[time-nuts] Discipline an oscillator with NTP?

[Poul-Henning Kamp]

In message <CABbxVHuz+Yo+fCH1qb3xSuppFPCNPbghOe1JBQsRDGQL_c+Q9w at mail.gmail.com>
, Chris Albertson writes:
>On Sat, Jul 23, 2011 at 10:40 AM, Bob Camp <lists at rtty.us> wrote:

>NTP's clock selection algorithm is pretty good.  If you choose a
>diverse set of servers then NTP will only use the subset of them that
>are self consistent.

That depends a lot on your definition of "good".

If you give the clock selection algoritm more than 5 choices, it
tends to be fickle and change reference server far too often.

The same will happen with fewer really good (=close) servers.

>So I think you can trust the consensus time from a set of five
>randomly selected pool servers.  It would be far easier to spoof WWV,
>just set up a transmitter.

NTPd does build a consensus, it picks a winner.

If you want to do something like this, the one thing you want to
do is hand-pick the NTP server you use, and clamp its minpoll/maxpoll
to the same value.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
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