NTP configuration
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 a
network so that the devices can provide diverse applications based on the consistent time.
The time of a local system running NTP can be synchronized to other reference sources, and can be used
as a reference source to synchronize other clocks.
Applications of NTP
An administrator is unable to keep time synchronized among all the devices within a network by
changing the system clock on each station because this would be a huge amount of work and would not
guarantee clock precision. NTP, however, allows quick clock synchronization within the entire network
and it ensures a high degree of clock precision.
Use NTP when all devices within the network must be consistent in timekeeping, for example:
• In analysis of the log information and debugging information collected from different devices in
network management, time must be used as reference basis.
• All devices must use the same reference clock in a charging system.
• To implement certain functions, such as scheduled restart of all devices within the network, all
devices must be consistent in timekeeping.
• To ensure the correct execution sequence when multiple systems process a complex event in
cooperation, the systems must all use the same reference clock.
• For incremental backup between a backup server and clients, timekeeping must be synchronized
between the backup server and all the clients.
NOTE:
• Clock stratum determines the accuracy of a server, which ranges from 1 to 16. Clock accuracy decreases
as the stratum number increases. The stratum of a reference clock ranges from 1 to 15. A stratum 16
clock is in the unsynchronized state.
• The local clock of an Ethernet switch cannot operate as a reference clock. It can serve as an NTP server
only after it is synchronized.
Advantages of NTP
• NTP uses a stratum to describe the clock precision, and is able to synchronize time among all
devices within the network.
• NTP supports access control and MD5 authentication.
• NTP can unicast, multicast or broadcast protocol messages.
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