Cisco ME 3800x and ME 3600x Switches Software Configuration Guide, Cisco IOS Release 15.4(3)S

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Updated:
June 7, 2018

Chapter: Configuring Synchronous Ethernet

Configuring Synchronous Ethernet

The ME 3800X and ME 3600X switches support Synchronous Ethernet (SyncE), which is the PHY-layer frequency-synchronization solution for IEEE 802.3 links. It is an evolution of the conventional Ethernet and Ethernet + SDH and SONET-based synchronization. SyncE is used to synchronize and send clock information to remote sites on the network. Each network element along the synchronization path must support SyncE. SyncE provides only frequency synchronization, not related to time or space.

Understanding SyncE

SyncE provides a method to synchronize the Ethernet network by having all Ethernet ports send data based on a reference clock. All devices supporting SyncE must send and receive data in cycles of fixed size and duration. The data size depends on the Ethernet speed. The rate of transmission is 8000 cycles per second. Each device must be able to support a system timing master, which is the synchronization source. A sync port is the port on which synchronization information is received. All SyncE frames coming from the sync port are the source of synchronization for all other ports on the device.

The switch 10 Gigabit Ethernet uplink ports or BITS interface support line clock recovery, sending and receiving clock information. Downlink ports do not perform clock recovery and can only send clock signals.

The switch supports TI (1544 kilobits/s) and E1 (2048 kb/s or 2048 KHz) clock timing synchronization.

Reference Clocks

A switch comes up in a free-run state, using the internal oscillator (Stratum 3) for synchronization. If there is a valid clock reference with a set priority, the switch locks to that reference. If there is no reliable clock source available, the switch remains in free-run mode. If the current clock becomes invalid, the switch goes into holdover mode and replays the saved clock from the last source. The switch SyncE LEDs show the status of the internal clock: locked (green), free run (off), or in a holdover state (amber).

The reference clock source can be:

  • A Building Integrated Timing Supply (BITS) clock input
  • A PHY-recovered clock from uplink ports. The ME 3800X and 3600X switch supports a PHY-recovered clock only from the small form-factor pluggable (SFP+) uplink ports with 10 Gigabit SFP+ or 1000BASE-X fiber SFP modules.

All uplink and downlink ports transmit data on the same reference clock.

The switch monitors each input clock for frequency accuracy and activity. An input clock with a frequency out-of-band alarm or an activity alarm is invalid. Invalid clocks are not selected as the reference clock.

During normal operation, the reference clock is selected based on an algorithm that uses the priority rankings that you assign to the input clocks by using the network-clock input-source priority global configuration command. Priority 1 is the highest, and priority 15 is the lowest. If you try to assign the same priority to more than one clock, error message appears. Unused input clocks are given a priority value of 0, which disables the clocks and makes them unavailable for selection. The clock selection is based on signal failure, priority, and manual configuration. If you have not manually configured a reference clock, the algorithm selects the clock with the highest priority that does not experience signal failure.

With this configuration, pure priority-based mode, an intermittent failure or changes in the network topology can cause timing loops or a loss of connectivity with the clock reference. The Ethernet Synchronous Messaging Channel (ESMC) with Synchronization Status Messages (SSM) provides a way to implement quality in synchronous networks.

Reference clocks operate in revertive or nonrevertive mode, configured by using the network-clock revertive global configuration command. The reverence clocks will be in non-revertive mode by default.

  • In revertive mode, if an input clock with a higher priority than the selected reference becomes available, the higher priority reference is immediately selected.
  • In nonrevertive mode, if a new input clock with a higher priority becomes available, the higher-priority clock is selected. This means, among all available input reference clocks, the higher-priority clock is selected.
  • In non revertive mode, when an input clock with a high priority present on the system becomes invalid or unavailable, a lower priority clock will be selected. However when the higher priority clock becomes available again it will not be selected.

Note In revertive mode of operation, when the lost high priority reference becomes available again, it is selected. However, in non-revertive mode of operation, the regained high priority reference is not selected.

You can use the network-clock switch privileged EXEC command to configure the input reference to be either forced or automatically selected by the selection algorithm based on the highest priority valid input clock. In revertive mode, the forced clock automatically becomes the selected reference. In nonrevertive mode, the forced clock becomes the selected reference only when the existing reference is invalidated or unavailable.

BITS Interface

The ME 3800X and ME 3600X switch supports a BITS interface through an RJ-45 connector. The connection can be used for sending and receiving T1 and E1 timing signals.

You can configure all Ethernet ports to send data referenced to the BITS recovered clock. The BITS signal is used as long as it does not have these faults:

  • loss of signal
  • out of frame
  • alarm-indication signal
  • remote alarm indication

The switch supports BITS IN and BITS OUT, and recovers and sends BITS timing, T1, E1. The switch does not support T1 or E1 data transmission. You can configure the BITS interface input and output, including line coding and line buildout (output). You can also shut down the BITS controller.

The switch supports these BITS configurations:

  • E1 Mode:

– 2048 KHz

– Framing mode: FAS, MFAS, FASCRC4, MFASCRC4 with line coding: AMI, HDB3

  • T1 Mode:

– Framing mode: D4 and ESF

– Line coding: AMI, B8ZS

– Line buildout (output): 0 to 133 feet, 133 to 266 feet, 266 to 399 feet, 399 to 533 feet, or 533 to 655 feet

Synchronous Ethernet and Ethernet Synchronization Messaging Channel

The ME3600/ME3800 switches support the following Synchronous Ethernet (SyncE) and Ethernet Synchronization Messaging Channel (ESMC) features:

  • Common IOS CLI configuration
  • Configuration on all ports, including BITS ports and copper ports
  • Can be enabled or disabled on individual ports
  • Synchronous Ethernet clock derived from user configuration
  • Synchronous Status Message (SSM) on BITS interface
  • Ethernet Synchronous Messaging Channel (ESMC) on all Ethernet ports

Note Cisco ME3600X-24CX switch does not support SSM.

Clock selection is configured by the user based on clock priority and ESMC/SSM messages received from all sources and ports.

A Synchronous Status Message (SSM) informs the peer about the quality of the local clock source and is used to detect and avoid timing loops. SSMs are transported over the Ethernet Synchronization Messaging Channel (ESMC). All SSM information transported over Ethernet ports must be in the ESMC message format (G.8264).

The BITS port can be configured as a T1 or E1 interface.

  • For T1s, SSM messages are transported over the 4 Kbps datalink channel.
  • For E1s, SSM messages are transported over the E1 signaling channel.

Configuration

To configure synchronous ethernet

1. Replace existing syncE configurations with the new configurations given in the “Configuring Synchronous Ethernet” section.

2. Copy the changed configuration to startup-config

3. Reload the switch with the image.

Restrictions

T1 mode supports only D4 and ESF framing.

Configuring Synchronous Ethernet

The following sections show the old and new methods of configuring synchronous ethernet on the ME3600/ME3800 and ME3600X-24CX switches:

Configuring Input Clock and Priority

Old Configuration

Switch(config)# network-clock_select 2 ?
BITS BITS port clock
SYNCE Sync Ethernet
 
Switch(config)# network-clock_select 2 SYNCE ?
<0-1> port

New Configuration

Switch(config)# network-clock input-source ?
<1-250> Priority
Switch(config)# network-clock input-source 1 ?
external External Interface (BITS/SSU/GPS)
interface Specify Ethernet, Sonet or ToP Interface

SynchE as Clock Source Example Configuration

Switch(config)# network-clock input-source 1 interface tenGigabitEthernet ?
<0-0> TenGigabitEthernet interface number

BITS as Clock Source Example Configuration

Switch(config)# network-clock input-source 1 external 1/0/0 e1 ?
cas E1 Channel Associated Signal Mode
crc4 E1 With CRC4 Signal Mode
fas E1 Frame Alignment Signal Mode

Note Currently, the E1 and T1 modes cannot be configured independently.

The default values for the E1 mode are as follows:

  • Framing: FAS
  • Line coding: AMI

The default values for the T1 mode are as follows:

  • Framing: D4
  • Line coding: AMI
  • Line build out: 0-133ft

Configuring Hold-off timer

Old Configuration

Switch(config)# network-clock_select hold-off-timeout ?
<50-10000> holdoff-val in ms, default 300 ms

New Configuration

Switch(config)# network-clock hold-off ?
0 holdoff disable
<50-10000> msec (default 300 msecs)

Configuring Hold-over Timer

Old Configuration

Switch(config)# network-clock_select hold-timeout ?
<0-86400> hold-timeout-val
infinite Infinite hold-over.

New Configuration

CLI is not available.

Configuring Wait-to-Restore Timer

Old Configuration

Switch(config)# network-clock_select wait-to-restore-timeout ?
<0-720> wtr-val in seconds, default 300 seconds

New Configuration

Switch(config)# network-clock wait-to-restore ?
<0-86400> sec (default 300 seconds)

Configuring Revertive Mode

Old Configuration

Switch(config)# network-clock_select mode ?
nonrevert Specify non revertive mode.
revert Specify revertive mode.

New Configuration

Switch(config)# network-clock revertive
Switch(config)# no network-clock revertive

Configuring EEC Option

Old Configuration

Switch(config)# network-clock_select option ?
option1 EEC Option 1.
option2 EEC Option 2.

New Configuration

Switch(config)# network-clock synchronization ssm option ?
1 Synchronization networking Option I
2 Synchronization networking Option II
Switch(config)# network-clock synchronization ssm option 2 ?
GEN1 Option II Generation 1
GEN2 Option II Generation 2
 

Configuring BITS

New Configuration

Switch(config)# network-clock input-source 1 external 1/0/0 e1 ?
cas E1 Channel Associated Signal Mode
crc4 E1 With CRC4 Signal Mode
fas E1 Frame Alignment Signal Mode
 

Old Configuration

Switch(config)# controller BITS ?
 
input Configure BITS INPUT
output Configure BITS OUTPUT
shutdown Shut down BITS controller
 

Configuring BITS Input

New Configuration

Switch(config)# network-clock input-source 1 external 1/0/0 e1 ?
cas E1 Channel Associated Signal Mode
crc4 E1 With CRC4 Signal Mode
fas E1 Frame Alignment Signal Mode
 

Old Configuration

controller BITS input applique ?
E1 Link type E1
T1 Link type T1
 
Switch(config)# controller BITS input applique E1 ?
2048KHz 2048 KHz clock interface
framing BITS framing options for E1
 
Switch(config)# controller BITS input applique E1 framing ?
fas_crc4 FASCRC4
fas_nocrc FAS
mfas_crc4 MFASCRC4
mfas_nocrc MFAS
 
 
Switch(config)# controller BITS input applique E1 framing fas_crc4 linecode ?
ami AMI encoding
hdb3 HDB3 encoding
 

Configuring BITS Output

New Configuration

Router(config)# network-clock output-source system 1 external 1/0/0 e1 ?
cas E1 Channel Associated Signal Mode
crc4 E1 With CRC4 Signal Mode
fas E1 Frame Alignment Signal Mode

Old Configuration

Switch(config)# controller BITS output applique ?
E1 Link type E1
T1 Link type T1
 
Switch(config)# controller BITS output applique T1 framing ?
d4 D4
esf Extended Superframe
 
Switch(config)# controller BITS output applique T1 framing d4 linecode ?
ami AMI encoding
b8zs B8ZS encoding
 
 
Switch(config)# $ controller BITS output applique T1 framing d4 linecode ami line-build-out ?
 
0-133ft 0 ft to 133 ft
133-266ft 133 ft to 266 ft
266-399ft 266 ft to 399 ft
399-533ft 399 ft to 533 ft
533-655ft 533 ft to 655 ft
 

The controller BITS CLIs should be used to configure shutdown, linecode and line-build-out as these options are missing in netsync PI infrastructure CLIs. Once the netsync infrastructure CLIs implement these configuration options, the platform "controller BITS" CLIs will be deprecated.

Configuring Output Clock

Old Configuration

Switch(config)# network-clock_select output ?
<1-23> priority
output Configure BITS OUT (T4 = T0)
 
Switch(config)# network-clock_select output 2 SYNCE ?
<0-1> port
 

New Configuration

Switch(config)# network-clock output-source ?
line Line Input
system System clock (T0)
 

Tengig Clock for BITS OUT Example Configuration

Switch(config)# network-clock output-source line ?
<1-250> Priority
Switch(config)# $ network-clock output-source line 10 interface tenGigabitEthernet ?
<0-0> TenGigabitEthernet interface number
 

System Clock for BITS OUT Example Configuration

Switch(config)# network-clock output-source system ?
<1-250> Priority
Switch(config)# network-clock output-source system 10 external 1/0/0 ?
t1 T1 signal mode output

SyncE Show Commands

The following example shows how to display the SyncE network-clock information:

Switch# show network-clock synchronization ?
 
detail Detail
external External Interface (BITS/SSU/GPS)
global Display global parameters
interface Specify Ethernet or Sonet Interface
runtime Runtime Information
| Output modifiers
 
Switch# show network-clock synchronization detail
 

SyncE Debug Commands

The following example shows the network-clock (PI) debug command:

RB#debug network-clock ?
error Network clock error debugging
event Network clock event debugging
pal Network clock PAL debugging
platform Network clock platform debugging
sm Network clock state machine debugging
 

Configuring SyncE

SyncE limitations on copper ports:

Default SyncE Configuration

Synchronous Ethernet can only be configured on 10 Gigabit Ethernet interfaces.

1 Gigabit Ethernet interfaces transmit SyncE with no configuration required. No configuration is needed to send clock timing in uplink or downlink interfaces.

Configuring the Network Clock Selection

Beginning in privileged EXEC mode, follow these steps to configure the SyncE network clock.

 

Command
Purpose

Step 1

configure terminal

Enter global configuration mode.

Step 2

network-clock input-source priority [ external ] [ interface ]

Configure the input clock and its priority.

  • For priority, the range is from 1 to 15, with 1 being the highest priority and 15 the lowest. Unused input clocks are given a priority value of 0.
  • external —Select the external interface (BITS/SSU/GPS).
  • interface —Select the type of interface, Ethernet, Sonet or ToP.

Step 3

network-clock output-source system priority external

Configure the 10 Gigabit Ethernet ports for SYNC output:

  • For priority, the range is from 1 to 15, with 1 being the highest priority and 15 the lowest.
  • external —Select the external interface (BITS/SSU/GPS).

Step 4

network-clock revertive

(Optional) Configure the reference switching mode to determine the action to be taken if an input clock with a higher priority than the selected reference becomes valid.

  • revertive —The higher priority reference is immediately selected as the reference clock.

Step 5

end

Return to privileged EXEC mode.

Step 6

show network-clocks

Verify the configuration.

Step 7

copy running-config startup config

(Optional) Save your entries in the switch startup configuration file.

Enter the no network-clock priority or network-clock output-source to remove the selected priority. Enter the no network-clock revertive to select the other mode.

This example configures the BITS clock with a priority of 2 and the SyncE input port as 10 Gigabit Ethernet port 0/1 with the switching mode as nonrevertive.

Switch (config)# network-clock input-source 2 external 1/0/0 e1
Switch (config)# network-clock input-source 1 interface tenGigabitEthernet
Switch (config)# network-clock revertive
Switch (config)# end

Selecting the Network Clock

You can force selection of a particular network clock or select automatic clock selection where the switch uses the selection algorithm based on the priority and the validity of the input.

Beginning in privileged EXEC mode, use this step to set the SyncE network clock.

 

Command
Purpose

Step 1

network-clock { clear | set | switch }

Select one of these options:

  • clear —Use to clear network clock synchronization
  • set —Set network clock synchronization
  • switch —Switch selected synchronization source.

If the switch is in nonrevertive mode, the clock input does not change unless the current clock becomes invalid.

Step 2

show network-clocks

Verify the configuration.

Step 3

copy running-config startup config

(Optional) Save your entries in the switch startup configuration file.

Configuring Synce using ESMC and SSM

To enable ESMC process use the following steps:

 

Command
Purpose

Step 1

enable

Enter privileged EXEC mode.

Step 2

configure terminal

Enter global configuration mode.

Step 3

esmc process

Enables ESMC process.

Note Cisco ME3600X-24CX switch does not support SSM.

To configure the interface to send or receive a particular clock use the following steps:

 

Command
Purpose

Step 1

enable

Enter privileged EXEC mode.

Step 2

configure terminal

Enter global configuration mode.

Step 3

interface interface-id

Enter the interface ID, and enter interface configuration mode.

Step 4

network-clock source quality-level value { tx | rx }

Provides the forced QL value to the local clock selection process.

To configure BITS port to send or receive a particular-clock use the following steps:

 

Command
Purpose

Step 1

enable

Enter privileged EXEC mode.

Step 2

configure terminal

Enter global configuration mode.

Step 3

network-clock quality-level { tx | rx } value external port/slot

Forces the QL value for the line or external timing input and output

Monitoring SyncE

Use these privileged EXEC commands to view SyncE configuration on a switch:

  • show controller BITS
Switch# show controller BITS
 
Applique type is T1
Line Coding is B8ZS(Rx), B8ZS(Tx)
Framing is ESF(Rx), ESF(Tx)
Line Build Out is 0-133ft
No alarms detected.
 
  • show network-clock synchronization
Switch# 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 : TenGigabitEthernet0/2
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
Squelch Threshold: QL-ST3
sm(netsync NETCLK_QL_ENABLE), running yes, state 1A
Last transition recorded: (ql_mode_enable)-> 1A (begin)-> 1A (src_added)-> 1A (src_added)-> 1A (ql_change)-> 1A (ql_change)-> 1A (set_lo)-> 1A (clear_lo)-> 1A
 
Nominated Interfaces
 
Interface SigType Mode/QL Prio QL_IN ESMC Tx ESMC Rx
Internal NA NA/Dis 251 QL-ST3 NA NA
Te0/1 NA Sync/En 1 QL-FAILED - -
*Te0/2 NA Sync/En 2 QL-PRS - -
 
T4 Out
 
External Interface SigType Input Prio Squelch AIS
External 1/0/0 T1 ESF Internal 2 FALSE FALSE
 
Interface:
---------------------------------------------
Local Interface: Internal
Signal Type: NA
Mode: NA(Ql-enabled)
SSM Tx: DISABLED
SSM Rx: DISABLED
Priority: 251
QL Receive: QL-ST3
QL Receive Configured: -
QL Receive Overrided: -
QL Transmit: -
QL Transmit Configured: -
Hold-off: 0
Wait-to-restore: 300
Lock Out: FALSE
Signal Fail: FALSE
Alarms: FALSE
Slot Disabled: FALSE
SNMP input source index: 1
SNMP parent list index: 0
 
Local Interface: Te0/1
Signal Type: NA
Mode: Synchronous(Ql-enabled)
ESMC Tx: ENABLED
ESMC Rx: ENABLED
Priority: 1
QL Receive: QL-DUS
QL Receive Configured: -
QL Receive Overrided: QL-FAILED
QL Transmit: -
QL Transmit Configured: -
Hold-off: 300
Wait-to-restore: 300
Lock Out: FALSE
Signal Fail: TRUE
Alarms: FALSE
Slot Disabled: FALSE
SNMP input source index: 2
SNMP parent list index: 0
 
Local Interface: Te0/2
Signal Type: NA
Mode: Synchronous(Ql-enabled)
ESMC Tx: ENABLED
ESMC Rx: ENABLED
Priority: 2
QL Receive: QL-PRS
QL Receive Configured: -
QL Receive Overrided: -
QL Transmit: QL-DUS
QL Transmit Configured: -
Hold-off: 300
Wait-to-restore: 20
Lock Out: FALSE
Signal Fail: FALSE
Alarms: FALSE
Slot Disabled: FALSE
SNMP input source index: 3
SNMP parent list index: 0
 
External 1/0/0 t1 esf's Input:
Internal
Local Interface: Internal
Signal Type: NA
Mode: NA(Ql-enabled)
SSM Tx: DISABLED
SSM Rx: DISABLED
Priority: 2
QL Receive: QL-ST3
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
SNMP input source index: 1
SNMP parent list index: 1
 
  • show esmc
Switch# show esmc
 
Interface: GigabitEthernet0/0/0
Administrative configurations:
Mode: Synchronous
ESMC TX: Enable
ESMC RX : Enable
QL RX configured : NA
QL TX configured : NA
Operational status:
Port status: UP
QL Receive: QL-SSU-B
ESMC Information rate : 1 packet/second
ESMC Expiry: 5 second

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