NTP module

Web interface

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 (see Common table columns - IP). 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 a leap second will be removed
3 clock is in an unsynchronized state (warning)

Version number

The currently used version number. Recent version is NTPv4.


Poll

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


Stratum

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

Stratum 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


Precision

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.


Peer dispersion

This is the maximum error of the peer clock relative to the local clock over the network path between them.


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 response was sent to the client.


Number of clients

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


Jitter

The jitter (psi) is defined as the root-mean-square (RMS) average of the most recent offset differences, and it represents the nominal error in estimating the offset. Jitter is a quantity calculated for each server/client pair. The min/med/max values are the minimum/median/maximum jitter of all the clients that have connected to the server.


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. This also causes the jitter calculation to become invalid since the exact timestamps are needed.


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.