Stratum Levels; Holdover - Safran WR-Z16 User Manual

5.7 Holdover
OID
3.70x5.2
5.6.3

Stratum Levels

The NTP stratum is a measure for synchronization distance from the reference
clock which might not always reflect the timing performance such as jitter or
delay. In other words, a server synchronized to a stratum (n) server will be run-
ning at stratum (n+1) where the upper limit for stratum is 15.
5.7

Holdover

The WR-Z16 can be ordered with an optional holdover oscillator (OCXO) in order
to ensure an accuracy of 1.5µs even after 24 hours.
If this holdover oscillator is detected, it will be automatically enabled as a timing
source. Otherwise, when UNAVAILABLE, the device will announce itself directly
as Free-running with UNKNOWN accuracy.
90
Name
Stratum
Stratum 0: Corresponds to the reference clock sources that relays Coordin-
ated Universal Time (UTC). Stratum 0 servers should only be deployed
within a metrology institute and must not be available on the internet.
Stratum 1: Corresponds to the servers that are directly synchronized to
stratum 0. They can also be considered a Primary Reference Source (PRS)
such as calibrated GNSS receiver or Atomic Clocks. The Grand-Master node
is typically connected to an external reference that provides NTP with
Stratum 1.
Stratum 2: They are synchronized by a stratum 1 clock. It is the default
stratum level when NTP provider is set in manual mode.
Stratum 3: They are synchronized by a stratum 2 clock.
Stratum 4 and below: Devices that announce this level should only be used
for cross-validation or backup but not as the primary NTP reference to syn-
chronize a 3rd party device.
Stratum 15: It is the last valid stratum level defined by the NTP protocol.
Stratum 16: It is commonly used to indicate that the device is not syn-
chronized and thus does not provide any valid NTP time.
Value Type
• Stratum 0 Stratum announced by the corresponding
• Stratum 1 NTP server.
• Stratum 2
• Stratum 3
• Stratum 4
• Stratum 15
• Undefined
CHAPTER
Description
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5 WR-Z16 User Manual Rev. v5.0