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Note: When the Timescale is set to “GPS”, the GPS to UTC Off-

set must be set correctly. As of 5-August-2019, the offset

between UTC and GPS is 18 seconds.

2.8.9.7 NTP Reference Configuration

VersaSync's NTP Service needs to be setup such that it utilizes the time source ("input ref-

erence") you want it to use. There are two options for an NTP Server to derive its time

from:

The NTP Service uses VersaSync's System Time, i.e. typically the GNSS reference

(or IRIG, ASCII data input, etc.), and distributes that time over the NTP network. This

is called Stratum 1 Operation, because VersaSync will be the Stratum1 (or

primary) server. This is the most common configuration.

b. It is, however, also possible for NTP to utilize the time provided by

another

NTP

Server as a reference. In this case the other server would be Stratum 1, and Ver-

saSync would be Stratum 2 (or higher). This operating mode can be referred to as

Stratum2 operation, secondary server operation, or NTP Stratum Syn-

chronization.

With a GNSS-capable time server it is possible to combine these two configurations e.g., by

assigning a higher reference priority to (a.), and a lower "fallback" priority to (b.). For more

information on reference priority configuration, see "Configuring Input Reference Pri-

orities" on page154.

The NTP Stratum Model

The NTP Stratum model is a representation of the hierarchy of time servers in an NTP net-

work, where the Stratum level (0-15) indicates the device's distance to the reference

clock.

Stratum0 means a device is directly connected to e.g., a GPS antenna. Stratum0

devices cannot distribute time over a network directly, though, hence they must be linked

to a Stratum1 time server that will distribute time to Stratum2 servers or clients, and so

on. The higher the Stratum number, the more the timing accuracy and stability degrades.

The NTP protocol does not allow clients to accept time from a Stratum 15 device, hence

Stratum 15 is the lowest NTP Stratum.

A group of NTP servers at the same Stratum level (Stratum 2, for example) are con-

sidered NTP Peers to each other. NTP Servers at a

higher

Stratum level, on the other

hand, are referred to as NTP Servers.

2.8 Configuring Network Settings

CHAPTER 2 • VersaSync User Manual Rev. 7.0

105

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