[ntp:questions] SNTP with 1ms of precision?

Marcelo Pimenta marcelopimentacs at gmail.com
Thu Jun 17 17:58:30 UTC 2010

2010/6/17 David J Taylor <david-taylor at blueyonder.co.uk.invalid>

>  NTP can deliver a time accuracy of 1nsec?? I my point of view, NTP
>> includes
>> methods to estimate the round-trip path delay between the server and
>> client
>> but the performance is limited by SO stack latency, it is an Application
>> Layer protocol.
> Marcelo, here's what /my/ NTP achieves:
>  http://www.satsignal.eu/mrtg/performance_ntp.php
> The top three PCs (Pixie, Feenix and Stamsund) are each fed with a serial
> GPS/PPS signal from a Garmin GPS-18 LVC or GPS-18X LVC.  Three different
> operating systems.
> The bottom PCs are all Windows boxes of various versions, synced over a LAN
> including a cheapo Netgear GS608 1Gb/s switch, a WRT54GL Samknows
> performance measurement box, and a Netgear WNR2000v2 with wired and wireless
> connections.
> I don't know whether any of those LAN-connected boxes would meet your "1ms"
> requirement (although if there were all running FreeBSD they would likely be
> significantly better than when running Windows).
> Cheers,
> David


CONGRATULATIONS!!! Very good tests and presentations!! Very very good!!! You
gave me real results and all your reports are consistent and show that it's
impossible to have usec and nsec precision using NTP though Ethernet. You
have SO stack latency and it's a Layer 7 protocol!!!

One more time... congratulations!!! It's helped a lot!!! I hope you page be
on line forever =)   I have to see all things that you wrote over there yet
but... I think is everything that I was looking for.

Thank you very much

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