[ntp:questions] Re: Question to NTP developers

David L. Mills mills at udel.edu
Sat Aug 26 03:13:56 UTC 2006


Eugen,

It's not a good idea to use ntpdc for precision comparisons; ntpq is 
much more useful and truthful.

The display makes no sense. How is it that the GPS and PPS show huge 
jitter while the offsets are zero? Take a look with ntpq at 
rackety.udel.edu and note the offset and jitter. The jitter should 
settle down to the precision limit and the offset should not be much worse.

Dave

Eugen COCA wrote:
> Dave,
> 
> I have already compiled the kernels with these options. I used FreeBSD
> kernel time discipline until now, with this ntpd.conf:
> 
> server 127.127.20.1 minpoll 6 maxpoll 6 prefer
> fudge 127.127.20.1 flag3 1 time1 0.000
> 
>>From today morning at 11 o'clock local time, I changed the
> configuration to see what's happening:
> 
> server 127.127.20.1 minpoll 6 maxpoll 6 prefer
> fudge 127.127.20.1 flag3 0 time1 0.000
> 
> server 127.127.22.1 minpoll 4 maxpoll 4
> fudge 127.127.22.1 flag3 0 time1 0.000
> 
> Now, I have no pps sync disabled message, but I have *a lot* of:
> 
> Aug 25 20:03:40 ntp1 ntpd[49227]: kernel time sync enabled 2301
> Aug 25 20:03:58 ntp1 ntpd[49227]: kernel time sync enabled 2101
> 
> from 5 to 30 per hour !
> 
> The results seems to be better than before:
> 
> https://ecoca.eed.usv.ro/mrtg/time_servers_internet.html
> 
> Are there long term statistics collected somewhere ? With ntpdc/dmpeers
> I can see:
> 
>      remote           local      st poll reach  delay   offset    disp
> =======================================================================
> .GPS_NMEA(1)     127.0.0.1        0   64  377 0.00000  0.000000 0.03076
>  ntp3.usv.ro     80.96.120.253    1   64  377 0.00046  0.000016 0.03291
>  GPS-1.MIT.EDU   80.96.120.253    1  256  377 0.14668  0.000830 0.13341
> .ntp2.usv.ro     80.96.120.253    1   64  377 0.00026 -0.000005 0.05095
>  gps-2.mit.edu   80.96.120.253    1  256  377 0.14603  0.000258 0.09396
>  ptbtime1.ptb.de 80.96.120.253    1  256  377 0.04810 -0.001051 0.11606
>  ptbtime2.ptb.de 80.96.120.253    1  256  277 0.04805  0.000228 0.11227
> *PPS(1)          127.0.0.1        0   16  377 0.00000  0.000000 0.01576
>  ntp-p1.obspm.fr 80.96.120.253    1  256  377 0.06244  0.002924 0.10201
>  ntps1-1.cs.tu-b 80.96.120.253    1  256  277 0.05400 -0.000325 0.07597
> 




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