[ntp:questions] Befuddled and confused, again...

unruh unruh at wormhole.physics.ubc.ca
Mon Feb 15 21:26:36 UTC 2010

On 2010-02-15, Dave Baxter <spam at goes.nowhere.com> wrote:
> On 2010-02-14, Dave Baxter <spam at goes.nowhere.com> wrote:
>> [quoted text muted]
> GPSD as in Global Positioning System Diciplined.

No idea what gpsd stands for. It is program used to read the signals
from a gps receiver and deliver them to ntpd via the shm refclock. 

> Yes, it uses the DCD line (I think) to input the PPS signal from the GPS 
> receiver, a Garmin GPS16LVS in this case.  It's all configured and 
> working on a Win2k box, with the Meinberg port, but I want that physical 
> machine for something else, so I'm trying to get the FreeBSD version 
> going.

Now, I am not sure whether gpsd will run on bsd, but I suspect it should
not be hard to convert it to do so. The ioctl calls to the serial port
or parallel port may well be different, but there are very few of them
in the code. 

> NTP timekeeping via the internet is not reliable at the mS level, I 
> suffer time of day related WAN congestion, sometimes the end to end 
> latnecy can be over 1.5 seconds, but no packet loss, so the ISP says 
> that's good!   Hence my need for a local NTP source, as 'net based is 
> not a viable option for me at this time.

WOW. What kind of a wan is that? 

> Based on the Meinberg port of NTPD behaviour, the pull in time is not a 
> problem, as the thing is left on 24/7 and on a UPS.  If that lot ever 
> collapses, then by the time I've got everything else back up and 
> pumping, even NTPD has pulled in enough to keep Faros happy(ish.)  (It 
> might misidentify the ZL beacon signal's path perhaps, but the others 
> will measure OK.
> I suspect even Chrony wont tolerate variable network timing either.  Oh, 

Nope. It uses the ntp protocol, which has no ability to correct for
asymmetric round trip times.  Chrony's advantage might be in speed of
convergence.  But for that it needs good times. 

> it's asymetric and grosly variable ping to ping too, but as there is no 
> packet loss, they won't do anything to improve matters as I'm a "home" 
> (not busines) user...  After about 6PM local, everything becomes nice 
> and fast again, until 9AM the next day.  Traffic shaping by any other 
> name, except at weekends!
> I still do not know the exact path needed for the Make.conf file.

Sorry, I do not know what this question means. 

> Help?

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