RFC5905

RFC 5905, titled "Network Time Protocol Version 4 (NTPv4) Specification," defines the current standard for the Network Time Protocol. This protocol is designed to synchronize the clocks of computer systems over packet-switched, variable-latency data networks. NTPv4 is the latest revision of the NTP protocol, offering improvements in accuracy, robustness, and security over its predecessors.

The specification details the fundamental operation of NTP, which involves a hierarchical system of time sources. At the top of this hierarchy are highly accurate timekeeping devices, such as atomic clocks and GPS receivers, referred to as stratum 0 servers. These servers provide the reference time for stratum 1 servers, which then synchronize stratum 2 servers, and so on. The protocol uses a complex algorithm to calculate the offset and delay between client and server clocks, accounting for network jitter and latency to achieve high precision.

RFC 5905 also outlines the packet format used by NTP, which includes fields for version, mode, stratum, poll interval, and time stamps. It describes various NTP modes, including client, server, and broadcast modes, each serving different synchronization purposes. Furthermore, the document addresses security considerations, recommending the use of Network Time Security (NTS) for enhanced authentication and protection against spoofing and man-in-the-middle attacks. The widespread adoption of NTPv4 ensures that computer systems across the internet maintain consistent and accurate time, which is critical for various applications, including logging, distributed systems, and financial transactions.