PRP (Parallel Redundancy Protocol) is a fault-tolerant Ethernet protocol defined in IEC 62439-3. It ensures zero recovery time by transmitting identical Ethernet frames simultaneously over two separate and independent LANs—referred to as LAN A and LAN B. Each PRP-capable device uses two network interfaces and remains fully operational even if one of the networks fails. The receiving device accepts the first-arriving frame and discards the duplicate, avoiding retransmissions or delays and maintaining uninterrupted communication.
Compared to HSR (High-availability Seamless Redundancy), PRP offers full physical separation of network paths, which provides enhanced fault isolation and the ability to reuse existing network infrastructure. However, this comes at the cost of double the cabling, switches, and ports, which can increase system complexity and space requirements.
PRP is ideal for larger or existing installations where dual independent networks are already in place or where redundancy with maximum physical separation is required.
HSR, in contrast, uses a single-ring or mesh topology and achieves redundancy by sending duplicate frames in opposite directions through the same network infrastructure, making it more suitable for compact, distributed systems.
Only few devices like the DTS 4163.grandmaster support both HSR and PRP protocols as defined in IEC 62439-3. This allows the device to be used in a range of redundant network configurations, including HSR ring topologies, PRP dual-network setups, and in some cases, hybrid environments.
