Operation of an NTP Server

An NTP server operates by communicating with various upstream time sources and other NTP servers located throughout the internet. This includes servers operated by national laboratories as well as private organizations. Through these connections, the NTP server is able to aggregate time information from multiple independent sources to build the most accurate picture of universal time. It then compares its internal clock to this aggregate time data and makes gradual adjustments as needed, usually at a rate of 1 part in 10 million. Over time, this process drives the server's clock into precise synchronization with world time standards.

Distribution of Time to Clients

Once synchronized, the NTP Server can then distribute very accurate time to downstream client machines connected to it locally or elsewhere on the network. This outbound time distribution uses the NTP protocol to relay clock synchronization messages from the server to clients. When a client first connects, it will request a series of timestamps from the server, allowing it to compare server time to its own internal clock. It then performs similar gradual adjustments like the server to keep closely synchronized over time. Multiple clients can synchronize with a single NTP server simultaneously using the efficient NTP message format.

Monitoring and Configuration Options

Server administrators have tools available to monitor the synchronization process and configuration of an NTP server. The ntpq utility displays information about the servers the NTP server is communicating with such as response times, status and estimated accuracy of time kept by each peer. The ntpd daemon can also log synchronization details in a file for troubleshooting purposes. Various options exist to configure upstream servers, client access points, authentication and other settings specific to each deployment. Fine-tuning these settings helps optimize time distribution accuracy for all connected clients.

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