[ntp:questions] Re: Estimate of the number of people using the pool system

David L. Mills mills at udel.edu
Mon Oct 20 02:08:57 UTC 2003


The NTP clock discipline increases the poll interval until reaching
maxpoll when incidental jitter and wander, justify. However, there is no
reliable correlation between poll interval and nominal accuracy. In
other words, you can't pick a maxpoll out of the air and expect the
incidental jitter and wander to prevail less than any particular value.
In fact, if the incidental jitter and wander of the pool population is
truly in the tens of milliseconds, the poll interval will probably not
ramp up beyond the default anyway.

If you really are concerned about large client populations, you should
re-engineer the NTP design parameters to optimize for tens of
milliseconds rather than the nominal millisecond as now. This would
include raising both minpoll and maxpoll, as well as changing certain
averaging constants and step thresholds. If it comes to this, servers
should be prepared to light up the call-gap and kiss-o'-death gizmos.

New subject to swim the pool: What do you want to do about
authentication in case a terrorist hijacks one or more servers? I offer
the (optional) Autokey public-key scheme as candidate, which is now in
use here and in evaluation elsewhere. I'm not sure the servers and
potential clients will want to climb that mountain, but it would be good
to know the level of anxiety that prevails in the community and whether
such provisions might by some be considered necessary. Note in passing
that, as suggested for the national laboratory servers, the client and
server cryptographic configuration is largely automated and requires no
per-client operator interaction. And no, I don't think symmetric-key
(MD5) authentication is practical in the pool.


Adrian 'Dagurashibanipal' von Bidder wrote:
> Clinging to sanity, David L. Mills mumbled in his beard:
[While my cling to sanity certainly is tenuous, our fascist news server
won't let me include your message.]

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