3Com S7902E, Руководство по настройке

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NTP Configuration
When configuring NTP, go to these sections for information you are interested in:
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NTP Overview
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NTP Configuration Task List
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Configuring the Operation Modes of NTP
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Configuring the Local Clock as a Reference Source
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Configuring Optional Parameters of NTP
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Configuring Access-Control Rights
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Configuring NTP Authentication
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Displaying and Maintaining NTP
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NTP Configuration Examples
NTP Overview
Defined in RFC 1305, the Network Time Protocol (NTP) synchronizes timekeeping among distributed
time servers and clients. NTP runs over the User Datagram Protocol (UDP), using UDP port 123.
The purpose of using NTP is to keep consistent timekeeping among all clock-dependent devices within
the network so that the devices can provide diverse applications based on the consistent time.
For a local system running NTP, its time can be synchronized by other reference sources and can be
used as a reference source to synchronize other clocks.
Applications of NTP
An administrator can by no means keep time synchronized among all the devices within a network by
changing the system clock on each station, because this is a huge amount of workload and cannot
guarantee the clock precision. NTP, however, allows quick clock synchronization within the entire
network while it ensures a high clock precision.
NTP is used when all devices within the network must be consistent in timekeeping, for example:
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In analysis of the log information and debugging information collected from different devices in
network management, time must be used as reference basis.
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All devices must use the same reference clock in a charging system.
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To implement certain functions, such as scheduled restart of all devices within the network, all
devices must be consistent in timekeeping.
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When multiple systems process a complex event in cooperation, these systems must use that
same reference clock to ensure the correct execution sequence.
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For incremental backup between a backup server and clients, timekeeping must be synchronized
between the backup server and all the clients.
Advantages of NTP
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NTP uses a stratum to describe the clock precision, and is able to synchronize time among all
devices within the network.