[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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