[ntp:questions] Re: NTP hardware server broadcasting or being polled?

Danny Mayer mayer at gis.net
Thu Sep 30 03:07:50 UTC 2004

brad at shub-internet.org wrote in message news:<20040929092556.290$5E at newsreader.com>...
> the_determinant at hotmail.com (The Determinant) wrote:
> > If you have an NTP server (actual hardware) serving a network, should
> > the clients (PCs) be polling the server or should the server broadcast
> > the time to the clients? Which is a better configuration? Is the
> > answer different for a small or larger network?
> For a small network, polling mode is fine.  For a larger network,
> broadcast, multicast, or manycast would be preferred, in order to keep the
> load on the time servers to a reasonable level.
> What is "small" versus what is "large"?  That's hard to say.  For some
> people, anything more than about a dozen clients is "large", and for others
> the numbers have to be in the hundreds or thousands.  This is more of a
> judgement call on your part.
> Now, once you get into broadcast, multicast, or manycast modes, you should
> also investigate server authentication features, so that you can help
> ensure that a rogue server on your network can't subvert the time sync for
> your clients.  Spoofing is possible with polling mode, but would be a bit
> more difficult.

Multicast is currently the best way since nonparticipants don't get the
packet from the multicast server. I don't understand manycast at this
point. I don't believe that there is any advantage to running broadcast
over multicast.


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