IEC 62439-3:2012 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: duplication of the LAN, resp. duplication of the transmitted information. This second edition cancels and replaces the first edition published in 2010. It constitutes a technical revision. The main changes with respect to the previous edition are:
- specification of the interconnection of PRP and HSR networks;
- introduction of a suffix for PRP frames;
- clarification and modification of specifications to ensure interoperability;
- slackening of the specifications to allow different implementations;
- consideration of clock synchronization according to IEC 61588;
- introduction of test modes to simplify testing and maintenance.

This publication is to be read in conjunction with IEC 62439-1:2010.