[ntp:questions] zeroconf for ntpd?

Wolfgang S. Rupprecht wolfgang.rupprecht+gnus200705 at gmail.com
Wed May 23 15:45:41 UTC 2007

Steve Kostecke <kostecke at ntp.isc.org> writes:
> 1. Multicast associations can not compensate for changing network
> conditions at each poll.

I'm picturing a second class of home user or small business that would
be very happy to have their computers all within a second of the
correct time and within milliseconds of each others time.

Looking at the usage graphs of the pools, there are only 2-6 million
pools users.  That probably accounts for most of the ntp users in the
world.  The current estimates are over 400 million internet-connected
computers.  It is going to be challenging to pick up all these users
using any unicast-based scheme.

> 2. Muticast clients must use NTP authentication if they wish to control
> which multicast servers they will accept. This requirement impacts
> the autonomous configuration aspect of multicast (or manycast, for that
> matter).

This is the part that might be the easiest.  If a few well known
stratum 1's (say NIST itself) were to emit signed multicast packets
the clients could just pick the servers they trusted.  This obviously
isn't secure from playback attacks, but would keep misconfigured
servers from screwing things up too terribly.  (Although the playback
attacks could be dealt with by simply discarding any multicast packet
from a normally trusted server that was too much older than the time
being displayed in packets from other trusted servers.)

Wolfgang S. Rupprecht                http://www.wsrcc.com/wolfgang/
Hints for IPv6 on FC6 http://www.wsrcc.com/wolfgang/fedora/ipv6-tunnel.html

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