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HUAWEI NetEngine5000E Core Router
Configuration Guide - System Management
Principles of NTP
Figure 2-1
They both have their own system clocks. NTP implements automatic synchronization of their
clocks.
Suppose:
l
l
l
l
Figure 2-1 NTP basic principle diagram
Step1:
Step2:
Step3:
Step4:
The process of synchronizing system clocks is as follows:
1.
2.
3.
Issue 01 (2011-10-15)
shows the principles of NTP. Router A and Router B are connected through a WAN.
Before the system clocks of Router A and Router B are synchronized, the clock of
Router A is set to 10:00:00 am and the clock of Router B is set to 11:00:00 am.
Router B functions as an NTP time server. That is, Router A synchronizes its clock with
that of Router B.
One-way transmission of data packets between Router A and Router B takes one second.
Processing of data packets between Router A or Router B takes one second.
NTP packet
10:00:00 am
RouterA
RouterA
RouterA
NTP Packet received at 10:00:03 am
RouterA
Router A sends an NTP packet to Router B. The packet carries the originating timestamp
when it leaves Router A, which is 10:00:00 am (T
When the NTP packet reaches Router B, Router B adds its receiving timestamp to the NTP
packet, which is 11: 00:01 am (T
When the NTP packet leaves Router B, Router B adds its transmitting timestamp to the
NTP packet, which is 11:00:02 am (T
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Network
NTP packet
Network
NTP packet
10:00:00 am
Network
Network
).
2
).
3
2 NTP Configuration
RouterB
10:00:00 am
11:00:01 am
RouterB
11:00:01 am
11:00:02 am
RouterB
RouterB
).
1
15
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