Linux Journal: Understanding NTP Reachability Statistics

“You’re a typical system administrator, with a million and two
urgent things to do before you get to go home for the day. Next on
your list is bringing up a new NTP server for your department so
your systems can use the Network Time Protocol to synchronize their
clocks with a reference time source… You’ve already compiled and
installed ntpd for your platform and are ready to take the next
step.

“Keeping accurate time is an important aspect of both system
administration and network security. If you’ve ever had the dubious
pleasure of trying to match up log events on multiple systems, you
know how critical accurate timestamps can be in tracking an event
as it flows through your network.

“On a busy server, you may have dozens of similar log entries
every second. If your system clocks are even a few seconds apart,
you may have tremendous difficulty determining which event on
Server A matches up with the same event on Server B. NTP addresses
these issues by keeping system clocks synchronized with a reference
time source, often to within a few milliseconds even over the open
Internet…”

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