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Traffic Abnormal on an SNCP Ring Due to a Fiber Connection Error

Publication Date:  2012-07-25 Views:  58 Downloads:  0
Issue Description
Two OptiX Metro 1000 V300 NEs (NEs A and B) connect to two STM-1 interfaces on an OptiX OSN 3500 NE (NE C) through two 155 Mbit/s SNCP rings (rings A and B). NEs A and B also connect to two 2 Mbit/s tributary interfaces on another OptiX OSN 3500 NE (NE D) in the central telecommunication room. For details, see the Topology.doc. Optical fibers/cables on rings A and B are cut over. After the cutover, engineers find that the traffic on rings A and B is interrupted. The transmission equipment, however, does not report any alarm or performance event.
Alarm Information
Null.
Handling Process

1. Check the traffic configuration but find no problem. In addition, the traffic configuration is not modified during the cutover. Therefore, the problem is not caused by traffic configuration.

2. Check for an alarm on the transmission side but find that the transmission equipment does not report any alarm. Therefore, NEs A, B, and D do not have a problem in transmitting 2 Mbit/s traffic. The 2 Mbit/s connections between the transmission equipment and the switching equipment are also available.

3. Perform an outloop test on the 2 Mbit/s interface on NEs A, B, and D but find no problem. Therefore, the problem is not caused by the 2 Mbit/s connections between the transmission equipment and the switching equipment.

4. Perform an inloop test on the 2 Mbit/s tributary interface on NE A. Meanwhile, check the peer 2 Mbit/s interface on NE D by using a tester. The out-of-frame alarm is detected.

5. On NE D, deactivate the traffic between NE D and NE B. Then, protection switching occurs on the tributary board on NE A. The traffic on NE A is then restored successfully. Engineers suspect that optical fibers are incorrectly connected.

6. Modify the J0 byte to check the fiber connections on rings A and B. It is found that a fiber pair on ring A and a fiber pair on ring B differ from the connection settings on the T2000. For details, see the Topology.doc.

7. Correct the fiber connection errors. Then, the fault is rectified. 
Root Cause

1. Traffic configuration error

2. Loopback

3. Fiber connection error 
Suggestions

1. The transmission equipment may have a problem even if the transmission equipment does not report an alarm or performance event.

2. After cutover, ensure that the new fiber connections are consistent with the original fiber connections.

3. A tester can be used for troubleshooting.  

END