H3c-technologies H3C SecBlade NetStream Cards Manual do Utilizador descarregar pdf (Página 209)

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Symmetric peers mode

Figure 58 Symmetric peers mode

In symmetric peers mode, 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). 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); 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). 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 synchronized, the device whose local clock has a lower stratum level synchronizes the clock

of the other device.

Broadcast mode

Figure 59 Broadcast mode

In broadcast mode, 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). Clients listen to the

broadcast messages from servers. When 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.

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H3c-technologies H3C SecBlade NetStream Cards Manual do Utilizador Página 209