When configuring the routing platform, you can configure the transmit clock on each interface; the transmit clock aligns each outgoing packet transmitted over the routing platform’s interfaces. For both the routing platform and interfaces, the clock source can be the routing platform’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 routing platform’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:
- [edit interfaces interface-name]
-
clocking (internal | external);
Figure 5 illustrates the different clock sources.
Figure 5: Clock Sources
The M-series 320 routing platform supports 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. 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.
To configure external synchronization on the M-series 320 router, include the synchronization statement at the [edit chassis] hierarchy level.
For more information about the external synchronization interface, see the JUNOS System Basics Configuration Guide.
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