Figure 82: Mrp / E-Mrp Ring Redundant Structure; Figure 83: Single Network Using Rstp / E-Mrp - ABB UniGear Series Engineering Manual

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Media Redundancy Protocol (MRP) is a ring redundancy protocol defined in IEC 62439-2
standard. One of the Ethernet switches in the ring acts as a Ring Manager. There is exactly
one ring manger in the ring. With the help of the ring manager function, the two ends of a
backbone in a line structure can be closed to a redundant ring. The Ring Manager keeps the
redundant line open if the line structure is intact. If a segment fails, the ring manager imme-
diately closes the redundant line, and line structure is intact again. E-MRP is fast MRP with
decreased recovery time (Ring < 10 switches: < 10ms recovery time, Ring < 100 switches: <
40ms). It is supported by AFS family.
MRP provides shorter switching times than RSTP, it is limited to ring topology and it covers
much bigger networks in comparison to RSTP. Coupling RSTP, MRP and E-MRP networks is
possible.

Figure 82: MRP / E-MRP ring redundant structure

Figure 83: Single network using RSTP / E-MRP

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