CONTENTS

  Title Page

  Copyright Page

  Preface

  1      Introduction to the Digital Distributed Time Service

  1.1     DECdts Advantages
    1.1.1      Applications Support
    1.1.2      External Time-Provider Support
    1.1.3      Manageability
    1.1.4      Quantitative Inaccuracy Measurement

  1.2     Basic DECdts Concepts
    1.2.1      Time Measurement Factors
      1.2.1.1      Clock Error
      1.2.1.2      Communications and Processing Uncertainties
    1.2.2      Inaccuracy
    1.2.3      Synchronizing System Clocks
    1.2.4      How DECdts Adjusts System Clocks
    1.2.5      DECdts Time Representation
      1.2.5.1      Absolute Time
      1.2.5.2      Relative Time

  1.3     How DECdts Works
    1.3.1      Clerks
    1.3.2      Servers
      1.3.2.1      Local Servers
      1.3.2.2      Global Servers
      1.3.2.3      Couriers

  1.4     Interoperation with DECdns

  2      Managing DECdts

  2.1     The DECdts Management Interface
    2.1.1      Interface Components and Command Syntax
    2.1.2      DECdts Timestamp Syntax
    2.1.3      The DECnet Configuration Script
      2.1.3.1      DECnet/OSI for ULTRIX Configuration Script
      2.1.3.2      DECnet/OSI for VMS Configuration Script
    2.1.4      Accessing and Exiting the Management Interface

  2.2     Creating and Enabling DECdts
    2.2.1      Creating DECdts
    2.2.2      Enabling DECdts
    2.2.3      Designating Global Servers and Couriers
      2.2.3.1      Advertising Global Servers to DECdns
      2.2.3.2      Designating Global Servers with the Site-Specific Template
      2.2.3.3      Assigning the Courier Role to Servers
    2.2.4      Changing the DECdts Entity Type
      2.2.4.1      Changing the Entity Type-DECnet/OSI for ULTRIX Systems
      2.2.4.2      Changing the Entity Type-DECnet/OSI for VMS Systems

  2.3     Summary of Management Commands and Characteristics

  2.4     Routine Management Tasks
    2.4.1      Critical Commands and Characteristics
      2.4.1.1      The Servers Required Characteristic
      2.4.1.2      Use with Global Servers
      2.4.1.3      Use with Systems on Point-to-Point Lines
      2.4.1.4      The Maximum Inaccuracy Characteristic
      2.4.1.5      The Synchronization Hold Down Characteristic
      2.4.1.6      The Error Tolerance Characteristic
      2.4.1.7      The LAN Timeout, WAN Timeout, and Query Attempts Characteristics
    2.4.2      Server Management
      2.4.2.1      Matching the Epoch
      2.4.2.2      The Advertisement Interval and Check Interval Characteristics
    2.4.3      Modifying the System Time
      2.4.3.1      Updating the Time Monotonically
      2.4.3.2      Changing System Time Nonmonotonically
      2.4.3.3      Forcing System Synchronization
      2.4.3.4      Setting the System Clock to Local Time

  3      Problem Solving

  3.1     A Clerk System's Clock is Incorrect

  3.2     A Server System's Clock is Incorrect
    3.2.1      Large Inaccuracy On One Server
    3.2.2      Large Inaccuracy On All Servers

  3.3     Local Servers are Unavailable or Unresponsive

  3.4     Global Servers are Unavailable or Unresponsive

  3.5     The Advertise Command Fails
    3.5.1      Global Directory Not Configured
    3.5.2      Access Violation Messages

  DECdts Command Dictionary

  4      DECdts Command Dictionary

  4.1     The DTSS Entities

  4.2     Command Format
    4.2.1      Attribute Groups
    4.2.2      Prepositional Phrases
    4.2.3      NCL Access Control
    4.2.4      Wildcards

  4.3     Editing the Commands

  4.4     Accessing and Exiting the Management Interface

  4.5     Commands

  advertise dtss

  change dtss

  create dtss

  delete dtss

  disable dtss

  enable dtss

  set dtss

  show dtss

  show dtss global server

  show dtss local server

  synchronize dtss

  update dtss

  A   Event Messages

  B   Time-Providers and Time Services

  B.1     Criteria for Selecting a Time Source

  B.2     Sources of Coordinated Universal Time
    B.2.1      Telephone Services
    B.2.2      Radio Broadcasts
    B.2.3      Network Time Protocol
    B.2.4      Satellite

  B.3     World Time Zone Map

  C   Interoperation with NTP

  C.1     Getting the Time from Remote NTP Time Sources

  C.2     Giving the Time to NTP Nodes

  C.3     Preventing Loops

  Glossary

  FIGURES

  1-1        Time and Inaccuracy

  1-2        Computed Time

  1-3        Adjustment of the Clock

  1-4        Time Display Format

  1-5        Time Display Format Variants

  1-6        DECdts Operation

  2-1        Command Syntax

  2-2        Nonintersecting Time Interval

  4-1        Hierarchy of DTSS Module Entities

  4-2        Command Syntax

  B-1        World Time Zone Map

  C-1        Getting the Time from a Remote NTP Time Source (Scenario 1)

  C-2        Getting the Time from a Remote NTP Time Source (Scenario 2)

  C-3        Giving the Time to NTP

  C-4        Configuration Before Stratum 2 Node Fails

  C-5        Configuration After Stratum 2 Node Fails

  TABLES

  1-1        Time-Provider Programs and Related Time-Provider Suppliers

  2-1        DECdts Commands

  2-2        Settable dtss Characteristics

  4-1        Wildcard Characters

  B-1        Time-Provider Selection Criteria

  B-2        UTC Radio Stations and Managing Authorities

  B-3        Radio Receiver Manufacturers