[time-nuts] Warped back to 1993

Martin Burnicki martin.burnicki at burnicki.net
Sun Aug 11 15:45:31 EDT 2013


Bob Camp wrote:
> Hi
>
> The issue with the fudge option is that you need to engage it at
> exactly the right point. Put another way, there's a period between it
> failing and your entering a fudge that the NTP server is down.

The question is whether you know in advance *when* the problem will occur.

If you observe that your GPS sends a wrong date you are already after 
the point where the bug started to occur, so you can safely add a fudge 
value to get this working for the next 1024 weeks.

> With a
> couple lines of auto correct code in there, it would (essentially)
> never fail. If you are running a GPS, you enable the auto-correction
> and forget about it. My guess is that many GPS devices will
> eventually suffer from the wrap around. The  only way they could
> avoid it would be some sort of external correction (like continuous
> firmware updates) or a "no reverse" on the year. Both approaches have
> their drawbacks…..

Unless you know the source code of the firmware you can only assume what 
is the reason for the wrong date being sent. I'm not sure whether a 
piece of software like ntpd should try to work around all possible kinds 
of firmware bugs in all possible types of GPS receivers.

Martin



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