NTP Overview
357
NTP Overview
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:
■
For the increment backup between the backup server and client, NTP ensures
the clock synchronization between the two systems.
■
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.
■
Guarantee the normal operation of the inter-system (Remote Procedure Call).
■
Record for an application when a user logs in to a system, a file is modified, or
Basic Operating Principle of NTP
The following figure illustrates the basic operating principle of NTP:
Figure 93
Basic Operating Principle of NTP
In the figure above, Switch A and Switch B are connected via the Ethernet port.
They have independent system clocks. Before implementing automatic clock
synchronization on both Switches, it is assume that:
■
The clock on Switch A is set to 10:00:00am, and that on B is set to
11:00:00am.
■
Switch B serves as an NTP time server. That is, 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.
The system clocks are synchronized as follows:
Network
Network
NTP
消息包
10:00:00am
Network
Network
11:00:01am
NTP
消息包
10:00:00am
11:00:01am
11:00:02am
NTP
消息包
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
Summary of Contents for SuperStack 4
Page 6: ...18 ABOUT THIS GUIDE ...
Page 34: ...46 CHAPTER 1 GETTING STARTED ...
Page 62: ...74 CHAPTER 3 VLAN OPERATION ...
Page 69: ...PoE Configuration 81 ...
Page 70: ...82 CHAPTER 4 POWER OVER ETHERNET POE CONFIGURATION ...
Page 98: ...110 CHAPTER 5 NETWORK PROTOCOL OPERATION ...
Page 220: ...232 CHAPTER 8 ACL CONFIGURATION ...
Page 408: ...420 CHAPTER B RADIUS SERVER AND RADIUS CLIENT SETUP ...
Page 432: ...444 APPENDIX D 3COM XRN ...