[ntp:questions] Criteria for evaluating upstream server quality
Richard B. Gilbert
rgilbert88 at comcast.net
Sat Dec 22 15:19:43 UTC 2007
Pierre Dubuc wrote:
> I'd like to get opinions as to the weight of specific criteria for
> choosing upstream servers to get time from.
>
> For example, which of these is more important than the others, and why?
>
> - round-trip delay;
> - stratum;
> - server's own configuration;
> - and so on...
>
> For now, I've got the following billboard (refid's trimmed):
>
> mac> ntpq -pn | sort -k8.1,8.6n
> remote refid st t when poll reach delay offset jitter
> =========================================================================
> +132.205.7.81 132.205... 3 u 131 1024 377 5.897 -0.615 0.149
> -24.200.225.157 10.23.12.. 4 u 390 1024 377 5.776 -1.854 0.190
> -216.113.122.37 207.253... 3 u 77 1024 377 5.107 1.838 0.721
> +192.26.210.193 172.22.... 2 u 199 1024 377 6.229 -0.214 0.439
> -132.208.250.3 204.123... 2 u 7 1024 377 6.855 1.577 1.506
> *132.246.168.148 132.246... 2 u 70 1024 377 8.820 -0.307 0.764
> -199.212.17.21 142.135... 2 u 32 1024 377 9.314 -7.228 0.411
> -132.214.200.120 18.26.4... 2 u 34 1024 377 17.752 -2.384 1.486
> -209.87.233.53 209.87.... 2 u 205 1024 377 36.763 3.240 0.631
>
> I concede this may a bit too many servers for domestic use, but how do I
> choose which ones to remove?
>
NTPD has chosen the best servers. The very best, at the moment the
above ntpq banner was taken is the one marked with the "*". The runners
up are marked with "+". Note that this is subject to change, with time.
I'd drop the last two because of the longer round trip delays. That
will leave you with seven servers which is still a lot for most
purposes! You could get along with as few as four.
<snip>
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