The AIS insertion function enables service switchover of a port with a protection channel. For services that require good quality of service (QoS), when the Web LCT detects a specific QoS-affecting event (for example, the TIM_P), the Web LCT immediately inserts an AIS at the port. In this way, the related protection mechanism is triggered and the service at this port is switched to a protection channel to guarantee the QoS. You can also insert an AIS at the port and then query the opposite NE, either in the upstream direction or in the downstream direction, to see whether any alarm is generated. In this way you can check the correctness and connectivity of a trail.