3Com WX3000 operation manual Implementation Principle of NTP

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In network management, the analysis of the log information and debugging information collected from different devices is meaningful and valid only when network devices that generate the information adopts the same time.

The billing system requires that the clocks of all network devices be consistent.

Some functions, such as restarting all network devices in a network simultaneously require that they adopt the same time.

When multiple systems cooperate to handle a rather complex transaction, they must adopt the same time to ensure a correct execution order.

To perform incremental backup operations between a backup server and a host, you must make sure they adopt the same time.

NTP has the following advantages:

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Defining the accuracy of clocks by stratum to synchronize the clocks of all devices in a network quickly

Supporting access control (See Configuring Access Control Right) and MD5 encrypted authentication (See Configuring NTP Authentication)

Sending protocol packets in unicast, multicast, or broadcast mode

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The clock stratum determines the accuracy, which ranges from 1 to 16. The stratum of a reference clock ranges from 1 to 15. The clock accuracy decreases as the stratum number increases. A stratum 16 clock is in the unsynchronized state and cannot serve as a reference clock.

The local clock of the device cannot be set as a reference clock. It can serve as a reference clock source to synchronize the clock of other devices only after it is synchronized.

Implementation Principle of NTP

Figure 1-1 shows the implementation principle of NTP.

Device A is connected to Device B through Ethernet ports. Both having their own system clocks, they need to synchronize the clocks of each other through NTP. To help you to understand the implementation principle, we suppose that:

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Before the system clocks of Device A and Device B are synchronized, the clock of Device A is set to 10:00:00 am, and the clock of Device B is set to 11:00:00 am.

Device B serves as the NTP server, that is, the clock of Device A will be synchronized to that of Device B.

It takes one second to transfer an NTP message from Device A to Device B or from Device B to Device A.

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