Simple Network Time Protocol (SNTP) Version 4 for IPv4, IPv6 and OSI
RFC 4330
| Document | Type |
RFC - Informational
(January 2006; Errata)
Obsoleted by RFC 5905
|
|
|---|---|---|---|
| Last updated | 2015-10-14 | ||
| Stream | ISE | ||
| Formats | plain text pdf html bibtex | ||
| Stream | ISE state | (None) | |
| Consensus Boilerplate | Unknown | ||
| Document shepherd | No shepherd assigned | ||
| IESG | IESG state | RFC 4330 (Informational) | |
| Telechat date | |||
| Responsible AD | Thomas Narten | ||
| Send notices to | karen.odonoghue@navy.mil | ||
Network Working Group D. Mills
Request for Comments: 4330 University of Delaware
Obsoletes: 2030, 1769 January 2006
Category: Informational
Simple Network Time Protocol (SNTP) Version 4
for IPv4, IPv6 and OSI
Status of This Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2006).
Abstract
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.
Mills Informational [Page 1]
RFC 4330 SNTPv4 for IPv4, IPv6 and OSI January 2006
Table of Contents
1. Introduction ....................................................2
1.1. Specification of Requirements ..............................5
2. Operating Modes and Addressing ..................................5
3. NTP Timestamp Format ............................................6
4. Message Format ..................................................8
5. SNTP Client Operations .........................................13
6. SNTP Server Operations .........................................16
7. Configuration and Management ...................................19
8. The Kiss-o'-Death Packet .......................................20
9. On Being a Good Network Citizen ................................21
10. Best Practices ................................................21
11. Security Considerations .......................................24
12. Acknowledgements ..............................................24
13. Contributors ..................................................24
14. Informative References ........................................25
1. Introduction
The Network Time Protocol Version 3 (NTPv3), 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 NTP subnet of
servers and clients, and adjust the system clock in each participant.
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 protocol machine in terms of events,
states, transition functions and actions, and engineered algorithms
to improve the timekeeping quality and to mitigate several
synchronization sources, some of which may be faulty. To achieve
accuracies in the low milliseconds over paths spanning major portions
of the Internet, these intricate algorithms, or their functional
equivalents, are necessary. In many applications, accuracies on the
order of significant fractions of a second are acceptable. In simple
home router applications, accuracies of up to a minute may suffice.
In such cases, simpler protocols, such as the Time Protocol specified
in RFC 868 [POS83], have been used for this purpose. These protocols
involve an RPC exchange where the client requests the time of day and
the server returns it in seconds past a 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 jitter and clock
frequency wander characteristics. Many users of NTP in the Internet
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