The Flexible Fast-Path complexes for both working and protect circuits are programmed to process ingress. The inactive (protect) circuit however is programmed to ignore all packet data. To perform the switchover from working circuit to the protect circuit the Flexible Fast-Path complex for the working circuit is set to ignore all data while the Flexible Fast-Path complex of the protect circuit is changed to accept data.
The ADM or compatible head-end transmits a valid data signal to both the working and protection circuits. The signal on the protect line is ignored until the working circuit fails or degrades to the degree that requires a switchover to the protect circuit. When the switchover occurs all services including all their QoS and filter policies are activated on the protection circuit.