[ntp:questions] Query about NTP accuracy

Hal Murray hal-usenet at ip-64-139-1-69.sjc.megapath.net
Sun May 31 02:52:38 UTC 2009


In article <1243711613.525216 at news1nwk>,
 Brian Utterback <brian.utterback at sun.com> writes:
>David Woolley wrote:

>> It only requires 2.  The argument about having four initially is about 
>> having a clear majority even after rejecting one.
>
>I am not sure what you are saying. Are you saying that 4 servers allow 
>you to have a failed server and then outvote a falseticker. I don't 
>think that is true. And it definitely takes three servers to outvote 
>one falseticker in some cases. NTP deals in intervals, and it takes 
>two servers to define one interval, and then one more to make that 
>interval outvote all the others possible intervals. So, three servers 
>will always outvote a single falseticker, but two will not always 
>outvote a single falseticker.

What cases does it take 3 servers to outvote a falseticker?

I thought the idea behind using 4 severs was that 3 was the magic
number (2 could outvote a falseticker) and you still had 3 after
1 (of the 4) died.

-- 
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