This read-write Integer32 sets the threshold, in discarded cells, for the current 15-minute interval above which a Threshold Crossing Alarm (TCA) is generated for this queue. An admin configures this value to define what level of cell discard is considered abnormal enough to warrant an alert within any given 15-minute window. An admin managing a heavily-loaded QBIN queue would lower this threshold to get earlier warning of creeping congestion, or raise it to avoid nuisance alarms on a queue known to run near its limits.