The OSN3500 transport network fails the SNCP over MSP protection inversion due to the problem of setting the protection inversion condition for SNCP. This problem can be solved by setting the HP_UNEQ alarm as the SNCP inversion trigger condition.

Affected device types

OptiX OSN3500 II

OptiX OSN3500

Failure Category

Protection reversal fault

HP_UNEQ Alarm

Phenomenon Description

An SNCP over MSP ring, as shown in Figure 1.

Fig. 1 Network connectivity diagram

NE1, NE2, NE3, NE4 and NE5 form an MSP ring with an STM-1 link between NE1 and NE3. An SNCP VC-4 service is created between NE1 and NE3. This VC-4 service has a working source on the MSP working path and a protection source on the STM-1 link. the SNCP delay time is 100 ms. when the first fiber break occurs (between NE1 and NE2), the MSP inversion is normal. When the second fiber break occurs in the MSP ring (between NE3 and NE4), the SNCP service is interrupted and no SNCP protection inversion occurs.

Cause analysis

When fiber breakage occurs for the second time, check the SNCP inversion status. the SNCP inversion status of NE1 is normal, which is the reason why SCNP inversion does not occur. In this VC-4 link, NE1 reports HP_UNEQ alarms to the main control board and network management. Analyze the cross-connections on NE4 and find that no cross-connections are created. On NE5, the MSP protection paths are all traversed. It can be concluded that the NE4 protection is not crossed causing the problem, all VC-4 signals are null, and the HP_UNEQ alarm is reported on the downstream network element.

Procedure

Set the HP_UNEQ alarm as the SNCP inversion trigger condition. Test again, the inversion is successful.