Contents

Configuring synchronous Ethernet 1

About synchronous Ethernet 1

Quality levels of clocks· 1

Clock reference selection· 1

System clock QL distribution and SyncE port input QL updating· 1

Protocols and standards· 2

Configuring SyncE on an Ethernet interface· 2

Setting the clock mode on a copper SyncE GE port 2

Display and maintenance commands for SyncE· 3

Synchronous Ethernet configuration examples· 3

Example: Configuring synchronous Ethernet 3

 

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.

·     UNK—Synchronization quality unknown.

DNU clock sources cannot participate in clock reference selection.

Clock reference selection

The system clock uses the clock reference selected with the highest QL from the following sources. If these sources have the same QL, the system clock selects the clock reference by priority, from the highest to the lowest:

·     External clock sources.

·     Line clock sources input from interfaces.

·     Internal clock sources.

The system clock uses the QL of the selected reference. Clock reference selection process starts each time the QL of a source is updated.

 

	NOTE: If QLs are the same on two interfaces, the clock source input from the lower-numbered interface has priority.

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System clock QL distribution and SyncE port input QL updating

Distribution of the system clock QL

When distributing the QL of the system clock, the system uses the following rules:

·     If the clock reference is not from a SyncE port, the system distributes the QL out of all SyncE ports.

·     If the clock reference is from a SyncE port, the system distributes the QL out of all SyncE ports except for the reference input port. To prevent timing loops, the sent QL is DNU on the timing reference input port.

Input QL updating on SyncE ports

The default input QL is Unknown on a SyncE port. The port updates its input QL when it receives a quality level higher than Unknown. The Unknown level will be restored if the port does not receive ESMC packets within 5 seconds after the update.

Protocols and standards

·     ITU-T G.781, Synchronization Layer Functions

·     ITU-T G.813, Timing characteristics of SDH equipment slave clocks (SEC)

·     ITU-T G.823, The control of jitter and wander within digital networks which are based on the 2048 kbit/s hierarchy

·     ITU-T G.8261, Timing and Synchronization Aspects in Packet Networks

·     ITU-T G.8262, Timing Characteristics of a Synchronous Ethernet Equipment Slave Clock (EEC)

·     ITU-T G.8264/Y.1364, Distribution of Timing Information through Packet Networks

Configuring SyncE on an Ethernet interface

1.     Enter system view.

system-view

2.     Enter Layer 2 Ethernet interface view or Layer 3 Ethernet interface view.

interface interface-type interface-number

3.     Enable the synchronous mode.

synchronous mode

By default, Ethernet interfaces are in the non-synchronous mode. An interface can participate in the clock reference selection only when it is in the synchronous mode.

4.     Enable ESMC to transmit QL information.

esmc enable

By default, ESMC is disabled on Ethernet interfaces.

Setting the clock mode on a copper SyncE GE port

‌About this task

Configure the clock mode for a copper SyncE GE port based on its time synchronization direction.

Restrictions and guidelines

By default, a copper SyncE GE port automatically negotiates its clock mode with the remote end. To avoid a negotiation result that conflicts with your clock synchronization trail design, manually set the clock mode.

·     To derive timing from the upstream clock, set the clock mode to slave.

·     To provide timing for the downstream clock, set the clock mode to master.

Procedure

1.     Enter system view.

system-view

2.     Enter Layer 2 Ethernet interface view or Layer 3 Ethernet interface view.

interface interface-type interface-number

3.     Set the clock mode.

synce state { master | slave }

By default, the clock mode of a copper SyncE GE port is automatically negotiated.

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, configure SyncE between the devices.

Figure 1 Network diagram

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Procedure

# On Device A, enable the synchronous mode and ESMC on Ten-GigabitEthernet 1/0/1.

<DeviceA> system-view

[DeviceA] interface ten-gigabitethernet 1/0/1

[DeviceA-Ten-GigabitEthernet1/0/1] synchronous mode

[DeviceA-Ten-GigabitEthernet1/0/1] esmc enable

[DeviceA-Ten-GigabitEthernet1/0/1] quit

# On Device B, enable the synchronous mode and ESMC on Ten-GigabitEthernet 1/0/1.

<DeviceB> system-view

[DeviceB] interface ten-gigabitethernet 1/0/1

[DeviceB-Ten-GigabitEthernet1/0/1] synchronous mode

[DeviceB-Ten-GigabitEthernet1/0/1] esmc enable

[DeviceB-Ten-GigabitEthernet1/0/1] quit

Verifying the configuration

# Verify that ESMC is enabled on both Device A and Device B when they are connected to their respective clock references. The clock QLs of Device A and Device B are QL-PRC and QL-SEC, respectively. Device A provides more precise timing than Device B.

[DeviceA] display esmc

Interface   : Ten-GigabitEthernet1/0/1

Mode        : Synchronous

ESMC status : Enable

Port status : Up

Duplex mode : Full

QL received : QL-SEC

QL sent     : QL-PRC

ESMC information packets received : 2195

ESMC information packets sent     : 6034

ESMC event packets received       : 1

ESMC event packets sent           : 1

ESMC information rate             : 1 packets/sec

ESMC expiration                   : 5 seconds

[DeviceB] display esmc

Interface   : Ten-GigabitEthernet1/0/1

Mode        : Synchronous

ESMC status : Enable

Port status : Up

Duplex mode : Full

QL received : QL-PRC

QL sent     : QL-SEC

ESMC information packets received : 6034

ESMC information packets sent     : 2195

ESMC event packets received       : 1

ESMC event packets sent           : 1

ESMC information rate             : 1 packets/sec

ESMC expiration                   : 5 seconds

# Verify that QL information is exchanged correctly after synchronization between Device A and Device B. Ten-GigabitEthernet1/0/1 on Device B becomes a reference input port. The clock QL sent from Device B to Device A changes to QL-DNU.

[DeviceA] display esmc

Interface   : Ten-GigabitEthernet1/0/1

Mode        : Synchronous

ESMC status : Enable

Port status : Up

Duplex mode : Full

QL received : QL-DNU

QL sent     : QL-PRC

ESMC information packets received : 2573

ESMC information packets sent     : 6412

ESMC event packets received       : 1

ESMC event packets sent           : 1

ESMC information rate             : 1 packets/sec

ESMC expiration                   : 5 seconds

[DeviceB] display esmc

Interface   : Ten-GigabitEthernet1/0/1

Mode        : Synchronous

ESMC status : Enable

Port status : Up

Duplex mode : Full

QL received : QL-PRC

QL sent     : QL-DNU

ESMC information packets received : 6412

ESMC information packets sent     : 2573

ESMC event packets received       : 1

ESMC event packets sent           : 1

ESMC information rate             : 1 packets/sec

ESMC expiration                   : 5 seconds