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LCAS function doesn't operate due to LCAS is enabled after the Ethernet serive became abnormal

Publication Date:  2012-07-25 Views:  78 Downloads:  0
Issue Description
There are 6xVC3 SDH trails to transmit Ethermet service from NE "A" OSN 3500 (N2EGS2 board)  to NE "B" OSN 7500 (N2EGS2 board). 2 Ethernet trails are used for this (3xVC3 trails for each Ethernet trail). One Ethernet trail (trail "1") used protected SDH trails, second (trail "2") - extra SDH trails. After fiber cut happen in the MSP ring which the services path-through, trail "2" were interrupted, as result the Ethernet service between NEs "A" and "B" was interrupted. To partially restore the services (using normal trail "1") Customer decided to enable LCAS function on correspond Ethernet boards of both NEs. But when the LCAS where enabled the Ethernet service was still down and LCAS_FORP alarm was persisted on NE "A" (on the N2EGS2 board).

NE software version on both NEs is V100R008C02SPC200(5.xx.18.50P01)+SPH001
Alarm Information
Handling Process
1. Disable LCAS on both NEs (sink and source) transmit the problem Ethernet service.
2. On both NEs unbind affected SDH trails from VCTRUNKs belong to the service (left only non-affected SDH trails to transmit the Ethernet service)
3. On both NEs enable LCAS function on VCTRUNKs belong to the problem service
4. Add back affected SDH trail excluded from the transmission in point 3.

LCAS_FOPR alarm will disappear and LCAS protocol will operate properly to udjust Ethernet link capacity automatically.
Root Cause
To garantee the LCAS function will operate normally need to enable LCAS on both NEs (source and sink) where an Ethernet service is configured when the Ethernet service is in normal state (can transmit Ethernet traffic). If you enable the LCAS function when the Ethernet service became abnormal the LCAS protocol can be confused and LCAS_FOPR alarm will report on one or both NEs.
Enable LCAS function in advance when Ethernet services are in normal state, otherwise you can meet described problem