[ntp:questions] ntp server specs

Chris Albertson albertson.chris at gmail.com
Thu Apr 21 05:20:54 UTC 2011

On Wed, Apr 20, 2011 at 6:11 PM, Richard B. Gilbert
<rgilbert88 at comcast.net> wrote:
> On 4/20/2011 7:43 PM, Chris Albertson wrote:

> Two NTP servers does not constitute a solution to the problem.  If the two
> servers disagree, which one do you believe?

I'll argue that in the general case, you are right.  But in the
specific case where you have control of the servers you can cross
check them using other means outside of NTP. For example you might own
some radio clocks (like GPS)

Even with eight NTP servers how do you know all of them are not wrong
by the exact same amount. They would all agree.   You always need some
method to verify correctness that does not depend on the system you
are checking.

Back to the general case.  Yes if are unable to access the servers
except via NTP protocol then yes you had better use several of them.
if the servers are all independently managed you may assume that those
servers that agree are sowing the correct time.  But  if the servers
are managed by the same person, agreement does not mean they are all
correct.  I think agreement only indicates correctness if the servers
are independent

Hence I don't see the need for one person maintaining a large number
of identical servers

Chris Albertson
Redondo Beach, California

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