What is SNTP?
SNTP (Simple Network Time Protocol) is a simplified version of the NTP protocol, designed for basic time synchronization on devices that do not require high accuracy or complex correction algorithms.
When is SNTP used?
- In home routers
- In embedded systems (IoT, sensors)
- In client implementations with infrequent synchronization
Example: A Wi-Fi access point uses SNTP to synchronize its system time once a day.
How SNTP works
Mechanism
- The device sends a time request to an SNTP server (port 123/UDP)
- It receives a timestamp and applies it without calculating drift or performing statistical adjustments
Note: SNTP does not support a hierarchical stratum model as flexibly as NTP.
Comparison: SNTP vs NTP
| Characteristic | SNTP | NTP |
|---|---|---|
| Complexity | Minimal | High |
| Accuracy | Up to hundreds of milliseconds | Up to microseconds |
| Hierarchy support | Limited | Full |
| Drift correction | No | Yes |
| Use cases | IoT, SOHO devices | Servers, data centers |
FAQ
Is SNTP suitable for a server?
No. Full NTP is preferred for servers due to its accuracy and reliability.
Are SNTP and NTP compatible?
Yes. SNTP clients can query NTP servers, but not the other way around.
What port does SNTP use?
UDP 123 — the same as NTP.
Conclusion
SNTP is a simple way to synchronize system time without burdening the network stack. It is not suitable for precision-critical tasks but works well on devices operating autonomously or with limited resources.
