One of the essential services on your network is the supply of accurate time. This is required for authentication with Active Directory or other Kerberos-based mechanisms and to make timestamps useful in log files.

Network Time Protocol (NTP) uses UDP and the traditional port 123. This protocol dictates the number of seconds that have elapsed since midnight on January 1, 1900. NTP is 32 bit, which means that the maximum time will be reached in 2036; however, as only the difference in timestamps is used rather than the actual time, the date does not present an issue unlike UNIX time ending in 2038, which is a little more serious.

Once the time service is started and synchronized with another time source, the client time can be changed to match the server's time as long as the time is said to be sane. Insane time is said to be a server, offering a time with more than 1000 seconds offset to the client. Using this level of sanity, a client is prevented from...