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3Com Switch 8800 Configuration Guide Chapter 49 NTP Configuration
49-1
Chapter 49 NTP Configuration
49.1 Brief Introduction to NTP
49.1.1 NTP Functions
As the network topology gets more and more complex, it becomes important to
synchronize the clocks of the equipment on the whole network. Network Time Protocol
(NTP) is the TCP/IP that advertises the accurate time throughout the network.
NTP ensures the consistency of the following applications:
z For the increment backup between the backup server and client, NTP ensures the
clock synchronization between the two systems.
z For multiple systems that coordinate to process a complex event, NTP ensures
them to reference the same clock and guarantee the right order of the event.
z Guarantee the normal operation of the inter-system (Remote Procedure Call).
z Record for an application when a user logs in to a system, a file is modified, or
some other operation is performed.
49.1.2 Basic Operating Principle of NTP
The following figure illustrates the basic operating principle of NTP:
Network
Network
NTP
packet
10:00:00am
Network
Network
11:00:01am
NTP
packet
10:00:00am
11:00:01am 11:00:02am
NTP
packet
10:00:00am
NTP Packet received at 10:00:03
1.
2.
3.
4.
LS_A
LS_A
LS_A
LS_A
LS_B
LS_B
LS_B
LS_B
Figure 49-1 Basic operating principle of NTP
In the figure above, Ethernet Switch A and Ethernet Switch B are connected through
the Ethernet port. They have independent system clocks. Before implement automatic
clock synchronization on both switches, we assume that: