Working Principle Of Ntp - H3C S7500 Series Operation Manual

Operation Manual – NTP
H3C S7500 Series Ethernet Switches
Note:
The accuracy of a clock is determined by its stratum, which ranges from 1 to 16. The
stratum of the reference clock ranges from 1 to 15. The accuracy descends with the
increasing of stratum number. The clocks with the stratum of 16 are in unsynchronized
state and cannot serve as reference clocks.

1.1.2 Working Principle of NTP

The working principle of NTP is shown in
In Figure
(LS_B) through their Ethernet ports. Both of them have system clocks of their own, and
they need to synchronize the clocks of each other through NTP. For ease of
understanding, suppose that:
Before the system clocks of LS_A and LS_B are synchronized, the clock of LS_A
is set to 10:00:00am, and the clock of LS_B is set to 11:00:00am.
LS_B serves as the NTP time server, that is, the clock of LS_A will be
synchronized to that of LS_B.
It takes one second for a packet sent by one switch to reach the other.
NTP message
LS_A
1.
2. LS_A
LS_A
3.
NTP message received at 10:00:03 am
4.
LS_A
Figure 1-1 Working principle of NTP
1-1, The Ethernet switch A (LS_A) is connected to the Ethernet switch B
10:00:00 am
IP network
NTP message
IP network
NTP message
IP network
IP network
Figure 1-1.
10:00:00 am
10:00:00 am 11:00:01 am
1-2
Chapter 1 NTP Configuration
LS_B
11:00:01 am
LS_B
11:00:02 am
LS_B
LS_B