[ntp:questions] frequency adjusting only

maxime louvel m.louvel at gmail.com
Wed Apr 23 09:41:54 UTC 2008


I have checked the roundtrip delay with ntpq -p.
It seems that I always have 0.147 ms.
But I haven't monitored it properly, just each time I ran the command I got
this value

On Wed, Apr 23, 2008 at 7:30 AM, maxime louvel <m.louvel at gmail.com> wrote:

> HI again,
>
> I am thinking that NTP should behave correctly if the activity on the
> nodes (small temperature, hence frequency variation) and on the network
> (small latency of the switch) are roughly constant.
> But if not it will have some trouble, either to compensate the frequency
> change or to deal with the network delay latency.
>
> what do you think ?
>
> thanks,
>
> Maxime
>
>
> On Wed, Apr 23, 2008 at 7:12 AM, maxime louvel <m.louvel at gmail.com> wrote:
>
> > Hi,
> >
> > - my network contains only one switch, and all the node are in the same
> > room.
> > Thus I don't think cabling is a problem. I still have to check the
> > latency of the switch.
> >
> > - I can't use a GPS or other material. I though I wouldn't need any
> > because I don't won't a great accuracy with the real time, just between my
> > nodes. I also think it would have been easier and better to have a common
> > high precision time source (GPS)... But I can't afford that ;)
> >
> > Do you have an explanation of the so different performances observed in
> > your NTP synchronisations ?
> >
> > - I'm going to look at chrony, which at first glance seems usable in my
> > case.
> >
> > - I am already using the -x option, to be certain to avoid any step.
> >
> > Maxime
> >
> >
> > On Wed, Apr 23, 2008 at 2:10 AM, Unruh <unruh-spam at physics.ubc.ca>
> > wrote:
> >
> > > Steve Kostecke <kostecke at ntp.org> writes:
> > >
> > > >On 2008-04-22, Unruh <unruh-spam at physics.ubc.ca> wrote:
> > >
> > > >> Steve Kostecke <kostecke at ntp.org> writes:
> > > >>
> > > >> ??? In my experience, on a Lan ntpd shows an internode offset of
> > > about
> > > >> 5-15 usec, and on the internet (ADSL) an offset of about 200usec.
> > >
> > > >Here's an aggregated plot of the node offsets on my LAN over the last
> > > 24
> > > >hours. I see +3/-5 milliseconds, not anything near 5-15 microseconds.
> > >
> > > >
> > > http://support.ntp.org/bin/viewfile/Users/SteveKostecke?rev=1;filename=typical_aggregate_lan_offsets.png
> > >
> > > I agree those are pretty bad. HOw are they hooked up? It looks like
> > > one of
> > > the hops is via a telephone modem!
> > >
> > > See www.theory.physics/chrony/chrony.html
> > > Mind you those are running with maxpoll 7 not maxpoll 10 (Its my lan
> > > and
> > > ntp server, and I'll do what I want to.)
> > >
> > >
> > > >--
> > > >Steve Kostecke <kostecke at ntp.org>
> > > >NTP Public Services Project - http://support.ntp.org/
> > >
> > > _______________________________________________
> > > questions mailing list
> > > questions at lists.ntp.org
> > > https://lists.ntp.org/mailman/listinfo/questions
> > >
> >
> >
> >
> > --
> > Maxime Louvel
> > 0044 7964 5555 80
> > 43 Allen road
> > Whitemore reans
> > WV60AW Wolverhampton
> > United Kingdom
> >
>
>
>
> --
> Maxime Louvel
> 0044 7964 5555 80
> 43 Allen road
> Whitemore reans
> WV60AW Wolverhampton
> United Kingdom
>



-- 
Maxime Louvel
0044 7964 5555 80
43 Allen road
Whitemore reans
WV60AW Wolverhampton
United Kingdom



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