Configuring the Automatic Clock Source Selection Mode
Context
A switch supports three clock source selection modes: automatic, manual, and forcible. By default, a switch works in automatic clock source selection mode.
Clock source priority
The default priority for a clock source is 0, indicating that this clock source does not participate in clock source selection. To enable the clock source to participate in clock source selection, specify a priority for it.
A lower priority value indicates a higher priority of a clock source.
Clock source SSM quality level
An SSM is a group of codes used to indicate the clock quality level on a synchronized network. SSM reflects the level of synchronous timing signals transmitted on a synchronous timing link. A higher clock accuracy indicates a higher SSM quality level. A device can be configured to select a clock source according to the SSM quality level.
SSM quality levels are sorted in descending order of preference: primary reference clock (PRC), Synchronization Supply Unit A (SSU-A), Synchronization Supply Unit B (SSU-B), SDH equipment clock (SEC), Unknown, and Do Not Use (DNU).
- If no SSM quality level is specified for clock source selection, the switch selects the clock source to be traced based on the priorities configured for the clock sources.
- If an SSM quality level is specified for clock source selection:
- The switch selects the clock source to be traced based on the SSM quality levels of clock sources.
- If there are multiple clock sources with the same SSM quality level, the switch selects the clock source to be traced based on the priorities of these clock sources.
Procedure
- Run system-view
The system view is displayed.
- Run clock clear slot slot-id
The clock source selection mode is restored to automatic.
If a clock source has been selected manually or forcibly, run this command to restore the automatic mode.
- Run clock
ssm-control on
SSM quality levels are enabled to participate in automatic clock source selection.
By default, SSM quality levels are used for clock source selection.
- Run clock run-mode normal slot slot-id
The system clock running mode is set to the normal mode.
By default, the system clock works in normal mode.