (PRP) were engineered to provide bumpless recovery. By sending duplicate data packets over two independent paths simultaneously, these protocols ensure that if one path fails, the destination still receives the data from the other without a single millisecond of interruption.