The SafetyConsumer uses the MNR to detect mis-timed SPDUs, e.g., such SPDUs which are continuously repeated by an erroneous network element which stores data. A different MNR is used in every RequestSPDU of a given SafetyConsumer, and a ResponseSPDU will only be accepted if its MNR is matching the MNR of the corresponding RequestSPDU.

The checking for correctness of the MNR is only performed by the SafetyConsumer.