[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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