[ntp:questions] Syncing to nearby vs. faraway servers

Dave Hart davehart at gmail.com
Tue Jun 16 01:47:25 UTC 2009


On Mon, Jun 15, 2009 at 11:35 PM, Richard B.
Gilbert<rgilbert88 at comcast.net> wrote:
> The best choices, other things being equal, are the servers with the
> lowest round trip delays.

As usual, though, all other things are not equal.  Notice a number of
the nearby servers have higher apparent jitter in the peers billboard
snapshot.  Look at individual associations using "ntpq -cas -p" to
correlate peer to association ID then "ntpq -c 'rv ___'" filling in
the blank with the association ID.  Root dispersion plus dispersion
from that output gives an estimate of maximum error for you from that
source.

Jitter (variability in apparent offset) is a killer.  Low delay plus
high jitter is not better than high delay plus low jitter.

Cheers,
Dave Hart



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