Technical Documentation

Configuring the JUNOS Software to Support an External Clock Synchronization Interface for M Series and T Series Routers

The M320, M40e, M120, T320, T640, and T1600 routers support an external synchronization interface that can be configured to synchronize the internal Stratum 3 clock to an external source, and then synchronize the chassis interface clock to that source.

This feature can be configured for external primary and secondary interfaces that use Building Integrated Timing System (BITS), SDH Equipment Timing Source (SETS) timing sources, or an equivalent quality timing source. When internal timing is set for SONET/SDH, Plesiochronous Digital Hierarchy (PDH), or digital hierarchy (DS-1) interfaces on the Physical Interface Cards (PICs), the transmit clock of the interface is synchronized to BITS/SETS timing and is traceable to timing within the network.

Routers that support an external clock synchronization interface include:

  • M320, M40e, and M120 routers
  • T320, T640, and T1600 routers

To configure external synchronization on the router, include the synchronization statement at the [edit chassis] hierarchy level:

[edit chassis]synchronization {signal-type (t1 | e1);switching-mode (revertive | non-revertive);y-cable-line-termination;transmitter-enable;validation-interval seconds;primary (external-a | external-b);secondary (external-a | external-b);}

Use the synchronization statement options to specify a primary and secondary timing source. To do this, configure the following options:

  • For the M320 router, specify a signal type mode for interfaces, either t1 or e1. For the M40e router, only the t1 signal type mode is supported. The default setting is t1.
  • For the T320, T640, and T1600 routers, external clock interfaces are supported on the Sonic Clock Generators (SCG).
  • Specify the switching mode as revertive if a lower-priority synchronization can be switched to a valid, higher-priority synchronization.
  • For the M320 router, specify that a single signal should be wired to both Control Boards (CBs) using a Y-cable. For the M40e router, the signal is wired to the CIP and Y-cable functionality is embedded in this system.

    The y-cable-line-termination option is not available on the M40e, M120, and T Series routers.

  • Control whether the diagnostic timing signal is transmitted.

    The transmitter-enable option is not available on the M120 and T Series routers.

  • Set a validation interval. The validation-interval option validates the synchronized deviation of the synchronization source. If revertive switching is enabled and a higher-priority clock is validated, the clock module is directed to the higher-priority clock, and all configured and active synchronizations are validated. The validation timer resumes after the current validation interval expires. The validation interval can be a value from 90 through 86400 seconds. The default value is 90 seconds. For the M120 router, the range for the validation-interval option is 30 through 86400 and the default value is 30.
  • Specify the primary external timing source using the primary (external-a | external-b) statement.
  • Specify the secondary external timing source using the secondary (external-a | external-b) statement.

Published: 2010-04-26