Network Time Protocol Version 4: Protocol and Algorithms Specification
Embed This Widget
Add the script tag and a data attribute to embed this widget.
Embed via iframe for maximum compatibility.
<iframe src="https://ipfyi.com/iframe/entity//" width="420" height="400" frameborder="0" style="border:0;border-radius:10px;max-width:100%" loading="lazy"></iframe>Paste this URL in WordPress, Medium, or any oEmbed-compatible platform.
https://ipfyi.com/entity//Add a dynamic SVG badge to your README or docs.
[](https://ipfyi.com/entity//)Use the native HTML custom element.
D. Mills, J. Martin, J. Burbank, W. Kasch · 2010-06
Abstract
RFC 5905 defines Network Time Protocol version 4 (NTPv4), a protocol for synchronizing clocks of computer systems over packet-switched networks. NTPv4 operates over UDP port 123 and uses a hierarchical system of time servers (strata) to distribute Coordinated Universal Time (UTC) with sub-millisecond accuracy over the public Internet and microsecond accuracy on local area networks.
Why This RFC Matters
Accurate time synchronization is foundational to modern distributed systems, security protocols, financial transactions, logging, and distributed databases. TLS certificate validation, Kerberos authentication, and database replication all depend on synchronized clocks. NTP is one of the oldest continuously operating Internet protocols, with a public NTP infrastructure serving billions of clients globally. NTPv4 introduced improved algorithms for clock filtering, selection, combining, and discipline, as well as support for IPv6 and extension fields. The protocol's stratum model — where Stratum 0 devices are atomic clocks and GPS receivers — provides the authoritative time reference for the Internet.