This read-only counter, in frames, tallies frames this switch itself sent with the BECN bit set, actively telling the far-end sender to reduce its rate because of congestion detected in the return direction. If the far end doesn't respond to a climbing count here by slowing down, congestion and eventual discards on this VC are likely to persist or worsen. This counter rising steadily while casfVcCountReceivedFrames from that same remote end stays flat would suggest the congestion notification is being ignored by the sender.