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Configuration Guide - Device Management

CloudEngine 12800 and 12800E V200R005C10

This document describes the configurations of Device Management, including device status query, hardware management, Information Center Configuration, NTP, Synchronous Ethernet Configuration, Fault Management Configuration, Energy-Saving Management Configuration, Performance Management Configuration, Maintenance Assistant Configuration, and OPS Configuration.
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Clock Source Selection

Clock Source Selection

Factors in Selecting the Clock Source

The clock source priority and Synchronous Status Message (SSM) quality level are the factors in selecting the clock source:
  • Clock source priority

    A clock source does not have a default priority and does not participate in clock source selection by default. To enable a clock source to participate in clock source selection, specify a priority for it.

    A smaller priority value indicates a higher priority.

  • Clock source SSM quality level

    An SSM is a group of codes that indicate the clock quality level on a synchronization network. SSM directly reflects the level of a synchronous timing signal transmitted on a synchronous timing link. A higher clock accuracy indicates a higher SSM quality level. You can determine whether to enable a switch to select the clock source based on the SSM quality level.

    SSM quality levels are Primary Reference Clock (PRC), Transit Node Clock (SSU-A), Local Node Clock (SSU-B), SDH Equipment Clock (SEC), Unknown (UNK), and Do Not Use (DNU) in descending order.

Clock Source Selection Sequence

When multiple clock sources are available on the network, a switch selects the clock source according to the following rules:
  1. If no SSM quality level is specified for clock source selection, the switch selects the clock source to trace based on the priorities configured for the clock sources.
  2. If an SSM quality level is specified for clock source selection:
    1. The switch selects the clock source to trace based on the SSM quality levels of clock sources.
    2. If there are multiple clock sources with the same SSM quality level, the switch selects the clock source to trace based on the priorities of these clock sources.

Clock Source Selection Modes

A switch supports three clock source selection modes: automatic, manual, and forcible modes.
  • Automatic mode: The system uses the automatic clock source selection algorithm to determine the clock source to be traced based on the priorities and SSM quality levels of clock sources.

  • Manual mode: The clock source to be traced is manually specified using commands, and this clock source must have the highest SSM quality level.

  • Forcible mode: The clock source to be traced is forcibly specified using commands, and this clock source can be any clock source.

For details about protection switching of different clock source selection modes, see Protection Switching.

NOTE:

You are advised to use the default automatic clock source selection mode because a switch can dynamically select the optimal clock source to be traced based on the SSM quality level.

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Updated: 2019-04-20

Document ID: EDOC1100074722

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