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

Ron Frazier (NTP) timekeepingntplist at c3energy.com
Tue Mar 13 19:48:42 UTC 2012


On 3/13/2012 2:55 PM, Ron Frazier (NTP) wrote:
> On 3/13/2012 2:40 PM, Chris Albertson wrote:
>> On Tue, Mar 13, 2012 at 9:52 AM, 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
>> Looks to me like that GPS, maybe lock lock and was able to "coast" on
>> hold over for a while then fell off a cliff.     If you have a log of
>> satellite  signal to noise ratios you might be able to figure out why.
>>
>> The internet servers appear to be 100% reliable seeing as they all 
>> agree.
>>
>> These kinds of things are why some hobbysts end up buying multiple GPS
>> (different brands)  Otherwise it is hard to sort out a GPS firmware
>> bug from a solar storm or just that there were not sats visable to
>> your indoor antenna for a few minutes
>>
>> I think your goal is to learn about all of this so these problems are
>> a good thing.  No one learns much from working systems.   But if the
>> goal is a reliable NTP server, the pool NTP servers can't be beat
>> except by a good timing mode GPS, that has good self diagnostics and
>> PPS.  The self diagnostics part is important
>
> The link you quoted just now is not the one that bugs me so much 
> today.  This one is the one that bugs me today, where my clock was 
> stepped by 50 seconds for some reason.
>
> http://dl.dropbox.com/u/9879631/drifting02b%20-%20peerstats%20insane.jpg
>
> When I get the Sure board, I plan to hang it on the pc in tandem with 
> this GPS and compare.
>
> Sincerely,
>
> Ron
>
>

I put the following in ntp.conf to allow the clock to coast in local 
mode if the GPS goes insane.

#######################################################################
# Allow system to coast on local clock if GPS is insane

server 127.127.1.1        minpoll 3 maxpoll 6          # LCL, local clock
fudge  127.127.1.1 stratum 12                          # increase stratum

#######################################################################

Does it make any difference if the last digit of the IP address is 0 or 
1 or something else?

Sincerely,

Ron


-- 

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Ron Frazier
timekeepingdude AT c3energy.com



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