General
Media Redundancy Protocol (MRP) is a PROFINET specific ring protocol ensuring redundancy in the network, which can significantly decrease network downtime. It is a token based ring protocol with a master-slave hierarchy.
All the nodes in the PROFINET network part of the ring are connected using ring topology (that is, the last node is connected directly to the first node). If, at any point, the connection between two nodes would break, the data will flow the other way instead, guaranteeing that data can be sent to/from the IO Controller to the IO Device(s). The self-healing time is approximately 200 ms.
The Media Redundancy Master (MRM) is responsible for checking the functional capability of the ring network, by sending out cyclic tokens. The Media Redundancy Clients (MRC) basically work as switches that pass on the tokens. The Anybus CompactCom supports acting as a Media Redundancy Client (MRC). It also supports propagating link change to the Media Redundancy Master.
If port 2 of the device is inactivated in the Ethernet Host Object (F9h), support for MRP is removed. See Ethernet Host Object (F9h) , instance attribute #13, for more information.