SNTP (Simple Network Time Protocol)

networkingprogramming

Simple Network Time Protocol: a reduced subset of NTP that speaks the same wire protocol with far less of the algorithm behind it.

The confusion worth clearing up is that SNTP is not a different protocol. It is defined as a subset of NTP, uses the same packet format and the same port, and a server cannot tell whether a client is running a full implementation or a simple one. The difference is entirely in what the client does with the answer. Full NTP polls several sources, discards outliers, weighs the survivors, estimates the frequency error of the local oscillator and corrects for it continuously. SNTP typically asks one server and applies the result. That is fine for a device that needs to be roughly right - an access point, a camera, a small appliance - and unsuitable for anything that will be used as a time source for something else, because errors do not average out when there is nothing to average. The practical rule is the one that gets violated in every network eventually: an SNTP client must never be configured as a server for other devices, because it will faithfully propagate a bad answer it had no means of detecting.

Also known as: simple network time protocol, rfc 4330

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