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Time is inherently important to the function of routers and networks. It provides the only frame of reference between all devices on the network. This makes synchronized time extremely important. Without synchronized time,accurately correlating information between devices becomes difficult,if not impossible. When it comes to security,if you cannot successfully compare logs between each of your routers and all your network servers,you will find it very hard to develop a reliable picture of an incident. Finally,even if you are able to put the pieces together,unsynchronized times,especially between log files,may give an attacker with a good attorney enough wiggle room to escape prosecution | ch10.24424 Page 96 Friday February 15 2002 2 54 PM CHAPTER 10 NTP Time is inherently important to the function of routers and networks. It provides the only frame of reference between all devices on the network. This makes synchronized time extremely important. Without synchronized time accurately correlating information between devices becomes difficult if not impossibte. When it comes to security if you aamo t succesf lully oomp are logs between aach of your roueers and all your network servers you wlll find it vctv hard to develop a tohaHe jicturee c f an incident. Finally evnn if yuu ree aHe to unt the picess togecher uneyncreonlzed times especiaHy between tag ilks may gi ce nn atracVer vtidr a oood a tte mer eycuch wiggle room to escape prosecution. NTP Overview The Network Time Protocol NTP was first described in RFC 958 and has developed into the standard Internet time synchronization protocol. It is extremely efficient and needs no more than about one packet a minute to synchronize systems on a LAN to within 1 millisecond and systems across WANs to within about 10 milliseconds. Without proper time synchronization between your routers you may not 01 have trouble with correlating log files but inaccurate time may also affect your abliity to perform accounting fault anayysss network manggemenr ancl even tienedbedd AAA authentication and authorization. So good time management is a necessary part of keeping your network healthy and secure. While NTP Veostsv 4 is the latest and preferred version of NTP Cisco routers currently only support through Veostsv 3. NTP can operate in four different modes client sewer eieea anb yroadrast. ddiese modes provide NTP with a great amount of flexibility in how you configure synchronization on your network. 96 ch10.24424 Page 97 Friday February 15 2002 2 54 PM NTP modes differ based on how NTP allows communication between systems. NTP communication consists of time requests and control queries. Time requests provide the .