[ntp:questions] Peer Review of ntpq -c rv

David Lord snews at lordynet.org
Thu Mar 8 11:54:24 UTC 2012


Ron Frazier (NTP) wrote:
> On 3/7/2012 11:59 AM, David Lord wrote:
>> Alby VA wrote:
>>> On Mar 7, 10:59 am, David Lord <sn... at lordynet.org> wrote:
>>>> Alby VA wrote:
>>>>>  I'm looking to get a little feedback on if the following output of my
>>>>> Sure GPS / FreeBSD
>>>>> setup looks like its running smoothly and keeping time correctly.
>>>>> assID=0 status=0115 leap_none, sync_atomic, 1 event,
>>>>> event_clock_reset,
>>>>> version="ntpd 4.2.... at 1.2349-o Mon Feb 20 22:00:33 UTC 2012 (1)",
>>>>> processor="amd64", system="FreeBSD/9.0-RELEASE", leap=00, stratum=1,
>>>>> precision=-19, rootdelay=0.000, rootdisp=0.269, refid=PPS,
>>>>> reftime=d301d22f.dc1393c2  Wed, Mar  7 2012  7:25:19.859,
>>>>> clock=d301d230.cc08bad9  Wed, Mar  7 2012  7:25:20.797, peer=41909,
>>>>> tc=4, mintc=3, offset=-0.034, frequency=-25.214, sys_jitter=0.002,
>>>>> clk_jitter=0.002, clk_wander=0.001
>>>>>  Here are my website graphs/stats I've been keeping since day 1.
>>>>> NTP Clock Offset:http://godzilla.empire.org:9999/
>>>>> NTP Offset from 
>>>>> UTC:http://godzilla.empire.org:9999/godzilla_ntp-b.html
>>>> Could you also post output from ntpq -p
>>>>
>>>> I don't have a pc with recent FreeBSD but the desktop
>>>> I updated to NetBSD-6 only 2 hours ago gives:
>>>>
>>>> remote                refid        st t poll reach delay offset jitter
>>>> +ntp1.lordynet.org    81.187.61.74  2 u  512   377 0.450 -4.961  3.024
>>>> *ntp0.lordynet.org.uk .MSFa.        1 u  512   377 0.642 -0.828  4.785
>>>> +<local pc>           .PPSb.        1 u  512   377 1.572 -1.935  3.187
>>>> -<local pc2>          81.187.61.74  2 u  512   377 1.553 -6.075  3.892
>>>>
>>>> Does the Sure have a PPS output you can use?
>>>>
>>>> <Local pc> is using a Sure with PPS
>>>> # ntpq -c rv -p me6000
>>>> associd=0 status=0119 leap_none, sync_pps, 1 event, leap_armed,
>>>> version="ntpd 4.2.6p5....",
>>>> processor="i386", system="NetBSD/5.1_STABLE",
>>>> .....
>>>> offset=-0.001 sys_jitter=0.004
>>>>
>>>> David
>>>
>>>
>>>
>>>
>>> Here is my ntpq -p  output:
>>>
>>>
>>> [alby at godzilla.empire.org(tcsh):6] ntpq -p
>>>      remote           refid      st t when poll reach   delay
>>> offset  jitter
>>> ============================================================================== 
>>>
>>> -ntp.alaska.edu  .GPS.            1 u  133  128  377  120.428
>>> -2.464   0.371
>>> +utcnist2.colora .ACTS.           1 u   53  128  377   66.362
>>> -4.215   0.429
>>> -time-a.nist.gov .ACTS.           1 u  670  128  240   16.473
>>> 2.627  17.066
>>> +tick.usask.ca   .GPS.            1 u  110  128  377  104.848
>>> -3.473   1.482
>>> -cronos.cenam.mx .GPS.            1 u   49  128  377  100.163
>>> 10.784  27.096
>>> oPPS(0)          .PPS.            0 l    6   16  377    0.000
>>> -0.018   0.002
>>> *GPS_NMEA(0)     .GPSb.           0 l    9   16  377    0.000
>>> -36.164  18.050
>>> [alby at godzilla.empire.org(tcsh):7]
>>>
>>
>> Sorry I misread your message and had in my mind that you
>> were getting msec offsets rather than usec. I canceled my
>> reply after posting.
>>
>> The offsets still look to be high for what can be achieved
>> from pps but are not reflected in the jitter.
>>
>>
>> David
>>
> 
> 
> Correct me if I'm wrong, but, doesn't that last line mean 36 ms of 
> offset with 18 ms of jitter?
> 

Yes that is the offset from the NMEA. The NMEA in this case
is only used to obtain the "second" value of the clock. PPS
on the line above is used to condition the system clock which
at that poll had offset of -0.018 ms and jitter of 0.002 ms.

David



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