scope:

IEC 62439-4:2010(E) is applicable to high-availability automation networks based on the ISO/IEC 8802-3 (IEEE 802.3) (Ethernet) technology. It specifies a redundancy protocol that is based on the duplication of the network, the redundancy protocol being executed within the end nodes, as opposed to a redundancy protocol built in the switches. The switchover decision is taken in each node individually. The cross-network connection capability enables single attached end nodes to be connected on either of the two networks. It cancels and replaces IEC 62439 published in 2008 and constitutes a technical revision. It includes the following significant technical changes with respect to IEC 62439 (2008): - adding a calculation method for RSTP (rapid spanning tree protocol, IEEE 802.1Q), - adding two new redundancy protocols: HSR (High-availability Seamless Redundancy) and DRP (Distributed Redundancy Protocol), - moving former Clauses 1 to 4 (introduction, definitions, general aspects) and the Annexes (taxonomy, availability calculation) to IEC 62439-1, which serves now as a base for the other documents, - moving Clause 5 (MRP) to IEC 62439-2 with minor editorial changes, - moving Clause 6 (PRP) was to IEC 62439-3 with minor editorial changes, - moving Clause 7 (CRP) was to IEC 62439-4 with minor editorial changes, and - moving Clause 8 (BRP) was to IEC 62439-5 with minor editorial changes, - adding a method to calculate the maximum recovery time of RSTP in a restricted configuration (ring) to IEC 62439-1 as Clause 8, - adding specifications of the HSR (High-availability Seamless Redundancy) protocol, which shares the principles of PRP to IEC 62439-3 as Clause 5, and - introducing the DRP protocol as IEC 62439-6.