[ntp:questions] General ntp architecture question

Steve Kostecke kostecke at ntp.org
Mon Aug 2 17:18:43 UTC 2010

> Richard B. Gilbert <rgilbert88 at comcast.net> wrote:
>> Don't use two servers! It is written that a man with two clocks can
>> never be certain what time it is. Four servers is generally regarded
>> as the minimum. A configuration of five servers can survive the
>> failure of two servers and a configuration of seven servers is able
>> to survive the failure of three.
> This chat comes up all the time, but it is not realistic. When
> you have two GPS receivers and the driver software monitors their
> reception status (as opposed to blindly assuming they are locked),
> having two receivers provides redundancy against failure of one.

This argument also fails to differentiate between relying on time
servers operated by others and a time server that you have control over.

If you are totally reliant on remote time servers (controlled by others)
then you do want sufficient redundancy to protect yourself against
"false tickers" (or broken time sources).

Steve Kostecke <kostecke at ntp.org>
NTP Public Services Project - http://support.ntp.org/

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