Contents

Configuring network synchronization· 1

About network synchronization· 1

Clock sources· 1

Clock reference selection factors· 1

Clock mode on a port 2

Restrictions and guidelines· 2

Configuring automatic reference selection parameters· 2

Configuring the SSM quality level of a line clock source· 2

Setting a priority for a clock source· 3

Configuring synchronous Ethernet 4

About synchronous Ethernet 4

Quality levels of clocks· 4

Clock reference selection· 4

Restrictions and guidelines· 4

Configuring SyncE on an Ethernet interface· 4

Display and maintenance commands for SyncE· 5

Synchronous Ethernet configuration examples· 5

Example: Configuring synchronous Ethernet 5

 

Configuring network synchronization

About network synchronization

The network clock monitoring module provides network clock synchronization for the device. It ensures that all ports on the device operate at the same clock rates for network synchronization.

The network clock monitoring module provides the following functions:

·     Provides highly precise, reliable timing signal to interfaces on the device.

·     Constantly monitors the clock status on the interfaces.

·     Selects a clock reference from available clock sources, and then distributes its timing signal to network devices.

·     Performs phase lock to maintain a deterministic relationship between the input and output signals in frequency and phase.

Clock sources

A clock source provides timing signals to a device. Clock sources can be classified into the following three categories in descending order of precision:

·     PTP—Timing signal obtained through PTP.

·     Line clock—Timing signal extracted from the signal received on the specified port from a higher-level device. The port is called a line processing unit (LPU) port.

·     Local clock source—38.88 MHz timing signal generated by a crystal oscillator on the clock daughter card. The local clock signal has the lowest precision.

Clock reference selection factors

When a device receives clock signals from multiple clock sources, it will select one of them as the clock reference. The factors considered for clock reference selection include the clock source Synchronization Status Message (SSM) level and priority, which together determine selection of the clock reference in automatic clock reference selection.

The S6116 switch uses PTP for clock reference selection. For more information about PTP, see PTP configuration in the configuration guide for the device.

Clock source SSM quality level

SSM level is transmitted in a synchronization distribution trail to indicate the quality of the clock source. The SSM quality levels are as follows, from the highest to the lowest in synchronization quality:

·     PRC—G.811 primary reference clock.

·     SSU-A—G.812 primary-level SSU.

·     SSU-B—G.812 second-level SSU.

·     SEC—SDH equipment clock.

·     Unknown—Synchronization quality unknown.

·     DNU—Do not use for synchronization.

Clock source priority

You can configure a higher priority for a high-precision, high-reliability clock source so that it can be selected as clock reference preferentially. The smaller the priority value, the higher the priority. For example, a clock source with a priority value of 1 will be selected over a clock source with a priority value of 3.

Clock mode on a port

The clock mode of a port on an S6116 switch depends on the PTP selection result. For more information about PTP, see PTP configuration in the configuration guide for the device.

A port can operate in one of the following clock modes:

·     Master—The port provides timing to the peer end. The timing signal is derived from the network clock monitoring module.

¡     If automatic reference selection is used, the timing signal is derived from the reference clock selected by the network clock monitoring module.

¡     If manual reference selection is used, the timing signal is derived from the manually specified clock reference.

¡     If the manually specified clock reference is not available, the port outputs the timing signal generated by the local clock.

·     Slave—The port uses the timing signal received from the peer end. For the network clock monitoring module to extract timing signal from a port, you must place the port in slave clock mode. If the port is in master clock mode, the module does not extract the timing signal from the incoming traffic on the port.

Restrictions and guidelines

Only management Ethernet interfaces support network synchronization.

Configuring automatic reference selection parameters

Configuring the SSM quality level of a line clock source

Restrictions and guidelines

This feature is applicable to the synchronous Ethernet network scenario where the interface role is master and ESMC is enabled on the interface.

To modify the SSM level of a line clock source, first remove the priority configuration for the PTP timing signal.

Procedure

1.     Enter system view.

system-view

2.     Assign an SSM quality level to a clock source.

network-clock source lpuport interface-type interface-number ssm { dnu | prc | sec | ssua | ssub | unknown }

By default, the SSM quality level of a line clock source is SSU-B.

Clock sources with an SSM level of DNU cannot be used, and such sources will not participate in automatic clock reference selection.

3.     (Optional.) View the SSM level carried in the ESMC message sent from the clock source.

After you assign an SSM level to a clock source, the SSM level will be carried in the ESMC message sent from the clock source.

display esmc

The SSM level assignment configuration takes some time to take effect. You can use this command to check whether the configuration has taken effect.

Setting a priority for a clock source

About this task

In an automatic reference selection process, clock sources with higher priority levels will be selected as the clock reference preferentially.

Restrictions and guidelines

The smaller the priority value, the higher the priority. A clock source with a priority of 255 will not participate in automatic clock reference selection.

When synchronous Ethernet is not configured, the device automatically selects the clock reference through PTP. You need to configure the priority level for the PTP timing signal on non-master devices.

Procedure

1.     Enter system view.

system-view

2.     Set a priority for a clock source.

network-clock source { lpuport interface-type interface-number | ptp } priority priority

By default, the priority of a clock source is 255.

Configuring synchronous Ethernet

About synchronous Ethernet

Synchronous Ethernet (SyncE) provides high-quality frequency synchronization on Ethernet at the physical layer. It can provide the same level of clock precision as SONET/SDH.

Transferring frequency signals at the physical layer, SyncE functions regardless of the network conditions such as congestion, packet loss, and delay.

Quality levels of clocks

SyncE devices use an Ethernet synchronization messaging channel (ESMC) to transmit the quality level (QL) of their system clocks. A SyncE device uses QL information to select the optimal clock reference from all available timing sources for its system clock.

The following are the QLs supported by the device, from the highest to the lowest:

·     PRC—G.811 primary reference clock.

·     SSU-A—G.812 primary-level SSU.

·     SSU-B—G.812 second-level SSU.

·     SEC—SDH equipment clock.

·     DNU—Do not use for synchronization. A clock source of DNU level cannot be used for clock synchronization.

·     UNK—Synchronization quality unknown.

Synchronous Ethernet uses two ESMC message transmission modes: heartbeat transmission mode and event-driven transmission mode.

·     Heartbeat transmission mode: This mode sends ESMC messages periodically, usually once per second.

·     Event-driven transmission mode: This mode sends ESMC messages triggered by specific events. For example, when the system clock of the device changes, the device will immediately send an ESMC event message with the latest system clock QL.

Clock reference selection

The switch selects the clock reference through PTP. For more information about PTP, see PTP configuration in the configuration guide for the device.

Restrictions and guidelines

Only management Ethernet interfaces support Synchronous Ethernet.

SyncE is used for hardware frequency tuning and needs to be used in conjunction with PTP. For more information about PTP, see PTP configuration in the configuration guide for the device.

Configuring SyncE on an Ethernet interface

1.     Enter system view.

system-view

2.     Enter management Ethernet interface view.

interface M-GigabitEthernet 0/0/0

3.     Enable the synchronous mode.

synchronous mode

By default, Ethernet interfaces are in the non-synchronous mode.

4.     Enable ESMC on the interface.

esmc enable

By default, ESMC is disabled on interfaces.

Display and maintenance commands for SyncE

Execute display commands in any view.

 

Task	Command
Display ESMC information.	display esmc [ interface interface-type interface-number ]

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Synchronous Ethernet configuration examples

Example: Configuring synchronous Ethernet

Network configuration

As shown in Figure 1, Device A and Device B support synchronous Ethernet. Configure M-GigabitEthernet 0/0/0 on Device A and M-GigabitEthernet 0/0/0 on Device B to operate in synchronous mode, and enable ESMC on the interfaces for them to exchange QL through ESMC messages.

Figure 1 Network diagram

 

Procedure

# Configure PTP on Device A and Device B. For the configuration procedure, see PTP configuration in the configuration guide for the device.

# Configure M-GigabitEthernet 0/0/0 on Device A to operate in synchronous mode, and enable ESMC on the interface.

<DeviceA> system-view

[DeviceA] interface M-GigabitEthernet0/0/0

[DeviceA-M-GigabitEthernet0/0/0] synchronous mode

[DeviceA-M-GigabitEthernet0/0/0] esmc enable

[DeviceA-M-GigabitEthernet0/0/0] quit

# Configure M-GigabitEthernet 0/0/0 on Device B to operate in synchronous mode, and enable ESMC on the interface.

<DeviceB> system-view

[DeviceB] interface M-GigabitEthernet 0/0/0

[DeviceB-M-GigabitEthernet 0/0/0] synchronous mode

[DeviceB-M-GigabitEthernet 0/0/0] esmc enable

[DeviceB-M-GigabitEthernet 0/0/0] quit

Verifying the configuration

# Display ESMC information on Device A.

[DeviceA] display esmc

Interface   : M-GigabitEthernet0/0/0

Mode        : Synchronous

ESMC status : Enable

Port status : Up

Duplex mode : Full

QL received : QL-SSU-B

QL sent     : QL-DNU

ESMC information packets received : 13465

ESMC information packets sent     : 13619

ESMC event packets received       : 5

ESMC event packets sent           : 6

ESMC information rate             : 1 packets/sec

ESMC expiration                   : 5 seconds

# Display ESMC information on Device B.

[DeviceB] display esmc

Interface   : GigabitEthernet1/0/1

Mode        : Synchronous

ESMC status : Enable

Port status : Up

Duplex mode : Full

QL received : QL-DNU

QL sent     : QL-SSU-B

ESMC information packets received : 9799

ESMC information packets sent     : 9802

ESMC event packets received       : 2

ESMC event packets sent           : 0

ESMC information rate             : 1 packets/sec

ESMC expiration                   : 5 seconds