Working Principle Of Ntp - H3C S5600 series Operation Manual

Operation Manual – NTP
H3C S5600 Series Ethernet Switches-Release 1510
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.
The local clock of an S5600 series switch cannot operate as a reference clock. And
an S5600 series switch can serve as a time server only when it is synchronized.

1.1.2 Working Principle of NTP

The working principle of NTP is shown in Figure 1-1.
In Figure 1-1, The Ethernet switch A (LS_A) is connected to the Ethernet switch B
(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.
1. 1. 1. 1. 1. 1. 1. 1.
2. 2. 2. 2. 2. 2. 2. 2.
3. 3. 3. 3. 3. 3. 3. 3.
4. 4. 4. 4. 4. 4. 4. 4.
Figure 1-1 Working principle of NTP
NTP Packet NTP Packet NTP Packet NTP Packet NTP Packet NTP Packet NTP Packet NTP Packet 10:00:00 am 10:00:00 am 10:00:00 am 10:00:00 am
10:00:00am 10:00:00am 10:00:00am 10:00:00am
Netw ork Netw ork Netw ork Netw ork Netw ork Netw ork Netw ork Netw ork
LS_A LS_A LS_A LS_A LS_A LS_A LS_A LS_A
NTP Packet 10:00:00 am NTP Packet 10:00:00 am
Netw ork Netw ork Netw ork Netw ork Netw ork Netw ork Netw ork Netw ork
LS_A LS_A LS_A LS_A LS_A LS_A LS_A LS_A
NTP Packet NTP Packet NTP Packet NTP Packet NTP Packet NTP Packet NTP Packet NTP Packet 10:00:00 am 11:00:01 am 11:00:02 am 10:00:00 am 11:00:01 am 11:00:02 am 10:00:00am 10:00:00am 10:00:00 am 11:00:01 am 10:00:00am 10:00:00 am 11:00:01 am 10:00:00am
Netw ork Netw ork Netw ork Netw ork Netw ork Netw ork Netw ork Netw ork
LS_A LS_A LS_A LS_A LS_A LS_A LS_A LS_A
NTP Packet received at 10:00:03 am NTP Packet received at 10:00:03 NTP Packet received at 10:00:03 am NTP Packet received at 10:00:03 am NTP Packet received at 10:00:03 NTP Packet received at 10:00:03 am NTP Packet received at 10:00:03 NTP Packet received at 10:00:03
Netw ork Netw ork Netw ork Netw ork Netw ork Netw ork Netw ork Netw ork
LS_A LS_A LS_A LS_A LS_A LS_A LS_A LS_A
LS LS LS LS LS LS _B _B _B _B _B _B
LS_B LS_B
NTP Packet10:00:00 am NTP Packet10:00:00am NTP Packet10:00:00am NTP Packet10:00:00 am NTP Packet10:00:00am NTP Packet10:00:00am 11:00:01 am 11:00:01 am 11:00:01 am 11:00:01am 11:00:01am 11:00:01am 11:00:01 am 11:00:01am
LS_B LS_B LS LS LS LS LS LS _B _B _B _B _B _B
11:00:01am 11:00:01am 11:00:01am 11:00:01am 11:00:02am 11:00:02am 11:00:02 am 11:00:02am 11:00:02am 11:00:02 am
LS_ LS_ B B
LS LS LS LS LS LS _B _B _B _B _B _B
LS_B LS_B LS LS LS LS LS LS _B _B _B _B _B _B
1-2
Chapter 1 NTP Configuration