This counts inbound frames marked with BECN, meaning the sender of this circuit's own traffic in the opposite direction is being told to slow down because congestion was detected on the return path. An admin sees this rise when the circuit's transmitting endpoint's upstream path is congested, and a TCP or SNA stack honoring BECN should reduce its send rate in response. For example, a burst of BECN-marked frames coinciding with a rise in cktOutLostFrames on the reverse direction would show the network correctly signaling the sender to back off during an actual overload event.