2.15.7 NTP Reference Configuration
NetClock's NTP Service needs to be setup such that it utilizes the time source ("input reference")
you want it to use. There are two options for an NTP Server to derive its time from:
a.
The NTP Service uses NetClock'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 NetClock 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 NetClock would be
Stratum 2
(or higher). This operating mode can be referred to as
Stratum 2 operation
,
secondary server operation
, or
NTP Stratum Synchronization
.
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 Priorities" on
page 163.
2.15.7.1 The NTP Stratum Model
The NTP Stratum model is a representation of the hierarchy of time servers in an NTP network,
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 can
not 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 considered
NTP
Peers
to each other. NTP Servers at a
higher
Stratum level, on the other hand, are referred to
as
NTP Servers
.
Note:
Internet Time Servers should be configured as NTP Servers and not as NTP
Peers.
If NetClock has no valid Timing System Reference, NTP Server or NTP Peers, the NTP Stratum
value is automatically downgraded to
Stratum 15
. This ensures that its NTP clients will no
longer use this NetClock unit as a time reference.
2.15.7.2 Configuring "NTP Stratum 1" Operation
When the Timing System references of your NetClock are normally available (rather than
being unavailable most of the time e.g., in areas with poor GNSS reception), it is advisable to
2.15 Configuring NTP
CHAPTER
2
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NetClock User Reference Guide
Rev.
16
103
Summary of Contents for NetClock 9400 Series
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