This counter tracks how many transmitted ATM cells were marked by the switch with the EFCI (Explicit Forward Congestion Indication) bit to signal downstream equipment that network congestion is occurring. A network engineer uses this to detect when the ATM switch is experiencing congestion and to validate that congestion notification is working as a feedback mechanism to slow down traffic sources. If this counter increases sharply during peak hours (from 1,000 to 50,000 EFCI cells per hour), it indicates the switch is experiencing backpressure and sources should reduce their transmission rates.