Whether an SS bit mismatch in the AU pointer during WDM product interconnection causes an AU_LOP alarm

Question:
According to SDH principles, in AU-4 and TU-3 frame structures, the SS bit of the AU pointer is fixed at 10. When Huawei SDH NE is interconnected with equipment of other vendors and receives the SS bit of a value rather than 10 from the peer end, the corresponding channel of a line board on the SDH NE reports the AU_LOP alarm. As a result, services fail to be provisioned or are interrupted. Do WDM devices have this issue?
Answer:
1. OTU boards (except OCU boards) on WDM NEs transparently transmit the SS bit and do not detect it. 2. OCU boards on WDM NEs process the SS bit. The normal value of the bit is 10. When the SS bit is set to 00, 01, or 11, an AU_AIS is inserted and services are impaired. The board does not report an alarm because it does not detect the AU_AIS signal on its WDM side. According to a test in which the test instrument is Agilent OmniBer 817 and is used to send STM-16 data, the H1 SS bit can be modified when the payload is set to Framed and Structed, and Column is set to All in the overhead setup settings. The test instrument reports an AU_AIS or PDH LOF alarm when the SS bit is set to 00, 01, or 11, and does not report alarms when the SS bit is set to 10. This issue is related to the chip processing mode. Because OCU boards use the same chip, they have this issue.

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