Selecting The Clock Source Based On The Ssm Quality Level; Establishing The Configuration Task - Huawei Quidway S9300 Configuration Manual

Quidway S9300 Terabit Routing Switch
Configuration Guide - Device Management
11.6 Selecting the Clock Source Based on the SSM Quality
Level
If the SSM quality level is used in clock source selection, the S9300 selects the clock source
based on the SSM quality level and then based on the priority.

11.6.1 Establishing the Configuration Task

Before configuring clock source selection based on the SSM quality level, familiarize yourself
with the applicable environment, complete the pre-configuration tasks, and obtain the required
data.
Applicable Environment
If multiple clock sources can obtain their SSM quality levels, the system can select the reference
clock source based on the SSM quality level. If no reference clock source is specified forcibly,
the clock board uses the clock source of the highest SSM quality level. If this clock source fails,
the clock source uses the clock source of the second highest SSM quality level. The SSM quality
level of the external clock source will change to the SSM quality level of the clock source selected
by the system.
The SSM quality level takes precedence over the priority in clock source selection; therefore,
the SSM quality level of the primary reference clock source must be the highest so that clock
syntonization can be implemented on the entire network.
The SSM quality levels, in descending order, are Primary Reference Clock (PRC),
Synchronization Supply Unit-T (SSU-T), Synchronization Supply Unit-L (SSU-L), SDH
Equipment Clock (SEC), and Do Not Use (DNU). If the SSM level of a clock source is DNU,
and if the SSM level is used in clock source selection, this clock source will not be selected as
the reference clock source. The default SSM quality level of the inner clock and system clock
(19.44 MHz) is SEC.
The primary reference clock must be stable. When configuring multiple clock sources, you need
to clock a backup clock transmission path. When clock signals are lost on the original clock
transmission path, a new clock source is selected and clock signals are transmitted on the backup
path.
Pre-configuration Tasks
Before selecting the clock source based on the SSM quality level, complete the following tasks:
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Issue 03 (2011-12-29)
Setting parameters of the link layer protocol and IP addresses for the interfaces to ensure
that the link layer protocol on the interfaces is in Up state.
Configuring the routing protocol to make the IP routes between the nodes reachable.
Cancelling the configuration of forcible clock source selection.
Ensuring the clock that will be configured to meet the following conditions:
– All clock sources provide valid clock signals.
– The result of frequency offset check does not affect clock source selection or the
frequency offset of the clock sources is within the specified range.
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11 Ethernet Clock Syntonization Configuration
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