This counter tracks frames dropped on the egress side of a port because the transmit queue depth was exceeded, though the MIB notes this counter is not supported on the FRSM12 card. When available, a rising value tells an administrator that outbound traffic is arriving faster than the port can drain its queue, a sign of egress congestion. For example, an engineer seeing complaints of dropped frames on a heavily subscribed T1 port would check this counter (on cards where it applies) to confirm queue overflow as the cause.