Glossary Updates12 new terms added to the glossaries · October 2, 2026, 22:44 CEST
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Glossary · Industrial communication

Network Time Protocol (NTP)

Also known as: NTP

German: Network Time Protocol (NTP)

In networking, the Network Time Protocol (NTP) synchronizes the clocks of computers and devices over IP networks to a reference time source, typically with an accuracy in the millisecond range on local networks. Version 4 is specified in RFC 5905.

  • Industrial communication
  • Standards

In one sentence

NTP synchronizes device clocks over IP networks to a reference time, typically to milliseconds on local networks (RFC 5905).

Example

All controllers, HMIs and the historian get their time from two NTP servers in the plant network, so alarm timestamps from different systems can be compared.

How it applies

  • Engineering: NTP is sufficient for event logging, alarm timestamps and IT systems. Plants usually run their own NTP servers, synchronized to GPS or a trusted upstream source, rather than relying on internet servers.
  • Operation: Correct time is essential for correlating alarms and logs across systems. A device that falls back to its default date after a power loss produces misleading records.
  • Security: NTP traffic should come from trusted sources; manipulated time can disturb certificate validation and log analysis. Network Time Security (NTS) adds authentication.
  • Documentation: The documentation team documents the time sources, the time zone and daylight saving handling (UTC is recommended internally) and the behavior when time synchronization fails.

NTP vs. PTP

NTP synchronizes to milliseconds over ordinary IP networks. Precision Time Protocol (PTP) reaches sub-microsecond accuracy with hardware timestamping and PTP-aware network components, as needed for motion control or Time-Sensitive Networking (TSN).

By knowledge.aitechdoc.world · Published September 26, 2026 · Last reviewed

Source: IETF RFC 5905, Network Time Protocol Version 4: Protocol and Algorithms Specification (2010)

Definitions follow the cited standards and specifications. Where a source is a copyrighted publication, such as an ISO, IEC or EN standard, the definition is a close paraphrase, not a verbatim quotation, so as not to infringe copyright. We recommend reading the original publication. The sections “How it applies” are editorial commentary by AI TechDoc Blog and are not part of any standard.

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