[ntp:questions] Can NTP sync within 1ms

William Unruh unruh at invalid.ca
Sun Apr 27 00:30:19 UTC 2014

On 2014-04-26, Paul <tik-tok at bodosom.net> wrote:
> On Fri, Apr 25, 2014 at 11:22 PM, William Unruh <unruh at invalid.ca> wrote:
>> I have 8 machines that reliably sync from one GPS PPS driven
>> machine (all using chrony) and they get time reliability of about
>> 10microseconds
> How do you determine the 10 micosec. value?

Two ways. One is to simply use the offset scatter as an estimate of the
time performace (It is at least some sort of upper bound, but as I have
said, not terribly accurate) and secondly by hooking a GS PPS to the
machine and looking at the offsets on that. 
> And why are you conflating NTP performance with Chrony performance?

BEcause they are comparable ( chrony is somthing like 2-3 times better
than ntpd, but not 1000 times better).
They both use ntp packet exchange to exchange time. ntpd uses a (slow)
very simply feedback loop, chrony uses a linear regression, but again
the two are comparable. 

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