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PTN 960 LOCV alarm troubleshooting

Publication Date:  2019-07-19 Views:  272 Downloads:  0

Issue Description

One commercial network reported  lots of MPLS_TUNNEL_LOCV alarms and other MPLS tunnel alarms.  The service switched to protection tunnel immediately automatically. 

Alarm Information


Handling Process

There are three ways to improve this issue:
1. Add one new event when detected SEU fault, because there is no reasonable event for it, so it need to do it in the new version, it should be R6C01 version.
2. Add heartbeat checking(reference to the pink line), it’s also need to do it in the new version, , it should be R6C01 version.
3. Add an exist alarm(such as HARD_BAD,HARD_ERR) in patch.

Root Cause

1. This log show CRAM of the FPGA fail, and detect by SEU monitoring, then record the information in the log. 
2. As the patch solution, About the SEU detection function, In the Patch Release   Notes of PTN960 SPH102.
3. From the log, confirm KNGE308a-PTN01z slot 4 receive direction there are ISIS HELLO packet drop count. 
4. R&D found out the PDU  header length should be 0x1B, but it actual receive 0x1A. So we consider the packet have been changed unexpected. And the fault bit is bit23, it have been fixed as “0” all the time.

5. Analyze the OAM packet,if bit23 fixed as “0”, then the DMAC will be change 0x4B to 0x4A,then it will drop when the MAC not match in MPLS forward module later.
6. SEU fault cause slot 4 EX1 change the packet, and then in the master control board can’t match the MAC it will drop the packet, so it report MPLS_TUNNEL_LOCV alarm.


Why there is no packet error checking alarm:
1.    if packet changed in zone 1, that is between BIP and checking BIP, if the packet changed, it will have alarm and have log too.
2.    If packet changed in zone 2, that is between checking BIP and insert CRC, this zone can’t check out, no way to report alarm.