NTP (Network Time Protocol)
NTP (Network Time Protocol) is a protocol, defined in RFC 5905, for synchronizing a device's clock against time servers arranged in a hierarchy of strata -- stratum 0 reference clocks, stratum 1 servers attached to them, and successive strata synchronizing from the stratum above. Most operating systems run an NTP client by default, quietly correcting clock drift in the background, which is why accuracy rarely gets a second thought until it's wrong. It matters beyond simply showing the right time: DNSSEC's RRSIG records carry explicit inception and expiration timestamps, and a device whose clock has drifted far enough can reject a valid signature as expired, or accept one that has genuinely expired, purely because its own idea of the current time is wrong. TLS certificate validity checks rest on the same assumption -- an inaccurate clock undermines a check that has nothing else wrong with it.
By AdminKit team, Netbase JSC · Updated