When configuring clock monitoring module,
go to these sections for information you are interested in:
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Clock
Monitoring Module Overview
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Clock
Monitoring Module Configuration Task List
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Configuring
Working Mode of the Clock Monitoring Module of the SRPU
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Configuring
Reference Source Priority
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Configuring
SSM for Reference Sources
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Stopping
the Clock Monitoring Module from Warming Up
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Setting
the Input Port of the Line Clock (LPU Port)
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Displaying
and Maintaining Clock Monitoring Module
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Clock
Monitoring Module Configuration Example
1.1 Clock Monitoring Module Overview
This section covers these topics:
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Introduction to Clock Monitoring
Module
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Classification of Clock
Sources
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Reference Source Level
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Working Mode of the Clock
Monitoring Module
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Working Mode of the Port
Clock
1.1.1 Introduction to Clock Monitoring Module
Clock monitoring module is responsible for
providing highly-precise, highly-reliable SDH (synchronous digital hierarchy)
line interface 38.88 MHz clock signals for different service interface cards.
It implements such functions as input clock source automatic selection,
software phase-lock, and real-time monitoring of the clock status of the
interface card.
Currently, the clock monitoring module
supports 18 reference clock sources (referred to as reference source
hereafter), among which the first and the second are Bits clock sources and
others are line clock sources. Each reference source corresponds to a slot. The
specific relationship is decided by device hardware. The following figure shows
the reference-slot relationship of the S9500 series switches:
Figure 1-1 Relationship between
reference source and slot
1.1.2 Classification of Clock Sources
Clock sources can be classified into three
categories according to different sources of the clock source of the clock
monitoring module:
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Local clock source: 38.88 MHz clock signals
generated by a crystal oscillator inside the clock monitoring module.
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Bits clock source: clock signals generated by a
Bits clock device. The signals are sent to the clock monitoring module through
a specific interface on the SRPU (switch and router processing unit) and then
sent to all interface cards by the clock monitoring module.
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Line clock source: clock signals provided by the
upper level device. Its precision is lower than Bits clock source. The signals
are derived from the specific WAN interface and then sent to the clock
monitoring module, which sends the signals to all interface cards in turn.
1.1.3 Reference Source Level
The reference source level is decided
together by the priority and the synchronization status marker (SSM) level of
the reference source.
I. Priority of the reference
source
You can set a high priority for the
reference source with high-precision and high-reliability to make it be
selected as the clock source with precedence.
II. SSM level of the reference
source
SSM, also known as synchronization quality
marker, is used to indicate the synchronization timing signal level on a synchronization
timing transmission link.
The priority of SSM level of the reference
source, ranging from high to low includes:
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PRC: G.811 clock signal
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TNC: G.812 transit node clock signal
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LNC: G.812 local node clock signal
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SETS: SDH device clock source signal
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unknown: Unknown synchronization quality
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DNU: DoNotUse
The reference source whose SSM level is DNU
cannot be used as a clock source.
1.1.4 Working Mode of the Clock Monitoring Module
of the SRPU
The working mode of the clock monitoring
module is also the mode it adopts to choose the clock source, including the
manual mode and the auto mode.
I. Manual mode
In this mode, the clock source is
configured manually. The clock monitoring module does not switch the clock
source automatically, but just tracks the user-configured primary reference
source. If the primary reference source is lost, the clock monitoring module enters
a hold state.
II. Auto mode
In auto mode, the clock source is selected
by the system automatically. When the primary clock source is lost or in free
run status, the clock monitoring module selects another clock source based on
the following rules:
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If SSM level is not activated, the clock source
is decided by reference source priority. If two reference sources have the same
priority, the one with the smaller reference source number (1 to 18) is
selected. When the reference source with the highest priority is missing, the
next available reference source with the highest priority is selected. When the
former clock source becomes available, the system switches to that clock again.
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If SSM is activated, the clock source is decided
by the SSM level. If two reference sources have the same SSM level, the
reference source priority takes effect, in the way described above.
The following clock
sources are excluded in clock selection (when SSM is activated):
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Clock sources whose signals are missing;
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Clock sources whose priority is 255. By default,
the priority of all clock sources is 255.
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Clock sources whose SSM level is DNU (DoNotUse).
1.1.5 Working Mode of the Port Clock
Depending on the source of the port clock,
a port of an S9500 series switch supports two clock modes:
I. Master mode
In this mode, the system uses the clock
signals provided by the clock monitoring module. The signals include local
clock signals and clock signals derived from LPU Port. If you have configured
on the device to derive clock signals from LPU Port, these derived signals are
adopted; otherwise, local clock signals are adopted.
II. Slave mode
In this mode, the system uses line clock
signals. Only when you specify a port as the LPU Port (clock signal input port)
of the device can the system derive the clock source from the line signals
received on the port and then send the clock source information to the clock
monitoring module, which then sends the information to all interface cards.
When connected to SONET/SDH switches, a switch
should be configured as to work in slave clock mode, because the SONET/SDH network
clock is more precise than that of the switch.
1.2 Clock Monitoring Module Configuration Task List
The following
configurations are applicable to the S9500 series Ethernet switches whose SRPU
is installed with a clock module. For information about the SRPUs installed with
a clock module, refer to Installation Manual.
Complete these tasks to configure clock
monitoring module:
1.3 Configuring Working Mode of the Clock Monitoring Module of the SRPU
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To do…
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Use the command…
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Remarks
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Enter system view
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system-view
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—
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Configure the work mode of the clock
monitoring module
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clock { auto
| manual source source-number }
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Optional
Auto mode by default
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1.4 Configuring Reference Source Priority
In auto mode, the clock monitoring module
selects a reference source based on SSM level and reference source priority.
Follow these steps to configure reference
source priority:
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To do…
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Use the command…
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Remarks
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Enter system view
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system-view
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—
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Configure the reference source priority
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clock priority value source source-number
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Required
255 by default.
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1.5 Configuring SSM for Reference Sources
You can use the following two ways to derive
the SSM level of a reference source:
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The interface card derives the SSM level from
the Bits clock source, and reports the SSM level to the SRPU, which sends the
SSM level to the clock monitoring module.
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Or you can configure SSM level as needed, as shown
in the table in Configuring
SSM Levels for the Reference Source:
Follow these steps to set the way of deriving
SSM level:
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To do…
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Use the command…
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Remarks
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Enter system view
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system-view
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—
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Set the way to derive SSM level
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clock forcessm { on | off } source source-number
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Optional
By default, the SSM level is set by users.
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The bits for transmitting Bits clock source
information can be configured as sa4, sa5, sa6, sa7
and sa8. They are 5 bits in timeslot 0 of the even frame in a multi-frame
as specified by ITU-TG.704 CRC4. The network administrator can choose one from
the five bits to carry SSM information.
Follow these steps to set the bit for
transmitting Bits clock source information:
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To do…
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Use the command…
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Remarks
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Enter system view
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system-view
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—
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Set the bits for transmitting the Bits
clock source information
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clock sa-bit { sa4
| sa5 | sa6 | sa7 | sa8 } source source-number
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Optional
sa4 is the
default bit for transmitting the Bits clock source information.
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Follow these rules to manually set the SSM
level for the clock source:
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For the line clock source, the SSM level
configured is that of the clock source.
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For Bits clock source, if the input signal is a
2048 kbps (E1) signal and the clock forcessm off source is executed, the
clock source adopts the SSM level derived from the input signals and the SSM
configured is omitted.
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For Bits clock source, if the input signal is a
2048 KHz signal or a 2048 kbps signal and the clock forcesssm on source
command is executed, the clock source adopts the SSM level configured.
Follow these steps to set the SSM level:
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To do…
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Use the command…
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Remarks
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Enter system view
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system-view
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—
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Set the SSM level of the reference source
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clock ssm
{ dnu | lnc | prc | sets | tnc | unknown
} source source-number
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Required
By default, the SSM level of all
reference sources is unknown.
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No matter the SSM levels are obtained
through clock signals or configured manually, you have to activate them before
they can take effect.
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When SSM is activated, the SSM levels become the
decisive factor in clock source automatic selection.
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When SSM is not activated, you can still set and
view the SSM levels, but they are ignored in clock source automatic selection.
Follow these steps to activate or
deactivate SSM:
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To do…
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Use the command…
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Remarks
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Enter system view
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system-view
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—
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Activate/deactivate SSM
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clock ssmcontrol { on | off }
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Optional
SSM is deactivated by default.
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1.6 Stopping the Clock Monitoring Module
from Warming Up
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To do…
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Use the command…
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Remarks
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Enter system view
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system-view
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—
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Stop the clock monitoring module from
warming up
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clock stop warm-up
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Required
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1.7 Setting the Input Port of the Line
Clock (LPU Port)
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To do…
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Use the command…
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Remarks
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Enter system view
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system-view
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—
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Set the LPU port of the line clock
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clock lpuport { interface-type interface-number }
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Optional
By default, the clock LPU port is the
first configurable port by port name in alphabetical order of the interface
board
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Enter interface view
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interface interface-type interface-number
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—
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Set the LPU port to work in Slave mode
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clock slave
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Optional
The LPU port works in Slave mode by
default.
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For a POS interface card, if you set the port clock to work in Slave
mode, you must use the clock lpuport command to set the LPU port of the
clock source of the interface card.
1.8 Displaying and Maintaining Clock Monitoring Module
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To do…
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Use the command…
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Remarks
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View the clock base phase
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display clock basephase
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Available in any view
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View the current configuration of the
clock monitoring module
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display clock config
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View the detailed information of the
clock monitoring module
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display clock device
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View the D/A value of the DAC inside the
clock monitoring module
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display clock d/a
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View the input clock source port of the
line board
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display clock lpuport
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View the lock state of the clock
monitoring module
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display clock phase-lock-state
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View the priority of all reference
sources
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display clock priority
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View the self-test result of the clock
monitoring module
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display clock self-test-result
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View the state of all reference sources
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display clock source
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View the SSM level of all reference
sources
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display clock ssm-level
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View the SSM level of the output clock signal.
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display clock ssm-output
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View the clock monitoring module version
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display clock version
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View the work mode of the clock
monitoring module of the SRPU
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display clock work-mode
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1.9 Clock Monitoring Module Configuration
Example
I. Network requirements
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Two S9508 switches Switch A and Switch B are
connected through their POS interfaces. They are equipped with the clock
monitoring modules on their SRPUs, and thus you can configure the
synchronization clock parameters.
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The synchronization clock of Switch A is
provided by its clock monitoring module.
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Switch B adopts the line clock from Switch A to
synchronize with the SDH line of Switch A.
II. Network diagram
Figure
1-2 Network diagram of system clock configuration
III. Configuration procedure
1)
Configure Switch A (Master clock).
# Set the interface POS 1/1/1 to work in
master clock mode, using local clock signals.
<Sysname> system-view
[Sysname] interface pos 1/1/1
[Sysname-Pos1/1/1] clock master
2)
Configure Switch B (Slave clock).
# Set the LPU port on Switch B to POS 1/1/1.
<Sysname> system-view
[Sysname] clock lpuport pos 1/1/1
# Set the interface POS 1/1/1 to work in
slave clock mode.
[Sysname] interface pos 1/1/1
[Sysname-Pos1/1/1] clock slave
# Enable the clock source obtained from POS
1/1/1; set the clock to work in manual mode and use clock source 8 as the
primary clock source, which corresponds to slot 1 (refer to Figure 1-1).
[Sysname] clock manual source 8
Through the above configurations, all the
other POS interface cards get the same clock frequency derived by the clock module
from the line clock of POS 1/1/1. In this way, all the service cards of the switch
can get precise, reliable, synchronized SDH line interface.
