IEC 62439-2:2016 is applicable to high-availability automation networks based on the ISO/IEC/IEEE 8802-3 (IEEE 802.3) (Ethernet) technology. This part of the IEC 62439 series specifies a recovery protocol based on a ring topology, designed to react deterministically on a single failure of an inter-switch link or switch in the network, under the control of a dedicated media redundancy manager node.This second edition cancels and replaces the first edition published in 2010. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:- adding a protocol extension to select the media redundancy manager automatically;- adding a protocol to redundantly connect media redundancy protocol rings.This publication is to be read in conjunction with IEC 62439-1:2010.