Chapter 35. Network Time Protocol

   

Chapter Syllabus

35.1 Introduction to NTP

35.2 Configuring the NTP Server

35.3 Configuring NTP Client

35.4 Using SAM to Configure NTP

Network Time Protocol (NTP) is used to synchronize a system clock with a reliable time source. Clock synchronization of all hosts on a network is often needed when you are running applications over a network that uses time in calculations. A common example of this is the use of incremental backup where file modification time is compared with the time of the previous backup. If the incremental backups are performed over a network, differences in system clock time among hosts may result in a wrong file selection. Manual synchronization of time on a large network is a particularly difficult task.

The NTP daemon runs on all participating hosts. It is started at system boot time and may act as a client, server, or both simultaneously . Every system synchronizes its time with one or more of the available resources. These resources are categorized depending on the accuracy of the time. Considered the most accurate resource is time from global positioning system (GPS) satellites or aradio broadcast. The least accurate is the system clock of one of the hosts on the network. Usually one or more hosts on the network use a reliable external source, while other hosts on the network use these systems as their time server.

NTP can be configured using the command line or SAM. During startup, the NTP daemon ( xntpd ) checks its configuration file and synchronizes its clock with a reliable time source provided in the configuration file. The daemon then maintains a file to track any drift in local time.

In this chapter, we will start with an introduction to Network Time Protocol and the terminology used with it. Different types of reference time sources will be discussed. Then you will see how to configure the xntpd daemon and the NTP server and client. In the last part of the chapter, you will use SAM to configure NTP.


   
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HP Certified
HP Certified: HP-UX System Administration
ISBN: 0130183741
EAN: 2147483647
Year: 2000
Pages: 390
Authors: Rafeeq Rehman

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