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Network Time Protocol (version 1) specification and implementation (RFC1059) Disclosure Number: IPCOM000001866D
Original Publication Date: 1988-Jul-01
Included in the Prior Art Database: 2000-Sep-12

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

D.L. Mills: AUTHOR


This document describes the Network Time Protocol (NTP), including the architectures, algorithms and protocols to synchronize local clocks in a set of distributed clients and servers. The protocol was first described in RFC-958 [24], but has evolved in significant ways since publication of that document. NTP is built on the Internet Protocol (IP) [10] and User Datagram Protocol (UDP) [6], which provide a connectionless transport mechanism; however, it is readily adaptable to other protocol suites. It is evolved from the Time Protocol [13] and the ICMP Timestamp message [11], but is specifically designed to maintain accuracy and robustness, even when used over typical Internet paths involving multiple gateways and unreliable nets.

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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