or using both Syncs. This method works for several options in 1588, with Layer 2 / Layer 3 operation, and with peer-to-peer / end-to-end delay measurement. IEC 62439-3 defines these two profiles as: L3E2E (Layer 3, end-to-end) that addresses the requirements of ODVA L2P2P (Layer 2, peer-to-peer) that addresses the requirements of power utility in IEC 61850 and has been adopted by IEEE in IEC&IEEE 61850-9-3. Legacy versions The original standard IEC 62439:2010 incremented the sequence number of the Redundancy Control Trailer (RCT) in the PRP frames on a per-connection basis. This gave a good error detection coverage but made difficult the transition from PRP to the High-availability Seamless Redundancy (HSR) protocol, which uses a ring topology instead of parallel networks. The revised standard IEC 62439-3:2012 aligned PRP with HSR using the same duplicate discard algorithm. This allowed building transparent PRP-HSR connection bridges and nodes that can operate both as PRP (DANP) and HSR (DANH). The old IEC 62439:2010 standard is sometimes referred to as PRP-0 as it is still used in some control systems, and PRP 2012 as "PRP". Applications An interesting application of PRP was found in the area of wireless communication as "Timing Combiner" [], yielding significant improvement in packet loss and timing behaviour over parallel redundant wireless links. See also High-availability Seamless Redundancy Media Redundancy Protocol IEC/IEEE 61850-9-3 References External links ZHAW Tutorial on Parallel Redundancy Protocol (PRP) PRP in the Wireshark Wiki Tutorial on Parallel Redundancy Protocol (PRP) Tutorial on High-availability Seamless Redundancy (HSR) Tutorial on Precision Time Protocol with seamless redundancy in PRP and HSR Commercial implementation for Microsoft Windows by Siemens SIMATIC Networking standards Network protocols