[ntp:questions] ARRGH!!! I woke up to a 50 SECOND clock error.

unruh unruh at invalid.ca
Wed Mar 14 17:39:47 UTC 2012


On 2012-03-14, Ron Frazier (NTP) <timekeepingntplist at c3energy.com> wrote:
> On 3/14/2012 3:03 AM, unruh wrote:
>> On 2012-03-13, Ron Frazier (NTP)<timekeepingntplist at c3energy.com>  wrote:
>>    
>>> Hi all,
>>>
>>> I just woke up to a 50 SECOND clock error.  Prior to the error, with my
>>> PC locked into the GPS and the internet servers noselected, here's what
>>> my peerstats looked like.  Baseline is the GPS.  Colored lines are
>>> internet servers.
>>>
>>> http://dl.dropbox.com/u/9879631/drifting01-peerstats.20120312.jpg
>>>      
>> Looking at this graph, I see that the nmea source was already difting
>> before the sudden jump. It lost 30ms wrt the other servers in the 20
>> hours beforehand. Then it went crazy for a while and jumped to 80 ms
>> ahead. I agree that this does seem to be that gps device. Which one is
>> it?
>>
>> But that jump is 120ms not 50 sec.
>>
>> I recently had a Garmin 18 go nuts-- giving massive amounts of noise.
>>
>>
>>    
>
> That's very interesting.  David Taylor also said he saw this NMEA 
> wandering effect on the Garmin.  Did your Garmin recover?  And, is it 
> based on a SIRF chipset?

No idea. It is the old Garmin 18LVC (not 18x)

>
> In another thread, someone else with a BU-353 said he saw an "offset 
> storm" like the one in my graph.
>
> Sincerely,
>
> Ron
>
>>    
>>> Here is what was showing on the Meinberg Time Server Monitor when I woke up:
>>>
>>> http://dl.dropbox.com/u/9879631/drifting02a%20-%20insane.jpg
>>>
>>> And the graph of the peerstats for that time:
>>>
>>> http://dl.dropbox.com/u/9879631/drifting02b%20-%20peerstats%20insane.jpg
>>>
>>> The clock error was REAL, as confirmed by my atomic wrist watch.
>>>
>>> However, the loopstats graph for the same time period shows no problem
>>> with the GPS:
>>>
>>> http://dl.dropbox.com/u/9879631/drifting02c%20-%20gps%20NOT%20insane.jpg
>>>
>>> So, I shut down NTPD and reset the time with a batch file that calls
>>> ntpdate and querys the New York NIST server:
>>>
>>> http://dl.dropbox.com/u/9879631/drifting02d%20-%20set%20with%20ntpdate.jpg
>>>
>>> Here is the time server monitor shortly after NTPD restart:
>>>
>>> http://dl.dropbox.com/u/9879631/drifting02e%20-%20shortly%20after%20ntpd%20restart.jpg
>>>
>>> And after a 2nd restart:
>>>
>>> http://dl.dropbox.com/u/9879631/drifting02f%20-%202nd%20ntpd%20restart%20after%20insane.jpg
>>>
>>> And here are the current peerstats, which look normal.  The offset to
>>> the internet servers tends to drift and will eventually cross the zero
>>> line and get positive.
>>>
>>> http://dl.dropbox.com/u/9879631/drifting02g%20-%20peerstats%20after%20insane%20and%202nd%20reset.jpg
>>>
>>> The GPS appears to have been stable all through this, and was never
>>> powered off or unplugged.  It looks like NTPD went crazy and reset my
>>> clock for some reason.
>>>      
>> It also reset all of the remote servers at the same time? Since it was
>> an offset of your system with respect to the remote systems.
>>    
>>> Here are the peerstats and loopstats during the insane period.
>>>
>>> http://dl.dropbox.com/u/9879631/loopstats.20120313-1-restart%20around%201350%20utc
>>> http://dl.dropbox.com/u/9879631/peerstats.20120313-1-insane
>>>
>>> Here is my current ntp.conf:
>>>
>>> http://dl.dropbox.com/u/9879631/ntp.conf
>>>
>>> My system is Windows 7, NTP 4.2.7p259, GPS GlobalSat BU-353 USB NMEA
>>> only with GPGGA sentence at 57,600 baud.
>>>
>>> If anyone can shed some light on what happened, please do.  It's driving
>>> me bonkers.  I don't believe the GPS is at fault, and I suspect NTPD.
>>>      
>> Again, the remote servers all agree. The GPS time does not (driving your
>> system time) .
>>
>>
>>    
>>> Thanks in advance.
>>>
>>> Sincerely,
>>>
>>> Ron
>>>
>>>
>>>      
>
>
>



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