Broadcast: The NTP server broadcasts its presence to local networks, and the clients respond through a packet exchange to determine round-trip time and delay. Broadcast mode can be used to synchronize large numbers of hosts on an IP address block.
Manycast: The clients send an NTP broadcast to a destination network. Once an NTP server responds to the client broadcast, the client will continue to use that specific NTP server. This is useful when hosts are mobile and don't know the address of the current NTP server. Manycast is only available in NTP 4, which is not yet a formal IETF RFC.
Multicast: NTP clients and servers are configured to use the multicast group address (224.0.1.1) for sending and receiving NTP messages. Make sure your intervening routers support multicast as well. This model is for environments with mobile devices and destination networks that support multicast.
1. Download the production Unix tarball and patches. Those are available from www.ntp.org/downloads.html.
2. Unzip and untar the archive. Follow the directions in the readme file to compile and install the programs.
3. Get a list of public time servers on the Internet (www.eecis.udel.edu/~mills/ntp/servers.html). Follow the access policies of the public servers located here.
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