[ntp:questions] National time standard differences

Joseph Gwinn joegwinn at comcast.net
Tue Feb 9 13:44:43 UTC 2010


In article <c2bcn.37983$Ym4.23174 at text.news.virginmedia.com>,
 "David J Taylor" 
 <david-taylor at blueyonder.delete-this-bit.and-this-part.co.uk.invalid> 
 wrote:

> > I've setup an NTP server in the south east asia region synchonising
> > with regional NTP servers as well as a couple of servers I am
> > responsible for in the US.
> >
> > remote        st t when poll reach   delay   offset  jitter
> > ==============================================
> > +Japan         1 u  454 1024  377   87.402   -0.560   0.056
> > *Japan         1 u  476 1024  377   87.277   -0.810   1.542
> > -NorthAmerica  2 u  427 1024  377  285.387  -17.741   5.084
> > -NorthAmerica  2 u  429 1024  377  307.208  -17.061   0.083
> >
> > Is the above delta seen between Japanese and North American time
> > sources purely the delta between the outbound / return network path or
> > something else?
> >
> > Chris
> 
> Chris,
> 
> Most likely asymmetrical paths, yes.  

The wide area networks used for international connections are typically 
SONET rings, which are inherently asymmetrical.  

As one works around a ring, the poll response time is constant (being 
the perimeter of the ring), while the out and back times vary with 
position on the ring with respect to the server one is polling.

Joe Gwinn




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