This counter records the number of priority-tagged frames discarded by this port's Acceptable Frame Policy during the archived historical interval. A historical nonzero value tells the admin exactly when devices began sending priority-tagged frames that this port's frame-acceptance policy rejects, useful for correlating with a device or config change. For example, if a VoIP phone started losing QoS tagging benefits last week, the admin would check cmEthernetTrafficPortHistoryAPFD around that date to see if the port began discarding its tagged frames then.