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Cisco ONS 15454 SDH Troubleshooting Guide, R5.0
July 2005
Chapter 1 General Troubleshooting
1.11.4 ONS 15454 SDH Switches Timing Reference
1.11.4 ONS 15454 SDH 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 BITS input is not functioning.
Possible Cause Sync Status Messaging (SSM) message is set to Do Not Use for Synchronization
(DUS).
Possible Cause The synchronous status messaging (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 SDH internal clock operates at a Stratum 3E level of accuracy.
This gives the ONS 15454 SDH 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 SDH 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.
1.11.5 Holdover Synchronization Alarm
Symptom The clock is running at a different frequency than normal and the holdover synchronization
(HLDOVRSYNC) condition 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 2-124 for a detailed description of this alarm.
Note The ONS 15454 SDH supports holdover timing per the ITU when provisioned for external
(BITS) timing.
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