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Network Time Protocol (Version 3) Specification, Implementation (RFC1305)

IP.com Disclosure Number: IPCOM000002125D
Original Publication Date: 1992-Mar-01
Included in the Prior Art Database: 2001-Nov-09

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

David L. Mills: AUTHOR

Abstract

This document 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 local 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. (Download file contains alternative document format.)

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Network Working Group                           David L. Mills

Request for Comments: 1305                      University of Delaware

Obsoletes RFC-1119, RFC-1059, RFC-958           March 1992

                   Network Time Protocol (Version 3)

               Specification, Implementation and Analysis

Note: This document consists of an approximate rendering in ASCII of the

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are not available.

Abstract

This document 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 local

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.

Status of this Memo

This RFC specifies an IAB standards track protocol for the Internet

community and requests discussion and suggestions for improvements.

Please refer to the current edition of the <169>IAB Official Protocol

Standards<170> for the standardization state and status of this

protocol. Distribution of this memo is unlimited.

Keywords: network clock synchronization, standard time distribution,

fault-tolerant architecture, maximum-likelihood estimation, disciplined

oscillator, internet protocol, high-speed networks, formal

specification.

Preface

This document describes Version 3 of the Network Time Protocol (NTP). It

supersedes Version 2 of the protocol described in RFC-1119 dated

September 1989. However, it neither changes the protocol in any

significant way nor obsoletes previous versions or existing

implementations. The main motivation for the new version is to refine

the analysis and implementation models for new applications at much

higher network speeds to the gigabit-per-second regime and to provide

for the enhanced stability, accuracy and precision required at such

speeds. In particular, the sources of time and frequency errors have

been rigorously examined and error bounds established in order to

improve performance, provide a model for correctness assertions and

indicate timekeeping quality to the user. The revision also incorporates

two new optional features, (1) an algorithm to combine the offsets of a

number of peer time servers in order to enhance accuracy and (2)

improved local-clock algorithms which allow the poll intervals on all

synchronization paths to be substantially increased in order to reduce

network overhead. An overview of the changes, which are described in

detail in Appendix D, follows:

1.

In Version 3 The local-clock algorithm has been overhauled to im...