Table of Contents

Chapter 1 Clock Monitoring Configuration. 1-1

1.1 Clock Monitoring Module Overview. 1-1

1.1.1 Introduction to Clock Monitoring Module. 1-1

1.1.2 Classification of Clock Sources. 1-2

1.1.3 Reference Source Level 1-2

1.1.4 Working Mode of the Clock Monitoring Module of the SRPU. 1-3

1.1.5 Working Mode of the Port Clock. 1-3

1.2 Clock Monitoring Module Configuration Task List 1-4

1.3 Configuring Working Mode of the Clock Monitoring Module of the SRPU. 1-5

1.4 Configuring Reference Source Priority. 1-5

1.5 Configuring SSM for Reference Sources. 1-5

1.5.1 Setting the Way of Deriving SSM Level 1-5

1.5.2 Setting the Bit Position for Transmitting Bits Clock Source Information. 1-6

1.5.3 Configuring SSM Levels for the Reference Source. 1-6

1.5.4 Activating/Deactivating SSM.. 1-7

1.6 Stopping the Clock Monitoring Module from Warming Up. 1-7

1.7 Setting the Input Port of the Line Clock (LPU Port) 1-7

1.8 Displaying and Maintaining Clock Monitoring Module. 1-8

1.9 Clock Monitoring Module Configuration Example. 1-9

 

Chapter 1  Clock Monitoring Configuration

When configuring clock monitoring module, go to these sections for information you are interested in:

l           Clock Monitoring Module Overview

l           Clock Monitoring Module Configuration Task List

l           Configuring Working Mode of the Clock Monitoring Module of the SRPU

l           Configuring Reference Source Priority

l           Configuring SSM for Reference Sources

l           Stopping the Clock Monitoring Module from Warming Up

l           Setting the Input Port of the Line Clock (LPU Port)

l           Displaying and Maintaining Clock Monitoring Module

l           Clock Monitoring Module Configuration Example

1.1  Clock Monitoring Module Overview

This section covers these topics:

l           Introduction to Clock Monitoring Module

l           Classification of Clock Sources

l           Reference Source Level

l           Working Mode of the Clock Monitoring Module

l           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:

l           Local clock source: 38.88 MHz clock signals generated by a crystal oscillator inside the clock monitoring module.

l           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.

l           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:

l           PRC: G.811 clock signal

l           TNC: G.812 transit node clock signal

l           LNC: G.812 local node clock signal

l           SETS: SDH device clock source signal

l           unknown: Unknown synchronization quality

l           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:

l           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.

l           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.

 

 

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

 

 

Complete these tasks to configure clock monitoring module:

Task		Remarks
Configuring Working Mode of the Clock Monitoring Module of the SRPU		Optional
Configuring Reference Source Priority		Optional
Configuring SSM for Reference Sources	Setting the Way of Deriving SSM Level	Optional
	Setting the Bit Position for Transmitting Bits Clock Source Information	Optional
	Configuring SSM Levels for the Reference Source	Optional
	Activating/Deactivating SSM	Optional
Stopping the Clock Monitoring Module from Warming Up		Optional
Setting the Input Port of the Line Clock		Optional

 

1.3  Configuring Working Mode of the Clock Monitoring Module of the SRPU

To do…	Use the command…	Remarks
Enter system view	system-view	—
Configure the work mode of the clock monitoring module	clock { auto | manual source source-number }	Optional Auto mode by default

 

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:

To do…	Use the command…	Remarks
Enter system view	system-view	—
Configure the reference source priority	clock priority value source source-number	Required 255 by default.

 

1.5  Configuring SSM for Reference Sources

1.5.1  Setting the Way of Deriving SSM Level

You can use the following two ways to derive the SSM level of a reference source:

l           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.

l           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:

To do…	Use the command…	Remarks
Enter system view	system-view	—
Set the way to derive SSM level	clock forcessm { on | off } source source-number	Optional By default, the SSM level is set by users.

 

1.5.2  Setting the Bit Position for Transmitting Bits Clock Source Information

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:

To do…	Use the command…	Remarks
Enter system view	system-view	—
Set the bits for transmitting the Bits clock source information	clock sa-bit { sa4 | sa5 | sa6 | sa7 | sa8 } source source-number	Optional sa4 is the default bit for transmitting the Bits clock source information.

 

1.5.3  Configuring SSM Levels for the Reference Source

Follow these rules to manually set the SSM level for the clock source:

l           For the line clock source, the SSM level configured is that of the clock source.

l           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.

l           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:

To do…	Use the command…	Remarks
Enter system view	system-view	—
Set the SSM level of the reference source	clock ssm { dnu | lnc | prc | sets | tnc | unknown } source source-number	Required By default, the SSM level of all reference sources is unknown.

 

 

1.5.4  Activating/Deactivating SSM

No matter the SSM levels are obtained through clock signals or configured manually, you have to activate them before they can take effect.

l           When SSM is activated, the SSM levels become the decisive factor in clock source automatic selection.

l           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:

To do…	Use the command…	Remarks
Enter system view	system-view	—
Activate/deactivate SSM	clock ssmcontrol { on | off }	Optional SSM is deactivated by default.

 

1.6  Stopping the Clock Monitoring Module from Warming Up

To do…	Use the command…	Remarks
Enter system view	system-view	—
Stop the clock monitoring module from warming up	clock stop warm-up	Required

 

1.7  Setting the Input Port of the Line Clock (LPU Port)

To do…	Use the command…	Remarks
Enter system view	system-view	—
Set the LPU port of the line clock	clock lpuport { interface-type interface-number }	Optional By default, the clock LPU port is the first configurable port by port name in alphabetical order of the interface board
Enter interface view	interface interface-type interface-number	—
Set the LPU port to work in Slave mode	clock slave	Optional The LPU port works in Slave mode by default.

 

 

1.8  Displaying and Maintaining Clock Monitoring Module

To do…	Use the command…	Remarks
View the clock base phase	display clock basephase	Available in any view
View the current configuration of the clock monitoring module	display clock config
View the detailed information of the clock monitoring module	display clock device
View the D/A value of the DAC inside the clock monitoring module	display clock d/a
View the input clock source port of the line board	display clock lpuport
View the lock state of the clock monitoring module	display clock phase-lock-state
View the priority of all reference sources	display clock priority
View the self-test result of the clock monitoring module	display clock self-test-result
View the state of all reference sources	display clock source
View the SSM level of all reference sources	display clock ssm-level
View the SSM level of the output clock signal.	display clock ssm-output
View the clock monitoring module version	display clock version
View the work mode of the clock monitoring module of the SRPU	display clock work-mode

 

1.9  Clock Monitoring Module Configuration Example

I. Network requirements

l           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.

l           The synchronization clock of Switch A is provided by its clock monitoring module.

l           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.