10-4
Cisco ASR 1000 Series Aggregation Services Routers Software Configuration Guide
OL-16506-10
Chapter 10 Synchronous Ethernet Support
Restrictions and Usage Guidelines
QL-Disabled Mode
In QL-disabled mode, the following parameters contribute to the selection process:
•
Signal failure
•
Priority
•
External commands
If no external commands are active, the algorithm selects the reference (for clock selection) with the
highest priority that does not experience a signal fail condition. For multiple inputs having the same
highest priority, the existing reference is maintained (if it belongs to highest priority group). Otherwise,
an arbitrary reference from highest priority group is selected.
Restrictions and Usage Guidelines
This section lists the restrictions and usage guidelines for configuring the SyncE on a Cisco ASR 1000
Router:
•
If the network clock algorithm is enabled, use the system clock as Tx clock (synchronous mode) for
its Ethernet interfaces. You cannot change the synchronous mode on a per interface basis.
•
You can configure a maximum of eight ports as a clock source for a Cisco ASR 1000 Router.
•
The SyncE feature is SSO-coexistent, but not SSO-compliant. The clock selection algorithm is
restarted on a switchover. During the switchover, the router goes into hold-over mode.
•
The SyncE interfaces in WAN mode cannot be used for QL-enabled clock selection. You should
either use them with the system in QL-disabled mode, or disable the ESMC on the interfaces, and
use them as QL-disabled interfaces.
•
It is recommended that you do not configure multiple input sources with the same priority as this
impacts the T
SM
(Switching message delay).
•
You cannot implement the network-clock based clock selection algorithm and the new algorithm
simultaneously. Both these algorithms are mutually exclusive.
•
Only metronome SPAs are supported with the new G.781-based clock selection algorithm
(Netsync).
•
The Line-to-external configuration for the clock cleanup is supported only if the line interface and
the external interface are on the same metronome SPA.
Configuring Synchronous Ethernet
This section describes how to configure SyncE on the Cisco ASR 1000 Series Router.
You can implement SyncE on the Cisco ASR 1000 Series Router, using three different configurations:
•
Configuring Clock Recovery from SyncE, page 10-5
•
Configuring Clock Recovery from a BITS Port, page 10-7
•
Configuring a SyncE Using the Line-to-External Method, page 10-9
