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.

Important!

Because the initial timing mode is External, the network element enters the holdover mode if no timing input reference signals are available at turnup.

If the timing input reference signals are applied but the timing input reference signal format is improperly provisioned, the network element enters the holdover mode and an inc. sync. ref. LOF alarm is reported.

System synchronization characteristic

When the Main slots are equipped with Very Large Fabric (VLF) circuit packs, the network element supports provisionable SONET or SDH system synchronization. When the System Synchronization Characteristic parameter is provisioned to SONET, DS1 timing references, SONET sync status messages, and SONET synchronization characteristics apply. When the System Synchronization Characteristic parameter is provisioned to SDH, E1 timing references, SDH sync status messages, and SDH synchronization characteristics apply as specified in ITU-T GR.813 Option 1. When the Main slots are equipped with non-VLF circuit packs, the network element supports SONET system synchronization only.

The System Synchronization Characteristic parameter is generally provisioned when the system is integrated into a network and should not be changed unless you are reconfiguring the network and have been instructed to do so. If the System Synchronization Characteristic parameter of an in-service system is changed, circuit pack failures and service interruptions may occur.

Since there are different parameters and values associated with SONET and SDH synchronization, the provisioned values associated with the external timing references and the synchronization status messages revert to the appropriate defaults when the System Synchronization Characteristic parameter is changed.

Important!

If the External timing mode is provisioned and the System Synchronization Characteristic is changed, the expected timing input reference signal, if previously valid, would no longer match the expected characteristics and a timing input reference signal failure is declared.

If the External or Line timing mode is provisioned with timing output reference signals and the System Synchronization Characteristic is changed, the network elements that use timing output reference signal would declare a timing input reference signal failure.

Since the interpretation of the synchronization status message S1 byte is different for SONET and SDH, the changed interpretation of the incoming synchronization status messages and the changed outgoing synchronization status messages also cause alarms/conditions to be reported at the local network element and at the connected network elements.

Beginning in Release 9.1, the initial default state of the DS1 external timing source is in-service (IS). Now, if the external timing source is invalid or missing, the system declares two alarms, inc. DS1 sync. ref. LOS and holdover mode active . Prior to 9.1, the default state of the timing source was AUTO and the external timing source was not alarmed.

Timing modes

Alcatel-Lucent 1665 DMXtend 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 Stratum 3 Traceable (ST3) clock.

• External: In the External timing mode, the network element derives timing from one of the two timing input reference signals.

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

Timing output signals

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

When the Main slots are equipped with VLF circuit packs, DS1 or E1 timing output reference signals are supported. When the System Synchronization Characteristic parameter is provisioned to SONET, DS1 timing references are supported. When the System Synchronization Characteristic parameter is provisioned to SDH, E1 timing references are supported.

When the Main slots are equipped with non-VLF circuit packs, only DS1 timing output reference signals are supported.

Clock mode switching

Revertive or nonrevertive clock mode switching is supported in the External or 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 External or Line timing mode. Synchronization Autoreconfiguration must be enabled when the network element is provisioned to 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 to Revertive-1, the circuit pack/port in Main/Function/Growth slot 1 (Line) or Ref-1 (External) is designated primary.

If the Reference Switching parameter is provisioned to Revertive-2, circuit pack/port in Main/Function/Growth slot 2 (Line) or Ref-2 (External) is designated primary.

If the Reference Switching parameter is provisioned to 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 1665 Data Multiplexer Extend (DMXtend) Alarm Messages and Trouble Clearing Guide, 365-372-326.

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.

Synchronization autoreconfiguration

Synchronization autoreconfiguration is supported on OC-n line references and external timing input/output references.

Synchronization autoreconfiguration on OC-n line references is supported when Sync messaging is enabled on the OC-n ports provisioned as optical synchronization sources. Sync messaging must be enabled on the OC-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 on OC-n line references, 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.

When Synchronization Status Message (SSM) support is enabled on external timing input/output references, the system automatically reconfigures between the two companion timing reference input and output signals when the active signal fails or a higher quality Sync Status Message is available on the other signal. The switch is revertive or nonrevertive depending on the provisioned value of the Reference Switching parameter.

Synchronization Status Messages on DS1 external references are only supported when the ESF frame format is provisioned. Synchronization Status Messages on E1 external references are only supported when the CRC4 frame format is provisioned.

When the Main slots are equipped with VLF circuit packs, SONET or SDH synchronization status messages and quality levels are supported. When the System Synchronization Characteristic parameter is provisioned to SONET, SONET synchronization status messages and quality levels are supported. When the System Synchronization Characteristic parameter is provisioned to SDH, SDH synchronization status messages and quality levels are supported.

When the Main slots are equipped with non-VLF circuit packs, only SONET synchronization status messages and quality levels are supported.

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.

You must login 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.