Network Synchronization Support

Most of the services that are provided over networks must be fully synchronized with one another in order to operate efficiently. If the network devices that constitute a network do not operate at the same clock rates, there is an overall decrease in the performance of the network and a consequent degradation in the quality of the services offered by the network. This document explains how to configure network synchronization on the Cisco ASR 1000 Series Aggregation Services Routers.

Finding Feature Information

Your software release might not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the Feature Information for Network Synchronization Support.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to http:/​/​www.cisco.com/​go/​cfn . An account on Cisco.com is not required.

Contents

This guide covers the following topics:

Prerequisites for Network Synchronization Support

The following goals must be taken into account while designing the synchronization plan for a network:

  • Synchronize the greatest number of network elements to the smallest number of independent clock sources. Ideally, all the network elements should be synchronized to a single clock source.
  • Use clock sources of the highest quality (in terms of stability and long-term accuracy).
  • To ensure resiliency of synchronization, plan for possible failure of the clock sources, network elements, and network trunks.

Network Synchronization Overview

Synchronous Ethernet (SyncE), which is defined by the Telecommunication Standardization Sector (ITU-T) standards, such as G.8261 and G.8262, leverages the PHY layer of the Ethernet to transmit clock information to remote sites.

SyncE provides a cost-effective alternative to the Synchronous Optical Networking (SONET) networks. For SyncE to work, each network element along the synchronization path must support SyncE. To implement SyncE, the bit clock of the Ethernet is aligned to a reliable clock that is traceable to the Primary Reference Clock (PRC).

Note

The 2-Port Gigabit Synchronous Ethernet SPA (SPA-2X1GE-SYNCE) is not supported on ASR 1002-x chassis.

Features Supported on ASR 1000 Platforms

Platform Support

Features Supported

Features Not Supported

ASR 1001-X

Synchronous Ethernet Feature is supported with Built-in Gigabit and 10-Gigabit Ethernet Ports

NetClk Feature

ASR1002-X

Synchronous Ethernet Feature is supported with Built-in Gigabit Ethernet Ports.

NetClk Feature

ASR1001

—

NetClk and Network Synchronization Feature

Ethernet Line Card

ASR1000-2T+20X1GE


Note
Network-Clocking feature is not supported with SFP-GE-T on any of the ASR1000 platforms.

Cisco ASR 1000 Series Aggregation Services Routers have a dedicated external interface known as BITS interface to recover clocking information from a Synchronization Supply Unit (SSU). They use this clock for SyncE. The BITS interface supports E1 (European SSUs) and T1 (American BITS) framing.


Note
The Cisco ASR 1001-X Router does not have an on-board BITS port, hence it does not support those features that use BITS ports.

The below table lists the framing modes for a BITS port on the Cisco ASR 1002-X Router.

Table 1 Framing Modes for a BITS or SSU Port on the Cisco ASR 1002-X Router

BITS or SSU Port Support Matrix

Framing Modes Supported

SSM or QL Support

Tx Port

Rx Port

T1

T1 ESF

Yes

Yes

Yes

T1

T1 SF

Yes

Yes

Yes

T1

T1 D4

Yes

Yes

Yes

E1

E1 CRC4

Yes

Yes

Yes

E1

E1 FAS

Yes

Yes

Yes

E1

E1 CAS

Yes

Yes

Yes

E1

E1 CAS CRC4

Yes

Yes

Yes

2048 kHz

2048 kHz

Yes

Yes

Yes

The below table lists the framing modes for a BITS port on the other Cisco ASR 1000 Series Aggregation Services Routers.

Table 2 Framing Modes for a BITS or SSU Port on the Other Cisco ASR 1000 Series Aggregation Services Routers

BITS or SSU Port Support Matrix

Framing Modes Supported

SSM or QL Support

Tx Port

Rx Port

T1

T1 ESF

No

No

Yes

T1

T1 SF

No

No

Yes

E1

E1 CRC4

No

No

Yes

E1

E1 FAS

No

No

Yes

E1

E1 CAS

No

No

Yes

E1

E1 CAS CRC4

No

No

Yes

2048 kHz

2048 kHz

No

No

Yes

You can configure network synchronization on the Cisco ASR 1000 Series Aggregation Services Routers by using one of the following features:

  • Clock Recovery from SyncE

When this feature is configured, the system clock is recovered from the SyncE clocking source (SyncE-enabled interfaces only). The router uses this clock as the Tx clock for other supported Shared Port Adapters (SPAs).

  • Clock Recovery from an External Interface

When this feature is enabled, the system clock is recovered from a BITS clock source.

  • Clock Recovery from a GPS (10M) Source

Note
This feature is supported only on the Cisco ASR 1002-X Router.

When this feature is enabled, the system clock is recovered from a GPS (10M) clock source.

  • Line to External

Note
This feature is not supported on the Cisco ASR 1002-X Router.

When this feature is enabled, the clock received from an Ethernet is forwarded to an external SSU. The SyncE feature provides the clock cleanup functionality. When a router is in the middle of a synchronization chain, the received clock may experience unacceptable wander and jitter. The router recovers the clock from the SyncE interface, converts it to the format required for the BITS interface, and sends it to an SSU through the BITS port. The SSU then performs a cleanup and sends it back to the BITS interface. The cleaned up clock is received from the SSU and is used as the Tx clock for the SyncE ports. In the context of the Cisco ASR 1000 Series Aggregation Services Routers, the interface from which the clock is recovered and the BITS port to the SSU must reside on the same card.

  • System to External: The system clock is used as the Tx clock for an external interface. By default, the system clock is not transmitted through the external interface.
  • A SyncE-enabled Cisco ASR 1000 Series Router provides the Squelching feature. In this feature, an alarm indication signal (AIS) is sent to the Tx interfaces if the clock source goes down. When the Line to External feature is configured, if the line source goes down at any point of time, an AIS is transmitted through the external interface to the SSU. System to External: If the router loses all the clock sources, an AIS is sent through the external interface to the SSU.

Squelching can be performed only on external devices, such as SSUs and PRCs.

You can have a maximum of eight clock sources configured on a Cisco ASR 1000 Series Router. On a router that supports the Network Synchronization feature, you can configure selection of the clock source on the basis of the quality of the clock source. With this feature configured, the clock source that offers the best quality is made the default clock source. If the highest level of quality is offered by more than one clock source, the clock source with the highest priority is made the default clock source. You can also manage synchronization by using the following management options:

  • Hold-Off Time: If a clock source goes down, the router waits for a specific hold-off time before removing the clock source from the clock selection process. By default, the value of hold-off time is 300 milliseconds (ms).
  • Wait to Restore: If a SyncE interface comes up, the router waits for a specific period of time before considering the SyncE interface for synchronization source. By default, the value is 300 seconds.
  • Force Switch: Forcefully selects a synchronization source irrespective of whether the source is available or within the specified range.
  • Manual Switch: Manually select a synchronization source, provided the clock source has a higher quality level than the currently active clock.

The following table lists the SPAs that support network synchronization.

Table 3 SPAs supporting Network Synchronization

SPA Type

SPA Name

ASR 1001-X Built-in SPA

BUILT-IN-2T+6X1GE

ASR1002-X Built-in SPA

6XGE-BUILT-IN

Synchronous Ethernet

SPA-2XGE-SYNCE

Serial and Channelized SPA

SPA-1XCHSTM1/OC3

SPA-1XCHOC12/DS0

SPA-8XCHT1/E1-V2 (Supported on the Cisco ASR 1002-X Router and the Cisco ASR1001-X Router, from Cisco IOS XE Release 3.11 onwards)

CEOP

SPA-1CHOC3-CE-ATM

SPA-24CHT1-CE-ATM

ATM

SPA-1XOC3-ATM-V2
SPA-3XOC3-ATM-V2
SPA-1XOC12-ATM-V2
SPA-2CHT3-CE-ATM
POS SPA-2XOC3-POS
SPA-4XOC3-POS

SPA-4XOC3-POS-V2

SPA-8XOC3-POS

SPA-1XOC12-POS

SPA-2XOC12-POS

SPA-4XOC12-POS

SPA-8XOC12-POS

SPA-1XOC48-POS/RPR

SPA-2XOC48POS/RPR

SPA-4XOC48POS/RPR

SPA-OC192POS-XFP


Note
For more information on SPA support matrix see, http:/​/​www.cisco.com/​en/​US/​docs/​interfaces_modules/​shared_port_adapters/​configuration/​ASR1000/​ASRspasw.html

Note
Netsync feature on SPA-2XGE-SYNCE is not supported on the Cisco ASR 1001-X Router.

Synchronization Status Message and Ethernet Synchronization Messaging Channel

Network clocking uses the following mechanisms to exchange the quality level of the clock between the network elements:

Synchronization Status Message

Network elements use Synchronization Status Messages (SSM) to inform the neighboring elements about the Quality Level (QL) of the clock. Non-Ethernet interfaces, such as optical interfaces and T1 or E1 SPA frames, use SSM. The key benefits of SSMs are:

  • Prevents timing loops.Provides fast recovery when a part of the network fails.
  • Ensures that a node gets timing from the most reliable clock source.

Ethernet Synchronization Messaging Channel

In order to maintain a logical communication channel in synchronous network connections, Ethernet relies on a channel called the Ethernet Synchronization Messaging Channel (ESMC), which is based on the IEEE 802.3 Organization-Specific Slow Protocol (OSSP) standards. ESMC relays the SSM code that represents the quality level of the Ethernet Equipment Clock (EEC) in a physical layer.

The ESMC packets are received only for the ports configured as clock sources, and transmitted on all the SyncE interfaces in the system. These packets are then processed by the clock selection algorithm on route processors (RP) and are used to select the best clock. The Tx frame is generated based on the QL value of the selected clock source, and sent to all the enabled SyncE ports.

Clock Selection Algorithm

The clock selection algorithm selects the best available synchronization source from the nominated sources. This algorithm exhibits nonrevertive behavior among the clock sources with the same QL value, and always selects the signal with the best QL value. For clock option 1, the default is revertive, and for clock option 2, the default is nonrevertive.

The clock selection process works in the following modes:

When multiple selection processes are present in a network element, all the processes work in the same mode.

QL-Enabled Mode

In QL-enabled mode, the following parameters contribute to the selection process:

  • Quality level
  • Signal fail via QL-FAILED
  • Priority
  • External commands.

If no external commands are active, the algorithm selects the reference (for clock selection) with the highest QL that does not experience a signal fail condition. If multiple inputs have the same highest QL, the input with the highest priority is selected. For multiple inputs having the same highest priority and QL, the existing reference is maintained (if it belongs to the highest priority and QL group). Otherwise, an arbitrary reference from the highest priority and QL group is selected.

QL-Disabled Mode

In QL-disabled mode, the following parameters contribute to the selection process:

  • Signal failure
  • Priority
  • External commands

If no external commands are active, the algorithm selects the reference (for clock selection) with the highest priority that does not experience a signal fail condition. For multiple inputs having the same highest priority, the existing reference is maintained (if it belongs to highest priority group). Otherwise, an arbitrary reference from highest priority group is selected.

product="name=">Hybrid Mode

Restrictions for Network Synchronization

This section lists the restrictions for configuring network synchronization on a router.

  • If the network clock algorithm is enabled, use the system clock as the Tx clock (synchronous mode) for the Ethernet interfaces of the corresponding router. You cannot change the synchronous mode on a per-interface basis.
  • You can configure up to eight ports as clock sources on a router.
  • The SyncE feature coexists with SSO, but is not SSO-compliant. The clock selection algorithm is restarted on a switchover. During switchover, the router goes into holdover mode.
  • The SyncE interfaces in the WAN mode cannot be used for QL-enabled clock selection. You must either use them with the system in QL-disabled mode, or disable the ESMC on the interfaces, and use them as QL-disabled interfaces.
  • We recommend that you do not configure multiple input sources with the same priority because this impacts the TSM (switching message delay).
  • You cannot implement the network clock-based clock selection algorithm and the new algorithm simultaneously. Both these are mutually exclusive.
  • The Line to External feature for clock cleanup is supported only if the line interface and the external interface are on the same metronome SPA.

Note
The Line to External feature is not supported on the Cisco ASR 1002-X Router.

Configuring Network Synchronization

You can configure network synchronization on the Cisco ASR 1000 Series Aggregation Services Routers by performing one of the following procedures:

Configuring Clock Recovery from SyncE

This section describes how to configure clock recovery by using the SyncE method.

SUMMARY STEPS

    1.    configure terminal

    2.    network-clock synchronization automatic

    3.    network-clock synchronization ssm option {1 | 2 {GEN1 | GEN2}}

    4.    interface gigabitethernet slot/card/port

    5.    synchronous mode

    6.    exit

    7.    network-clock input-source priority {interface interface-name slot/card/port | {external slot/card/port}}

    8.    exit


DETAILED STEPS
     Command or ActionPurpose
    Step 1configure terminal


    Example:
    Router# configure terminal
     

    Enters the global configuration mode.

     
    Step 2network-clock synchronization automatic


    Example:
    Router(config)# network-clock synchronization automatic
     

    Enables the network clock selection algorithm. This command disables the Cisco-specific network clock process, and turns on the G.781-based automatic clock selection process.

     
    Step 3network-clock synchronization ssm option {1 | 2 {GEN1 | GEN2}}


    Example:
    Router(config)# network-clock synchronization ssm option 2 GEN1
     

    Configures the equipment to work in a synchronization network. The option_id value 1 refers to a synchronization network design for Europe. This is the default value. The option_id value 2 refers to a synchronization network design for the U.S.

     
    Step 4interface gigabitethernet slot/card/port


    Example:
    Router(config)# interface gigabitethernet 0/2/0
     

    Specifies the Gigabit Ethernet interface to be configured:

    slot/card/port—Specifies the location of the interface.

     
    Step 5synchronous mode


    Example:
    Router(config-if)# synchronous mode
     

    Sets the mode to synchronous mode.

     
    Step 6exit


    Example:
    
 

    Example:
    Router(config)# exit
    
 
          		 

    
Exits the global configuration mode.
    

 
      
    

    Step 7network-clock input-source priority {interface interface-name slot/card/port | {external slot/card/port}}
     

    Example:
    
 

    Example:
    Router(config)# network-clock input-source 1 interface gigabitethernet 0/2/0
    
 

    Example:
    
 

    Example:
    Router(config)# network-clock input-source 1 external R0 2048k
    
 
          		 

    
Enables clock recovery from SyncE.
    


    
The Cisco ASR1006 router supports two RP ports, one active and the other standby.
    

 
      
    

    Step 8exit
     

    Example:
    Router(config)# exit
    
 
          		 

    
Exits the global configuration mode.
    

 
      
    

    

    

    Examples
    

    
The following example shows how to configure clock recovery from SyncE:
    

    Router# configure terminal
Router(config)# network-clock synchronization automatic
Router(config)# network-clock synchronization ssm option 2 GEN1
Router(config)# interface gigabitethernet 0/2/0
Router(config-if)# synchronous mode
Router(config)# exit
Router(config)# network-clock input-source 1 interface gigabitethernet 0/2/0
Router(config)# exit

    

    

    

    

    Configuring Clock Recovery from a BITS Port
    

    
This section describes how to configure clock recovery from a BITS port. BITS port can be configured either as an input-source or an output-source.
    

    

    Configuring Clock
	 Recovery with a BITS Port as an Input-Source 
    

    
		
     This section
		  describes how to configure clock recovery with a BITS port as an input-source.
		
    

	 
    
SUMMARY STEPS
      1.   
      enable
		  
      

      2.   
      configure 
				terminal
		  
      

      3.   
      network-clock 
				synchronization 
				automatic
		  
      

      4.   
      network-clock 
				synchronization 
				ssm 
				option
				
				{1 
				| 
				2 
				{GEN1 
				| 
				GEN2}}
		  
      

      5.   
      network-clock 
				input-source 
				priority 
				{external 
			 slot/card/port}
		  
      

      6.   
      exit
		  
      


    DETAILED STEPS
       Command or ActionPurpose
      Step 1enable
		  
       

      Example:
			 
      Router# enable
      

		   
            		 
			 
       Enables the
				privileged EXEC mode. 
			 
      

			 
       Enter your
				password if prompted.
			 
      

		   
      
      

      Step 2configure 
				terminal
		  
       

      Example:
			 
      Router# configure terminal
      

		   
            		 
			 
       Enters the
				global configuration mode.
			 
      

		   
      
      

      Step 3network-clock 
				synchronization 
				automatic
		  
       

      Example:
			 
      Router(config)# network-clock synchronization automatic
      

		   
            		 
			 
       Enables the
				network clock selection algorithm. This command disables the Cisco-specific
				network clock process, and turns on the G.781-based automatic clock selection
				process.
			 
      

		   
      
      

      Step 4network-clock 
				synchronization 
				ssm 
				option
				
				{1 
				| 
				2 
				{GEN1 
				| 
				GEN2}}
		  
       

      Example:
			 
      Router(config)# network-clock synchronization ssm option 2 GEN1
      

		   
            		 
			 
       Configures the
				equipment to work in the synchronization network. The option_id value 1 refers
				to synchronization network design for Europe. This is the default value. The
				option_id value 2 refers to the synchronization network design for the U.S.
			 
      

		   
      
      

      Step 5network-clock 
				input-source 
				priority 
				{external 
			 slot/card/port}
		  
       

      Example:
			 
      Router(config)# network-clock input-source 1 External 0/3/0 t1 esf
      

		   

      Example:
			 
      

		   

      Example:
			 
      Router(config)# network-clock input-source 1 External R0 t1 esf
      

		   

      Example:
			 
      Router(config)# network-clock input-source 1 external r0 e1 cas crc4 120 linecode
      

		   
            		 
			 
       Enables clock
				recovery from a BITS port.
			 
      

			 
      Note   
                
               Routers with
				dual hardware support, such as the Cisco ASR 1006 Router, can have two RP
				ports, wherein one RP is active and the other is standby. Both the active and
				standby RP BITS ports can be configured as output sources.
			 
      

		   
      
      

      Step 6exit
		  
       

      Example:
			 
      Router(config)# exit
      

		   
            		 
			 
       Exits the
				global configuration mode.
			 
      

		   
      
      

      

      

      Examples
      

      
The following example shows how to configure clock recovery from a BITS port for a Metronome SPA:
      

      Router# configure terminal
Router(config)# network-clock synchronization automatic
Router(config)# network-clock synchronization ssm option 2 GEN1
Router(config)# network-clock input-source 1 external 0/3/0 t1 esf
Router(config)# exit

      

      
The following example shows how to configure clock recovery from a BITS port for RP BITS on Cisco ASR 1000 Series Aggregation Services Routers with dual RP:
      

      Router# configure terminal
Router(config)# network-clock synchronization automatic
Router(config)# network-clock synchronization ssm option 2 GEN
Router(config)# network-clock input-source 1 External R0 t1 esf 
Router(config)# exit

      

      

      

      
The following example shows how to configure clock recovery with BITS as the input source on the Cisco ASR 1002-X Series Aggregation Services Routers on the E1 Common Channel Signal mode:
      

      Router# configure terminal
Router(config)# network-clock synchronization automatic
Router(config)# network-clock synchronization ssm option 2 GEN
Router(config)# network-clock input-source 1 external r0 e1 cas crc4 120 linecode
Router(config)# exit

      

      

      

      

      Configuring a SyncE
	 Using the System-to-External Method
      

      
		
       This section
		  describes how to configure SyncE using System-to-External method.
		
      

	 
      
SUMMARY STEPS
        1.   
      enable
		  
        

        2.   
      configure 
			 terminal
		  
        

        3.   
       network-clock
			 synchronization automatic
		  
        

        4.   
       network-clock
			 synchronization ssm option {option_id {GEN1 | GEN2}}
		  
        

        5.   
      network-clock 
				output-source 
				system
				
				priority 
				{external 
				slot/card/port 
				[2m 
				| 
				10m]}
		  
        

        6.   
       exit
		  
        


      DETAILED STEPS
         Command or ActionPurpose
        Step 1enable
		  
         

        Example:
			 
        Router# enable
        

		   
              		 
			 
         Enables the
				privileged EXEC mode. 
			 
        

			 
         Enter your
				password if prompted.
			 
        

		   
      
        

        Step 2configure 
			 terminal
		  
         

        Example:
			 
        Router# configure terminal
        

		   
              		 
			 
         Enters the
				global configuration mode.
			 
        

		   
      
        

        Step 3 network-clock
			 synchronization automatic
		   

        Example:
			 
        Router(config)# network-clock synchronization automatic
        

		   
              		 
			 
         Enables the
				network clock selection algorithm. This command disables the Cisco-specific
				network clock process, and turns on the G.781-based automatic clock selection
				process.
			 
        

		   
      
        

        Step 4 network-clock
			 synchronization ssm option {option_id {GEN1 | GEN2}}
		   

        Example:
			 
        

		   

        Example:
			 
        

		   

        Example:
			 
        Router(config)# network-clock synchronization ssm option 2 GEN1
        

		   
              		 
			 
         Configures the
				equipment to work in a synchronization network. The option_id value 1 refers to
				a synchronization networks design for Europe. This is the default value. The
				option_id value 2 refers to a synchronization networks design for the U.S.
			 
        

			 
        
			 
        

			 
        
			 
        

		   
      
        

        Step 5network-clock 
				output-source 
				system
				
				priority 
				{external 
				slot/card/port 
				[2m 
				| 
				10m]}
		  
         

        Example:
			 
        

		   

        Example:
			 
        

		   

        Example:
			 
        Router(config)# network-clock output-source system 1 external 4/0/0 t1 sf
        

		   
              		 
			 
         Configures the
				system clock to be used on external Tx interfaces.
			 
        

		   
      
        

        Step 6 exit
		   

        Example:
			 
        Router(config)# exit
        

		   
              		 
			 
         Exits the
				global configuration mode.
			 
        

		   
      
        

        

        

        Examples
        

         The following example
		shows how to configure SyncE using System-to-External method:
	 
        

        Router>enable
Router# configure terminal
Router(config)# network-clock synchronization automatic
Router(config)# network-clock synchronization ssm option 2 GEN1
Router(config)# network-clock input-source 1 External 5/3/0 t1 sf 
Router(config)# exit

        

         The following example
		shows how to configure clock cleanup using an SSU:
	 
        

        Router(config)# network-clock output-source line 1 interface GigabitEthernet1/0/0 External 1/0/0 t1 sf
Router(config)# network-clock input-source 1 External 5/3/0 t1 sf
        

        

        

        

        Configuring Clock
	 Recovery with a BITS Port as an Output-Source 
        

        
		
         This section
		  describes how to configure clock recovery from a BITS port as an output-source.
		
        

		

        Note
         BITS
		  configuration as output sources is supported only on Cisco ASR 1002-X Router.
		
        

	 
        
SUMMARY STEPS
          1.   
      enable
		  
          

          2.   
      configure 
				terminal
		  
          

          3.   
      network-clock 
				synchronization 
				automatic
		  
          

          4.   
      network-clock 
				synchronization 
				ssm 
				option
				
				{1 
				| 
				2 
				{GEN1 
				| 
				GEN2}}
		  
          

          5.   
      network-clock 
				output-source 
				priority 
				{external slot/card/port}
		  
          

          6.   
      exit
		  
          


        DETAILED STEPS
           Command or ActionPurpose
          Step 1enable
		  
           

          Example:
			 
          Router# enable
          

		   
                		 
			 
           Enables the
				privileged EXEC mode. 
			 
          

			 
           Enter your
				password if prompted.
			 
          

		   
      
          

          Step 2configure 
				terminal
		  
           

          Example:
			 
          Router# configure terminal
          

		   
                		 
			 
           Enters the
				global configuration mode.
			 
          

		   
      
          

          Step 3network-clock 
				synchronization 
				automatic
		  
           

          Example:
			 
          Router(config)# network-clock synchronization automatic
          

		   
                		 
			 
           Enables the
				network clock selection algorithm. This command disables the Cisco-specific
				network clock process, and turns on the G.781-based automatic clock selection
				process.
			 
          

		   
      
          

          Step 4network-clock 
				synchronization 
				ssm 
				option
				
				{1 
				| 
				2 
				{GEN1 
				| 
				GEN2}}
		  
           

          Example:
			 
          Router(config)# network-clock synchronization ssm option 2 GEN1
          

		   
                		 
			 
           Configures the
				equipment to work in synchronization network. The option_id value 1 refers to
				synchronization networks design for Europe. This is the default value. The
				option_id value 2 refers to the synchronization networks design for the U.S.
			 
          

		   
      
          

          Step 5network-clock 
				output-source 
				priority 
				{external slot/card/port}
		   

          Example:
			 
          Router(config)# network-clock output-source system 1 External 0/3/0 t1 esf
          

		   

          Example:
			 
          

		   

          Example:
			 
          Router(config)# network-clock output-source 1 External R0 t1 esf
          

		   

          Example:
			 
          Router(config)# network-clock output-source 1 external r0 e1 cas crc4 120 linecode
          

		   
                		 
			 
           Enables clock
				recovery from a BITS port.
			 
          

			 
          Note   
                
               For
				routers with dual hardware support such as the Cisco ASR 1006 Router can have
				two RP ports wherein one RP is active and the other is standby. Both the active
				and standby RP BITS ports can be configured as output sources.
			 
          

		   
      
          

          Step 6exit
		  
           

          Example:
			 
          Router(config)# exit
          

		   
                		 
			 
           Exits the
				global configuration mode.
			 
          

		   
      
          

          

          

          Examples
          

          
The following example shows how to configure clock recovery from a BITS port for a Metronome SPA:
          

          Router# configure terminal
Router(config)# network-clock synchronization automatic
Router(config)# network-clock synchronization ssm option 2 GEN1
Router(config)# network-clock output-source 1 external 0/3/0 t1 esf
Router(config)# exit

          

          
The following example shows how to configure clock recovery from a BITS port for RP BITS on Cisco ASR 1000 Series Aggregation Services Routers with dual RP:
          

          Router# configure terminal
Router(config)# network-clock synchronization automatic
Router(config)# network-clock synchronization ssm option 2 GEN
Router(config)# network-clock output-source 1 external R0 t1 esf 
Router(config)# exit

          

          

          

          

          Configuring a SyncE
	 Using the System-to-External Method
          

           This section
		describes how to configure SyncE using System-to-External method.
	 
          

          
	 
          

          
	 
          

           The following example
		shows how to configure clock recovery with BITS as output-source on Cisco ASR
		1002-X Series Aggregation Services Routers on a E1 Common Channel Signal Mode:
	 
          

          Router# configure terminal
Router(config)# network-clock synchronization automatic
Router(config)# network-clock synchronization ssm option 2 GEN
Router(config)# network-clock output-source 1 external r0 e1 cas crc4 120 linecode
Router(config)# exit

          

          

          

          Configuring SyncE by Using the Line to External Feature
          

          

          
This section describes how to configure network synchronization by using the Line to External feature.
          



          Note
          
The Line to External feature is not supported on the Cisco ASR 1002-X Router.
          


          
SUMMARY STEPS
            1.   
      configure terminal
            

            2.   
      network-clock synchronization automatic
            

            3.   
      network-clock synchronization ssm option {1 | 2 {GEN1 | GEN2}}
            

            4.   
      interface gigabitethernet slot/card/port
            

            5.   
      synchronous mode
            

            6.   
      exit
            

            7.   
      network-clock output-source line priority {interface interface-name} {external slot/card/port}
            

            8.   
      exit
            


          DETAILED STEPS
             Command or ActionPurpose
            Step 1configure terminal
             

            Example:
            Router# configure terminal
            
 
                  		 

            
Enters the global configuration mode.
            

 
      
            

            Step 2network-clock synchronization automatic
             

            Example:
            Router(config)# network-clock synchronization automatic
            
 
                  		 

            
Enables the network clock selection algorithm. This command disables the Cisco-specific network clock process, and turns on the G.781-based automatic clock selection process.
            

 
      
            

            Step 3network-clock synchronization ssm option {1 | 2 {GEN1 | GEN2}} 

            Example:
            Router(config)# network-clock synchronization ssm option 2 GEN1
            
 

            Example:
            
 
                  		 

            
Configures the equipment to work in a synchronization network. The option_id value 1 refers to a synchronization network design for Europe. This is the default value. The option_id value 2 refers to a synchronization network design for the U.S.
            

 
      
            

            Step 4interface gigabitethernet slot/card/port
             

            Example:
            Router(config)# interface gigabitethernet 0/2/0
            
 
                  		 

            
Specifies the Gigabit Ethernet interface to be configured: 
            


            
slot/card/port—Specifies the location of the interface. 
            

 
      
            

            Step 5synchronous mode
             

            Example:
            Router(config-if)# synchronous mode
            
 
                  		 

            
Changes to the synchronous mode.
            

 
      
            

            Step 6exit
             

            Example:
            Router(config)# exit
            
 
                  		 

            
Exits the specific configuration mode.
            

 
      
            

            Step 7network-clock output-source line priority {interface interface-name} {external slot/card/port}
             

            Example:
            Router(config-if-srv)# network-clock output-source line 1 interface gigabitethernet 0/2/0 external 0/3/0
            
 
                  		 

            
Configures the line clock to be used on external Tx interfaces.
            


            Note   
                
              
This command is supported only on the Metronome SPA. 
            

 
      
            

            Step 8exit
             

            Example:
            Router(config)# exit
            
 
                  		 

            
Exits the global configuration mode.
            

 
      
            

            

            

            Examples
            

            
The following example shows how to configure a SyncE using the Line to External method:
            

            Router# configure terminal
Router(config)# network-clock synchronization automatic
Router(config)# network-clock synchronization ssm option 2 GEN1
Router(config)# interface gigabitethernet 0/2/0
Router(config-if)# synchronous mode
Router(config)# exit
Router(config)# network-clock output-source line 1 interface gigabitethernet 0/2/0 external 0/3/0
Router(config)# exit

            

            

            

            

            

            Managing Synchronization 
            

            
Manage synchronization on a Cisco ASR 1000 Series Aggregation Service Router using the following management commands:
            

            • network-clock synchronization mode QL-enabled command
              • 

            

            
Use the network-clock synchronization mode QL-enabled command in the global configuration mode to configure the automatic selection process for the QL-enabled mode. This succeeds only if the SyncE interfaces are capable of sending SSMs. 
            

            
The following example shows how to configure network clock synchronization (QL-enabled mode) in the global configuration mode:
            

            Router(config)# network-clock synchronization mode QL-enabled

            

            • 
esmc process command
              • 

            

            
Use the esmc process command in the global configuration mode to enable the ESMC process at system level. The no form of this command disables the ESMC process. The no form of this command fails if no SyncE-capable interface is installed on the platform. 
            

            
The following example shows how to enable the ESMC process in the global configuration mode:
            

            Router(config)# esmc process

            

            • esmc mode [tx | rx] command
              • 

            

            
Use the esmc mode [tx | rx] command in the interface configuration mode to enable the ESMC process at the interface level. The no form of the command disables the ESMC process. 
            

            
The following example shows how to enable ESMC in the interface configuration mode:
            

            Router(config-if)# esmc mode tx

            

            • network-clock quality-level command
              • 

            

            
Use the network-clock source quality-level command in the interface configuration mode to configure the QL value for ESMC on a gigabit Ethernet 
port. The value is based on global interworking options:
            

            • 

              • 
If Option 1 is configured, the available values are QL-PRC, QL-SSU-A, QL-SSU-B, QL-SEC, and QL-DNU.
                • 

              • 
If Option 2 is configured with GEN 2, the available values are QL-PRS, QL-STU, QL-ST2, QL-TNC, QL-ST3, QL-SMC, QL-ST4, and QL-DUS.
                • 

              • 
If Option 2 is configured with GEN1, the available values are QL-PRS, QL-STU, QL-ST2, QL-SMC, QL-ST4, and QL-DUS
                • 

              

              • 

            

            
The following example shows how to configure the network-clock source quality-level in the interface configuration mode:
            

            Router(config-if)# network-clock source quality-level QL-PRC rx

            

            
Use the network-clock quality-level command in the global configuration mode to configure the QL value for the SSMs on a BITS port. 
            

            
The following example shows how to configure network-clock quality-level command in the global configuration mode:
            

            Router(config)# network-clock quality-level rx qL-pRC external R0 2048k

            

            • 
network-clock wait-to-restore command
              • 

            

            
Use the network-clock wait-to-restore timer global command to set the wait-to-restore time. You can configure the wait-to-restore time to any value between 0 to 86400 seconds. The default value is 300 seconds. The wait-to-restore timer can be set in the global configuration mode and the interface configuration mode. 
            

            
The following example shows how to configure the wait-to-restore timer in the global configuration mode:
            

            Router(config)# network-clock wait-to-restore 10 global

            

            
The following example shows how to configure the wait-to-restore timer in the interface configuration mode:
            

            Router(config)# interface gigabitethernet 0/2/0
Router(config-if)# network-clock wait-to-restore 10

            

            • 
network-clock hold-off command
              • 

            

            
Use the network-clock hold-off timer global command to configure hold-off time. You can configure the hold-off time to either 0 or any value between 50 to 10000 ms. The default value is 300 ms. The network-clock hold-off timer can be set in the global configuration mode and the interface configuration mode. 
            

            
The following example shows how to configure the hold-off timer:
            

            Router(config-if)# network-clock hold-off 50 global

            

            • 
network-clock switch force command
              • 

            

            
Use the network-clock switch force command to forcefully select a synchronization source irrespective of whether the source is available, and within range. 
            

            
The following example shows how to configure a force switch:
            

            Router# network-clock switch force interface gigabitethernet 0/2/0

            

            • 
network-clock switch manual command 
              • 

            

            
Use the network-clock switch manual command to manually select a synchronization source, provided the clock source has a higher quality level than the currently active clock. 
            

            
The following example shows how to configure a manual switch:
            

            Router# network-clock switch manual interface gigabitethernet 0/2/0

            

            • 
network-clock clear switch controller-id command
              • 

            

            
Use the network-clock clear switch controller-id command to clear the manual, or switch it on by force. 
            

            
The following example shows how to clear a switch:
            

            Router# network-clock clear switch t0

            

            • 
network-clock set lockout command
              • 

            

            
Use the network-clock set lockout command to lockout a clock source. A clock source flagged as lockout is not selected for SyncE. To clear the lock-out on a source, use the network-clock clear lockout command. 
            

            
The following example shows how to lock out a clock source:
            

            Router# network-clock set lockout interface gigabitethernet 0/2/0

            

            
The following example shows how to clear the lock out on a clock source:
            

            Router# network-clock clear lockout interface gigabitethernet 0/2/0

            

            

            

            Verifying the Network Synchronization Configuration
            

            
Use the following commands to verify the network synchronization configuration:
            

            • 
Use the show network-clock synchronization command to display the output:
              • 

            

            Router# show network-clock synchronization 
Symbols:     En - Enable, Dis - Disable, Adis - Admin Disable
             NA - Not Applicable
             *  - Synchronization source selected
             #  - Synchronization source force selected
             &  - Synchronization source manually switched
Automatic selection process : Enable
Equipment Clock : 1544 (EEC-Option2)
Clock Mode : QL-Enable
ESMC : Enabled
SSM Option : GEN1
T0 : External R0 t1 esf
Hold-off (global) : 300 ms
Wait-to-restore (global) : 300 sec
Tsm Delay : 180 ms
Revertive : No
Force Switch: FALSE
Manual Switch: FALSE
Number of synchronization sources: 2
sm(netsync NETCLK_QL_ENABLE), running yes, state 1A
Last transition recorded: (src_rem)-> 1A (src_added)-> 1A (src_rem)-> 1A (src_added)-> 1A (ql_change)-> 1A (sf_change)-> 1A (force_sw)-> 1C (clear_sw)-> 1A (sf_change)-> 1A (sf_change)-> 1A
 
Nominated Interfaces
 Interface            SigType     Mode/QL      Prio  QL_IN  ESMC Tx  ESMC Rx
Internal             NA          NA/Dis       251   QL-ST3    NA        NA
Gi1/2/0              NA          Sync/En      1     QL-FAILED -         -
*External R0          T1 ESF      NA/En        2     QL-STU    NA        NA

            

            • 
Use the show network-clock synchronization detail command to display all the details of network clock synchronization parameters at the global and interface level, as shown in the following example:
              • 

            

            Router# show network-clock synchronization detail
Symbols:     En - Enable, Dis - Disable, Adis - Admin Disable
             NA - Not Applicable
             *  - Synchronization source selected
             #  - Synchronization source force selected
             &  - Synchronization source manually switched
Automatic selection process : Enable
Equipment Clock : 1544 (EEC-Option2)
Clock Mode : QL-Enable
ESMC : Enabled
SSM Option : GEN1
T0 : External R0 t1 esf
Hold-off (global) : 300 ms
Wait-to-restore (global) : 300 sec
Tsm Delay : 180 ms
Revertive : No
Force Switch: FALSE
Manual Switch: FALSE
Number of synchronization sources: 2
sm(netsync NETCLK_QL_ENABLE), running yes, state 1A
Last transition recorded: (src_rem)-> 1A (src_added)-> 1A (src_rem)-> 1A (src_added)-> 1A (ql_change)-> 1A (sf_change)-> 1A (force_sw)-> 1C (clear_sw)-> 1A (sf_change)-> 1A (sf_change)-> 1A
 
Nominated Interfaces
Interface            SigType     Mode/QL      Prio  QL_IN  ESMC Tx  ESMC Rx
Internal             NA          NA/Dis       251   QL-ST3    NA        NA
Gi1/2/0              NA          Sync/En      1     QL-FAILED -         -
*External R0          T1 ESF      NA/En        2     QL-STU    NA        NA
Interface:
---------------------------------------------
Local Interface: Internal
Signal Type: NA
Mode: NA(Ql-enabled)
SSM Tx: Disable
SSM Rx: Disable
Priority: 251
QL Receive: QL-ST3
QL Receive Configured: -
QL Receive Overrided: -
QL Transmit: -
QL Transmit Configured: -
Hold-off: 0
Wait-to-restore: 0
Lock Out: FALSE
Signal Fail: FALSE
Alarms: FALSE
Slot Disabled: FALSE
Local Interface: Gi1/2/0
Signal Type: NA
Mode: Synchronous(Ql-enabled)
ESMC Tx: Disable
ESMC Rx: Enable
Priority: 1
QL Receive: QL-PRS
QL Receive Configured: -
QL Receive Overrided: QL-FAILED
QL Transmit: QL-DUS
QL Transmit Configured: -
Hold-off: 300
Wait-to-restore: 300
Lock Out: FALSE
Signal Fail: FALSE
Alarms: TRUE
Slot Disabled: FALSE
Local Interface: External R0
Signal Type: T1 ESF
Mode: NA(Ql-enabled)
SSM Tx: Disable
SSM Rx: Enable
Priority: 2
QL Receive: QL-STU
QL Receive Configured: -
QL Receive Overrided: -
QL Transmit: -
QL Transmit Configured: -
Hold-off: 300
Wait-to-restore: 300
Lock Out: FALSE
Signal Fail: FALSE
Alarms: FALSE
Slot Disabled: FALSE

            

            • 
Use the show esmc command to display the ESMC configuration output:
              • 

            

            Router# show esmc 
Interface: GigabitEthernet0/0/0
  Administative configurations:
    Mode: Synchronous
    ESMC TX: Enable
    ESMC RX: Enable
    QL TX: -
    QL RX: -
    Operational status:
    Port status: UP
    QL Receive: QL-PRC
    QL Transmit: QL-DNU
    QL rx overrided: -
    ESMC Information rate: 1 packet/second
    ESMC Expiry: 5 second
Interface: GigabitEthernet0/0/0
  Administrative configurations:
    Mode: Synchronous
    ESMC TX: Enable
    ESMC RX: Enable
    QL TX: -
    QL RX: -
    Operational status:
    Port status: UP
    QL Receive: QL-DNU
    QL Transmit: QL-DNU
    QL rx overrided: QL-DNU
    ESMC Information rate: 1 packet/second
    ESMC Expiry: 5 second

            

            • 
Use the show esmc detail command to display all the details of the ESMC parameters at the global and interface level, as shown in the following example:
              • 

            

            Router# show esmc detail 
Router#show esmc detail
Interface: GigabitEthernet0/0/0
  Administative configurations:
    Mode: Synchronous
    ESMC TX: Enable
    ESMC RX: Enable
    QL TX: -
    QL RX: QL-PRS
  Operational status:
    Port status: UP
    QL Receive: QL-DUS
    QL Transmit: QL-ST3
    QL rx overrided: QL-DUS
    ESMC Information rate: 1 packet/second
    ESMC Expiry: 5 second
    ESMC Tx Timer: Running
    ESMC Rx Timer: Running
    ESMC Tx interval count: 1
    ESMC INFO pkts in: 0
    ESMC INFO pkts out: 256
    ESMC EVENT pkts in: 0
    ESMC EVENT pkts out: 0

            

            

            

            Troubleshooting the
	 Network Synchronization Configuration
            


            Note
             Before you
		troubleshoot, ensure that all the network synchronization configurations are
		complete.
	 
            

             The following table
		provides information about troubleshooting scenarios that you may encounter
		while configuring network synchronization.
	 
            


            Table 4 Troubleshooting
		Scenarios 
            
				
             Problem
				
            

			             		

				
             Solution
				
            

			             		

            
            

            
				
             Incorrect
				  clock selection
				
            

			             		

				
            •  Verify that there are no alarms on
					 the interfaces. Use the show network-clock synchronization detail command to
					 check this.
				  
              • 

            •  Ensure that the nonrevertive
					 configurations are in place.
				  
              • 

            

			             		

            

            
				
             Incorrect QL
				  values
				
            

			             		

				
             Ensure that
				  there is no framing mismatch with the SSM option.
				
            

			             		

            

            
				
             Incorrect
				  clock limit set or queue limit disabled mode
				
            

			             		

				
            •  Verify
					 that there are no alarms on the interfaces. Use the show network-clock
					 synchronization detail RP command to confirm.
				  
              • 

            •  Use the 
					 show 
						network-clock 
						synchronization command to confirm if the system
					 is in revertive mode or nonrevertive mode and verify the nonrevertive
					 configurations as shown in this example:
				  
              • 

            

				
             Router#show
				  network-clock synchronization 
				
            

				
             Symbols: En -
				  Enable, Dis - Disable, Adis - Admin Disable 
				
            

				
             NA - Not
				  Applicable 
				
            

				
             * -
				  Synchronization source selected 
				
            

				
             # -
				  Synchronization source force selected 
				
            

				
             & -
				  Synchronization source manually switched 
				
            

				
            
				
            

				
             Automatic
				  selection process : Enable 
				
            

				
             Equipment
				  Clock : 1544 (EEC-Option2) 
				
            

				
             Clock Mode :
				  QL-Enable 
				
            

				
             ESMC :
				  Enabled 
				
            

				
             SSM Option :
				  GEN1 
				
            

				
             T0 : External
				  R0 t1 esf 
				
            

				
             Hold-off
				  (global) : 300 ms 
				
            

				
            
				  Wait-to-restore (global) : 300 sec 
				
            

				
             Tsm Delay :
				  180 ms 
				
            

				
             Revertive :
				  No 
				
            

				
             Force Switch:
				  FALSE 
				
            

				
             Manual
				  Switch: FALSE 
				
            

				
             Number of
				  synchronization sources: 2 
				
            

				
             sm(netsync
				  NETCLK_QL_ENABLE), running yes, state 1A 
				
            

				
             Last
				  transition recorded: (src_rem)-> 1A (src_added)-> 1A (src_rem)-> 1A
				  (src_added)-> 1A (ql_change)-> 1A (sf_change)-> 1A (force_sw)-> 1C
				  (clear_sw)-> 1A (sf_change)-> 1A (sf_change)-> 1A 
				
            

			             		

            

            
				
             Incorrect QL
				  values observed when you use the 
				  show 
					 network-clock 
					 synchronization 
					 detail 
				  command
				
            

			             		

				
             Use the 
				  network-clock 
					 synchronization 
					 SSM (option 
					 1 
					 |option 
					 2) command to confirm that there is no framing
				  mismatch. Use the 
				  show 
					 run 
					 interface command to validate the framing for a
				  specific interface. For SSM 
				  option 1
				  , framing should be SDH or E1, and for SSM 
				  option 2
				  , it should be T1.
				
            

			             		

            

            
				
             Mismatched
				  Physical line coding mechanisms between clock source and input source on the
				  router
				
            

			             		

				
             To ensure
				  that this feature works correctly, both the ends need to be configured with
				  identical physical line coding mechanism and encapsulation values.
				
            

			             		

            
            

            

            

            

            

            

            Additional References
            

            

            

            Related Documents
            


            

            
Related Topic
            

            		


            
Document Title
            

            		

            
            

            

            
Cisco IOS commands
            

            		


            
Cisco IOS Master Commands List, All Releases

            

            		

            
            

            

            


            

            Standards
            


            

            
Standard
            

            		


            
Title
            

            		

            
            

            

            
None
            

            		


            
—
            

            		

            
            

            

            


            

            MIBs
            


            

            
MIB
            

            		


            
MIBs Link
            

            		

            
            

            

            
None
            

            		


            
To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at this URL:
            


            
http:/​/​www.cisco.com/​go/​mibs

            

            		

            
            

            

            


            

            RFCs
            


            

            
RFC
            

            		


            
Title
            

            		

            
            

            

            
None
            

            		


            
—
            

            		

            
            

            

            


            

            Technical Assistance
            


            

            
Description
            

            		


            
Link
            

            		

            
            

            

            
The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.
            

            		


            
http:/​/​www.cisco.com/​cisco/​web/​support/​index.html

            

            		

            
            

            

            


            

            

            

            Feature Information
	 for Network Synchronization Support
            

            
		
             The following table
		  lists the features in this module and provides links to specific configuration
		  information. 
		
            

		
             Use Cisco Feature
		  Navigator to find information about platform support and software image
		  support. Cisco Feature Navigator enables you to determine which software images
		  support a specific software release, feature set, or platform. To access Cisco
		  Feature Navigator, go to 
		  http:/​/​www.cisco.com/​go/​cfn
		  . An account on Cisco.com is not required.
		
            

		

            Note
             The following
		  table lists only the software release that introduced support for a given
		  feature in a given software release train. Unless noted otherwise, subsequent
		  releases of that software release train also support that feature.
		
            

		

            Table 5 Feature
		  Information for Network Synchronization Support 
            
				  
             Feature
					 Name
				  
            

				            		

				  
             Releases
				  
            

				            		

				  
             Feature
					 Information
				  
            

				            		

            
            

            
				  
             Network
					 Synchronization Support
				  
            

				            		

				  
             Cisco IOS
					 XE 3.2S 
				  
            

				            		

				  
             In Cisco
					 IOS XE Release 3.2S, this feature was introduced on the Cisco ASR 1000 Series
					 Aggregation Service Routers.
				  
            

				            		

            

            
				  
             Network
					 Synchronization Support
				  
            

				            		

				  
             Cisco IOS
					 XE 3.7S 
				  
            

				            		

				  
             In Cisco
					 IOS XE Release 3.7S, the commands that are used to configure this feature have
					 been extended with the introduction of the Cisco ASR 1002-X Router.
				  
            

				            		

            

            
				  
             Network
					 Synchronization Support
				  
            

				            		

				  
             Cisco IOS
					 XE 3.12S
				  
            

				            		

				  
             In Cisco
					 IOS XE Release 3.12S, the commands that are used to configure this feature have
					 been extended to the Cisco ASR 1001-X Router.