132 CHAPTER 8: SYSTEM T IMEConfiguring theSystem TimeYou must select how the Webcache determines the current time duringthe Getting Started wizard, which automatically runs when you firstaccess the Webcache’s Web interface.You can change how the Webcache determines the current time at anypoint using the Time Configuration wizard. Select Device from theToolbar, then System > Management > Time Configuration in theNavigation Tree to access the wizard.You can configure the system time in either of the following ways: Configuring the System Time Using the Network Time Protocol — forfurther information, see page 134 Configuring the System Time Manually — for further information, seepage 134.3Com recommends that you use the Network Time Protocol to configurethe system time of the Webcache.Network TimeProtocolThe Network Time Protocol (NTP) is used to synchronize the time of clientmachines and servers with other well-known, highly accurate servers orreference time sources. It maintains a consistent Coordinated UniversalTime (UTC) within your network which is far more accurate than theinternal system clocks of client machines and prevents time drift fromoccurring on the Webcache.NTP provides client machine and server time accuracies typically within amillisecond on LANs, relative to a primary NTP server synchronized to UTCvia a Global Positioning Service (GPS) receiver. Such accuratetime-keeping is an essential part of the operation of the Webcache.NTP will only operate correctly if the Webcache can communicate withthe NTP server. The Webcache time will not be changed by the NTP serverif the two devices cannot communicate with each other, and will insteadsimply rely on the internal clock and the last manually configured time.Ensure that traffic on TCP port 123 is not blocked by a Firewall betweenthe Webcache and the NTP server.dua1611-5aaa04.book Page 132 Friday, November 29, 2002 8:56 PM
