[ntp:questions] Re: how many servers should I poll?

David J Taylor david-taylor at blueyonder.co.uk
Fri Aug 8 10:07:13 UTC 2003


> As to stratum, I have a couple of DCF radioclocks (situation B) and
> back that up with 3 pool.ntp.org servers (situation D+)
>
>
>   remote       refid          st t when poll reach  delay  offset jitter
>   ====================================================================
>   127.127.1.0 127.127.1.0      10 l   6   64  377   0.000   0.000
0.004
> +127.127.28.0  .DCF.           0 l   5   64  377   0.000  -0.046   0.166
> *127.127.28.1  .DCF.           0 l   6   64  377   0.000   1.269   0.050
>   192.168.1.255 0.0.0.0        16 -   -   64    0   0.000   0.000
4000.00
> -64.44.160.38  128.252.19.1    2 u   3   64  377 163.757   7.978   0.943
> +204.17.42.198 207.126.98.204  2 u  61   64  377 219.236   4.844   1.455
> -205.142.198.4 130.207.244.240 2 u   7   64  377 163.190   8.328   1.373

Mike,

I would be very wary of those servers with 160+ msec delay.

- they are not near to you - why not go for somewhere in Europe, France
even?

- I have seen asymmetrical delays on such long paths, it can longer for
the packet to travel one way than the other.  This will break some
assumptions in NTP, leading to a static offset.  OK, perhaps only 20msec,
but I don't know what you are aiming for.

Just a thought....

David





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