[ntp:questions] frequency adjusting only

Unruh unruh-spam at physics.ubc.ca
Wed Apr 23 17:32:38 UTC 2008


m.louvel at gmail.com (maxime louvel) writes:

>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

Yes. Mine are around 200us (.2ms) 


>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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