[ntp:questions] Re: ntp & adsl

David Woolley david at djwhome.demon.co.uk
Tue Jan 31 07:45:01 UTC 2006

In article <20060130213053.GP21673 at vanheusden.com>,
folkert at vanheusden.com (Folkert van Heusden) wrote:

>  GENERIC(0)      .DCFa.           0 l   23   64    3    0.000  -17.386  26.356  <- dcf77 receiver

> +auth1.xs4all.nl    2 u  973 1024  377    8.421    1.179   0.024  <- ntp server of my ISP

The maximum theoretical contribution from ADSL here is half of 8.421ms, and
in practice will be rather less.  I'd say that assymmetric loading of the
line causes much more problems than assymmetric speeds.  In fact the natural
assymmetric loading tends to act in the opposite direction from the speed

In this case, I would say that it was much more likely that the DCF clock
is reading wrongly, probably because it is not compensating for the group
delays/rise time in its filters, particularly the post detection filter.

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