RFC 1059 (rfc1059) - Page 1 of 58
Network Time Protocol (version 1) specification and implementation
Alternative Format: Original Text Document
Network Working Group D. Mills
Request for Comments: 1059 University of Delaware
July 1988
Network Time Protocol (Version 1)
Specification and Implementation
Status of this Memo
This memo describes the Network Time Protocol (NTP), specifies its
formal structure and summarizes information useful for its
implementation. NTP provides the mechanisms to synchronize time and
coordinate time distribution in a large, diverse internet operating
at rates from mundane to lightwave. It uses a returnable-time design
in which a distributed subnet of time servers operating in a self-
organizing, hierarchical master-slave configuration synchronizes
logical clocks within the subnet and to national time standards via
wire or radio. The servers can also redistribute reference time via
local routing algorithms and time daemons.
The NTP architectures, algorithms and protocols which have evolved
over several years of implementation and refinement are described in
this document. The prototype system, which has been in regular
operation in the Internet for the last two years, is described in an
Appendix along with performance data which shows that timekeeping
accuracy throughout most portions of the Internet can be ordinarily
maintained to within a few tens of milliseconds, even in cases of
failure or disruption of clocks, time servers or nets. This is a
Draft Standard for an Elective protocol. Distribution of this memo
is unlimited.
Table of Contents
1. Introduction 3
1.1. Related Technology 4
2. System Architecture 6
2.1. Implementation Model 7
2.2. Network Configurations 9
2.3. Time Scales 10
3. Network Time Protocol 12
3.1. Data Formats 12
3.2. State Variables and Parameters 13
3.2.1. Common Variables 15
3.2.2. System Variables 17
3.2.3. Peer Variables 18
3.2.4. Packet Variables 19
3.2.5. Clock Filter Variables 19
3.2.6. Parameters 20
Mills
