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Clock Source Overview

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

For example, interface A can transmit on interface A’s received clock (external, loop timing) or the Stratum 3 clock (internal, line timing, or normal timing). Interface A cannot use a clock from any other source. For interfaces such as SONET/SDH that can use different clock sources, you can configure the source of the transmit clock on each interface.

The clock source resides on the System Control Board (SCB) for M40 routers, the System and Switch Board (SSB) for M20 routers, the Control Board (CB) for M120 routers, and the Miscellaneous Control Subsystem (MCS) for M40e and M160 routers. M7i and M10i routers have a clock source on the Compact Forwarding Engine Board (CFEB) and Enhanced Compact Forwarding Engine Board (CFEB-E).

For T Series and MX Series, the clock source internal Stratum 3 clock resides on the SONET Clock Generator and Switch Control Board (SCB) respectively. By default, the 19.44-MHz Stratum 3 reference clock generates the clock signal for all serial PICs (SONET/SDH) and Plesiochronous Digital Hierarchy (PDH) PICs. PDH PICs include DS3, E3, T1, and E1 PICs.

Note: M7i and M10i routers do not support external clocking of SONET interfaces.

For information about clocking on channelized interfaces, see Channelized IQ and IQE Interfaces Properties. Also see Configuring the Clock Source on SONET/SDH Interfaces and Configuring the Channelized T3 Loop Timing.

For information about configuring an external synchronization interface that can be used to synchronize the internal Stratum 3 clock to an external source on the M40e, M120, M320, routers and T Series routers, see Junos OS Administration Library for Routing Devices, Configuring the Junos OS to Support an External Clock Synchronization Interface for M Series and T Series Routers.

For information about configuring Synchronous Ethernet on MX 80, MX240, MX480, and MX960 3D Universal Edge Routers, see Junos OS Administration Library for Routing Devices, Synchronous Ethernet Overview and Configuring Clock Synchronization Interface for MX Series Routers.

 

Related Documentation

 

Published: 2013-08-01

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