[ntp:questions] Regarding NTP configuration ntp.conf

Kevin Oberman oberman at es.net
Thu Dec 17 22:36:48 UTC 2009

> Date: Thu, 17 Dec 2009 14:24:56 +0800
> From: <arpit.gupta at Emerson.com>
> Sender: questions-bounces+oberman=es.net at lists.ntp.org
> Hi,
>   I wish to know that If I am providing 2 server names in ntp.conf
> without "prefer" option then with which server my system will sync the
> time. 
> I googled it I came to know that the server which has less "jitter" it
> will sync with. Other thing is both the servers are at same strand
> value. 
> Can anyone please explain it. I will be thankful to you .

I think you probably meant stratum instead of "strand". In any case, the
algorithm is a bit more complex than "jitter", but it is the dominant
contributor. I'm not entirely sure what you are asking, though. It sound
like you  found the answer.

I will say that having two servers is probably the worst case. You
really want three, five, or seven. Those allow for "good" servers to
out-vote a bad server. If you only have two, there is no indication as
to what the "best" time is. The jitter may be low, but the time may be
off by a lot. If you have three servers, if one goes bad, ntp will ignore
it and always pick from the servers that have about the sime time.
R. Kevin Oberman, Network Engineer
Energy Sciences Network (ESnet)
Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab)
E-mail: oberman at es.net			Phone: +1 510 486-8634
Key fingerprint:059B 2DDF 031C 9BA3 14A4  EADA 927D EBB3 987B 3751

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