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Operation Manual – NTP
H3C S3100 Series Ethernet Switches
NTP message
Device A
1.
Device A
2.
Device A
3.
NTP message received at 10:00:03 am
Device A
4.
Figure 1-1 Implementation principle of NTP
The procedure of synchronizing the system clock is as follows:
Device A sends an NTP message to Device B, with a timestamp 10:00:00 am (T
identifying when it is sent.
When the message arrives at Device B, Device B inserts its own timestamp
11:00:01 am (T
When the NTP message leaves Device B, Device B inserts its own timestamp
11:00:02 am (T
When receiving a response packet, the local time of Device A is 10:00:03 am (T4).
At this time, Device A has enough information to calculate the following two
parameters:
Delay for an NTP message to make a round trip between Device A and Device B:
Time offset of Device A relative to Device B:
Device A can then set its own clock according to the above information to synchronize
its clock to that of Device B.
For detailed information, refer to RFC 1305.
10:00:00 am
IP network
NTP message
IP network
NTP message
10:00:00 am
IP network
IP network
) into the packet.
2
) into the packet.
3
Delay = (T
Offset = ((T
2
1-3
Chapter 1 NTP Configuration
Device B
10:00:00 am
11:00:01 am
Device B
11:00:01 am
11:00:02 am
Device B
Device B
-T
)-(T
-T
).
4
1
3
2
-T
) + (T
-T
))/2.
1
3
4
)
1
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