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Cisco ONS 15454 Troubleshooting Guide, R8.5
November 2009
Chapter 1 General Troubleshooting
1.11.6 OC-3 and DCC Limitations
1.11.6 OC-3 and DCC Limitations
Symptom Limitations to OC-3 and DCC usage.
Possible Cause OC-3 and DCC have limitations for the ONS 15454.
Recommended Action For an explanation of OC-3 and DCC limitations, refer to the “Circuits and
Tunnels” chapter in the Cisco ONS 15454 Reference Manual.
1.11.7 ONS 15454 Switches Timing Reference
Symptom Timing references switch when one or more problems occur.
Possible Cause The optical or BITS input is receiving loss of signal (LOS), loss of frame (LOF), or
AIS alarms from its timing source.
Possible Cause The optical or building integrated timing supply (BITS) input is not functioning.
Possible Cause The synchronization status messaging (SSM) message is set to Do Not Use for
Synchronization (DUS).
Possible Cause SSM indicates a Stratum 3 or lower clock quality.
Possible Cause The input frequency is off by more than 15 ppm.
Possible Cause The input clock wanders and has more than three slips in 30 seconds.
Possible Cause A bad timing reference existed for at least two minutes.
Recommended Action The ONS 15454 internal clock operates at a Stratum 3E level of accuracy. This
gives the ONS 15454 a free-running synchronization accuracy of +/–
4.6 ppm and a holdover
stability of less than 255 slips in the first 24 hours or 3.7 x 10
–7
/day, including temperature.
ONS 15454 free-running synchronization relies on the Stratum 3 internal clock. Over an extended
time period, using a higher quality Stratum 1 or Stratum 2 timing source results in fewer timing slips
than a lower quality Stratum 3 timing source.
1.11.8 Holdover Synchronization Alarm
Symptom The clock is running at a different frequency than normal and the “HLDOVRSYNC” alarm
appears.
Possible Cause The last reference input has failed.
Recommended Action The clock is running at the frequency of the last known-good reference input.
This alarm is raised when the last reference input fails. See the “HLDOVRSYNC” alarm on
page 2-126 for a detailed description.
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