Note
•
Cisco NCS 5001 and NCS 5002 Routers do not support Global Positioning System (GPS).
•
Cisco NCS 5011 Router neither supports SyncE nor GPS.
Source and Selection Points
Frequency Synchronization implementation involves Sources and Selection Points.
A Source inputs frequency signals into a system or transmits them out of a system. There are two types of
sources:
•
Line interfaces: This includes SyncE interfaces.
•
Internal oscillator: This is a free-running internal oscillator chip.
Each source has a Quality Level (QL) associated with it which gives the accuracy of the clock. This QL
information is transmitted across the network using ESMC or SSMs contained in the SDH frames. This
provides information about the best available source the devices in the system can synchronize to. To define
a predefined network synchronization flow and prevent timing loops, you can assign priority values to the
sources on each router. The combination of QL information and user-assigned priority levels allow each router
to choose a source to synchronize its SyncE or SDH interfaces, as described in the ITU standard G.781.
A Selection Point is any point where a choice is made between several frequency signals and possibly one or
many of them are selected. Selection points form a graph representing the flow of timing signals between
different cards in a router running Cisco IOS XR software. For example, there can be one or many selection
points between different Synchronous Ethernet inputs available on a single line card. This information is
forwarded to a selection point on the RSP, to choose between the selected source from each card.
The output of a selection point can be used to drive the signals sent out of a set of interfaces.
Note
Restrictions
This section lists a few restrictions in configuring frequency synchronization and SyncE. They are:
•
SyncE is supported only on Cisco NCS 5001 and NCS 5002 Routers.
•
Cisco NCS 50xx Series Routers do not support GPS TOD Input/Output.
•
SyncE is supported only on the Hub-and-Spoke topology.
Configuring Frequency Synchronization
•
To enable Frequency Synchronization on the router, use
frequency synchronization
command in the
configuration mode.
•
To display the Quality Level (QL) of the Router, use
quality itu-t
command in the frequency
synchronization configuration mode.
System Management Configuration Guide for Cisco NCS 5000 Series Routers, IOS XR Release 6.2.x
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Frequency Synchronization
Restrictions