Use this procedure to configure timing for the VLNC60/61/62 providing ML-PPP service.

The system-timing-source {bits | ptp-1588 | free-running | ge | backplane} command is used to specify a common timing source for all the devices on the VLNC60/61/62 where:

• bits — Building Integrated Timing Supply. This is a timing supply traceable to a common Primary Reference Clock in the network. The shelf has a special T1/E1 input interface associated with each main slot for receiving this timing.

• ptp-1588 — Precision Timing Protocol-1588. This option specifies IEEE 1588 version 2 as a choice to drive the system timing. This is useful for remote locations where no high-quality reference clock signal is available.

  The IEEE 1588 protocol distributes time and frequency via Ethernet with expected end-point time-alignment time precision measured in nanoseconds. The protocol is designed to synchronize real-time clocks on the nodes of a distributed system that communicate using a network. The protocol uses a master/slave relationship to distribute timestamps from one device to the others.

• free-running — This option specifies that the System clock is in free-running mode. This option is recommended to be used only on the VLNC60/61/62. The clock is derived from a local SONET Stratum3 or SDH Type III (±4.6 ppm) oscillator in the VLNC60/61/62.

  This option is recommended to be used only when all T1/E1 interfaces offer MLPPP service. By default, VLNC60/61/62 circuit packs have their System Timing source set as Free Running.

• ge — This option specifies that the System clock is derived from SFP based GE (Ethernet interface). This is also known as the SyncE Line timing.

• backplane — This option specifies that the System clock is derived from the backplane 25 Mhz reference. In this mode timing is derived from the adjacent circuit pack. This is also known as the Backplane timing.

The timing-source {system | loop | differential} command specifies the timing source for the T1/E1 interfaces, where:

• system — The source of timing is derived from system timing configured using the system-timing-source command.

• loop — The clocking information recovered from the received signal of the T1/E1 interface is used to drive the transmit side of the same T1/E1 interface.

• differential — The clock is recovered from the real time protocol (RTP) differential timestamps on the incoming Pseudowire packet for the T1/E1. The reference timing for recovery of this clock is System.

Refer to the Alcatel-Lucent 1850 Transport Service Switch (TSS-5) Command Line Interface Guide, for help on using CLI commands.

Refer to Figure 18-2, Sample timing configurations for ML-PPP on VLNC60/61/62 for an example.