3Com Switch 7700, Руководство по настройке

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NTP 357
NTP
As the network topology gets more and more complex, it becomes important to
synchronize the clocks of the equipment on the entire network. Network Time
Protocol (NTP) is a TCP/IP feature that advertises the accurate time throughout the
network.
NTP ensures the consistency of the following applications:
■
Synchronizing the clock between two systems for incremental backup between
the backup server and client.
■
Referencing the same clock and guaranteeing correct processing for multiple
systems that coordinate to process a complex event.
■
Guaranteeing the normal operation of the inter-system (Remote Procedure
Call).
■
Recording an application when a user logs into a system, a file is modified, or
some other operation is performed.
Figure 7 illustrates the basic operating principle of NTP:
Figure 7 Basic Operating Principle of NTP
In page 357, Ethernet Switch A and Ethernet Switch B are connected to the
Ethernet port. They have independent system clocks. Before implementing
automatic clock synchronization on both switches, we assume that:
■
Before synchronizing the system clocks on Ethernet Switch A and B, the clock
on Ethernet Switch A is set to 10:00:00am, and the clock on B is set to
11:00:00am.
■
Ethernet Switch B serves as an NTP time server and Ethernet Switch A
synchronizes the local clock with the clock of B.
■
It takes 1 second to transmit a data packet from either A or B to the opposite
end.