Cisco 7600 Series Ethernet Services Plus (ES+) and Ethernet Services Plus T (ES+T) Line Card Configuration Guide
Network Clocking on Cisco 7600 Series Ethernet Services Plus Line Cards
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Table of Contents

Network Clocking on Cisco 7600 Series Ethernet Services Plus Line Cards

Contents

Information About Network Clocking

How to Configure Network Clocking

Configuring BITS Clock Support

Usage Guidelines

Example

Configuring 10GE Interface as Clock Source

Usage Guidelines

Example

Verifying the Clock Source

Clock Source Recovery

Cisco 7600 Synchronous Ethernet

Network Clocking on Cisco 7600 Series Ethernet Services Plus Line Cards

This chapter provides information about configuring network clocking on the following Cisco 7600 Series ES+ Extended Transport (ES+XT) line cards:

  • 76-ES+XT-2TG3CXL
  • 76-ES+XT-4TG3CXL

For more information about the commands in this chapter, see the Cisco IOS Release 12.2 SR Command References at http://www.cisco.com/en/US/products/ps6922/prod_command_reference_list.html .


NoteThe information provided in this chapter is applicable to both the ES+ and ES+T line cards unless specified otherwise.


Contents

This chapter contains the following sections:

Information About Network Clocking

The network clocking support for 76-ES+XT-2TG3CXL and 76-ES+XT-4TG3CXL line cards is built on top of the existing network clocking feature with SIP-200 and SIP-400 line cards. All the original network clock sources provided by SPA interfaces on SIP-200 and SIP-400 line cards operate the same way as before. Additionally, you can use network clocking support for the 76-ES+XT-2TG3CXL and 76-ES+XT-4TG3CXL to configure:

  • BITS clock source
  • 10GE interface clock source

These enhancements provide Synchronous Ethernet (SyncE) feature support for service provider applications making the 76-ES+XT-2TG3CXL and 76-ES+XT-4TG3CXL line cards the preferred choices for carrier Ethernet environments.

The 76-ES+XT-2TG3CXL or 76-ES+XT-4TG3CXL line cards operate in three different modes for clock synchronization depending on the configuration and the current source state.

  • Free-running—A line card that is not participating in network clocking or a line card that is actively sourcing the clock operates in free-running mode. In this mode, the line card internal oscillator generates the reference clock to the backplane.

Note In a nonpartcipating mode or a disabled mode, the line card distributes a Stratum 3-quality timing signal to an external reference clock. Other interfaces on different line cards receive either the backplane reference clock or the external reference clock depending on their configurations.



Note Line card operation is in free-running mode only if it is not participating in the system clocking, is configured as the active source using on-board oscillator, or does not currently have a valid clock source before the first clock synchronization; otherwise the line cards operate in normal mode.


  • Normal—In normal mode, the module synchronizes with an externally supplied network timing reference, sourced from one of the chassis BITS inputs or recovered from a network interface. In this mode, the accuracy and stability of the output signal is determined by the accuracy and stability of the input reference.
  • Holdover—In holdover mode, the network timing module generates a timing signal based on the stored timing reference used when operating in normal mode. Holdover mode is automatically selected when the recovered reference is lost or has drifted excessively.

Note You cannot configure the drift range; it is set internally on the line card to +/–9.2~12 ppm (parts per million) by default. This ppm setting is typical for applications that requires a clock quality level of Stratum 3/3E, ITU-T G.813 option 1.



NoteAll line cards operate in the free-running mode until the network clock is configured.


How to Configure Network Clocking

The following sections provide information on configuring network clocking:

Configuring BITS Clock Support

You can select and configure the BITS port on the 76-ES+XT-2TG3CXL or 76-ES+XT-4TG3CXL line card as the system clock source. This will synchronize the system backplane clock with the corresponding BITS port input clock and distribute the BITS port input clock across the chassis as the transmit clock reference for all other interfaces that support network clocking.

Usage Guidelines

Use the following guidelines:

  • When the network clocking configuration is present in the startup configuration, the clocking configuration is not applied until five minutes after the configuration has been parsed. This prevents clocking instability on the backplane when the interfaces and controllers come up out of order.
  • Network clocking is enabled by default for the 76-ES+XT-2TG3CXL and 76-ES+XT-4TG3CXL.
  • Cisco IOS Release 12.2(33)SRD1 does not support synchronization status messaging (SSM) through BITS input.
  • If there is a BITS clock source flap because of Loss of Signal (LOS), Loss of Frame (LOF), T1 Blue Alarm, or E1 Alarm Indication Signal (AIS), there is an interval of 150 seconds before the source becomes valid and active.
  • In the event of an Out-of-Range (OOR) switchover (revertive mode), the source switchover occurs when the clock offset crosses the +/–12 ppm threshold. If this occurs, you must reconfigure the source.

SUMMARY STEPS

1. enable

2. configure terminal

3. network-clock slot slot bits number {2m | e1 [crc4] | j1 [esf]| t1 [d4 | esf [133ft | 266ft | 399ft | 533ft | 655ft]}

4. network-clock select priority slot slot bits number

5. exit

Detailed Steps

To configure BITS clock support for the Cisco 76-ES+XT-2TG3CXL and 76-ES+XT-4TG3CXL, use the following commands.

 

Command
Purpose

Step 1

enable

 
Router# enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

 

Router# configure terminal

Enters global configuration mode.

Step 3

network-clock slot slot bits number {2m | e1 [crc4] | j1 [esf]| t1 [d4 | esf [133ft | 266ft | 399ft | 533ft | 655ft]}

 

Router(config)# network-clock slot 1 bits 0

(Optional) Configure BITS port signaling types.

The default signal type is T1 with ESF framing and a Line Build-Out Select value of 133 feet.

Step 4

network-clock select priority slot slot bits number

 

Router(config)# network-clock select 1 slot 1 bits 0

Names a source to provide timing for the network clock and specifies the selection priority for this clock source.

Step 5

exit

 

Router(config)# exit

Exits global configuration mode and returns to privileged EXEC mode.

Example

The following example shows how to configure BITS clock support for the Cisco 76-ES+XT-2TG3CXL and 76-ES+XT-4TG3CXL.

Router# enable
Router# configure terminal
Router(config)# network-clock slot 1 bits 0 ?
2m 2.048MHz square wave signal type
e1 E1 signal type
j1 Japan J1 signal type
t1 T1 signal type
 
Router(config)# network-clock slot 1 bits 0 t1 ?
d4 T1 D4 framing mode
esf T1 ESF framing mode
 
Router(config)# network-clock slot 1 bits 0 t1 d4 ?
133ft Line Build-Out Select 0 to 133 feet
266ft Line Build-Out Select 133 to 266 feet
399ft Line Build-Out Select 266 to 399 feet
533ft Line Build-Out Select 399 to 533 feet
655ft Line Build-Out Select 533 to 655 feet
 
Router(config)# network-clock slot 1 bits 0 t1 d4 266ft
 
Router(config)# network-clock select 1 slot 1 bits 0
Router(config)# exit
 

Configuring 10GE Interface as Clock Source

This will set up the line card to extract the received clock from the 10GE interface, either the LAN PHY or the WANPHY, and have the system backplane clock synchronized to it. Then the system will use it as the transmission clock reference for all other interfaces in the chassis that support the network clocking feature.

Usage Guidelines

Use the following guidelines:

  • When the network clocking configuration is present in the startup configuration, the clocking configuration is not applied until five minutes after the configuration has been parsed. This prevents clocking instability on the backplane when the interfaces/controllers come up out of order.
  • Network clocking is enabled by default for the 76-ES+XT-2TG3CXL and 76-ES+XT-4TG3CXL.
  • Cisco IOS Release 12.2(33)SRD1 does not support Ethernet Synchronization Message Channel (ESMC) on LAN PHY and SSM received from SONET/SDH frames for WANPHY.
  • If there is a clock source flap because of interface up and down events, there is an interval of 150 seconds before the source becomes valid and active.
  • In the event of an Out-of-Range (OOR) switchover (revertive mode), but the interface stays up, the source switchover occurs when the clock offset crosses the +/–12 ppm threshold. If this occurs, you must reconfigure the source.

SUMMARY STEPS

1. enable

2. configure terminal

3. interface TenGigabitEthernet slot/port

4. clock source {internal | line | loop}

5. exit

6. network-clock select priority interface TenGigabitEthernet slot/port

7. exit

Detailed Steps

To configure 10GE interface as the clock source, use the following commands.

 

Command
Purpose

Step 1

enable

 
Router# enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

 

Router# configure terminal

Enters global configuration mode.

Step 3

interface TenGigabitEthernet slot/port

 

Router(config)# interface tengigabitethernet 1/1

Specifies the Ten Gigabit Ethernet interface to configure, where:

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

Step 4

clock source {internal | line | loop}

 

Router(config-if)# clock source line

Select interface clock source type to ''Recover clock from line.'' This will make this interface eligible for system clock source selection.

Step 5

exit

 

Router(config-if)# exit

Exits interface configuration mode and returns to global configuration mode.

Step 6

network-clock select priority interface TenGigabitEthernet slot/port

 

Router(config)# network-clock select 1 interface TenGigabitEthernet 1/1

Names a source to provide timing for the network clock and specifies the selection priority for this clock source.

Example

The following example shows how to configure 10GE interface as the clock source.

Router# enable
Router# configure terminal
Router(config)# interface tengigabitethernet 1/1
Router(config-if)# clock source line
Router(config-if)# exit
Router(config)# network-clock select 1 interface TenGigabitEthernet 1/1
Router(config)# exit

Verifying the Clock Source

Use the show network-clocks command to verify network clocking on the route processor (RP) side.

Router# show network-clocks
Active source = Slot 1 BITS 0
Active source backplane reference line = Secondary Backplane Clock
Standby source = TenGigabitEthernet1/1
Standby source backplane reference line = Primary Backplane Clock
(Standby source not driving backplane clock currently)
 
 
All Network Clock Configuration
---------------------------------
Priority Clock Source State Reason
1 POS3/0/1 Hardware not present
2 Slot 1 BITS 0 Valid
3 TenGigabitEthernet1/1 Valid
 
Current operating mode is Revertive
 
Current OOR Switchover mode is Switchover
 
 
There are no slots disabled from participating in network clocking
 
BITS Port Configuration
-------------------------
Slot Port Signal Type/Mode Line Build-Out Select
1 0 T1 D4 DSX-1 (133 to 266 feet)
 

Use the show platform hardware network-clocks command to verify output on the line card side.

 
Router-dfc# show platform hardware network-clocks
 
Local Loop Timing:
 
Port 1: N Port 2: N Port 3: N Port 4: N
 
Backplane Bus Status and Source:
 
Primary : Disabled, Port 0 RX_DEMAP Clock
Secondary : Enabled, BITS Rx Clock
BITS : Disabled, Port 0 RX_DEMAP Clock
 
ZL30138 Configuration and Status:
 
DPLL1: Lock (2)
Mode of Operation : Automatic Normal
Selected Reference : 4
Ref0 Priority : 15 Ref1 Priority : 15
Ref2 Priority : 15 Ref3 Priority : 15
Ref4 Priority : 00 Ref5 Priority : 15
Ref6 Priority : 15 Ref7 Priority : 15
 
Reference Monitoring: Custom A frequency 25000 kHz
Ref# SCM CFM GST PFM Mode Detected
----------------------------------------------------------
0 0 0 0 0 CustA 38.88 MHz
1 1 1 1 1 CustA not detected
2 0 0 0 1 CustA 38.88 MHz
3 1 1 1 1 CustA not detected
4 0 0 0 0 Auto 1.544 MHz
5 1 1 1 1 Auto not detected
6 1 1 1 1 Auto not detected
7 0 0 0 0 Auto 8 kHz
 
BITS Configuration and Status:
 
Signal Type : T1 D4 Framing
Clock Divider : 1.544 MHz
Status : Good

Clock Source Recovery

For clock source recovery on the 76-ES+XT-2TG3CXL and 76-ES+XT-4TG3CXL, consider the following guidelines:

With BITS port as the clock source:

  • Clock state shows “Hardware not present” if the line card is removed.
  • Clock becomes “Validate but not present” if BITS Rx reports LOS, LOF, Blue Alarm (T1), or AIS (E1)
  • If there are no BITS RX alarms, the clock state is "Valid”.

With 10GE ports as the clock source:

  • Clock state shows Hardware not present if the line card is removed.
  • Clock becomes Validate but not present if the interface is down.
  • If interface goes back up, the clock state is "Valid".

For both 10GE port clock recovery and BITS port clock recovery, when the clock source is recovered, the line card will send notification to the RP. Then after a 150-second debounce period, the RP sends a control message to every participant to synchronize with the valid clock source again.

Cisco 7600 Synchronous Ethernet

Synchronous Ethernet (SyncE) defined by the ITU-T standards such as G.8261 and G.8262 leverages the PHY layer of Ethernet to transmit clock information to the remote sites. SyncE over Ethernet provides a cost-effective alternative to the 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 traceable to Primary Reference Clock (PRC).

For more information on SyncE, Synchronization Status Message (SSM),Ethernet Synchronization Messaging Channel (ESMC) and their configurations, please see: “Cisco 7600 Synchronous Ethernet Support” section.