NTP

[cko015]

How often does an NTP client request time from a server or is it a settable parameter that can be changed?

[Patrick Wallek · Accepted solution]

For just about anything you could ever want to know about NTP, go here

http://www.eecis.udel.edu/~mills/ntp.html

and here

http://www.ntp.org/

[James R. Ferguson]

Hi Kerilyn:

If you do 'ntpq -p' you will see a column headed "Poll". This is the interval (in seconds) the server is queried. Generally its 1024 seconds for servers and 64 for an external clock such as a GPS. The 'minpoll' and 'maxpoll' values can be adjusted but are better left alone.

See the Technical Knowledge Base document #KBRC00015657 for more information.

Regards!

...JRF...

[A. Clay Stephenson]

It is a rather complicated adaptive algorithm. Depending upon the stability, quality, and reachability of the time sources, and the stability of the local client's clock --- and you should have more than 1 (typically at least 3 time sources) the polling starts out at 64 seconds and diminishes to about 1024 seconds. In any event, if you are concerned about loading an NTP server; the overhead, even with many, many clients is quite trivial and gets better the longer the server is up.

You can use the ntpq -p timeserver command to get these values for your environment. As the dispersion decreases the poll seconds increases.
You reduce the frequency of polling by using a good network and good time sources.

[Chauhan Amit]

There are two ways Client can get information from Server:
a) Configuring a Client to Use Server Polling
A polling client has information about its server and contacts it for time information over a network. A typical /etc/ntp.conf file for a client that is using gama as its timeserver is as shown next.

# vi /etc/ntp.conf
server gama
driftfile /var/adm/ntp.drift

Multiple timeservers may be used in the configuration file. The default polling time for the timeserver is once every 64 seconds. At every poll time, drift in the local time and the server time is recorded. If the drift is high, the next polling time is scheduled to occur earlier. If the drift is low, the next polling time is later.

b )Configuring a Client to Use Server Broadcast
A broadcast client does not contact any server for time information but listens for broadcast time information from a broadcast timeserver. The configuration for the broadcast NTP client is like the following.

# vi /etc/ntp.conf
broadcastclient yes
driftfile /var/adm/ntp.drift

Hope this helps.