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In case of failure of the active timing source, switch to the next ready timing
source.
This algorithm is based on the "Best Master Clock Algorithm (BMCA)" detailed in
the PTP IEEE 1588-2019 standard but acts only in case of failure and not when the
"best" source appears in the network. It also enforces the evaluation of the timing
sources in a rank order configured by the user. FOCA algorithm has been
designed to provide a "safer" approach than BMCA or even ABMCA (Alternate
BMCA) to handle switching between multi- references. Its main characteristics
are:
The following figure depicts a configuration where the first two timing sources
are employing WR protocol, followed by an external GNSS receiver connected to
the front panel reference (GM) and finally ending with the holdover to slowly drift
until corrective maintenance. It also illustrates how the two strategies of the
FOCA algorithm behave.
Figure 5-1:
down (blue) & re-evaluation (purple)
An example of the behavior is given by the scenario illustrated in the next image
where the following events are shown:
CHAPTER
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5
WR-Z16 User Manual Rev. v5.0
Provides a deterministic behavior.
Does not allow a new (rogue) node to become the active reference.
Recovers back to normal state must be done under the supervision of an
operator.
Allows switching between cross WR/PTP profiles and multiple external tim-
ing sources.
Has been designed with tree network topology in mind and it is not optim-
ized for ring topology.
Multi-timing sources handle by FOCA policy with its two strategies: only fall-
5.1 Multi-sources & Resiliency
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