RFC 2030 (rfc2030) - Page 2 of 18

Simple Network Time Protocol (SNTP) Version 4 for IPv4, IPv6 and OSI

RFC 2030             SNTPv4 for IPv4, IPv6 and OSI          October 1996


1. Introduction

   The Network Time Protocol (NTP) Version 3 specified in RFC-1305
   [MIL92] is widely used to synchronize computer clocks in the global
   Internet. It provides comprehensive mechanisms to access national
   time and frequency dissemination services, organize the time-
   synchronization subnet and adjust the local clock in each
   participating subnet peer. In most places of the Internet of today,
   NTP provides accuracies of 1-50 ms, depending on the characteristics
   of the synchronization source and network paths.

   RFC-1305 specifies the NTP Version 3 protocol machine in terms of
   events, states, transition functions and actions and, in addition,
   engineered algorithms to improve the timekeeping quality and mitigate
   among several synchronization sources, some of which may be faulty.
   To achieve accuracies in the low milliseconds over paths spanning
   major portions of the Internet of today, these intricate algorithms,
   or their functional equivalents, are necessary. However, in many
   cases accuracies in the order of significant fractions of a second
   are acceptable. In such cases, simpler protocols such as the Time
   Protocol [POS83], have been used for this purpose. These protocols
   usually involve an RPC exchange where the client requests the time of
   day and the server returns it in seconds past some known reference
   epoch.

   NTP is designed for use by clients and servers with a wide range of
   capabilities and over a wide range of network delays and jitter
   characteristics. Most users of the Internet NTP synchronization
   subnet of today use a software package including the full suite of
   NTP options and algorithms, which are relatively complex, real-time
   applications (see http://www.eecis.udel.edu/~ntp). While the software
   has been ported to a wide variety of hardware platforms ranging from
   personal computers to supercomputers, its sheer size and complexity
   is not appropriate for many applications. Accordingly, it is useful
   to explore alternative access strategies using simpler software
   appropriate for less stringent accuracy expectations.

   This document describes the Simple Network Time Protocol (SNTP)
   Version 4, which is a simplified access strategy for servers and
   clients using NTP Version 3 as now specified and deployed in the
   Internet, as well as NTP Version 4 now under development. The access
   paradigm is identical to the UDP/TIME Protocol and, in fact, it
   should be easily possible to adapt a UDP/TIME client implementation,
   say for a personal computer, to operate using SNTP. Moreover, SNTP is
   also designed to operate in a dedicated server configuration
   including an integrated radio clock. With careful design and control
   of the various latencies in the system, which is practical in a
   dedicated design, it is possible to deliver time accurate to the



Mills                        Informational