Advantages of ntp, How ntp works – H3C Technologies H3C WX6000 Series Access Controllers User Manual
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Advantages of NTP
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NTP uses a stratum to describe the clock precision, and is able to synchronize time among all
devices within the network.
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NTP supports access control and MD5 authentication.
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NTP can unicast, multicast or broadcast protocol messages.
How NTP Works
shows the basic workflow of NTP. Device A and Device B are interconnected over a network.
They have their own independent system clocks, which need to be automatically synchronized through
NTP. For an easy understanding, we assume that:
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Prior to system clock synchronization between Device A and Device B, the clock of Device A is set
to 10:00:00 am while that of Device B is set to 11:00:00 am.
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Device B is used as the NTP time server, namely, Device A synchronizes its clock to that of Device
B.
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It takes 1 second for an NTP message to travel from one device to the other.
Figure 6-1 Basic work flow of NTP
IP network
IP network
IP network
IP network
Device B
Device A
Device B
Device A
Device B
Device A
Device B
Device A
10:00:00 am
11:00:01 am
10:00:00 am
NTP message
10:00:00 am
11:00:01 am
11:00:02 am
NTP message
NTP message
NTP message received at 10:00:03 am
1.
3.
2.
4.
The process of system clock synchronization is as follows:
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Device A sends Device B an NTP message, which is timestamped when it leaves Device A. The
time stamp is 10:00:00 am (T1).
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When this NTP message arrives at Device B, it is timestamped by Device B. The timestamp is
11:00:01 am (T2).
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When the NTP message leaves Device B, Device B timestamps it. The timestamp is 11:00:02 am
(T3).