A count of the number of unique Event OAMPDUs received on this interface. Event notification OAMPDUs may be sent in duplicate to increase the probability of being successfully received, given the possiblity that a frame may be lost in transit. An Event Notification OAMPDU is indicated by a valid frame with (1) a destination MAC address that equals the reserved MAC address for Slow Protocols (see 43B of [802.3ah]), (2) a lengthOrType field that equals the reserved type for Slow Protocols, (3) a Slow Protocols subtype that equals the subtype reserved for OAM, and (4) an OAMPDU code that equals the OAM Event code. An Event Notification OAMPDU is uniquely identified by its Sequence Number field. Discontinuities of this counter can occur at re-initialization of the management system, and at other times as indicated by the value of the ifCounterDiscontinuityTime.