The ring network of the OSN6800 device group was newly launched, and ODU1-SNCP/N protection was activated. Engineers reported that a switchover occurred one day and there was no recovery, but there was no problem with the optical cable. The corresponding ND2 optical port had an ODU_SNCP_PS alarm. What are the possible reasons? (Multiple choice)
A . Related circuit board failure;
B . The service configuration is incorrect, or there is redundant service crossover at the service source and sink points;
C . A minor alarm ODU1_PM_LCK exists on the relevant circuit board;
D . The PM overhead of the related circuit board is set to "LCK insertion" as enabled
Answer: ABCD