[ntp:questions] Sure GPS - Very High Jitter and Offset

Chris Albertson albertson.chris at gmail.com
Sat Aug 20 18:32:12 UTC 2011

On Thu, Aug 18, 2011 at 11:16 AM, Ken Link <klink at numberzero.org> wrote:
> Question (hopefully last) about the behavior in this state. While
> there is an 'o' next to the GPS clock, meaning it's the PPS peer, ntpd
> also selects another peer with a '*' (the other peers are from the NTP
> pool). Why does it select an additional peer? The only preferred peer
> in ntp.conf is the GPS device. Shouldn't ntpd get the time AND pps
> from the GPS clock?
> Running "ntpq -c assoc" shows the GPS clock as the pps.peer and the
> pool source as sys.peer.

ntpd computes the time from the set of ref. clocks that pass the clock
selection criteria.   It is best to think of it that way rather than
thinking it selects the "best" and syncs to it.  Rather ntpd selects an
acceptable set of clocks,

In your case it mmay be that the Sure GPS' NMEA data is not very god
compared to the pool sever.


Chris Albertson
Redondo Beach, California

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