[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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