3Com Switch 8800 Advanced Software V5 Configuration Guide

1064 CHAPTER 85: NTP CONFIGURATION
An administrator can by no means keep synchronized time among all the devices
within a network by changing the system clock on each station, because this is a
huge amount of workload and cannot guarantee the clock precision. NTP,
however, allows quick clock synchronization within the entire network while it
ensures a high clock precision.
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.
How NTP Works Figure 312 shows the basic work flow of NTP. Device A and Device 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:
■ Prior to system clock synchronization between Device A and Device B, the clock
of Device A is set to 10:00:00am while that of Device B is set to 11:00:00am.
■ Device B is used as the NTP time server, namely Device A synchronizes its clock
to that of Device B.
■ It takes 1 second for an NTP message to travel from one device to the other.
Figure 312 Basic work flow of NTP
The process of system clock synchronization is as follows:
IP network
IP network
IP network
IP network
Device BDevice A
Device B
Device A
Device B
Device A
Device B
Device A
10:00:00 am 11:00:01 am
10:00:00 am
NTP message 10:00:00 am 11:00:01 am 11:00:02 am
NTP message
NTP message
NTP message received at 10:00:03 am
1.
3.
2.
4.