[ntp:questions] how will this effect stability

Richard B. gilbert rgilbert88 at comcast.net
Wed Feb 14 15:16:39 UTC 2007


marknmbox-88 at yahoo.com wrote:
> I am in an environment where the path to and from a
> time server can vary from milliseconds to a second and
> the return path may vary within the same range.  The
> transit time for each direction will be independent of
> the time for the other.  Thus the path to the server
> may take a few mills but the return path can take a
> second.  The sum of both paths can range from a few
> mills to seconds.
> 
> Will this cause ntpd problems with accuracy or
> stability or will the ntp calculations not be
> effected?
> 
> I have had several discussions about this and need
> someone who is more familar with the actual
> calculations to help me out.


NTP will have a great deal of difficulty coping with this sort of 
environment.  NTP has to assume symmetry in the outgoing and return 
paths.  The jitter and synchronization distance are both going to be 
high and maybe high enough that ntpd will reject the server!

If you can't fix the network connection, consider getting a hardware 
reference clock.  The Garmin GPS18LVC is available for less than $85 US.
This gives you a reference that is both stable and accurate and will let 
your NTP subnet synchronize quite closely.  Some soldering is required!




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