Use this procedure to provision the network element synchronization functions.

To configure a network for the flow of valid timing signals between network elements under normal and failure conditions requires a well thought out synchronization plan. This procedure assumes such a synchronization plan exists and describes how to configure a network element accordingly.

Timing modes

Alcatel-Lucent 1850 TSS-5 supports the following provisionable timing modes to synchronize all synchronous outgoing signals:

• Free Running: In the Free Running timing mode, the network element derives timing from the internal SONET minimum clock (SMC) or an SDH Equipment Clock (SEC).

• Line: In the Line timing mode, the network element derives timing from one incoming OC-n/STM-n line.

• Line with Output Timing: In the Line timing mode, the network element derives timing from one incoming OC-n/STM-n line and distributes DS1 or E1 timing output reference signals.

• Backplane: Backplane timing mode supports SyncE. Beginning in Release 7.2.2, the VLNC55 can derive timing from the backplane (when the adjacent pack is a VLNC42B). SyncE timing is passed from the VLNC42B to the VLNC55. Timing recovered from the backplane is used to time all SyncE outgoing GE/FE signals on the VLNC42B. Timing recovered from the backplane is also used to time the SONET/SDH and GbE interfaces on the VLNC55.

Timing output signals

Timing output reference signals to external equipment are supported when the network element is provisioned for the Line timing mode. In the Line timing modes, Output Timing can be Enabled or Disabled. Timing output reference signals are not supported in the Free Running timing mode. The timing output reference signals are derived from the provisioned OC-n/STM-n line timing source.

The Alcatel-Lucent 1850 TSS-5 supports DS1 or E1 timing output reference signals. When the system interface standard parameter is provisioned to SONET, DS1 timing references are supported. When the system interface standard parameter is provisioned to SDH, E1 timing references are supported. Refer to Procedure 6-2: Provision system parameters to provision the interface standard parameter.

When the system interface standard parameter is provisioned to SDH, the External synchronization output - source and Wait-to-Restore parameters are provisionable. The external synchronization output, if enabled, may be derived from the line timing reference or the system clock. The Wait-to-Restore interval specifies the time (in minutes) that the reference must remain good before being considered as an available timing reference.

Clock mode switching

Revertive or nonrevertive clock mode switching is supported in the Line timing mode. When revertive clock mode switching is provisioned, the network element automatically exits holdover mode (reverts) when the fault condition clears. When nonrevertive clock mode switching is provisioned, the network element remains in holdover.

Reference switching

Revertive or nonrevertive reference switching is supported in the Line timing mode. Synchronization Autoreconfiguration must be enabled when the network element is provisioned for the Line timing mode. Reference switching is not supported when Synchronization Autoreconfiguration is disabled and the timing mode is Line timing.

The Reference Switching parameter determines whether or not the system reverts to the provisioned primary reference (Revertive-1 or Revertive-2) when the fault condition clears.

If the Reference Switching parameter is provisioned Revertive-1, the main-1-1 port (equipment unprotected) or the circuit pack/port in the Main 1 slot (equipment protected) is designated primary .

If the Reference Switching parameter is provisioned Revertive-2, the main-1-2 port (equipment unprotected) or the circuit pack/port in the Main 2 slot (equipment protected) is designated primary .

If the Reference Switching parameter is provisioned Nonrevertive, the network element does not revert to the original active reference when the fault condition clears.

When a manual revertive reference switch is performed, the system reports a manual reference switch standing condition indicating a revertive reference switch is active. A manual reference switch reset must be performed to switch back to the designated primary reference and clear the manual reference switch standing condition. Refer to the Alcatel-Lucent 1850 Transport Service Switch (TSS-5) Maintenance and Trouble-Clearing Guide.

When a manual nonrevertive reference switch is performed, the system does not report any standing conditions or alarms since both references are designated for service.

Optical synchronization source

Optical Synchronization Source is supported in the Line timing mode only. In the Line timing mode, this is the optical line from which system timing is initially derived. If Synchronization Autoreconfiguration is disabled, this is the only line from which timing is derived.

Synchronization autoreconfiguration

Synchronization autoreconfiguration is supported in the Line timing mode when Sync messaging is enabled on the OC-n/STM-n ports. Sync messaging must be enabled on the OC-n/STM-n ports prior to enabling Synchronization Autoreconfiguration. It is recommended that Synchronization Autoreconfiguration be enabled to provide the most reliable network synchronization.

When Synchronization Autoreconfiguration is enabled, the system automatically reconfigures between line timing sources when the active timing source fails or a higher quality Sync Status Message is available on the other source. The switch is revertive or nonrevertive depending on the provisioned value of the Reference Switching parameter.

The Alcatel-Lucent 1850 TSS-5 supports SONET and SDH synchronization status messages and quality levels. When the system interface standard parameter is provisioned to SONET, SONET synchronization status messages and quality levels are supported. When the system interface standard parameter is provisioned to SDH, SDH synchronization status messages and quality levels are supported. Refer to Procedure 6-2: Provision system parameters to provision the interface standard parameter.

If Synchronization Autoreconfiguration is disabled, the system enters into holdover when the active timing source fails or the Sync Status Message quality level falls below the provisioned level.

Synchronous Ethernet

NOTICE Service-disruption hazard

When synchronous Ethernet is enabled, traffic interruptions may occur at the far-end port if flow control is enabled.

When synchronous Ethernet is enabled, it is recommended that flow control be disabled at the far-end port.

Synchronous Ethernet is supported by the faceplate and backplane Gigabit Ethernet ports of the VLNC52/55 SONET/SDH Transport circuit pack. When Synchronous Ethernet support is enabled, the Gigabit Ethernet transmit interface is synchronized to the system clock and generates Ethernet Synchronization Messaging (ESSM) to transport the timing quality.

Synchronization Status Messaging provides a mechanism for downstream Ethernet switches to determine the traceability of the synchronization distribution scheme back to the primary reference clock (PRC) or highest quality clock that is available.

Beginning in Release 7.2.2, the VLNC55 can derive timing from the backplane (when the adjacent pack is a VLNC42B). SyncE timing is passed from the VLNC42B to the VLNC55. Timing recovered from the backplane is used to time all SyncE outgoing GE/FE signals on the VLNC42B. Timing recovered from the backplane is also used to time the SONET/SDH and GbE interfaces on the VLNC55.

You must log in as a Privileged user to complete this procedure.

Prior to performing this procedure:

1. Refer to Before you begin and Required equipment in this chapter.

2. Obtain the work instructions for this procedure and ensure that a synchronization plan exists for the system.