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SNCP did not switch due to wrong service configuration.

Publication Date:  2012-07-25 Views:  111 Downloads:  0

Issue Description

Equipment Type: OSN3500+and Metro 1000V3
NE Version:
T2000 Version: T2000V200R007C03
Customer reported that services of particular ring are not switched to protected path whenever the fiber cut occured in working path of SNCP. SNCP ring capacity is STM-16 and in ring all NEs are Metro1000V3 and ADM NE is OSN3500.

Alarm Information

No alarm, but services did not shift to protection when working direction get down.

Handling Process

Following steps were performed to handle the issue.
1- Services were checked end to end but no issue found. 
2- Checked the status of line card and cross-connect by giving loop back section by section but no issue found at none of the Metro 1000V3.  
3- Checked the link losses in the whole ring but no abnormality found.
4- cheked the service configuration on ADM OSN3500, found tha service are add drop on SLQ16 board are VC4 level while the services are configured in the Metro 1000 V3 are on VC12 level, so during time of switching signal failure alarm are not reporting to respective VC12 becuase SNCP protect the path of service so it must be on same VC level.

Root Cause

Following are the possible causes.
1-Line board SLQ16 of protection path of SNCP are faulty.
2-first SCB board of Metro1000V3, which are directly connected with the protection path slot SLQ16 are faulty, which cause  failure of protection switching.
3-SDH configuration are deleted from one of SCB which cause switching failure.
4-Wrong service configuration in side of protection path.


The principle of the SNCP is "dual-fed and signal selection" and it is able to protect  path of the service and must be configured on same VC level, either VC12 or VC3 or VC4.