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1.11.4 ONS 15454 SDH Switches Timing Reference
1.11.4 ONS 15454 SDH Switches Timing Reference
Symptom
1.11.5 Holdover Synchronization Alarm
Symptom
(HLDOVRSYNC) condition appears.
Note
Cisco ONS 15454 SDH Troubleshooting Guide, R5.0
1-134
Timing references switch when one or more problems occur.
The optical or BITS input is receiving loss of signal (LOS), loss of frame (LOF), or
Possible Cause
AIS alarms from its timing source.
The optical or BITS input is not functioning.
Possible Cause
Sync Status Messaging (SSM) message is set to Do Not Use for Synchronization
Possible Cause
(DUS).
The synchronous status messaging (SSM) indicates a Stratum 3 or lower clock
Possible Cause
quality.
Possible Cause
The input frequency is off by more than 15 ppm.
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.
Possible Cause
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
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.
The clock is running at a different frequency than normal and the holdover synchronization
Possible Cause
The last reference input has failed.
The clock is running at the frequency of the last known-good reference input.
Recommended Action
This alarm is raised when the last reference input fails. See the
page 2-124
for a detailed description of this alarm.
The ONS 15454 SDH supports holdover timing per the ITU when provisioned for external
(BITS) timing.
Chapter 1
General Troubleshooting
–7
/day, including temperature.
"HLDOVRSYNC" alarm on
July 2005
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