4.1 Introduction to NTP
This part describes the application and working principles of NTP.
NTP(Network Time Protocol) aims to synchronizing 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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Network management: Analysis on logs or debugging information collected from different
switchs should be performed based on time.
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Charging system: requires the clocks of all devices to be consistent.
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Completing certain functions: For example, timing restart of all the switchs in a network
requires the clocks of all the switchs be consistent.
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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.
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Incremental backup between the backup server and clients: Clocks on the backup server
and clients should be synchronized.
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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Defining clock accuracy by means of stratum to synchronize the time of network devices
in a short time
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Supporting access control and MD5 authentication
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Transmitting packets in unicast, multicast, or broadcast mode
Principles of NTP
shows the principles of NTP. Switch A and Switch B are connected through a WAN.
They both have their own system clocks. NTP implements automatic synchronization of their
clocks.
Suppose:
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Before the system clocks of Switch A and Switch B are synchronized, the clock of Switch
A is set to 10:00:00 am and the clock of Switch B is set to 11:00:00 am.
Quidway S2700 Series Ethernet Switches
Configuration Guide - Network Management
4 NTP Configuration
Issue 01 (2011-07-15)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
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