Engineering Book from C.H.I.P.S.

Computer Network Time Synchronization
The Network Time Protocol
by David L. Mills

Computer Network Time Synchronization takes a broad look at the architecture, protocols, and algorithms involved in time dissemination, distribution, and synchronization.


  • Examines the technological infrastructure of time dissemination, distribution, and synchronization
  • Describes design network configuration options appropriate for public and private NTP networks
  • Demonstrates how to predict and calibrate performance based on statistics from NTP clients and servers
  • Provides a basis to evaluate the cryptanalytic strengths and vulnerabilities of the NTP model
  • Explains the operating principles of NTP and how the protocol works in practice


Basic Concepts

  • Time Synchronization
  • Time Synchronization Protocols
  • Computer Clocks
  • Processing Time Values
  • Correctness and Accuracy Expectations
  • Security
  • NTP in the Internet
  • Parting Shots

How NTP Works

  • General Infrastructure Requirements
  • How NTP Represents the Time
  • How NTP Reckons the Time
  • How NTP Disciplines the Time
  • How NTP Clients and Servers Associate
  • How NTP Discovers Servers
  • How NTP Manages Network Resources
  • How NTP Avoids Errors
  • How NTP Performance Is Determined
  • How NTP Controls Access
  • How NTP Watches for Terrorists
  • How NTP Clocks Are Watched
  • Parting Shots

In the Belly of the Beast

  • Process Flow
  • Packet Processing
  • Clock Filter Algorithm
  • Selection Algorithm
  • Clustering Algorithm
  • Combining Algorithm
  • Huff-'n-Puff Filter
  • Mitigation Rules and the Prefer Peer
  • Poll Process
  • Parting Shots

Clock Discipline Algorithm

  • Feedback Control Systems
  • Phase and Frequency Discipline
  • Weight Factors
  • Poll Interval Control
  • Popcorn and Step Control
  • Clock State Machine

NTP Subnet Configuration

  • Automatic Server Discovery
  • Manual Server Discovery and Configuration
  • Evaluating the Sources
  • Selecting the Stratum
  • Selecting the Number of Configured Servers
  • Engineering Campus and Corporate Networks
  • Engineering Home Office and Small Business Networks
  • Hardware and Network Considerations

NTP Performance in the Internet

  • Performance Measurement Tools
  • System Clock Latency Characteristics
  • Characteristics of a Primary Server and Reference Clock
  • Characteristics between Primary Servers on the Internet
  • Characteristics of a Client and a Primary Server on a Fast Ethernet
  • Results from an Internet Survey
  • Server and Network Resource Requirements

Primary Servers and Reference Clocks

  • Driver Structure and Interface
  • Reference Clock Drivers

Kernel Timekeeping Support

  • System Clock Reading Algorithm
  • Clock Discipline Algorithms
  • Kernel PLL/FLL Discipline
  • Kernel PPS Discipline
  • Clock Adjust Algorithm
  • Proof of Performance
  • Kernel PLL/FLL Discipline Performance
  • Kernel PPS Discipline

Cryptographic Authentication

  • NTP Security Model
  • NTP Secure Groups
  • Autokey Security Protocol

Indentity Schemes

  • X509 Certificates
  • Private Certificate (PC) Identity Scheme
  • Trusted Certificate (TC) Identity Scheme
  • Schnorr (IFF) Identity Scheme
  • Guillou-Quisquater (GQ) Identity Scheme
  • Mu-Varadharajan (MV) Identity Scheme

Analysis of Errors

  • Timestamp Errors
  • Sawtooth Errors
  • Maximum Error Budget
  • Expected Error Budget

Modeling and Analysis of Computer Clocks

  • Computer Clock Concepts
  • Mathematical Model of the Generic Feedback Loop
  • Synthetic Timescales and Clock Wranglers

Metrology and Chronometry of the NTP Timescale

  • Scientific Timescales Based on Astronomy and Atomic Physics
  • Civil Timescales Based on Earth Rotation
  • How NTP Reckons with UTC Leap Seconds
  • On Numbering the Calendars and Days
  • On the Julian Day Number System
  • On Timescales, Leap Events, and the Age of Eras
  • The NTP Era and Buddy Epoch
  • Comparison with Other Computer Timescales
  • Primary Frequency and Time Standards
  • Time and Frequency Dissemination

NTP Reference Implementation

  • NTP Packet Header
  • Control Flow
  • Main Program and Common Routines
  • Peer Process
  • System Process
  • Clock Discipline Process
  • Clock Adjust Process
  • Poll Process

Technical History of NTP

  • On the Antiquity of NTP
  • On the Proliferation of NTP around the Globe
  • Autonomous Authentication
  • Autonomous Configuration
  • Radios, We Have Radios
  • Hunting the Nanoseconds
  • Experimental Studies
  • Theory and Algorithms
  • Growing Pains
  • As Time Goes By


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Computer Network Time Synchronization
The Network Time Protocol
by David L. Mills

2006 304 pages $108.95 + shipping
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