This counter counts the Continuity Check cells received on the Virtual Channel Link, which are periodic heartbeat signals used to verify that the remote end is still connected and responsive. Network engineers use this to confirm that the virtual channel is alive and that the far-end equipment is actively monitoring the connection, which is critical for automatic failover detection. A steady count of 1 Continuity Check cell per second (3,600 per hour) is normal; if it drops to zero, the far end has either crashed or the connection is broken.