Ntp Implementation Mode - H3C S7500 Series Operation Manual

Operation Manual – NTP
H3C S7500 Series Ethernet Switches
The procedures of synchronizing system clocks are as follows:
LS_A sends an NTP packet to LS_B, with the timestamp identifying the time when
it is sent (that is, 10:00:00am, noted as T
When the packet arrives at LS_B, LS_B inserts its own timestamp, which identifies
11:00:01am (noted as T
Before this NTP packet leaves LS_B, LS_B inserts its own timestamp once again,
which identifies 11:00:02am (noted as T
When receiving the response packet, the local time of LS_A is 10:00:03am.
At this time, LS_A has enough information to calculate the following two parameters:
The delay for an NTP packet to make a round trip between LS_A and LS_B: delay
= (T
The time offset of LS_A with regard to LS_B: offset = ((T
LS_A can then set its own clock according to the above information to synchronize its
clock to that of LS_B.
For the detailed information, refer to RFC1305.

1.1.3 NTP Implementation Mode

To accommodate networks of different structures and switches in different network
positions, NTP can operate in multiple modes, as described in the following.
I. Client/Server mode
Filters and selects a clocks
and synchronize the local
clock to that of the preferred
server
Figure 1-2 NTP implementation mode: client/Sever mod
) into the packet.
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-T )-(T -T ).
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Client
Clock synchronization
Response packet
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Server
Network
Wor
auto
request packet
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1-3
Chapter 1 NTP Configuration
-T ) + (T -T
2 1 3
ks in server mode
matically and send
sponse packet
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