Description of the problem

The lower service point of the low-order SNCP ring of an OSN3500 device is configured on a node of the ring multiplexing segment ring, and the SNCP service is configured on the working channel of the ring multiplexing segment ring, but the protection of this SNCP is not configured on the ring multiplexing segment ring. The service point on the working channel of this low-order SNCP service is connected to another site in the ring multiplexing segment, and a power failure at this site causes the multiplexing segment ring to be inverted, and then the low-order SNCP service is interrupted, but there are no alarms for this low-order SNCP service.

Processing

First, check whether the reversal of this multiplexing segment is successful. By querying the K-byte events of the whole ring and the reversal page switching, the page switching is correct at the power-down site and the sites at both ends of the ring, and the other sites on the ring of the multiplexing segment have all entered the pass-through page correctly, which indicates that the reversal of the multiplexing segment is correct. Then check whether the reversal event of the SNCP where the interrupted service is located is correct, and find that there is no reversal event generated by this SNCP at the time point of power down, indicating that this SNCP has been working in the working channel, and because the working channel of this SNCP has been selected and received in the protection channel of the multiplexing segment due to the reversal of the multiplexing segment, and because the corresponding channels of the reversed site of the multiplexing segment ring have been configured with the service, thus the misconnection occurs, resulting in the low-passing of the multiplexing segment. A misconnection occurs, resulting in a low-order SNCP service interruption without an alarm.

Root Cause

The root cause of this problem is that the service is misconnected when the service point on the SNCP is powered down, resulting in service interruption without alarms.

Solution

Emergency recovery measure: Forcibly invert the SNCP to the protection channel. Complete solution: Configure the protection of SNCP on the ring of multiplexed segments and configure it as recoverable.

Recommendations and Summary

Low-order jobs are configured on the multiplexed segment ring and misconnections cannot be avoided. When low-order SNCP is coupled with MSPs, it is recommended that SNCP jobs not be configured on the multiplexed segment ring.

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