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CX11x, CX31x, CX710 (Earlier Than V6.03), and CX91x Series Switch Modules V100R001C10 Configuration Guide 13

The documents describe the configuration of various services supported by the CX11x&CX31x&CX91x series switch modules The description covers configuration examples and function configurations.
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NTP Overview

NTP Overview

This section describes the definition, purpose, and version evolution of NTP.


The Network Time Protocol (NTP) is an application layer protocol in the TCP/IP protocol suite. NTP is used to synchronize the time among a set of distributed time servers and clients. NTP is implemented based on the Internet Protocol (IP) and User Datagram Protocol (UDP). NTP packets are transmitted using UDP port 123.


As network topologies become increasingly complex, clock synchronization becomes more important for devices on the entire network. If a system clock is modified manually by network administrators, the workload is heavy and the modification is error-prone, which affects clock precision. NTP is formulated as a networking protocol for clock synchronization between devices on a network.

NTP applies to the following situations where all the clocks of the devices on a network need to be consistent:
  • In network management, analysis of logs or debugging messages collected from different routers requires time for reference.
  • An accounting system requires that the clocks of all the devices be consistent.
  • When several systems work together to process a complicated event, they have to refer to the same clock to ensure a correct execution order.
  • Incremental backup between a backup server and clients requires that their clocks be synchronized.
  • Some applications need to obtain the time in which a user logs in a system and a document is modified.

Version Evolution

NTP is evolved from the Time Protocol and the ICMP Timestamp message but is specifically designed to maintain accuracy and robustness. Table 3-13 shows the NTP version evolution.
Table 3-13 NTP version evolution
Version Date Protocol Number Description
NTPv1 June 1988 RFC 1059 NTPv1 puts forward complete NTP rules and algorithms for the first time, but it does not support authentication and control messages.
NTPv2 September 1989 RFC 1119 NTPv2 supports authentication and control messages.
NTPv3 March 1992 RFC 1305 NTPv3 uses correctness principles and improves clock selection and filter algorithms, and it is widely used.
Updated: 2019-12-13

Document ID: EDOC1000041694

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