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In client/server mode, a client can be synchronized to a server, but a server cannot be synchronized to
a client.
Symmetric peers mode
Figure 8
Symmetric peers mode
In symmetric peers mode:
1.
Devices that work in symmetric active mode and symmetric passive mode exchange NTP
messages with the Mode field 3 (client mode) and 4 (server mode).
2.
Then the device that works in symmetric active mode periodically sends clock synchronization
messages, with the Mode field in the messages set to 1 (symmetric active).
3.
The device that receives the messages automatically enters symmetric passive mode and sends a
reply, with the Mode field in the message set to 2 (symmetric passive).
This exchange of messages establishes symmetric peers mode between the two devices, so the two
devices can synchronize, or be synchronized by, each other. If the clocks of both devices have been
synchronized, the device whose local clock has a lower stratum level synchronizes the clock of the other
device.
Broadcast mode
Figure 9
Broadcast mode
In broadcast mode:
1.
A server periodically sends clock synchronization messages to broadcast address
255.255.255.255, with the Mode field in the messages set to 5 (broadcast mode).