Stratum Levels; Holdover - Safran WR-ZEN Series 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- ZEN can be ordered with an optional holdover oscillator (OCXO) in
order to ensure an accuracy of 1.5µs even after 24 hours.
104
Name
Stratum • Stratum 0
• Stratum 1
• Stratum 2
• Stratum 3
• Stratum 4
• Stratum 15
• Undefined
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 announced by the corresponding
NTP server.
CHAPTER
Description
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5 WR-ZEN Series User Manual Rev. v5.1