This counter tracks frames that were deferred before transmission because of activity already on the link. Deferred frames are a normal, expected part of half-duplex Ethernet's carrier-sense behavior -- the router politely waiting its turn rather than colliding -- so unlike the collision counters, a moderate steady rate here on a busy shared segment is not itself a fault indicator; only a sudden, disproportionate spike relative to traffic volume would warrant investigation. On a shared half-duplex hub-connected segment carrying multiple devices' traffic, this counter might tick up regularly during busy periods purely because the CDD-564 has to wait for the wire to go idle before it can send.