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NTP Stratum Hierarchy

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NTP query: client requests timeLayer 7 · ApplicationNTP

Version

NTP v4 (RFC 5905)

Port

UDP 123

NTP query: client requests timeLayer 7 · ApplicationNTP

Version

NTP v4 (RFC 5905)

Port

UDP 123

NTP stratum: distance from the clock source

Stratum 0 devices are the reference clocks: GPS receivers, atomic clocks, radio time signals. They have no network connectivity — they're hardware connected directly to Stratum 1 servers.

Stratum 1 servers (like Google's time.google.com or Cloudflare's time.cloudflare.com) sync directly from hardware. Each hop adds one stratum. Your server is typically Stratum 3 or 4.

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