[ntp:questions] large dispersion

Richard B. Gilbert rgilbert88 at comcast.net
Fri May 25 00:09:04 UTC 2007


Dave wrote:
> On May 23, 1:16 pm, "Richard B. Gilbert" <rgilber... at comcast.net>
> wrote:
> 
>>Dave wrote:
>>
>>>I'm experiencing large values of dispersion when I use 'ntpq -p':
>>
>>>3:22pm:ntp>ntpq -p
>>>     remote           refid      st t when poll reach   delay
>>>offset    disp
>>>==============================================================================
>>>*10.2.100.10     .GPS.            1 u   25   64  377     0.46
>>>943.557  439.36
>>>3:22pm:ntp>
>>
>>> but when I look at the peerstats log file, my dispersion is low:
>>
>>>3:22pm:ntp>tail /var/ntp/ntpstats/peerstats.log
>>>54243 54804.018 10.2.100.10 9634 0.617563 0.00046 0.31154
>>>54243 54868.013 10.2.100.10 9634 0.813226 0.00043 0.32210
>>>54243 54932.018 10.2.100.10 9634 0.099169 0.00046 0.55225
>>>54243 54996.010 10.2.100.10 9634 0.300057 0.00047 0.28690
>>>54243 55060.014 10.2.100.10 9634 0.584358 0.00044 0.31111
>>>54243 55124.009 10.2.100.10 9634 0.781632 0.00047 0.32353
>>>54243 55188.014 10.2.100.10 9634 0.065932 0.00043 0.55287
>>>54243 55252.013 10.2.100.10 9634 0.657674 0.00044 0.37859
>>>54243 55316.018 10.2.100.10 9634 0.943557 0.00046 0.43936
>>>54243 55380.013 10.2.100.10 9634 0.139388 0.00044 0.59772
>>>3:23pm:ntp>
>>
>>> I'm also concerned with the large amount of maximum/estimated error
>>>when I use the xntpdc command 'kerninfo':
>>
>>>xntpdc> kerninfo
>>>pll offset:           0 us
>>>pll frequency:        -391.137 ppm
>>>maximum error:        524704 us
>>>estimated error:      408368 us
>>>status:               0089
>>>pll time constant:    2
>>>precision:            1 us
>>>frequency tolerance:  512 ppm
>>>pps frequency:        0.000 ppm
>>>pps stability:        512.000 ppm
>>>pps jitter:           200 us
>>>calibration interval: 4 s
>>>calibration cycles:   0
>>>jitter exceeded:      0
>>>stability exceeded:   0
>>>calibration errors:   0
>>>xntpdc>
>>
>>>Here is the output of the pstats command:
>>
>>>xntpdc> pstats 10.2.100.10
>>>remote host:          10.2.100.10
>>>local interface:      10.2.100.5
>>>time last received:   3s
>>>time until next send: 61s
>>>reachability change:  2947s
>>>packets sent:         59
>>>packets received:     59
>>>bad authentication:   0
>>>bogus origin:         0
>>>duplicate:            0
>>>bad dispersion:       15
>>>bad reference time:   0
>>>candidate order:      1
>>>xntpdc>
>>
>>>And lastly, my ntp.conf file:
>>
>>>3:25pm:inet>more ntp.conf
>>>server 10.2.100.10             # NTP server
>>
>>>driftfile /etc/ntp.drift          # Drift available for next restart
>>>logfile /var/ntp/ntp.log       # NTP logging
>>
>>>statsdir /var/ntp/ntpstats/
>>>statistics loopstats peerstats clockstats
>>>filegen loopstats file loopstats.log type day link enable
>>>filegen peerstats file peerstats.log type day link enable
>>>filegen clockstats file clockstats.log type day link enable
>>>3:25pm:inet>
>>
>>>Anyone have any ideas? I have a GPS signal coming in to a Brandywine
>>>NTA-100, which is configured at 10.2.100.10. Thanks in advance!
>>
>>If you are using "X"ntpdc you would appear to be using a version that
>>may be as much as ten years old!   Just what are you using and what are
>>  you running it on?
> 
> 
> Wow you're right. Heres the version printout:
> xntpdc 3-5.93e Mon Sep 20 15:47:24 PDT 1999 (1)
> 
> I'm running this on a Sun Fire 4200, Solaris 10. Something this old
> comes installed on Solaris 10?
> 

Yup!

I think it has something to do with the fact that there is, as yet, no 
RFC for NTP V4.  There is a committee, God help us, working on one.  I 
think it has been about a year now with no visible results!

I'd suggest grabbing a more recent version of the code from somewhere. 
Sun Freeware and Blastwave sites should both have Solaris versions more 
recent than what Sun ships.  There have been quite a few fixes and 
enhancements since 3-5.93e.

If you want/are able to build your own, try the ntp.org web site; there 
are links there to download the source to the stable and development 
versions which are, I believe, at 4.2.something.




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