IEC 62439-3:2016 is applicable to high-availability automation networks based on the Ethernet technology. This part of IEC 62439 specifies two redundancy protocols designed to provide seamless recovery in case of single failure of an inter-bridge link or bridge in the network, which are based on the same scheme: parallel transmission of duplicated information. This third edition cancels and replaces the second edition published in 2012. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: - technical corrections and extension of specifications; - consideration of IEC 61588 clock synchronization with end-to-end delay measurement alongside the existing peer-to-peer delay measurement in PRP.