This value sets the upper limit of incoming unicast traffic on a port, measured over a 1-second interval in the unit chosen by hh3cStormCtrlUnicastUnit, above which the port is put into controlled status. An admin tunes this to guard against unknown-unicast flooding, which can occur when MAC address tables age out under heavy churn. For example, a value of 5000 with the unit set to packetsPerSecond caps unicast traffic at 5000 packets per second before the port throttles.