H3C Technologies H3C SR8800 - Manual (Page 68)

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A device working in the symmetric active mode periodically sends clock synchronization messages, with
the Mode field in the message set to 1 (symmetric active); the device that receives this message
automatically enters the symmetric passive mode and sends a reply, with the Mode field in the message
set to 2 (symmetric passive). By exchanging messages, the symmetric peers mode is established between
the two devices. Then, the two devices can synchronize, or be synchronized by, each other. If the clocks
of both devices have been already synchronized, the device whose local clock has a lower stratum level
will synchronize the clock of the other device.
Broadcast mode
Figure 23 Broadcast mode
In the broadcast mode, a server periodically sends clock synchronization messages to the broadcast
address 255.255.255.255, with the Mode field in the messages set to 5 (broadcast mode). Clients listen
to the broadcast messages from servers. After a client receives the first broadcast message, the client and
the server start to exchange messages, with the Mode field set to 3 (client mode) and 4 (server mode) to
calculate the network delay between client and the server. Then, the client enters the broadcast client
mode and continues listening to broadcast messages, and synchronizes its local clock based on the
received broadcast messages.
Multicast mode
Figure 24 Multicast mode
In the multicast mode, a server periodically sends clock synchronization messages to the user-configured
multicast address, or, if no multicast address is configured, to the default NTP multicast address 224.0.1.1,
with the Mode field in the messages set to 5 (multicast mode). Clients listen to the multicast messages
from servers. After a client receives the first multicast message, the client and the server start to exchange
messages, with the Mode field set to 3 (client mode) and 4 (server mode) to calculate the network delay