[ntp:questions] Re: NTP Pool rules vs. four-server advice
davids at webmaster.com
Tue Dec 20 01:20:39 UTC 2005
"Brian Utterback" <brian.utterback at sun.removeme.com> wrote in message
news:do6n6k$rol$1 at news1brm.Central.Sun.COM...
> servers can protect from certain classes of falseticker situations
> involving one falseticker, but some combinations may not be prevented.
This is really not true. If we define falseticker as "a clock that is so
far off that we are screwed if we trust it", the only possibilities are:
1) There are no falsetickers, in which case, it doesn't matter which
clock we follow.
2) There is one falseticker and two accurate clocks. In which case,
using either of the two clocks in closest agreement is fine. You cannot put
the falseticker close enough to the other two clocks to confuse us without
making it no longer a falseticker.
3) There is more than one falseticker, in which case we know we can't
keep accurate time.
The mathematical argument for why you need four clocks considers *you*
to be one of the clocks. If there's you, and three configured references,
then you do have four clocks.
You do not need four servers to protect against one inaccurate or
More information about the questions