NTP

NTP, the Network Time Protocol standardized in RFC 5905, is one of the oldest protocols on the internet, built to keep the clocks of networked computers in agreement despite variable network latency. It uses a hierarchy of time sources — stratum levels rooted in reference clocks — and statistical filtering to converge machines to within milliseconds of a common time. It runs quietly underneath almost everything else.

• Stratum hierarchy - Time flows from stratum 0 reference clocks outward, each level a step further from the source.
• Latency compensation - Round-trip measurement and filtering correct for network delay when computing offset.
• Wide margin of accuracy - Typically synchronizes hosts to within a few milliseconds over the public internet.
• Ubiquitous deployment - Runs on servers, routers, phones, and embedded devices without most operators ever thinking about it.
• Security extensions - Network Time Security (NTS) adds authentication to guard against spoofed time.

Accurate, synchronized time is a silent precondition for trustworthy API operations. Token expiry and OAuth flows depend on clocks agreeing about “now,” TLS certificate validity is time-bound, request signing and idempotency windows assume aligned timestamps, and distributed logs and traces only line up if every host shares a clock. When clock skew creeps in, the symptoms surface as mysterious authentication failures and out-of-order events — which is why NTP, invisible as it is, sits underneath dependable API infrastructure.