Clock Source Priority; Clock Reference Selection; Clock Mode On A Port - H3C SR6600-X Configuration Manual

Clock source priority

For a clock source to be selected as the clock reference, assign it a lower priority value than other clock
sources. The lower the priority value, the better the clock source. For example, the clock source with a
priority of 1 is better than the clock source with a priority of 3.

Clock reference selection

The network clock monitoring module supports automatic and manual clock reference selection.
Automatic reference selection
In an automatic reference selection process, the network clock monitoring module uses the SSM quality
level, clock source priority, and clock source number to make a selection decision. The use of SSM in the
automatic reference selection process is user configurable.
The selection process is as follows:
1. If SSM is enabled for automatic reference selection, the module selects the clock source with the
highest SSM quality level.
2. If SSM is disabled for automatic reference selection, or clock sources have the same SSM quality
level, the module selects the clock source with the lowest priority value. (A lower priority value
indicates a better clock source.)
3. If the clock sources have the same priority, the module selects the clock source that has the lowest
slot-number/subslot-number/port-number sequence.
After selecting the best reference, the network clock monitoring module distributes the selected timing
signal to all interface cards, and locks the timing to the reference signal. When the traced timing signal
is lost, the network clock monitoring module selects the next optimal clock reference. When the signal of
the best clock source can be traced again, the module selects the best clock source to replace the less
optimal clock source as the reference.
NOTE:
A clock source will not be selected as the reference if the clock source is in one of the following situations:
The timing signal cannot be detected.
•
The clock source priority is 255.
•
The SSM quality level is DNU.
•
Manual reference selection
If you specify a clock source as the reference, the network clock monitoring module does not change the
clock reference automatically. When the signal of the specified clock reference is lost, the module
changes to the holdover state. In this state, the module continues to distribute the signal of the clock
reference to the interface cards.

Clock mode on a port

IMPORTANT:
Set the clock mode to slave on the port connected to a SONET/SDH device, because the SONET/SDH
clock is more precise.
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