H3C Technologies H3C WX3000E Series Wireless Switches - Manual (Page 18)

9
NTP configuration
NTP overview
NTP is typically used in large networks to dynamically synchronize time among network devices. It
guarantees higher clock accuracy than manual system clock setting. In a small network that does not
require high clock accuracy, you can keep time synchronized among devices by changing their system
clocks one by one.
NTP runs over UDP and uses UDP port 123.
NTP application
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 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:
• 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.
• When multiple systems process a complex event in cooperation, these systems must use that same
reference clock to ensure the correct execution sequence.
• For incremental backup between a backup server and clients, timekeeping must be synchronized
between the backup server and all the clients.
NTP advantages
• 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.
How NTP works
Figure 5 shows how NTP synchronizes the system time between two devices, in this example, Device A
and Device B. Assume that:
• Prior to system clock synchronization between Device A and Device B, the clock of Device A is set
to 10:00:00 am while that of Device B is set to 11:00:00 am.