[Wylug-discuss] NTP question

[Nigel Metheringham]

On 26 Mar 2010, at 10:41, Richard Ibbotson wrote:
> 
> You are supposed to use three servers to get an average value if I 
> remember rightly.  See also...

Going a little into pedant mode...

NTP is different from many other time protocols, in that it believes very much in the idea of the right time - and averaging several time sources does not give a time that is more accurate than any of the individual sources.

So NTP wants several time sources so it can evaluate them against one another and decide which is right - it then syncs to the source it believes is the best one, but continues to monitor the others to build up an idea of source quality (based on their self-proclaimed stratum and accuracy, and on the jitter seen from the source).

You need at least 3 time sources so you can detect one that has gone rogue and is reporting incorrectly.

	Nigel.