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Keeping Time With Your Network

One way to synchronize is to set each network device and PC clock manually. That's like a Navy quartermaster keeping accurate time at sea by synchronizing his watch with a reference clock or chronometer on the ship, and then setting each clock onboard to his watch. This method requires military-like discipline and more resources than most IT departments have. A clock's time can drift several seconds each day if it's left unattended. Time discrepancies among clocks can go from minutes to hours quickly and cause problems with automated actions, data logging and synchronization.

An easier way to keep time is to automate time synchronization in your servers and workstations. Two of the most common approaches use NTP (Network Time Protocol, RFC 1305) 3 and SNTP (Simple Network Time Protocol, RFC 2030) 4. NTP and SNTP synchronize time across geographically dispersed networks over UDP (User Datagram Protocol) Port 123. NTP supports multiple, redundant time sources for always-on, accurate time synchronization, and it can synchronize time to the millisecond.

NTP Network Map

click to enlarge

How It Works

NTP servers operate in a hierarchal network; each level of the hierarchy is called a stratum. Stratum 0, the first level, represents the reference clock. The reference clock can be a GPS (Global Positioning System) signal or the National Institute for Standards and Technology's Automated Computer Time Service (ACTS)--both time-dissemination services. No NTP servers operate at Stratum 0.

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