Introduction To Ntp - Huawei S9300 Configuration Manual

S9300&S9300E Terabit Routing Switch
Configuration Guide - Network Management

4.1 Introduction to NTP

This part describes the application and working principles of NTP.
Network Time Protocol (NTP) synchronizes clocks of all devices in a network. It keeps all the
clocks of these devices consistent, and enables devices to implement various applications based
on the uniform time.
Any local system that runs NTP can be time synchronized by other clock sources, and also
functions as a clock source to synchronize other clocks. In addition, mutual synchronization can
be performed by exchanging NTP packets.
NTP packets are encapsulated in UDP packets for transmission and the port used by the NTP
protocol is 123.
NTP Application
NTP is applied to the following situations where all the clocks of hosts or switchs in a network
need to be consistent:
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When all the devices on a network need to be synchronized, it is almost impossible for an
administrator to manually change the system clock by executing command lines. This is because
the work load is heavy and clock accuracy cannot be ensured. NTP can quickly synchronize the
clocks of network devices and ensure their precision.
NTP has the following advantages:
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Principles of NTP
Figure 4-1
They both have their own system clocks. NTP implements automatic synchronization of their
clocks.
Suppose:
Issue 01 (2012-03-15)
Network management: Analysis on logs or debugging information collected from different
switchs should be performed based on time.
Charging system: requires the clocks of all devices to be consistent.
Completing certain functions: For example, restart of all the switchs in a network requires
the clocks of all the switchs be consistent.
Several systems working together on the same complicate event: Systems have to take the
same clock for reference to ensure a proper sequence of implementation.
Incremental backup between the backup server and clients: Clocks on the backup server
and clients should be synchronized.
User login time: Some applications need to know the time when user logs in to the system
and the file revision time.
Defines clock accuracy by means of stratum to synchronize the time of network devices in
a short time
Supports access control and MD5 authentication
Transmits packets in unicast, manycast, or broadcast mode
shows the principles of NTP. Switch A and Switch B are connected through a WAN.
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