Timing Loop - Alcatel-Lucent 1643 AMS User's Operation Manual

Timing provisioning

Timing loop

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Introduction
If a timing plan is not engineered correctly, a timing loop may occur. In a timing loop
the timing signal that is received by a network element cannot be traced back to an
independent reference. The reference signal that a network element receives in a timing
loop, depends on the timing signal that this network element sends out itself. In the
figure below an example of a timing loop is given. Both network elements get a timing
reference which depends on itself.
Timing loop sketched
Timing loop
In a timing loop the timing reference of a network element is derived from the timing
output of the same network element. Due to this, the reference signal becomes very
instable. This affects the performance of the network in a negative way.
To prevent timing loops, the quality level and priority for every port must be
provisioned correctly. By disabling certain ports timing loops can be avoided.
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365-312-807R7.2
Issue 4, May 2007
Alcatel-Lucent - Proprietary
See notice on first page
7-13