[ntp:questions] Re: Using NTP in broadcast mode with no reverse link

Ben Gamsa ben at somanetworks.com
Wed Dec 3 00:20:05 UTC 2003


Dale Worley <worley at dragon.ariadne.com> wrote in message news:<87wu9g55ef.fsf at netnews.comcast.net>...
> mayer at gis.net (Danny Mayer) writes:
> > It should be receive-only. You didn't post your config file so we have
> > no way of knowing how you set things up. You should only have
> > broadcastclient in your configuration file. broadcastclient puts it
> > into promiscous mode (usually) to receive broadcasts on the local link.
> > It's up to a broadcast server to broadcast the packets.
> 
> Here's what I see in the documentation:
> 
>     http://www.eecis.udel.edu/~mills/ntp/html/assoc.html
> 
>     Association Modes
> 
>     Broadcast/Multicast Modes
> 
>     The server generates broadcast messages continuously [...]. A
>     broadcast client responds to the first message received by waiting a
>     short interval [...]. Then, the client polls the server in burst mode
>     in order to quickly set the host clock and validate the source. This
>     normally results in a volley of eight client/server cycles at 2-s
>     intervals during which both the synchronization and cryptographic
>     protocols run concurrently.
> 
> Dale


Yup, that's exactly what I see in practice.  I've also found that if it
has problems during that burst mode, it will remain in client-poll mode,
and never switch to only listening on the broadcast.

    ben



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