H3C S3100 8C SI User Manual

Operation Manual – NTP
H3C S3100 Series Ethernet Switches Chapter 1 NTP Configuration
1-3
IP network
IP network
IP network
IP network
Device BDevice 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.
Figure 1-1 Implementation principle of NTP
The procedure of synchronizing the system clock is as follows:
z Device A sends an NTP message to Device B, with a timestamp 10:00:00 am (T
1
)
identifying when it is sent.
z When the message arrives at Device B, Device B inserts its own timestamp
11:00:01 am (T
2
) into the packet.
z When the NTP message leaves Device B, Device B inserts its own timestamp
11:00:02 am (T
3
) into the packet.
z 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:
z Delay for an NTP message to make a round trip between Device A and Device B:
Delay = (T
4
-T
1
)-(T
3
-T
2
).
z Time offset of Device A relative to Device B:
Offset = ((T
2
-T
1
) + (T
3
-T
4
))/2.
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.

H3C S3100 8C SI Specifications

General

Brand	H3C
Model	S3100 8C SI
Category	Switch
Language	English