Network Time Protocol is a network protocol used for clock synchronization that is, to synchronize the computer clock times in the network. Network Time Protocol can operate in four different modes, they are:

  • Client mode
  • Server mode
  • Peer mode
  • Broadcast/Multicast mode

NTP Client Mode

An NTP client is a network device that is used to make an initial request with the external NTP time server for the time to synchronize its own clock. NTP clients are configured to NTP time servers like ‘Galleon Systems’ NTP servers.

When an NTP server broadcasts and if the clients are set up to ‘listen’ the broadcasts instead of making the initial request for the time, clients start to receive the time. On a network infrastructure, the NTP client mode device does not provide any synchronization service. 

NTP Server mode

NTP server is a network device and it operates an NTP service. By utilizing the network time protocol, these devices supply time information to NTP clients.  And it supplies time information to authorized NTP clients only and it will not receive any time synchronized information from any unauthorized devices.

The very common internet configuration is the client/server model. In this mode, the client will send requests to the server, and the client will expect the response within milliseconds even though the time source is unavailable or extremely busy.

A client distributes a network time protocol to one or more than one servers and the actions are based on replies received from the sever. Before returning the message the server will exchange the address, ports, overwrite some of the fields in the message and recalculate the checksum.

The returned message makes the client to calculate the server time by concerning the local time and make a change in the clock accordingly.

NTP Peer mode

Peered devices will act as a back-up to each other and each peer will have one or more than one primary reference sources but none of the peer devices has authority over the other.

If one of the peers lose all its time reference source or if it stops operating completely, then the remaining peer devices automatically reconfigure so that that time values will flow from the surviving peers to all others across the network.

Broadcast/Multicast mode

In broadcast/multicast mode the NTP server simply broadcast/multicast time synchronization information to all NTP clients in that network.  If the time accuracy and reliability have no importance, in that cases the clients can be configured to use the broadcast/multicast modes. Usually, these modes are not setup for servers that have dependent clients.

The main benefit of these modes is that the clients do not need to be configured to any particular server, the same configured file can be used by enabling all operating clients.