Overview Of Configuring Out-Of-Band Clocking Between Two Cem Spas - Cisco ASR 1000 Series Software Configuration Manual

Configuring Out-of-Band Clocking
• A CEM SPA cannot be configured as both a master and slave clock. To reconfigure a SPA's clock type,
you must first remove the existing clock configuration (master or slave).
• Pseudowires for out-of-band clocking are configured under the virtual CEM interface that represents
the recovered clock interface. This process differs from normal CEM pseudowires, which are configured
under the port (controller interface). When no network clock is available, the virtual CEM interface goes
down and the pseudowire is disabled. This process is reversed when a valid network clock becomes
available again. Normal CEM interfaces never go down, even if the associated physical link is down.
• The master clock pseudowire and slave clock pseudowire should be on different CEM SPAs.
Router Sending Clock (Master Clock)
• You must select the common telecom 19.44MHz clock as the recovered clock to use for the master
clock.
• A maximum of 64 out-of-band clock channels can be configured from the CEM SPAs that provides the
master clock signal.
• The out-of-band clock channel (pseudowire) is configured under the virtual CEM interface that represents
the SPA from which the master clock is recovered. The xconnect command used to create the clock
channel must specify the destination for the clock signal.
• The out-of-band clock stream is sent in SAToP (unframed) format.
Router Recovering Clock (Slave Clock)
• The out-of-band clock signal is always recovered in adaptive mode. The clock signal can then be used
to drive all of the ports on the CEM SPA.
• Two CEM circuits (a primary and a secondary out-of-band channel) can be configured under a slave
clock interface, one for each of two master clock signals. This way, the SPA can receive a master clock
signal from two separate sources (that is, two master clocks).
• Under the slave clock interface, the xconnect command (used to create the out-of-band clock channel)
must specify the router from which the master clock is recovered.

Overview of Configuring Out-of-band Clocking Between Two CEM SPAs

The following section provides a high-level overview of the procedure for configuring out-of-band clocking
between two CEM SPAs. Detailed steps are provided in the sections that follow.
Before you begin, determine which CEM SPAs have TDM devices connected to them. You must configure
an out-of-band clock channel to deliver the clock signal from each SPA that sends TDM data to every destination
SPA that receives the data.
1 Use the recovered clock command to identify the CEM SPA that is to send TDM data across the MPLS
network. This SPA's clock is used as the master clock for out-of-band clocking.
2 Configure the master and slave clock interfaces to represent the source (clock master) and destination
(clock slave) for the out-of-band clock signal. The master and slave clock interfaces (and pseudowires)
should be configured on different SPAs.
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