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
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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 of today use a software distribution available from www.ntp.org. The distribution, which includes the full suite of NTP options,Show full document text