1-11 NTP ConfigurationWhen configuring NTP, go to these sections for information you are interested in:z NTP Overviewz NTP Configuration Task Listz Configuring the Operation Modes of NTPz Configuring Optional Parameters of NTPz Configuring Access-Control Rightsz Configuring NTP Authenticationz Displaying and Maintaining NTPz NTP Configuration ExamplesNTP OverviewDefined in RFC 1305, the Network Time Protocol (NTP) synchronizes timekeeping among distributedtime 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 withinthe 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 beused as a reference source to synchronize other clocks.Applications of NTPAn administrator can by no means keep time synchronized among all the devices within a network bychanging the system clock on each station, because this is a huge amount of workload and cannotguarantee the clock precision. NTP, however, allows quick clock synchronization within the entirenetwork while it ensures a high clock precision.NTP is used when all devices within the network must be consistent in timekeeping, for example:z In analysis of the log information and debugging information collected from different devices innetwork management, time must be used as reference basis.z All devices must use the same reference clock in a charging system.z To implement certain functions, such as scheduled restart of all devices within the network, alldevices must be consistent in timekeeping.z When multiple systems process a complex event in cooperation, these systems must use thatsame reference clock to ensure the correct execution sequence.z For incremental backup between a backup server and clients, timekeeping must be synchronizedbetween the backup server and all the clients.Advantages of NTPz NTP uses a stratum to describe the clock precision, and is able to synchronize time among alldevices within the network.z NTP supports access control and MD5 authentication.
