Operation Manual – NTP
H3C S5500-EI Series Ethernet Switches
Chapter 1 NTP Configuration
1-2
z
In analysis of the log information and debugging information collected from
different devices in network management, time must be used as reference basis.
z
All devices must use the same reference clock in a charging system.
z
To implement certain functions, such as scheduled restart of all devices within the
network, all devices must be consistent in timekeeping.
z
When multiple systems process a complex event in cooperation, these systems
must use that same reference clock to ensure the correct execution sequence.
z
For increment backup between a backup server and clients, timekeeping must be
synchronized between the backup server and all the clients.
Advantages of NTP:
z
NTP uses a stratum to describe the clock precision, and is able to synchronize
time among all devices within the network.
z
NTP supports access control and MD5 authentication.
z
NTP can unicast, multicast or broadcast protocol messages.
1.1.2 How NTP Works
Figure 1-1
shows the basic work flow of NTP. Switch A and Switch B are interconnected
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:
z
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.
z
Switch B is used as the NTP time server, namely Switch A synchronizes its clock
to that of Switch B.
z
It takes 1 second for an NTP message to travel from one switch to the other.
