NTP module

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NTP statistics.png

The NTP module processes NTP traffic. It stores the NTP servers, including their clients, and further NTP related information. The following documentation is based on the RFCs. See also http://www.faqs.org/rfcs/rfc1305.html

NTP server IP

This is the IP of a seen NTP server. This status is assigned when this IP has sent a NTP with flag 4. Therefore every clock that is configured as a reference clock will be stored as a server.

Alternative name

This column shows all known name information about the server IP.

Leap indicator

If the leap indicator is set to 1 respectively 2 a leap second will be inserted respectively removed this day. A leap indicator of 0 means that everything is okay and no insertion or removing of leap seconds is necessary. The clock is unsynchronized if the leap indicator is set to 3 (warning).

Leap indicator explanation
0 no second will be removed/inserted
1 a leap second will be inserted
2-15 a leap second will be removed
16 clock is in an unsynchronized state (warning)

Version number

The current used version number. Recent version is NTPv4.


The minimum intervall in seconds between transmitted messages. It is specified in log2.


The stratum is the hierarchy level of the NTP server and represents the distance from the reference clock.

Leap indicator explanation
0 unspecified
1 primary reference (e.g. an atom clock)
2-15 one plus the stratum of the reference clock
16 indicates an unsynchronized state


The precision of the reference time clock, more precise: A precision value 25ms indicates that the reference clock is able to maintain this precision.

Root delay

This number indicates the total roundtrip delay to the primary reference source at the root of this subnet.

Root dispersion

This is the maximum error relative to the primary reference source at the root of this subnet.

Last origin timestamp

Time at the client when the request was sent to the server.

Last receive timestamp

Time at the server when the client request arrived.

Last reference timestamp

Time when the system clock was last set.

Last transmit timestamp

Time at the server when the resonse was sent to the client.

Number of clients

The number of NTP users that use this clock as a reference.

Remark for chrony users

Chrony sets the reference timestamp to zero and the received/transmit timestamp to a random value. Only the origin timestamp is correct.

Rows without values

It can happen that rows have no values respectively show only ‘-‘ for most values. This indicates that this server/client has received a NTP packet but didn’t send a response to the client/server. That means that this server/client is recorded as a NTP member, but there is no further information about it, because it never sent a NTP packet.