In the FTTB/C scenario, the ONU is connected to the phone as an AG device, and there is no sound when the SIP protocol is off-hook. The possible reason is?

In the FTTB/C scenario, the ONU is connected to the phone as an AG device, and there is no sound when the SIP protocol is off-hook. The possible reason is?
A . There is packet loss in the upper layer network of the olt
B. The status of the MG interface on the ONU side is abnormal
C. Voice server failure
D. The route between ONU and IMS is unreachable

View Answer

Answer: B