Using the xntpd daemon, you can configure a system to synchronize with other hosts using the following methods known as ``association modes'':
A general guideline is to configure all hosts, except for those at the strata furthest from stratum 1 servers, to operate in symmetric active mode.Configure hosts that are furthest from stratum 1 servers to operate in client mode or in broadcast client mode. Use broadcast client mode if your hosts are on a high-speed LAN that supports broadcasts efficiently, especially if there are twenty or more hosts.
If you do opt for broadcast client mode on those hosts, you must configure the time servers on the local network to be both in broadcast mode (to send broadcast NTP packets on the local network) and in symmetric active mode (to poll hosts which are nearer stratum 1).
In client mode, a host polls other hosts to get the current time. From among all of the hosts polled, the local host selects one with which to synchronize.
To configure a host in client mode, there must be a server statement in its NTP configuration file which specifies the name or IP address of each time server to be polled.
In broadcast client or multicast client mode, a host does not poll. Instead, it listens for NTP packets that are broadcast or multicast over the local network.
To configure a host in broadcast or multicast client mode, include a broadcastclient yes statement or a multicastclient yes statement in its NTP configuration file.
In symmetric active mode, a host polls other hosts and responds to polls from those hosts. In addition, hosts retain time-related information about the hosts with which they are communicating.
To configure a host in symmetric active mode, include a peer statement in its NTP configuration file. The name or IP address of each time server must be specified in the peer statement.