Help us improve your experience.

Let us know what you think.

Do you have time for a two-minute survey?

 
ON THIS PAGE
 

Interface and Router Clock Sources

For both the router and interfaces, the clock source can be the router’s internal Stratum 3 clock, which resides on the control board, or an external clock that is received from the interface configured.

Interface and Router Clock Sources Overview

When configuring the router, you can configure the transmit clock on each interface; the transmit clock aligns each outgoing packet transmitted over the router’s interfaces. For both the router and interfaces, the clock source can be the router’s internal Stratum 3 clock, which resides on the control board, or an external clock that is received from the interface you are configuring. For example, interface A can transmit on interface A’s received clock (external, loop timing) or the Stratum 3 clock (internal, line timing). Interface A cannot use a clock from any other source.

By default, each interface uses the router’s internal Stratum 3 clock. To configure the clock source of each interface, include the clocking statement at the [edit interfaces interface-name] hierarchy level:

System reference clocks can be generated from different system components, depending on the router type. For example, Figure 1 illustrates the different clock sources on the M120 router.

Figure 1: M120 Router Clock Sources M120 Router Clock Sources

Configure an External Clock Synchronization Interface

The M40e, M120, M320, 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 the external source.

This feature can be configured for external primary and secondary interfaces that use Building Integrated Timing System (BITS) or 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), and digital hierarchy (DS1) interfaces on the Physical Interface Cards (PICs), the transmit clock of the interface is synchronized to BITS/SETS timing and traceable to timing within the network.

Routers and switches that support an external clock synchronization interface include:

  • M40e, M120, and M320 routers

  • T640 and T1600 routers

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

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

  • For the M120 and M320 routers, specify a signal type mode for interfaces, either t1 or e1. For the M40e, T640, and T1600 routers, only the t1 signal type mode is supported. The default setting is t1.

  • For the T640 and T1600 routers, external clock interfaces are supported on the SONET Clock Generators (SCG-T-EC). The external clock interfaces on the SONET Clock Generators (SCG-T) are not supported.

  • 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, T640, and T1600 routers.

  • Control whether the diagnostic timing signal is transmitted.

    The transmitter-enable option is not available on the M120, T640, and T1600 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 86,400 seconds. The default value is 90 seconds. For the M120 router, the range for the validation-interval option is 30 through 86,400 and the default value is 30.

  • Specify the primary external timing source by using the primary (external-a | external-b) statement.

  • Specify the secondary external timing source by using the secondary (external-a | external-b) statement.