Operation Manual – NTPH3C S3100 Series Ethernet Switches Chapter 1 NTP Configuration1-1Chapter 1 NTP Configuration1.1 Introduction to NTPNetwork time protocol (NTP) is a time synchronization protocol defined in RFC 1305. Itis used for time synchronization between a set of distributed time servers and clients.Carried over UDP, NTP transmits packets through UDP port 123.NTP is intended for time synchronization between all devices that have clocks in anetwork so that the clocks of all devices can keep consistent. Thus, the devices canprovide multiple unified-time-based applications (See section 1.1.1 ).A local system running NTP can not only be synchronized by other clock sources, butalso serve as a clock source to synchronize other clocks. Besides, it can synchronize,or be synchronized by other systems by exchanging NTP messages.1.1.1 Applications of NTPAs setting the system time manually in a network with many devices leads to a lot ofworkload and cannot ensure accuracy, it is unfeasible for an administrator to performthe operation. However, an administrator can synchronize the clocks of devices in anetwork with required accuracy by performing NTP configuration.NTP is mainly applied to synchronizing the clocks of all devices in a network. Forexample:z In network management, the analysis of the log information and debugginginformation collected from different devices is meaningful and valid only whennetwork devices that generate the information adopts the same time.z The billing system requires that the clocks of all network devices be consistent.z Some functions, such as restarting all network devices in a networksimultaneously require that they adopt the same time.z When multiple systems cooperate to handle a rather complex transaction, theymust adopt the same time to ensure a correct execution order.z To perform incremental backup operations between a backup server and a host,you must make sure they adopt the same time.NTP has the following advantages:z Defining the accuracy of clocks by stratum to synchronize the clocks of all devicesin a network quicklyz Supporting access control (See section1.4 ) and MD5 encrypted authentication(See section 1.5 )z Sending protocol packets in unicast, multicast, or broadcast mode
