What is NTP?
NTP stands for Network Time Protocol. It is a protocol with which devices and systems synchronise their clocks with a reliable time source over a network.
NTP is essential for correct log ordering, process control and security in both IT and OT environments.
🎯 Why is NTP important?
- Ensures time consistency in logs and alarms
- Supports security mechanisms such as certificate validation and audit trails
- Synchronisation of data in SCADA, Historian, Batch Control
- Essential for forensic investigation and incident analysis
- Reduces errors in time-sensitive control
⚙️ How does NTP work?
- Devices connect to an NTP server via UDP port 123
- The server sends a timestamp in response
- The client adjusts its system clock
- NTP automatically compensates for network delays
- Internal clocks are gradually adjusted to avoid sudden jumps
🧱 Typical NTP hierarchy
Stratum 0 – GPS, atomic clock or radio time → Stratum 1 – Directly connected NTP server (e.g. on site) → Stratum 2 – Servers on your network (e.g. Domain Controller, firewall) → Clients – PLCs, SCADA, workstations, Historian
🏭 NTP in OT networks
- Historian and Batch Control require accurate timestamps
- Alarm Management depends on the correct sequence of events
- Redundancy and failover only work properly with synchronised time
- In OT environments, an internal NTP server is safer than a public one
- Segmentation requires each zone to have a suitable time source
⏱ NTP and alternatives
| Protocol | Application |
|---|---|
| NTP | Standard and broadly supported (<10 ms accuracy) |
| SNTP | Simple NTP, suitable for lightweight applications |
| PTP | Precision Time Protocol – for sub-millisecond accuracy |
| IRIG-B | Time synchronisation in energy/distribution networks |
✅ Benefits of NTP
- Reliable and reproducible time synchronisation
- Easy to implement and maintain
- Necessary for auditing, security and process logic
- Essential in OT convergence and SIEM integration
📌 In summary
NTP ensures that all your systems are aligned on time — crucial for accurate records, security and reliable production automation.