An NE Became Unreachable to the NMS After Line Boards Were Cold Reset

Lower-rate multiport line boards preempted DCC resources of higher-rate line boards after line boards were cold reset during an NE upgrade or expansion. As a result, the NE became unreachable to the NMS. The fault was rectified by releasing DCC resources on lower-rate line boards.

Product

OptiX OSN 3500, OSN 2500, OSN 7500

Fault Type

• DCN fault
• DCC_CHAN_LACK

Symptom

Before an NE upgrade or expansion, the NE did not report any alarms, and DCC communication was normal. After an NE was upgraded or expanded, line boards reported the DCC_CHAN_LACK alarms, and the NE became unreachable to the NMS.

Cause Analysis

During an NE upgrade or expansion, line boards were cold reset, and DCC resources were re-allocated. The lower-rate line boards preempted DCC resources of the higher-rate line boards. As a result, the NE became unreachable to the NMS.

Procedure

1. Checked whether there were any bit errors in DCC byte transmission. The transmit end sent DCC bytes, but the receive end did not receive any. Therefore, this issue was not related to bit errors.
2. Went to the site and checked the NE status.
   1. Connected a PC directly to the NE, and logged in to the NE.
   2. Checked the ECC protocol settings. The settings were correct. Therefore, this issue was not related to the ECC protocol settings.
   3. Performed a switchover from the active SCC board to the standby SCC board. The DCC_CHAN_LACK alarms persisted. Therefore, this issue was not related to an SCC board.
   4. Removed the lower-rate line boards. The higher-rate line boards immediately began to transmit data. The DCC_CHAN_LACK alarms cleared, and NEs communicated properly with each other. It was inferred that the lower-rate line boards preempted DCC resources of the higher-rate line boards, blocking the NMS from reaching the NE.
       NOTE:

      • Generally, an SCC board supports multiple DCC working modes, and some DCC working modes provide more DCC resources.
      • In the default DCC working mode for the N1GSCC board, the D1 to D3 bytes function as physical transmission channels and 10 optical ports are DCC-enabled.
      • Generally, a lower-rate line board has multiple optical ports. For example, an SLT1 board has 12 optical ports. After the line boards were cold reset, DCC resources were re-allocated. The lower-rate line boards preempted DCC resources of the higher-rate line boards. The higher-rate line boards failed to obtain DCC resources, blocking the NMS from reaching the NE.
   5. Re-installed the lower-rate line boards.
3. Checked for the DCC_CHAN_LACK alarm on the NMS after the NE was running properly. The DCC_CHAN_LACK alarm persisted, and the NE became unreachable again.
4. Released DCC resources from optical ports on the lower-rate line boards. The optical ports on the higher-rate line boards restored to transmit data. The DCC_CHAN_LACK alarm cleared, and the NE became reachable from the NMS. It was determined that the lower-rate line boards preempted DCC resources of the higher-rate line boards, blocking the NMS from reaching the NE.
    NOTICE:

   Before an NE upgrade or expansion, properly allocate DCC resources. Specifically, release some DCC resources from lower-rate multiport line boards so high-rate line boards can obtain sufficient DCC resources upon cold resetting.

Related Information

None

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