The offset may be a function of distance.
Try this experiment:
Set up your ntp.conf file to have three servers (all examples assume you
are located in Eastern USA):
1. A relatively unused stratum 1 or 2 server as close to you as possible.
2. A relatively unused stratum 1 or 2 server about 1,000 miles away (e.g.,
ntp.melancthon.net)
3. A relatively unused stratum 1 or 2 server more than 2,000 miles away
(e.g., ntp1.tp.pl, ntp2.tp.pl, time.coi.pw.edu.pl, ntp.certum.pl).
On my computer, the offset is proportional to distance:
Remote Refid Stratum Type When Poll
Reach Delay Offset Jitter
BR-350P GPS 0 Local clock 7 16
017 0.000 -17.653 2.345
FreeNAS time-c.nist.gov 2 Unicast server 16 16
017 0.238 0.008 0.037
nist1-pa.ustiming.org ACTS 1 Unicast server 15 16
017 28.844 0.135 3.158
2a01:1102:0:b::2 ATOM 1 Unicast server 16
16 017 120.732 -5.145 2.151
2a01:1100:1::2 ATOM 1 Unicast server 15 16
017 128.756 -3.931 4.635
213.222.200.99 PPS 1 Unicast server 13 16
017 110.727 -0.968 4.119
ntp.coi.pw.edu.pl OCX0 1 Unicast server 14
16 017 122.100 -4.253 0.584
serenity.melancthon.net india.colorado.edu 2 Unicast server 35 32
003 53.520 2.019 3.556
Charles Elliott
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]] On
> Behalf Of mike cook
> Sent: Thursday, September 11, 2014 2:08 PM
> To: Questions List
> Subject: Re: [ntp:questions] Compensating for asymmetric delay on a
> per-peer/server basis?
>
>
> Le 11 sept. 2014 à 18:48, Rob a écrit :
>
> > Paul <[email protected]> wrote:
> >> As an aside has anyone tried shaping traffic to make the
> >> upstream/downstream latencies similar? It would seem more efficient
> >> to apply network solutions to network problems if possible.
> >
> > That does not work. The asymmetry is not caused by traffic but by
> > modem parameters.
>
> Did I miss something? The OP did not offer any evidence that there
> was path asymmetry, just that there was an unexplained offset between
> two GPS sync'd servers. It is often not possible to identify the origin
> of such an offset, but it would help if the suggested feature was
> implemented to take care of these corner cases. I saw that Dr Mills was
> in agreement back in 2005 but that the implementation is complex. If
> anyone wants a subject for an MSc project, this could be it.
>
> >
> > _______________________________________________
> > questions mailing list
> > [email protected]
> > http://lists.ntp.org/listinfo/questions
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