How Ntp Works - H3C S5500-EI series Operation Manual

Operation Manual – NTP
H3C S5500-EI Series Ethernet Switches
In analysis of the log information and debugging information collected from
different devices in network management, time must be used as reference basis.
All devices must use the same reference clock in a charging system.
To implement certain functions, such as scheduled restart of all devices within the
network, all devices must be consistent in timekeeping.
When multiple systems process a complex event in cooperation, these systems
must use that same reference clock to ensure the correct execution sequence.
For increment backup between a backup server and clients, timekeeping must be
synchronized between the backup server and all the clients.
Advantages of NTP:
NTP uses a stratum to describe the clock precision, and is able to synchronize
time among all devices within the network.
NTP supports access control and MD5 authentication.
NTP can unicast, multicast or broadcast protocol messages.

1.1.2 How NTP Works

Figure 1-1
over a network. They have their own independent system clocks, which need to be
automatically synchronized through NTP. For an easy understanding, we assume that:
Prior to system clock synchronization between Switch A and Switch B, the clock of
Switch A is set to 10:00:00 am while that of Switch B is set to 11:00:00 am.
Switch B is used as the NTP time server, namely Switch A synchronizes its clock
to that of Switch B.
It takes 1 second for an NTP message to travel from one switch to the other.
shows the basic work flow of NTP. Switch A and Switch B are interconnected
1-2
Chapter 1 NTP Configuration