[ntp:questions] Two servers, one client : one problem
david at ex.djwhome.demon.invalid
Wed May 4 06:49:49 UTC 2011
Richard B. Gilbert wrote:
> NTP is hierarchical! It expects to get time from an external source
> such as NTP servers on the internet. The hierarchy starts with an
> "atomic clock" such as those operated by NIST or equivalent. These are
There is nothing that prevents an atomic clock (no quotes) being used at
any level in the hierarchy. Good means much better than the estimated
error contributions between the standard and the ntp client.
The key requirement, that is being violated here, is that the top
stratum sources should be good approximations to the same time scale.
"atomic clock" in quotes is marketing hype for devices that may coast
with un-temperature controlled crystal accuracy for 24 hours, but then
be resynchronised, within about 100ms to a radio transmission derived
from an atomic clock calibrated to a national standard, which is in turn
calibrated (after the fact) to UTC.
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