This memorandum describes the Simple Network Time Protocol Version 4
(SNTPv4), which is a subset of the Network Time Protocol (NTP) used
to synchronize computer clocks in the Internet. SNTPv4 can be used
when the ultimate performance of a full NTP implementation based on
RFC 1305 is neither needed nor justified. When operating with
current and previous NTP and SNTP versions, SNTPv4 requires no
changes to the specifications or known implementations, but rather
clarifies certain design features that allow operation in a simple,
stateless remote-procedure call (RPC) mode with accuracy and
reliability expectations similar to the UDP/TIME protocol described
in RFC 868.

This memorandum obsoletes RFC 1769, which describes SNTP Version 3
(SNTPv3), and RFC 2030, which describes SNTPv4. Its purpose is to
correct certain inconsistencies in the previous documents and to
clarify header formats and protocol operations for NTPv3 (IPv4) and
SNTPv4 (IPv4, IPv6, and OSI), which are also used for SNTP. A
further purpose is to provide guidance for home and business client
implementations for routers and other consumer devices to protect the
server population from abuse. A working knowledge of the NTPv3
specification, RFC 1305, is not required for an implementation of
SNTP.