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

Ron Frazier (NTP) timekeepingntplist at c3energy.com
Thu Mar 8 12:43:08 UTC 2012


On 3/8/2012 6:54 AM, David Lord wrote:
> 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

OK.  Now I get it.  Thanks.

Ron


-- 

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Ron Frazier
timekeepingdude AT c3energy.com



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