Multi-Sources & Resiliency; Timing Sources; Foca: The Failover Clock Algorithm - Safran WR-ZEN Series User Manual

5.1 Multi-sources & Resiliency
5.1 Multi-sources & Resiliency
To ensure continued operation over possible failures, the WR-ZEN incorporates
an innovative system that handles multiple timing sources. It also synthesizes
these timing sources into a simplified state (a.k.a Virtual Clock State) to ease the
monitoring of the device and distributes a common timing information to the
down layers.
5.1.1

Timing Sources

The WRZ-OS can handle multiple timing sources in order to discipline the local
oscillator of the device. These timing sources can be of different types:
Then, a maximum total of 5 timing sources of the same or different types can be
handled.
meters shared by all the timing sources and how they are used to determine their
states.
5.1.2

FOCA: The Failover Clock Algorithm

The FOCA has been designed for the purpose of automatically switching from
one timing source to another by applying the following policy:
In case of failure of the active timing source, switch to the next ready timing
source.
60
External Reference (Front panel connectors)
White Rabbit (High-Accuracy PTP)
NTP (Survey mode only) → Coming soon!
Holdover (Always used as last timing source if available)
Note: PTP as timing source: A pure PTP timing source (slave) should
not be selected if the timing is then re-distributed using WR (mas-
ter). Indeed, the jittered correction run by PTP clock is not com-
patible with the precision needed for WR/HA distribution.
Note: NTP Timing source (Survey mode): Due to its poor accuracy,
NTP protocol is always in Survey Mode and thus cannot actively dis-
cipline the local clock.
"FOCA: The Failover Clock Algorithm" below details the common para-
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5 WR-ZEN Series User Manual Rev. v5.1