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HP DECnet-Plus for OpenVMS
DECdts Management
Part Number: BA406-90003
January 2005
This manual introduces HP DECnet-Plus Distributed Time Service
(DECdts) concepts and describes how to manage the software and
system clocks.

Revision/Update Information:

This manual supersedes DECnet-Plus
DECdts Management (AA-PHELC-TE).

Operating Systems:

OpenVMS I64 Version 8.2
OpenVMS Alpha Version 8.2

Software Version:

HP DECnet-Plus for OpenVMS
Version 8.2
HP DECnet-Plus Distributed Time
Service Version 2.0

Hewlett-Packard Company
Palo Alto, California

© Copyright 2005 Hewlett-Packard Development Company, L.P.
Confidential computer software. Valid license from HP required for possession, use, or copying.
Consistent with FAR 12.211 and 12.212, Commercial Computer Software, Computer Software
Documentation, and Technical Data for Commercial Items are licensed to the U.S. Government
under vendor’s standard commercial license.
The information contained herein is subject to change without notice. The only warranties for HP
products and services are set forth in the express warranty statements accompanying such products
and services. Nothing herein should be construed as constituting an additional warranty. HP shall
not be liable for technical or editorial errors or omissions contained herein.
Intel and Itanium are trademarks or registered trademarks of Intel Corporation or its subsidiaries
in the United States and other countries.
UNIX is a registered trademark of The Open Group.
Printed in the US

Contents
Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

vii

1 Introduction to the HP DECnet-Plus 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 Representation . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.2.5.2
Relative Time Representation . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1–2
1–2
1–3
1–4
1–4
1–4
1–4
1–5
1–5
1–5
1–6
1–8
1–9
1–10
1–11
1–12
1–12
1–14
1–14
1–14
1–15
1–16

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 Startup 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
Controlling LAN Devices Used by DECdts . . . . . . . . . . . . . . . . . . . . . .
2.2.4
Designating Global Servers and Couriers . . . . . . . . . . . . . . . . . . . . . .
2.2.4.1
Advertising Global Servers to DECdns . . . . . . . . . . . . . . . . . . . . .
2.2.4.2
Designating Global Servers Using the BIND Database . . . . . . . . .
2.2.4.3
Designating Global Servers with the Site-Specific Template . . . . .
2.2.4.4
Assigning the Courier Role to Servers . . . . . . . . . . . . . . . . . . . . . .
2.2.5
Changing the DECdts Entity Type . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2–1
2–1
2–2
2–2
2–3
2–3
2–3
2–4
2–4
2–5
2–5
2–5
2–8
2–8
2–8

iii

2.2.6
Option to Disable DECdts at System Boot . . . . . . . . . . . . . . . . . . . . . .
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 . . . . . . . . . . . . . . . . . . . . .

2–9
2–9
2–11
2–11
2–11
2–13
2–13
2–14
2–14
2–15
2–17
2–18
2–18
2–18
2–19
2–19
2–20
2–21
2–21

3 Problem Solving
3.1
3.2
3.2.1
3.2.2
3.3
3.4
3.5
3.5.1
3.5.2

A Clerk System’s Clock is Incorrect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
A Server System’s Clock is Incorrect . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Large Inaccuracy On One Server . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Large Inaccuracy On All Servers . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Local Servers are Unavailable or Unresponsive . . . . . . . . . . . . . . . . . . . . .
Global Servers are Unavailable or Unresponsive . . . . . . . . . . . . . . . . . . . .
The Advertise Command Fails . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Global Directory Not Configured . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Access Violation Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3–1
3–2
3–2
3–3
3–4
3–5
3–5
3–6
3–6

4 DECdts Command Dictionary
4.1
4.2
4.2.1
4.2.2
4.2.3
4.2.4
4.3
4.4
4.5

The DTSS Entities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Command Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Attribute Groups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Prepositional Phrases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
NCL Access Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Wildcards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Editing the Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Accessing and Exiting the Management Interface . . . . . . . . . . . . . . . . . . .
Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
advertise dtss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
change dtss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
create dtss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
delete dtss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
disable dtss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
enable dtss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
set dtss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
show dtss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4–1
4–2
4–3
4–3
4–4
4–4
4–5
4–5
4–5
4–6
4–7
4–8
4–9
4–10
4–11
4–12
4–15

show dtss decnet global servers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
show dtss decnet local servers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
synchronize dtss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
update dtss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4–22
4–25
4–28
4–29

A Event Messages
B Time-Providers and Time Services
B.1
B.2
B.2.1
B.2.2
B.2.3
B.2.4
B.3

Criteria for Selecting a Time Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Sources of Coordinated Universal Time . . . . . . . . . . . . . . . . . . . . . . . . . . .
Telephone Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Radio Broadcasts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Network Time Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Satellite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
World Time Zone Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

B–1
B–2
B–2
B–3
B–5
B–5
B–5

C Interoperation with NTP
C.1
C.2
C.3

Getting the Time from Remote NTP Time Sources . . . . . . . . . . . . . . . . . .
Giving the Time to NTP Nodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Preventing Loops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

C–1
C–3
C–4

Time and Inaccuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Computed Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Adjustment of the Clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Time Display Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Time Display Format Variants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DECdts Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Command Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DECdts Timestamp Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Nonintersecting Time Interval . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Hierarchy of DTSS Module Entities . . . . . . . . . . . . . . . . . . . . . . . . . . .
Command Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
World Time Zone Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Getting the Time from a Remote NTP Time Source (Scenario 1) . . . . .
Getting the Time from a Remote NTP Time Source (Scenario 2) . . . . .
Giving the Time to NTP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Configuration Before Stratum 2 Node Fails . . . . . . . . . . . . . . . . . . . . .
Configuration After Stratum 2 Node Fails . . . . . . . . . . . . . . . . . . . . . .

1–6
1–8
1–9
1–10
1–11
1–13
2–1
2–2
2–16
4–1
4–3
B–6
C–2
C–3
C–4
C–5
C–6

Glossary
Index
Figures
1–1
1–2
1–3
1–4
1–5
1–6
2–1
2–2
2–3
4–1
4–2
B–1
C–1
C–2
C–3
C–4
C–5

Tables
1–1
2–1
2–2
4–1
B–1
B–2
B–3

Time-Provider Programs and Related Time-Provider Suppliers . . . . . .
DECdts Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Settable DTSS Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Wildcard Characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Time-Provider Selection Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
UTC Radio Stations and Managing Authorities . . . . . . . . . . . . . . . . . .
Radio Receiver Manufacturers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1–3
2–10
2–10
4–4
B–2
B–3
B–5

Preface
The HP DECnet-Plus Distributed Time Service (DECdts) is a networkwide
service that runs on the OpenVMS operating system. DECdts enables systems
to synchronize their clocks with all other clocks in the network. This manual
describes DECdts concepts, how to use the DECdts software to manage system
clocks, and how to solve problems once you have configured the software. For
information on installing and configuring DECdts, see the DECnet-Plus for
OpenVMS Introduction and User’s Guide, the DECnet-Plus Planning Guide, and
the HP DECnet-Plus for OpenVMS Installation and Configuration manuals.

Intended Audience
This manual is intended for two audiences: network managers who administer
DECdts, and server managers who are in charge of day-to-day operations of
DECdts server systems. Both audiences should have a sound understanding
of DECdts concepts before using the software. The management and problemsolving presentations may apply to either of the two audiences, depending on the
topology of the network. (For small networks, one person often takes the roles of
network manager and server manager.)
Network managers who are planning a DECdts implementation should refer
to the DECdts information in the DECnet-Plus for OpenVMS Introduction
and User’s Guide, the DECnet-Plus Planning Guide, and HP DECnet-Plus
for OpenVMS Installation and Configuration before installing and using the
software.
The concepts portion of the manager’s guide may also be useful as background
information for programmers or managers of client applications that use DECdts.
Programmers should read the DECnet-Plus DECdts Programming for DECdts
internals information and programming concepts.

Document Structure
This manual is organized into four chapters. The first chapter introduces DECdts
and basic time synchronization concepts. The second chapter describes how to
manage DECdts, the third chapter describes common DECdts problems and how
to solve them, and the fourth chapter describes management commands. The
appendices contain reference information including event messages, time-provider
sources, and interoperation with Network Time Protocol (NTP).

Related Documents
For a list of additional documents that are available, refer to the DECnet-Plus for
OpenVMS Introduction and User’s Guide.

vii

Reader’s Comments
HP welcomes your comments on this manual or any of the DECnet-Plus
documents. Please send comments to either of the following addresses:
Internet

openvmsdoc@hp.com

Mail

Hewlett-Packard Company
OSSG Documentation Group, ZKO3-4/U08
110 Spit Brook Rd.
Nashua, NH 03062-2698

How To Order Additional Documentation
For information about how to order additional documentation and for online
versions of most DECnet-Plus documentation, visit the following World Wide Web
address:
http://www.hp.com/go/openvms/doc/

Conventions
The following conventions apply to this book.
Convention

Meaning

special type

Indicates a literal example of system output or user input. In
text, indicates command names, keywords, node names, file
names, directories, utilities, and tools. On a DECnet-Plus for
OpenVMS system, enter the word or phrase in the exact case
shown.
You can abbreviate command keywords to the smallest number
of characters that OpenVMS, NCL, DECdns, DECdts, and the
other utilities accept, usually three characters.

viii

italic

Indicates a variable.

text style

Indicates a new term defined either in the text or in the
Introduction and User’s Guide glossary or important text.

Return

Indicates that you press the Return key.

Ctrl/x

Indicates that you press the Control key while you press the
key noted by x.

[]

In command format descriptions, indicates optional elements.
You can enter as many as you want.

{}

In command format descriptions, indicates you must enter at
least one listed element.

1
Introduction to the HP DECnet-Plus Distributed
Time Service
This chapter gives a conceptual overview of the HP DECnet-Plus Distributed
Time Service (DECdts) and its functions. Some basic time and clock concepts,
DECdts time representation, and basic DECdts operation are also presented.
DECdts is a software-based service that provides precise, fault-tolerant clock
synchronization for systems in local area networks (LANs) and wide area
networks (WANs). The clock synchronization provided by DECdts enables
distributed computing applications to determine event sequencing, duration,
and scheduling. DECdts software is packaged with the HP DECnet-Plus for
OpenVMS software.
DECdts consists of software components on a group of cooperating systems; it
conforms to the client/server model used in many of HP’s distributed processing
products. In the DECdts implementation, each server supplies the time to many
client systems and applications through intermediaries called clerks. Clerks
reside on their client systems. (Note that throughout this document, the term
entity is used to refer to the server or clerk process when they have the same
functions.)
Most DECnet nodes have a clerk that adjusts the clock on its client system; at
regular intervals, clerks obtain time values from one or several servers in the
network. The nodes that do not have DECdts clerks have DECdts servers; in
addition to providing time values to clerks, servers also adjust the system clocks
on their host systems. Servers can also obtain reference time values from sources
of standardized time that are outside the network.
Because no device can measure the exact time at any particular instant, DECdts
expresses the time as an interval containing the correct time. In the DECdts
model, the DECdts entity (clerk or server) on a given system obtains time
intervals from several servers, and computes the intersection where the intervals
overlap. The DECdts entity then adjusts the clock of its client system to the
midpoint of the computed intersection. When the entity receives a time interval
that does not intersect with the majority of received intervals, it rejects the
nonintersecting value. This mechanism allows a DECdts entity to ignore random
faulty values when computing new times, thereby ensuring that defective server
clocks do not affect its client system.
DECdts also permits the importation of time values from outside sources, such
as the U.S. National Institute for Standards and Technology (NIST). Many
standards bodies disseminate time signals by radio, telephone, and satellite;
commercial devices (time-providers) are available to receive and interpret these
signals. DECdts offers a time-provider interface (TPI) that describes how a
time-provider process can pass time values to a DECdts server and propagate
them in the network. The time-provider interface also permits distributed time
services from other vendors to interoperate with DECdts.

Introduction to the HP DECnet-Plus Distributed Time Service 1–1

DECdts provides many other services for computer networks running distributed
applications. A summary of its major features and benefits follows:
•

Correctness—DECdts maximizes the probability that a client will receive
the correct time. DECdts uses Coordinated Universal Time (UTC) as a base
reference, and defines any time interval containing UTC as correct.

•

Quantitative Time Measurement—DECdts uses specific measurement and
manufacturer’s specifications to determine the accuracy of the times reported
by servers.

•

Fault Tolerance—DECdts reports servers whose time values do not
intersect with the majority, and does not use their time values during clock
synchronizations.

•

NCL Management—Through its management interface, DECdts offers
Network Control Language (NCL) support for controlling and monitoring the
software.

•

Applications Programming Interface (API)—DECdts provides an
interface that allows applications to obtain, compare, and calculate UTC time
values.

•

Local Time Translation—When displaying time values, DECdts translates
the UTC times it uses internally into local time values.

•

Automatic Local Time Updates—After the initial configuration of a
DECnet-Plus system, DECdts updates the system time automatically
according to the rule in effect for the geographical location of the system.

•

Monotonicity—DECdts usually provides unidirectional clock adjustment to
ensure that clocks do not run backwards. The enable and change commands
also allow nonmonotonic clock adjustment if desired.

•

Automatic Configuration—DECdts entities use multicast messages
to obtain the locations of servers in a LAN, and the HP DECnet-Plus
Distributed Name Service (DECdns) or a site-specific configuration file to
obtain the locations of servers in a WAN.

•

Efficiency—Complexity is placed in the servers; network overhead is
minimal.

1.1 DECdts Advantages
DECdts offers all the features normally provided by a time service, but it also
has several unique features that enhance network performance. This section
describes these DECdts features.

1.1.1 Applications Support
Operating systems and distributed applications require synchronized time
measurements to coordinate their processes. DECdts synchronizes the system
clocks in a network with each other, and in the presence of an external timeprovider, to the UTC time standard. Any distributed application that reads the
system clock (the majority of applications) needs DECdts. As the number of
distributed applications and systems in a network increase, DECdts becomes
increasingly vital to process coordination.

1–2 Introduction to the HP DECnet-Plus Distributed Time Service

There are several types of existing applications that use the synchronized
time DECdts provides to system clocks. These applications must reference
synchronized system clocks to coordinate the events that occur throughout the
network. Applications use synchronized clocks for the following functions:
•

Event measurement. Applications can read the system clock to start and
stop timers and measure the elapsed time between events.

•

Event reporting. Applications can read the clock when an event occurs and
append a timestamp to the event report.

•

Event scheduling. Applications can read the system clock and add a
relative time to determine the occurrence of a future event.

•

Event sequencing. Applications can determine the order of events by
reading the event report timestamps derived from the synchronized system
clock.

For new applications, DECdts provides an applications programming interface
(API). The API provides routines that new applications can use to obtain and
manipulate binary timestamps. The DECdts API supports ANSI C language
constructs. See DECnet-Plus DECdts Programming for further information on
the DECdts API.

1.1.2 External Time-Provider Support
For most networks, it is desirable to synchronize the system clocks with the
UTC time standard. Many commercial devices are available for obtaining the
UTC time provided by standards organizations; these devices receive signals
by short-wave radio, satellite, and telephone. If your network is larger than a
single LAN, HP recommends that you use at least one external time-provider
in combination with the DECdts software. For a list of time-provider hardware
suppliers, see Appendix B. Sample time-provider programs are provided with
the DECdts software on DECdts server systems. The programs are located in
sys$common:[syshlp.examples.dtss].
See Table 1–1 for a list of currently available time-provider programs and related
time-provider hardware or software suppliers.
Table 1–1 Time-Provider Programs and Related Time-Provider Suppliers
Time-Provider
Type

File Name

Related Supplier

dtss$ntp_provider.c

Various

Time-provider
program
for Internet
Network Time
Protocol

dtss$provider_acts.c

U.S. NIST (North America)

TPP for data
communications

dtss$provider.c

Traconex, Spectracom, Heath, Hopf
(North America & Europe)

TPP for RF
receivers

DECdts servers can synchronize with time-providers by means of the timeprovider interface (TPI), which is described in the DECnet-Plus DECdts
Programming guide. The TPI specifies the communications between the DECdts
server process and the time-provider process.

Introduction to the HP DECnet-Plus Distributed Time Service 1–3

When a DECdts server attempts to synchronize, it uses the TPI to check for
a time-provider process. If one is available, the server synchronizes only with
the time-provider. If no time-provider is connected to the server, the server
synchronizes with other servers in the network.
By connecting a time-provider to a DECdts server, you can ensure that the server
is synchronized closely with UTC. When other servers request a time from the
server with the time-provider (the TP server), the TP server’s precise time is
propagated throughout the network. See Section 1.2 for further information on
time-providers and the server synchronization process.

1.1.3 Manageability
The DECdts entity runs as a background process; little or no input is required
from the system manager to synchronize the system clock after DECdts is initially
configured. DECdts is also fault tolerant; it prevents malfunctioning clocks from
providing the wrong time to other clocks in the network. Occasionally, however,
system managers may need to perform the following functions:
•

Identify system clock problems

•

Adjust system clocks

•

Change DECdts attributes due to varying WAN conditions

DECdts provides a full-featured management interface that allows system
managers to adjust system clocks, change the values of the DECdts management
parameters, and add or subtract servers from the network.
To aid in solving problems with system clocks, DECdts provides event reporting,
which notifies system operators and managers in the rare event that a system
clock is inaccurate or fails to synchronize. For further information on solving
synchronization problems with DECdts, see Chapter 3, Problem Solving, and
Appendix A, Event Messages.

1.1.4 Quantitative Inaccuracy Measurement
Unlike other network time services, DECdts uses manufacturer’s specifications
and direct observation to determine the inaccuracy of system clocks relative to
UTC. DECdts appends an inaccuracy measurement to each time value that it
uses internally; this measurement takes into account cumulative clock error,
communications delays, and processing delays. DECdts uses combined time
and inaccuracy measurements from one or several sources to calculate the most
accurate new clock settings for client systems. See Section 1.2.3 for further
information on the DECdts synchronization process.

1.2 Basic DECdts Concepts
This section describes time measurement factors, DECdts synchronization
concepts, DECdts system clock adjustment, and DECdts time representations.
Read this section to gain a basic understanding of DECdts concepts before
progressing to Chapter 2, Managing DECdts.

1.2.1 Time Measurement Factors
This section describes the factors that affect time measurement and explains how
DECdts handles them.

1–4 Introduction to the HP DECnet-Plus Distributed Time Service

1.2.1.1 Clock Error
DECdts uses UTC as its time standard, and defines any difference between UTC
and the time of a system clock as clock error.
All system clocks have common properties that contribute to clock error and
interfere with the synchronization process. This section describes some of
these properties; Section 1.2.2 explains how DECdts handles these problems
to accurately synchronize networked system clocks.
System clock error tends to increase over time; the rate of change of error is
known as drift. If each system clock in a network started at the same time
and ran at the same rate, the clocks would remain synchronized. Because each
system clock drifts at a different rate, however, the system clocks throughout a
network tend to become desynchronized. The difference between any two clock
readings is known as the skew between the clocks. The clocks used in many
OpenVMS computer systems have a specified maximum drift of 8 seconds per
day. If uncorrected for several days, the skew between networked system clocks
can inhibit the performance of distributed applications.
DECdts constantly tracks the drift of each system clock in the network and
periodically synchronizes the clocks to reduce the skew among them. The DECdts
server and clerk adjust the clocks in their client systems as the final step in this
repeating synchronization process.
1.2.1.2 Communications and Processing Uncertainties
Communications delays can inhibit the synchronization process, especially when
two systems communicate over a WAN or low-speed link. DECdts can cope with
the known processing delays required to send and receive messages between
systems. Because of the varying quality of communications links, however,
the time required to send, receive, and acknowledge messages varies from one
message to the next. These delays cannot be known exactly, because transit over
the network and the time required to read an incoming timestamp both vary.
Rather than using estimates of communications and processing delays, DECdts
records all known error factors that accompany a time measurement sent over the
network. This measurement enables DECdts to determine the relative quality
of a time source regardless of its geographic location or changing conditions on
communications links.

1.2.2 Inaccuracy
To synchronize system clocks to the most accurate settings, DECdts needs a way
to determine the accuracy of time sources relative to each other and to UTC. This
section describes how DECdts determines the relative accuracy of any time source
available in the network.
DECdts uses an inaccuracy value, or tolerance, to determine the relative
accuracy of time values that it obtains from system clocks and external timeproviders. This DECdts feature effectively transforms each time value into an
interval, or range, rather than a point on a continuum.
Inaccuracy values are determined by three factors:
•

Drift. When reading a clock, DECdts calculates the amount of time that the
clock may have drifted since DECdts previously synchronized and adjusted
the clock. Drift is the largest component of most inaccuracy values.

Introduction to the HP DECnet-Plus Distributed Time Service 1–5

•

Communications delay. The inaccuracy also consists of the uncertain
portions of the communications delays between systems. Although DECdts
compensates for processing delays, it cannot predict or directly measure the
varying delays that occur on network links. The inaccuracy values that a
clerk or server obtains from colocated systems on a LAN tend to be much
lower than those obtained from servers outside the LAN.

•

Leap seconds. UTC time is measured by atomic clocks, which are extremely
stable. The standard, however, keeps time based on the earth’s position.
Because of the slowing of the earth’s rotation, it occasionally becomes
necessary to advance UTC time by 1 second; these events are known as
leap seconds. Leap seconds can occur in the final second of any month,
and normally occur about once every 18 months. At the end of each month,
DECdts accounts for leap seconds by increasing the inaccuracy measurements
of client system clocks by 1 second; DECdts later adjusts the clocks to remove
the extra second of inaccuracy if an external time-provider determines that a
leap second did not actually occur.
Without DECdts to correct it, a system clock’s inaccuracy is always increasing.
For example, suppose that a clock starts with a UTC time of 00:00:00.000
(midnight) and zero inaccuracy. Because of drift, when the clock next
shows a time of 00:00:00.000, the inaccuracy is 8 seconds. UTC time can
be 23:59:52.000 or 00:00:08.000, but is probably somewhere in between.
Therefore, the system time is an interval containing UTC time and bounded
by the inaccuracy, as shown in Figure 1–1. Using the DECdts format for
displaying time, the combined time and inaccuracy interval is expressed as
follows: 1990-08-03-00:00:00.000I08.000.

Figure 1–1 Time and Inaccuracy
Hardware
clock time
Boundary of
inaccuracy

(Midnight)

Boundary of
inaccuracy

00:00:00.00

00:00
30

−8

Key:
= Coordinated Universal Time (UTC)
ZK−1996A−GE

1.2.3 Synchronizing System Clocks
To maintain uniform system times, DECdts servers and clerks periodically
synchronize the clocks in all network systems. The DECdts entity on each
system performs these synchronizations by requesting that servers send their
combined clock and inaccuracy values (time intervals) to the originating system.

1–6 Introduction to the HP DECnet-Plus Distributed Time Service

The entity then uses the values sent by the servers to compute a new system
time.
DECdts servers and clerks have slightly different synchronization procedures.
Before attempting to synchronize with other systems, a DECdts server always
checks to see whether an external time-provider is connected to the system. If no
time-provider is available, the server requests times from other servers. When
the server synchronizes with its peer servers, the server uses its current system
time as one of the input values for computing a new system time.
Most network systems run the DECdts clerk process. Clerks cannot have timeproviders, and they do not use the system time of their client systems to compute
new times. When a clerk is synchronizing its client system’s clock, the clerk uses
only the time values that it obtains from servers to compute a new system time.
When a DECdts clerk or server process requests several time intervals from
servers, it uses them to calculate a new time that is correct (contains UTC) and
that minimizes inaccuracy. When the servers respond and the DECdts entity has
calculated network communications uncertainties for each of the time values, the
entity has a set of intervals (t1 through t4 in Figure 1–2). Intervals t1, t3, and t4
are correct; because each of these intervals contains UTC, their intersection is the
smallest interval the entity can choose that also contains UTC. This intersection
is the computed time. The DECdts process uses the computed time interval to
adjust the clock on the system that receives the server values.
In addition to eliminating large inaccuracy values during synchronization,
DECdts also discards intervals received from potentially faulty clocks (t2 in
Figure 1–2). DECdts detects and rejects time intervals that do not intersect with
the majority of the intervals. When DECdts detects a nonintersecting interval,
it notifies the system manager by displaying an event message identifying the
server that sent the interval.
A server that has a high-drift clock or is far away in the network submits its time
to the DECdts entity (t1 in Figure 1–2), but the large time interval is ignored
because more accurate times are available. Note that in Figure 1–2, the midpoint
of correct time t1 is further from the computed time than that of the interval that
is declared nonintersecting (t2).
During the synchronization process, servers with the best accuracy have the
most influence in determining new system times throughout the network. In
Figure 1–2, the server that submitted time value t3 has the smallest correct
interval, and is therefore the closest to the computed time. Server systems
with external time-providers are usually the servers with the most accurate
times; beyond TP servers, those servers with the highest quality clocks and best
communications links tend to influence the time on other systems to the greatest
degree.
The synchronization process also reduces the skew between systems. The
computed time interval is often smaller than the interval supplied by any single
clock. Note that the computed time in Figure 1–2 is a smaller interval than any
of the source intervals. As the synchronization procedure is constantly repeated
on each network system, the skew between systems is reduced and they are more
closely synchronized. (However, if a time-provider is absent from the network,
the clocks may collectively drift away from UTC.)

Introduction to the HP DECnet-Plus Distributed Time Service 1–7

Figure 1–2 Computed Time

UTC

t4
Time

CT
Intersection of
correct intervals
(computed time)
ZK−3855A−GE

1.2.4 How DECdts Adjusts System Clocks
Each system clock in your network is based on an oscillator and operates with
a combination of hardware and software. The clock’s hardware contains a timer
that sends interrupts to the operating system at fixed intervals; each interrupt
is a single tick. A software register that contains the current value of the time
is incremented by a fixed amount (for example, 10 milliseconds) at each tick.
DECdts adjusts the rate of the clock by changing only the incremental value that
is added to the software register; DECdts does not directly affect the ticks of the
hardware clock. The management attribute clock resolution displays the tick
length of a system in nanoseconds.
DECdts adjusts system clocks at the rate of 100 to 1: it requires 100 time units
to adjust 1 time unit of error. For example, it takes 100 seconds to correct a
1-second error. This rate of adjustment exceeds the normal rate of drift, so that
synchronization is carried out without further significant interference from the
clock.
Figure 1–3 illustrates how DECdts changes the increment to the software
register. The top line represents a 10-millisecond increment to the normal clock
at every 10-millisecond tick. The middle line illustrates the adjustment to a fast
clock: DECdts slows the clock by incrementing the register by 9.9 milliseconds
instead of 10 at each tick. The bottom line illustrates the adjustment to a slow
1–8 Introduction to the HP DECnet-Plus Distributed Time Service

clock: DECdts speeds it up by incrementing the register by 10.1 milliseconds
instead of the usual 10 at each tick.
Figure 1–3 Adjustment of the Clock
NORMAL CLOCK

10
T

20
T

30
T

40
T

50
T

60
T

70
T

80
T

ADJUSTMENT TO A
FAST CLOCK

10.5
T

20.4
T

30.3
T

40.2
T

50.1
T

60
T

70
T

80
T

ADJUSTMENT TO A
SLOW CLOCK

9.5
T

19.6
T

29.7
T

39.8
T

49.9
T

60
T

70
T

80
T

T = Hardware tick
ZK−2323A−GE

It is occasionally preferable to set the system clock immediately, rather than
adjusting it gradually. DECdts provides this option for the following situations:
•

During system startup when you want to set the initial system time.

•

If it has been a long time since the last synchronization, and you decide
that the skews between system clocks are too large to wait for a gradual
adjustment.

•

When a network has had catastrophic hardware problems, causing a large
number of the clocks to become faulty.

•

When the time interval for a given clock does not intersect with the intervals
of other clocks, and the error exceeds a predetermined tolerance.

Note that this feature disrupts monotonicity, and it may affect other distributed
applications that depend upon DECdts.

1.2.5 DECdts Time Representation
Coordinated Universal Time (UTC) is the international time standard that has
largely replaced Greenwich Mean Time (GMT). The standard is administered
by the International Time Bureau (BIH), and is in widespread use. For all
its internal processes, DECdts uses opaque binary timestamps representing
UTC. You cannot read or disassemble a DECdts binary timestamp; the DECdts
applications programming interface (API) allows applications to interpret,
convert, or manipulate the timestamps. DECdts also translates the binary
timestamps to or from ASCII text for display on a client system.
Although DECdts uses UTC time internally, it converts UTC to the local time for
display on a client system. On OpenVMS VAX systems, you can determine the
offset of the displayed time from UTC by selecting a time zone when you install
the DECdts software. After the initial software installation, you can subsequently
display the local time for any system with the appropriate NCL command. See
Chapter 2, Managing DECdts, and Chapter 4, DECdts Command Dictionary, for
further information on displaying times.

Introduction to the HP DECnet-Plus Distributed Time Service 1–9

1.2.5.1 Absolute Time Representation
An absolute time is a point on a time scale. For DECdts, absolute times
reference the UTC time scale; absolute time measurements are derived from
system clocks or external time-providers. When DECdts reads a system clock
time, it records the time in an opaque binary timestamp that also includes the
inaccuracy and other information. When you use the DECdts management
interface to display an absolute time, it is converted to ASCII text as shown in
the following example:
1996-11-21-13:30:25.785-04:00I000.082
DECdts displays all times in a format that complies with the International
Organization for Standardization (ISO) Standard 8601 (1988). The ISO format
that generated the previous display example is detailed in Figure 1–4.
Figure 1–4 Time Display Format
Calendar date and time
component

TDF
component

Inaccuracy
component

CCYY−MM−DD−hh:mm:ss.fff[+|−]hh:mmIsss.fff
Century
Year

fractions
seconds

Month
Day
hour
minute

Inaccuracy
designator
minutes
hours
+|− TDF

second
fraction

In Figure 1–4, the relative time preceded by the plus (+) or minus (–) character
indicates the hours and minutes that the calendar date and time are offset
from UTC. The presence of this time differential factor (TDF) in the string
also indicates that the calendar date and time are the local time of the system,
not UTC. The character I indicates the beginning of the inaccuracy component
associated with the time.
Although the DECdts management interface displays all times in the previous
format, the interface also accepts the variations to the ISO format shown in
Figure 1–5.

1–10 Introduction to the HP DECnet-Plus Distributed Time Service

Figure 1–5 Time Display Format Variants
Calendar date and time
component

TDF
component

Inaccuracy
component

CCYY−MM−DDThh:mm:ss,fff[+|−]hh:mm +
− ss,fff
Century
fractions

Year
Month

seconds

Day

Inaccuracy
designator

Time
designator

minutes

hour

hours

minute

+|− TDF

second
fraction
ZK−4068A−GE

In Figure 1–5, the delineator T separates the calendar date from the time,
a comma separates seconds from fractional seconds, and the plus or minus
character indicates the beginning of the inaccuracy component.
DECdts offers a translation feature that changes UTC-based absolute times
to your local time whenever the time is displayed. The local time displayed is
derived from UTC and a TDF, which can have a positive or negative value. In
the previous example, the string ([+][–] hh:mm) denotes the TDF. When installing
a system, you select a time zone rule for the system, which determines the TDF
and any seasonal changes to the TDF. After the initial startup, all subsequent
output times reflect the local time. If an absolute time displayed by your system
does not contain TDF information, it is a UTC time.
1.2.5.2 Relative Time Representation
A relative time is a discrete time interval that is usually added to or subtracted
from another time. The TDF associated with absolute times is an example of
a relative time; relative times are normally used as input for commands or
system routines. The following example shows a relative time used in a DECdts
command:
21-08:30:25.000I00.300
Note that relative times do not use the calendar date fields, since these fields
concern absolute time. Positive relative times are not signed, while negative
relative times are preceded with the minus sign.
Relative times are often subtracted from or added to other relative or absolute
times. For example, if you say ‘‘I will meet you in an hour,’’ you add a relative
time of +01:00 to the present, absolute time. When you add or subtract a relative
time and an absolute time, the inaccuracy of the absolute time is carried over to
the resulting absolute time. For example,
1996-11-30-00:30:25.000I00.030 minus 00-00:15:25.000I00.000 equals
1996-11-30-00:15:00.000I00.030.
The relative times that DECdts uses internally are opaque binary timestamps.
Through its API, DECdts offers several calls to calculate new times using relative
binary timestamps.

Introduction to the HP DECnet-Plus Distributed Time Service 1–11

1.3 How DECdts Works
DECdts has two major software components:
•

Clerks

•

Servers

The following sections describe each component and explain how they interact to
provide time to client applications and to synchronize system clocks.

1.3.1 Clerks
Any system that is not a DECdts server is a DECdts clerk; most network systems
run clerk software. Clerks are the intermediaries between clients and servers.
Clerks also maintain server lists and perform the synchronization functions for
DECdts client systems. Clerks send multicast queries to all servers and build
server lists from the servers that respond. Clerks also contact known servers for
new server lists whenever the number of servers on their lists falls below the
minimum specified by the servers required attribute. (This attribute is one
of several settable DECdts characteristics available through the management
interface.)
After building a server list, a clerk can directly request time values from several
of the servers on the list. The clerk then receives these time values and uses
them to compute a new system time for its client system. Figure 1–6 illustrates
how DECdts builds server lists, passes time values around the network, and
synchronizes system clocks.

1–12 Introduction to the HP DECnet-Plus Distributed Time Service

Figure 1–6 DECdts Operation
S2

location

Server
Locations?

1A Each clerk solicits server locations via multicast messages; servers listen and respond.

1B Each server broadcasts its location via multicast messages; other servers listen.

Time?

S1
Time?

S2
S3

Time?

S3
S1
S2
Time?

C6
Time?
Time?

S1
S2
S3

2 Each clerk queries 1−3 servers for time values; each server queries all local servers for time values.
S1
S2
S3

(Clock
adjustment)

S1
S2
S3

3 Each server and clerk computes a new system time from the values received and adjusts its clock.
ZK−2764A−GE

Introduction to the HP DECnet-Plus Distributed Time Service 1–13

1.3.2 Servers
Servers provide many of the communications functions for DECdts.
External time-providers can be connected to servers, which then propagate
the precise time intervals they obtain from the time-providers throughout the
network.
Before one server can obtain time values from another, the servers must have the
same epoch number. Epochs divide the DECdts implementation into logically
separate areas; servers synchronize only with other servers that have the
same epoch number. All servers have the same epoch number when they are
created. Infrequently, you may wish to change a server’s epoch number (using the
management interface) to isolate it from the network to correct a problem.
The rest of this section describes the three types of DECdts servers: local servers,
global servers, and couriers.
1.3.2.1 Local Servers
A set of local servers reside on the same LAN and maintain their clocks by
synchronizing with each other. Local servers use the IEEE 802.2 (Ethernet)
protocol to communicate; because of the high throughput on this type of network,
the skews between the local servers on the LAN are normally maintained at
under 200 milliseconds.
Each local server advertises itself on the LAN by sending multicast messages
containing its address. Each server builds lists of the other servers in the LAN
by listening to the multicast messages. When a server synchronizes, it queries all
the other servers on its server list for time values. Servers that do not respond
are deleted from the list of servers.
Note
DECdts servers listen for multicast messages containing the following
(DECdts) multicast address: 09-00-2B-02-01-02. Servers ignore any
multicast messages containing addresses for other products.

Local servers perform time interval computations, adjust their clocks, and
provide time values to each other for synchronization purposes. Each server
must synchronize with every other server in the local set at periodic intervals.
At longer intervals, clerks request time values from the local servers. Clerks,
however, need only request intervals from the number of servers determined by
the servers required management parameter, which is usually a subset of all
the local servers.
1.3.2.2 Global Servers
WANs and many extended LANs require global servers. Local servers are
available only to the servers and clerks in a single LAN, but global servers
are available across an extended LAN or WAN. Any server can be configured
as both a local and a global server. The number of global servers is usually
small, but global servers have several important functions that enable DECdts
to synchronize every node in the network. Global servers are necessary in the
following situations:
•

When a network has multiple LANs or an extended LAN with bridges that
block multicast messages.

1–14 Introduction to the HP DECnet-Plus Distributed Time Service

•

When systems that are not on LANs have access to LANs through point-topoint links.

•

When clerks or local servers cannot access the required number of local
servers determined by the servers required management parameter.

DECdns is optional; if you have installed DECdns, it maintains a list of the
DECdts global servers that are registered with the advertise command. All
DECdts clerk and server systems are also DECdns clients. DECdts servers and
clerks also maintain their own lists of global servers, which are periodically
refreshed from the directories maintained by DECdns.
If you use the Local namespace or the Domain Name System (DNS/BIND) rather
than DECdns, DECdts systems use an alternate method of configuring and
locating global servers. For information on configuring global servers using the
Local namespace or DNS/BIND (referred to in DECnet-Plus as the Domain
namespace), see the file sys$common:[sysmgr]dtss$config_template.dat.
For information about the Local and Domain namespaces and about node
name syntax using these namespaces, see the HP DECnet-Plus for OpenVMS
Installation and Configuration manual.
Local servers and clerks request time values from global servers when they
cannot obtain the number of local server responses mandated by the servers
required attribute. Certain local servers also regularly request the time from
global servers; see Section 1.3.2.3 for a description of these servers.
1.3.2.3 Couriers
Designated local servers called couriers regularly communicate with global
servers. Couriers are local servers that request time values from one global server
at every synchronization. To ensure that all parts of the network contribute their
time values to synchronizations that occur on the LAN, couriers randomly select
a global server from before each synchronization. Couriers use the responses of
both local and global servers when synchronizing their own clocks.
Couriers provide networkwide synchronization through the following procedure:
1. Couriers request time values from at least one global server and all of the
local servers.
2. Couriers use the global server times and local server times to synchronize the
clocks in their systems.
3. Couriers relay newly computed clock times to other servers and clerks on the
LAN during future synchronizations.
For a network containing multiple LANs or point-to-point links, one server
on each LAN or segment should be configured as a courier; this configuration
ensures that various portions of the network remain synchronized and are not
isolated from each other.
Using the management interface, you can also designate one or more servers to
be backup couriers. These local servers temporarily assume courier functions
in the event that no courier servers are available on the LAN. In such a case,
the backup courier with the lowest numbered Ethernet address regularly
synchronizes with global servers until a courier is again available.

Introduction to the HP DECnet-Plus Distributed Time Service 1–15

1.4 Interoperation with DECdns
The HP DECnet-Plus Distributed Name Service (DECdns) provides a
networkwide registry called a namespace, which stores the names and
attributes of many types of network resources. DECdts global server names
are maintained as objects in the DECdns namespace in the default directory
ns:.DTSS_GlobalTimeServers, where ns is the name of the default namespace.
For further information on DECdns and namespace objects, see the HP DECnetPlus for OpenVMS DECdns Management guide.

1–16 Introduction to the HP DECnet-Plus Distributed Time Service

2
Managing DECdts
This chapter describes how to manage the HP DECnet-Plus Distributed Time
Service (DECdts) using the Network Command Language (NCL) and the NCL
management interface. The chapter begins with a brief introduction to basic
DECdts command syntax and procedures. The remainder of the chapter describes
how the commands are used to set the software variables and monitor the
DECdts implementation.

2.1 The DECdts Management Interface
DECdts uses the Network Command Language (NCL) for all configuration and
management functions. NCL provides consistency to the commands for HP’s
OpenVMS distributed system and networking products, enabling users to manage
different layered and bundled software with the same commands and syntax.
This section explains how to access and use the NCL command interface for
DECdts. For further information on NCL, refer to the HP DECnet-Plus for
OpenVMS Network Control Language Reference.

2.1.1 Interface Components and Command Syntax
DECdts conforms to HP’s Enterprise Management Architecture (EMA). Each
product that uses the architecture is assigned to a module. Each module is
made up of one or more entities, which control different functional areas of each
module. When you issue an NCL command, key in the directive, the keyword
node and the node ID (optional for the local node), the entity name, and an
attribute/value that is the object of the command. For some commands, you can
also provide an argument or prepositional phrase that modifies the command or
redirects its output. See Chapter 4, DECdts Command Dictionary, for detailed
information on the NCL commands and syntax you can use to manage DECdts.
A sample command is shown in Figure 2–1.
Figure 2–1 Command Syntax

ncl> set node my_node dtss servers required 3
Command Node

Node−ID

[Attribute]

Entity

Value

[Argument]
ZK−2763A−GE

Note
The DTSS module manages the DECdts software; you must enter the
appropriate DTSS entity name in all DECdts management commands.

Managing DECdts 2–1

You can enter DECdts commands in uppercase, lowercase, or any combination of
uppercase and lowercase, and you can shorten any command or keyword to its
minimum unique abbreviation of three characters. Usage examples are provided
in the reference pages for each command. You can spawn a subprocess from a
command procedure or program to issue the commands.

2.1.2 DECdts Timestamp Syntax
Once you begin using the command interface to manage DECdts, you will notice
that all responses to commands contain a timestamp that conforms to the input
and output format shown in Figure 2–2.
Figure 2–2 DECdts Timestamp Format
Calendar date and time
component

TDF
component

Inaccuracy
component

CCYY−MM−DD−hh:mm:ss.fff[+|−]hh:mmIsss.fff
Century
Year

fractions
seconds

Month
Day
hour
minute

Inaccuracy
designator
minutes
hours
+|− TDF

second
fraction

A typical DECdts time display looks like this:
1996-03-16-14:29:47.520-05:00I000.003
The timestamp uses the DECdts format that is explained in Chapter 1,
Introduction to the HP DECnet-Plus Distributed Time Service. In the previous
example, the year is 1996, the day is March 16, and the local time is 14 hours, 29
minutes, and 47.52 seconds. A negative time differential factor (TDF) of 5 hours
and an inaccuracy of 3 milliseconds are included in the timestamp.

2.1.3 The DECnet Startup Script
The net$configure configuration procedure does not generate the DECdts NCL
command file; it is installed when the DECnet-Plus software is installed.
The DECdts startup procedure runs as a detached process. The procedure follows:
1. The DECnet startup process in sys$startup:net$startup.com calls the
DECdts startup process in sys$startup:dtss$startup.com.
2. The dtss$startup process activates the detached process
sys$system:dtss$service.exe and invokes either
sys$common:[sys$startup]net$dtss_clerk_startup.ncl or

sys$specific:[sys$startup]net$dtss_server_startup.ncl, depending
on whether you have installed the server files at installation.
3. At system startup, the clerk_startup or server_startup process
automatically executes the create and enable commands through the
NCL management interface.

2–2 Managing DECdts

To further customize the system’s DECdts configuration at startup, you can edit
the default commands supplied in the startup files, add some of the commonly
used commands described in Section 2.2.2, or add other commands described later
in this chapter.

2.1.4 Accessing and Exiting the Management Interface
You can use either of two methods to start the NCL command interface and
access the NCL prompt. The first method follows:
$ run sys$system:ncl
ncl>
You can also access the NCL command interface using a second method:
$ mcr ncl
ncl>
After you start the management interface and the NCL prompt is displayed, you
can begin to enter commands. (See Section 2.2 for instructions on creating and
enabling DECdts.) Three NCL entities manage the DECdts software:
•

The dtss entity

•

The dtss decnet global servers entity

•

The dtss decnet local servers entity

Of the three entities, only the dtss entity has settable characteristics. Only the
show command is available for the dtss decnet global servers and dtss decnet
local servers entities.
When you finish a management session, exit from the command interface and
access the normal system prompt by entering the following command:
ncl> exit
%

2.2 Creating and Enabling DECdts
Once the operating system is functioning on your system and you have accessed
the NCL prompt, you can enter DECdts management commands. If you have
just completed the DECdts installation and startup procedures for the system,
the DECnet startup script executes the create and enable commands for you. If
you are restarting DECdts or have altered the startup script, you may need to
create and enable DECdts. This section describes these steps; Section 2.2.2 also
describes some common commands you may want to execute immediately after
enabling the service.

2.2.1 Creating DECdts
You cannot activate the DECdts process by entering the create command
interactively. To configure a system as a clerk or server, you must install the
desired clerk or server startup file and execute it. See Section 2.1.3 for further
details.
If your network has extended LAN or WAN links, establish where to install
couriers during the planning process. After you create a system as a server, you
can designate it as a courier by entering the following command. The available
roles are courier, noncourier, and backup courier.
ncl> set node splsys dtss courier role courier

Managing DECdts 2–3

Once you create all the servers, clerks, and couriers in your network, proceed to
enable them for the first synchronization.

2.2.2 Enabling DECdts
Use the enable command to turn on the DECdts software. When you enter the
command, the status attribute is set to on. The set clock argument is available
to abruptly set the clock to the computed time following the first synchronization.
If this is the initial system startup, set the argument’s value to true to permit
faster synchronization with the other systems.
Note
If you are enabling the first server on a LAN and clerks are already
operating on the LAN, ensure that the system clock is within 5 minutes
of UTC before entering the enable dtss set clock true command. If the
clock has more than 5 minutes of inaccuracy, clerks may synchronize to
the incorrect time and interfere with DECdns operation.

If the system’s clock is close to UTC, you can enter the set clock false argument
(the default setting). This setting dictates a gradual clock adjustment to the
computed time. Gradual adjustment prevents the clock from jumping forward or
backward. The adjustment rate is 100 to 1 (it takes 100 units of time to correct a
1-unit error), so adjusting the clock may be inappropriate for correcting an error
of hours or days.
The following example shows how to enter the enable command:
ncl> enable node splsys dtss set clock true
The DECdts systems in your network locate and synchronize with each other
regardless of the order in which you enable them. Enabling servers first,
however, allows the systems to synchronize faster.
Note that the initial synchronization may take longer than subsequent
synchronizations, because it depends on the presence of other systems. The
system on which you are enabling DECdts uses its hardware clock value until the
initial synchronization is completed.

2.2.3 Controlling LAN Devices Used by DECdts
The static device tables formerly used to determine the devices used by DECdts
have been removed. Now, DECdts uses the $DEVSCAN and $GETDVI system
services to build a list of devices that have the following characteristics:
•

a device class of DC$SCOM (synchronous communication device)

•

a device characteristic of DEV$V_NET

•

a device status of UCB$V_ONLINE and UCB$V_TEMPLATE

•

a device name in the form _ddcn:

You can use the logical name DTSS$ETHERNET_DEVICE to provide a list of
devices that DECdts should NOT use. All devices must be in the form _ddcn:,
where dd is the OpenVMS physical device name, c is the controller letter, and
n is the port number. The string is limited to 255 characters and can contain
spaces and other text which is ignored by DTS. For example, the following two
commands tell DECdts not to use the _EIA0: and _FWA0: devices.

2–4 Managing DECdts

$ DEFINE/SYSTEM DTSS$ETHERNET_DEVICE "Don’t use _EIA0: and _FWA0: "
$ DEFINE/SYSTEM DTSS$ETHERNET_DEVICE "_EIA0:_FWA0:"
Note
Unterminated network adapters can cause the dynamic device recognition
process to hang. Either terminate all network adapters or include
any unterminated devices in the DTSS$ETHERNET_DEVICE logical
definition.

2.2.4 Designating Global Servers and Couriers
If your network has WAN links or is an extended LAN, you may need to use
global servers and couriers to synchronize the systems in separate network
segments. Once you create and enable all the servers and clerks in the network,
you can assign global server and courier roles to selected local servers. Refer to
the HP DECnet-Plus for OpenVMS Installation and Configuration, DECnet-Plus
for OpenVMS Introduction and User’s Guide, and DECnet-Plus Planning Guide
manuals for advice on planning the location of global servers and couriers.
2.2.4.1 Advertising Global Servers to DECdns
To assign a server to the global set of servers, you can advertise the server to the
HP DECnet-Plus Distributed Name Service namespace. The DECdns namespace
contains a directory that is the repository (DECdns) for the name and address
information that DECdts uses to locate systems in extended LANs or WANs. If
you have installed DECdns, DECdts can call it at any time to obtain the locations
of systems that it cannot reach on the LAN.
The following example shows how to advertise a server to register it with DECdns
as a global server. Enter the system’s DECdns simple name as the argument to
server name. DECdns translates the simple name to a full name when it adds
the server to the time server directory.
ncl> advertise dtss server name acctg
See the advertise dtss command in Chapter 4 for information on removing a
server name from the global time server directory.
2.2.4.2 Designating Global Servers Using the BIND Database
DECdts supports getting information on the global servers from the BIND
database. If you want to use this feature of DECdts, you must use the
conventions discussed in this section.
You must set up canonical name (CNAME) records for each of the global servers
you intend to use. These records provide an alias for looking up the DECdts
global servers. These names are of the general form:
gbl_dtssn IN CNAME name
In this syntax, the n value is an integer. These integer values must start at 1 and
can go to some arbitrarily large number. The integer values must be contiguous
(no gaps). The reason is that DECdts stops scanning for the next higher integer
if it fails to find a record. The name value must be the name of an address (A)
record appearing in the BIND database.

Managing DECdts 2–5

A small sample BIND data base for the crosspoint.com domain is shown below.
There are two global servers defined in it: wzbang and case.
$ type CROSSPOINT_COM.DB
$ORIGIN crosspoint.com.
@
IN
SOA

wzbang.crosspoint.com. system.crosspoint.com. (
1
; Serial
10800 ; Refresh
3600
; Retry
604800 ; Expire
86400 ) ; Minimum

;
IN
;
case
wzbang
gbl_dtss1
gbl_dtss2

wzbang.crosspoint.com.

IN
A
161.114.94.62
IN
A
161.114.94.69
IN CNAME wzbang
IN CNAME case

When configuring the BIND resolver, you must pay attention to the domain that
the BIND server is in (especially if it is different from the local domain). You
should set the system domain to be the same domain of the BIND server that
you want to access. To change the system domain, use the set config command.
The set config command makes the change in the permanent database so that
the data survives reboots. For example, to set the domain to the crosspoint.com
domain, use the following command:
$ tcpip
TCPIP> set config name_service/domain=crosspoint.com
You can verify the resolver setting using the following command:
$ tcpip
TCPIP> show name_service
BIND Resolver Parameters
Local domain: DOM1.ASHFIELD.NET
System
State:

Started, Enabled

Transport: UDP
Domain:
crosspoint.com
Retry:
4
Timeout: 4
Servers:
wzbang.crosspoint.com
Path:
No values defined
Process
State:

Enabled

Transport:
Domain:
Retry:
Timeout:
Servers:
Path:
TCPIP>
Prior to doing a synchronization, DECdts extracts the information about global
DECdts servers from the BIND server and stores it in the temporary file
sys$manager:dtss$bind_data.tmp. The data is subsequently loaded into DECdts
in the in-memory global set. The data in this temporary file is in configuration

2–6 Managing DECdts

file format. DECdts generates only one of these files at a time and deletes the old
file prior to accessing the BIND server to get new data.
You can check to see if DECdts synchronized properly with a global server by
issuing the following command:
NCL>show dtss decnet global servers * all
Node 0 DTSS Decnet Global Servers wzbang.crosspoint.com
at 2004-03-11-04:10:40.130+10:00I0.410
Identifiers
Name

= wzbang.crosspoint.com

Status
Last Time Polled
Last Observed Time
Last Observed Skew
Used In Last Synchronization

= 2004-03-11-04:10:27.417+10:00I0.533
= 2004-03-11-04:10:27.430+10:00I0.379
= +0-00:00:00.013I0.911
= True

Characteristics
Transport

= DECnet

Node 0 DTSS Decnet Global Servers case.crosspoint.com
at 2004-03-11-04:10:40.130+10:00I0.410
Identifiers
Name

= case.crosspoint.com

Status
Last Time Polled
Last Observed Time
Last Observed Skew
Used In Last Synchronization

= 2004-03-11-04:10:27.417+10:00I0.533
= 2004-03-11-04:10:27.392+10:00I0.468
= -0-00:00:00.025I0.1000
= True

Characteristics
Transport

= DECnet

NCL>
The previous display confirms that DECdts synchronized with both case and
wzbang.
Troubleshooting
If DECdts does not synchronize with the global servers, verify that the
sys$manager:dtss$bind_data.tmp file is present. If the file exists, type it out
to see if the data looks valid. The following is an example of a valid file:
Global DECNET DOMAIN:wzbang.crosspoint.com
Global DECNET DOMAIN:case.crosspoint.com
If the file has no data or missing data you may have set up the canonical name
(CNAME) records for the global DECdts servers incorrectly.
If the temporary file data looks correct, you can turn on DECdts tracing in
sys$startup:dtss$startup by uncommenting the following line:
$ ! To turn on DTSS tracing (output to DTSS$ERROR.LOG),
$ ! uncomment the following line(s):
$ !
Define/system DTSS$TRACE 65535
After modifying the dtss$startup file, restart the DECdts server. The trace log
in the dtss$error.log file should have some lines referring to the BIND server.
This should give you an indication what is going wrong.

Managing DECdts 2–7

2.2.4.3 Designating Global Servers with the Site-Specific Template
If you have not installed DECdns in your network, you cannot use the advertise
command to designate a system as a global server. As an alternate means of
designating global servers, a site-specific template is supplied with the DECdts
kit. You can edit the template at each site to add a list of global server entries
and then rename the template file. Once you rename the file, the DECdts process
on the related system uses the information in the file to locate global servers
rather than attempting to contact the DECdns clerk software.
The site-specific global server
template is sys$common:[sysmgr]dtss$config_template.dat. The comments
in the file describe how to add global server entries and rename the file.
2.2.4.4 Assigning the Courier Role to Servers
Couriers serve an important role in maintaining synchronization between the
systems in separate parts of your network. A courier server functions like any
other server in the local set, but a courier also requests a time value from at
least one global server at every synchronization. This procedure enables a courier
server to propagate times from remote systems to a LAN, thereby keeping the
LAN in synchronization with all the other parts of the network.
There are three courier roles that you can assign to a server:
•

backup courier (the default setting)

•

courier

•

noncourier

The default role for the courier role characteristic is backup courier. If a server
system is connected to a time-provider, it configures itself with the noncourier
role after the first synchronization, overriding any setting you supply. A server
connected to a time-provider cannot have the courier role, because the server
process on that system requests only time values from the time-provider.
Use the courier setting to designate a server as the primary link to other
portions of your network. Use the backup courier setting to designate a server
as a secondary link to other areas of the network. A backup courier is effective
only if no other courier is available on the LAN.
Because there are no significant processing or overhead penalties associated with
the backup courier role, backup courier is the default setting. You can designate
one of the servers on a LAN as a courier and designate all the other servers on
the LAN as backup couriers. If you configure several servers as backup couriers
and the courier is unavailable, the backup courier with the lowest numbered
Ethernet address becomes the effective courier.
The following example shows how to assign the courier role to a server:
ncl> set node splsys dtss courier role courier

2.2.5 Changing the DECdts Entity Type
Once your network is running DECdts, you may decide you have too many or
not enough servers on a given LAN. Rather than adding unnecessary servers or
clerks to the LAN, you can change a clerk to a server or a server to a clerk.

2–8 Managing DECdts

The procedure to change the DECdts entity type varies according to whether the
system is a standalone node or part of a cluster. The following procedure turns
a standalone clerk to a server or changes all of the clerk satellites in a cluster
to servers; for the clustered environment, run the procedure on any one of the
clerks.
1. Enter the following commands for the clerk system:
ncl> disable dtss
ncl> delete dtss
2. Rename the clerk startup file to the server startup file as follows:
$ rename net$dtss_clerk_startup.ncl net$dtss_server_startup.ncl
3. Edit the file sys$common:[sysmgr]net$dtss_server_startup.ncl; change the
type setting in the create command from clerk to server.
4. If you plan to run a time-provider, you can install the time-provider examples
in the system’s sys$examples area by entering the following DCL command:
$ backup/log dnvosi010.n/save sys$examples:
5. Start the server by entering the following DCL command:
$ @sys$startup:dtss$startup
If you want to change a cluster satellite that is a clerk to a server, without
changing the other members of the cluster, enter the following command in place
of Step 3:
$ rename net$dtss_clerk_startup.ncl_$ sys$specific:[sysmgr]net$dtss_server_startup.ncl
You can reverse the previous procedure to change servers to clerks; edit
the file net$dtss_server_startup.ncl (found in sys$common:[sysmgr])
to change the create argument from server to clerk. Rename the file to
sys$common:[sysmgr]net$dtss_clerk_startup.ncl.

2.2.6 Option to Disable DECdts at System Boot
You can disable DECdts when the system boots. You should use this option when
another time provider controls the system clock.
To disable DECdts, do the following:
1. Add the following line to the sylogicals.com file:
$ define/system net$disable_dtss 1
2. Reboot the system.
The NET$DISABLE_DTSS logical name causes DECdts to leave the time
information set by the operating system unchanged.

2.3 Summary of Management Commands and Characteristics
There are several commands and characteristics you can use to manage
DECdts. This section contains a summary of the management commands
and characteristics that apply to DECdts servers and clerks. Table 2–1 contains
a list of these commands.

Managing DECdts 2–9

Table 2–1 DECdts Commands
Servers

Clerks

Arguments

DTSS Entity

advertise
change
create
delete
disable
enable
set
show
synchronize
update

server name
epoch, time
type

create
delete
disable
enable
set
show
synchronize

set clock

set clock
time

DTSS DECnet Global Servers
Entity

show
DTSS DECnet Local Servers
Entity

show
In the DTSS portion of Table 2–1, note that the set command does not have
arguments, but it does have characteristics that accompany the command to
modify its function. See Table 2–2 for the characteristics you can use with the
set command. The characteristics are fully described in this chapter and in
Chapter 4, the DECdts Command Dictionary.
The show command does not have arguments, but you can specify one or more
attribute groups with the command; that is, characteristics, counters,
identifiers, or status. See the show command in Chapter 4 for the attributes
and attribute groups you can append to the command.
Table 2–2 Settable DTSS Characteristics
Servers

advertisement interval
automatic tdf change
check interval
courier role
error tolerance
global directory
lan timeout

Clerks

automatic tdf change

error tolerance
global directory
lan timeout
(continued on next page)

2–10 Managing DECdts

Table 2–2 (Cont.) Settable DTSS Characteristics
Servers

Clerks

maximum inaccuracy
query attempts
servers required
synchronization hold down
wan timeout

Note that several commands and characteristics apply only to servers. If you
enter a server-related command or characteristic for a clerk, DECdts displays an
error message similar to the following:
Node 0 DTSS
AT 1996-09-11-17:00:35.541-04:00I1.847
FAILED IN DIRECTIVE: CHANGE
DUE TO: Directive NOT Supported

2.4 Routine Management Tasks
Once you create and enable DECdts on all your network systems and the systems
are synchronized, routine management tasks include performance enhancements,
reconfiguration of the network, and changes to local time. This section describes
how to perform these tasks.

2.4.1 Critical Commands and Characteristics
The DECdts entity has several commands and characteristics that modify and
improve the performance of servers and clerks. Use the set command to change
the values for many of the characteristics; use the show command to display the
values of characteristics at any time.
This section explains the commands and settable characteristics you can use
to manage clerks and servers after they have been installed and enabled. This
section also offers suggestions for various command and characteristic settings
depending on your network configuration.
2.4.1.1 The Servers Required Characteristic
The servers required characteristic specifies how many servers must supply
time values to the DECdts entity before it can synchronize the system clock.
For servers, the default and minimum recommended value for the servers
required characteristic is 3; servers require values from three servers to compute
a reliable new time. For clerks, the default value is 1 to permit synchronization
in a network with only one or two servers. Even though the default setting is
1 for clerks, HP strongly recommends you use a value of at least 3 if sufficient
servers are available in the network. The clerk cannot detect a faulty server
unless it gets time values from at least 3 servers.
Depending on whether it is a server or clerk, the entity has different
requirements of the servers in the network. The following requirements reflect
the default servers required settings.
•

Clerks require a value from one server.

Managing DECdts 2–11

•

Servers require values from at least two other servers. Each server uses its
own clock value when computing a new time.

To change the servers required value, enter the set command with the servers
required characteristic set to the desired value. The command accepts values
from 1 to 32. For example, the following command shows how to increase the
required number of servers to 4:
ncl> set node splsys dtss servers required 4
Once the DECdts nodes on your LAN have been running for more than
10 minutes, you can check the number of local servers in your system’s
synchronization list by issuing the show command for the dtss local server
entity:
ncl> show dtss decnet local servers *
Node 0:. DTSS Decnet Local Servers 00-00-04-00-01-fc (63.1)
AT 1996-02-21-11:22:18.008-05:00I0.103
Identifiers
ADDRESS

= 00-00-04-00-01-fc (63.1)

_______
Node 0:. DTSS Decnet Local Servers 01-00-04-00-02-fc (63.2)
AT 1991-02-21-11:22:18.032-05:00I0.103
Identifiers
ADDRESS

= 01-00-04-00-02-fc (63.2)

_______
Node 0:. DTSS Decnet Local Servers 02-00-04-00-03-fc (63.3)
AT 1991-02-21-11:22:18.036-05:00I0.103
Identifiers
ADDRESS

= 02-00-04-00-03-fc (63.3)

_______
Node 0:. DTSS Decnet Local Servers 03-00-04-00-04-fc (63.4)
AT 1991-02-21-11:22:18.040-05:00I0.103
Identifiers
ADDRESS

= 03-00-04-00-04-fc (63.4)

_______
In this example, the output reflects the servers required setting of 4. This
setting provides redundancy; when no global servers are in the network, the
system synchronizes even if a local server becomes unavailable.
Whenever the system cannot contact the number of servers determined by the

servers required setting, the system logs the event Too Few Servers Detected.
The log includes the number of servers currently available and the number
required. If you see this event displayed, see whether any of the servers are
unavailable, test the communications links to ensure that the system has not
been isolated from the servers, or add servers to the network.
You can use the servers required characteristic in other ways depending on your
network configuration. See the following cases.
•

If you have few systems in your network and you want to synchronize the
nodes regardless of server drift, lower the servers required value to 1 or 2.
Although the resulting synchronized time is a less reliable measure of UTC,

2–12 Managing DECdts

you increase the likelihood that the systems will synchronize. If the setting is
less than 3, however, the system will not be able to identify nonintersecting
(potentially faulty) servers.
•

To increase fault tolerance and ensure that the systems compute reliable
times, set the servers required value to 3 (the default setting for servers) or
higher. The systems can then identify potentially faulty servers and compute
the narrowest overlapping interval for the time values they receive. Keep in
mind, however, that your system will not synchronize until there are at least
three servers available.

The number of nodes in your network and the types of applications you use
determine whether guaranteed synchronization or reliable times and fault
tolerance are more important.
2.4.1.2 Use with Global Servers
If your network consists of more than a single LAN, it should have a set of global
servers. You can create global servers by advertising local servers to the HP
DECnet-Plus Distributed Name Service (DECdns) or by configuring the sitespecific template. See Section 2.2.4.1 for further information on advertising a
server as a global server.
The presence of global servers in your network can influence the value you choose
for the servers required characteristic. If the number of local servers available
to a system is less than the servers required setting, the system automatically
queries DECdns for a server name from the DECdns list of global time servers.
The system then adds the global server to its server list and requests time values
from the global and local servers.
You can check to see which global servers are known to a system by entering the

show command for the entity dtss decnet global server. DECdts then lists all
known global servers and specifies which global servers were used in the last
synchronization. The following example shows how to display all of the global
servers (the asterisk is a wildcard character).
ncl> show dtss decnet global servers * all
Node 0:. DTSS Decnet Global Servers ABC:.DTSS_GlobalTimeServers.sys
AT 1991-02-21-17:34:27.358-05:00I0.092
Identifiers
Name

= ABC:.DTSS_GlobalTimeServers.sys

Characteristics
Transport

= DECnet

2.4.1.3 Use with Systems on Point-to-Point Lines
If you are using DECdts on a system that connects to a LAN through a pointto-point WAN link, the solitary system never has more than one local server
available. If the system is a server, the default and recommended servers
required setting is 3; the server must query two global servers to synchronize. If
the system is configured as a clerk, it does not have any local servers, and must
query the number of global servers determined by the servers required attribute
to synchronize.

Managing DECdts 2–13

2.4.1.4 The Maximum Inaccuracy Characteristic
The maximum inaccuracy characteristic specifies the greatest allowable bound
on your system’s inaccuracy before DECdts causes the system to synchronize.
When the system exceeds the bound determined by the maximum inaccuracy
setting, DECdts forces the system to synchronize until the inaccuracy is reduced
to a level at or below the setting. The maximum inaccuracy setting is a trigger
for synchronization. You can vary the setting to vary the tolerance of intersystem synchronizations, but be aware that as the setting becomes lower, network
overhead rises. The default setting is 0.20 second (200 milliseconds).
The effects of the maximum inaccuracy setting on the system’s synchronization
behavior is summarized in the following steps:
1. The system’s clock value accumulates more inaccuracy than the maximum
inaccuracy value and the DECdts entity initiates a synchronization.
2. The DECdts entity computes a new time value.
3. The DECdts entity adjusts the system clock, using the new time value.
4. If the new clock setting still exceeds the maximum inaccuracy value, or if clock
drift later causes the inaccuracy to reach the value, the cycle is repeated.
Note that if synchronization repeatedly fails to achieve an inaccuracy that is
less than the maximum inaccuracy value, the system could be continuously
synchronizing. See Section 2.4.1.5 for information on how the synchronization
hold down characteristic prevents this loop.
The default maximum inaccuracy value is designed to keep the system accurate
enough for most applications without being intrusive to network communications
or system processing. If your network includes one or more time-providers that
ensure extremely low inaccuracy, you can lower the maximum inaccuracy value.
Raise the value in the following cases:
•

When a time-provider is not used in the network

•

When a system is part of a WAN-only network configuration

•

When the applications that call DECdts do not require the level of accuracy
achieved by the default setting

The following example shows how to change the maximum inaccuracy value
to 0.2 second:
ncl> set node splsys dtss maximum inaccuracy 00.200
2.4.1.5 The Synchronization Hold Down Characteristic
The synchronization hold down characteristic prevents your system from
synchronizing more often than the specified interval and prevents the maximum
inaccuracy characteristic from causing continuous synchronizations. As
mentioned in Section 2.4.1.4, the maximum inaccuracy characteristic causes
system synchronization as long as the system’s inaccuracy is above a specified
value. The synchronization hold down characteristic prevents synchronization
from occurring more frequently than the hold down value. (The value is
randomized to prevent several systems from synchronizing simultaneously and is
an average value.)

2–14 Managing DECdts

The maximum inaccuracy and synchronization hold down characteristics are
interdependent; system synchronization occurs automatically when both of the
following conditions are met:
•
•

The inaccuracy of its clock equals or exceeds the maximum inaccuracy value.
The time since the last synchronization equals or exceeds the

synchronization hold down value (slightly randomized).
Note that if the system reaches the synchronization hold down setting, but has
not yet reached the maximum inaccuracy setting, the system will not synchronize.
The default synchronization hold down value is 5 minutes for servers and 10
minutes for clerks. If you are trying to minimize the skew between systems, you
can lower the synchronization hold down value. For example, to make a clerk
synchronize every 5 minutes if its inaccuracy reaches 100 milliseconds, enter the
following command:
ncl> set node splsys dtss sync hold down 05:00.0000
The synchronization hold down characteristic does not prevent the synchronize
command from working. You can synchronize a system at any time by
entering this command. The hold down characteristic affects only automatic
synchronizations triggered by the maximum inaccuracy characteristic. For more
information on the synchronize command, see Chapter 4, DECdts Command
Dictionary.
2.4.1.6 The Error Tolerance Characteristic
The error tolerance characteristic determines how DECdts reacts if the system’s
clock is faulty. A faulty clock is a rare condition, but some causes of faulty clocks
include the following:
•

Defects in the clock hardware, including clock drift greater than the
manufacturer’s specifications

•

Malfunctioning time-providers

•

Hardware clock ticks lost by the operating system

•

The system memory containing the clock value is corrupted

•

The presence of an application running for an extended period of time at a
high IPL (thereby preventing clock updates)

During the synchronization process, DECdts detects that a system’s clock is
faulty if the clock value and its inaccuracy fail to intersect with those of the
servers used for synchronization. This process is shown in Figure 2–3, where
value t2 is faulty.

Managing DECdts 2–15

Figure 2–3 Nonintersecting Time Interval

UTC

t4
Time

CT
Intersection of
correct intervals
(computed time)
ZK−3855A−GE

If DECdts detects a nonintersecting (potentially faulty) time interval
during synchronization, the divergence of the nonintersecting time and the
system’s error tolerance setting determine how DECdts reacts. When the
nonintersecting time is detected, DECdts performs one of the following operations:
•

If the nonintersecting interval supplied by the clock is within the bounds of
the error tolerance, DECdts increases the inaccuracy of the value supplied by
the clock and adjusts the clock gradually.

•

If the nonintersecting time interval supplied by the clock is outside the
bounds of the error tolerance, DECdts immediately sets the clock to the new
computed time.

Before you change the default error tolerance setting, determine the
requirements of the applications that use the system time. Some distributed
applications, such as DECdns server software, require that systems have no
more than 5 minutes of inaccuracy. Larger error tolerances can prevent such
applications from properly sequencing DECdns namespace entries. For these
applications, set the error tolerance value to 5 minutes or less.

2–16 Managing DECdts

Some applications may require DECdts to adjust the system clock gradually
and monotonically (forward). You can increase the error tolerance setting
for these applications to ensure that the clock is abruptly set only in the event
of a catastrophic error. If you could set the error tolerance characteristic to
infinity, you could guarantee that the clock is never set abruptly. This setting
is not available, but you can enter any setting less than 1334399-21:21:00.685
(approximately 3650 years).
The default value for error tolerance is 5 minutes (00-00:05:00.0000). The
following example shows how to change the error tolerance setting to 3 minutes.
ncl> set node splsys dtss error tolerance 00-00:03:00.0000
2.4.1.7 The LAN Timeout, WAN Timeout, and Query Attempts Characteristics
When a system queries a server, it waits for a response for the period specified by
the lan timeout or wan timeout characteristic. The lan timeout setting applies
when the system is attempting to contact a local server; the wan timeout setting
applies when the system is attempting to contact a global server.
The query attempts characteristic determines how many times DECdts resets
the timeout timer before the system quits trying to contact a local server. Once
the timeout setting has elapsed the number of times determined by the query
attempts characteristic, the system quits querying the local server and does not
post an event. Global servers, however, are only queried once. If a global server
does not respond when queried, the DECdts process generates a Server Not
Responding event report and removes the server from the system’s list of global
servers. If a response from the local or global server is required in order to meet
the servers required setting, DECdts generates a Too Few Servers Detected
event report, and the system does not synchronize.
The default setting for the query attempts characteristic is 3. The following
example shows how to set the query attempts value.
ncl> set node splsys dtss query attempts 4
The default setting for the lan timeout characteristic is 2 seconds, and the
default setting for the wan timeout characteristic is 15 seconds. The WAN setting
is larger to account for the communications delay associated with WAN links.
It is unlikely that you will have to change the lan timeout setting. The WAN
setting, however, may need to be changed because of variations in WAN topologies
and transmission quality. In the following example, the wan timeout setting is
changed to 20 seconds:
ncl> set node splsys dtss wan timeout 20.00
If you continually receive Server Not Responding event reports for a global server,
increase the wan timeout setting. If you increase the setting and the event
reports continue, there may be a problem with the communications link to the
server, the server may be offline, or the server may not be enabled. The following
example shows how to display the status of a global server (enter the node name
displayed in the event message):
ncl> show node farsys dtss all status

Managing DECdts 2–17

2.4.2 Server Management
Some commands and characteristics are unique to server systems. Managing a
DECdts server involves some tasks in addition to normal system management.
These tasks include the following:
•

Setting a server’s epoch

•

Assigning the courier role to a server

•

Advertising a server to DECdns or configuring the site-specific template to
add the server to the list of DECdts global servers

•

Setting and using the check interval and advertisement interval
characteristics

Most of the tasks in the preceding list are performed at the initial system
startup. Setting up a system as a global server and assigning the courier role are
described in Section 2.2.4. This section describes the remaining tasks.
2.4.2.1 Matching the Epoch
At startup, a server’s epoch number must match those of the other servers with
which it synchronizes. When synchronizing, a server disregards clock values from
servers whose epoch numbers do not match its own.
When they are enabled initially, all DECdts servers have the epoch number 0
(zero); you need not change the epoch numbers at initial installation. Later, if
you add a server to an existing network, or change a clerk to a server, ensure that
the new server and the preexisting servers have matching epoch numbers. Enter
the following command to find out the epoch number of a preexisting server; you
must enter the server’s system ID.
ncl> show node splsys dtss epoch number
If the epoch of a server you have just created matches those of the other servers,
the new server can synchronize immediately. If the epochs do not match, however,
and you do not change the epoch of the new server, the new server ignores the
preexisting servers. The following example shows how to change a server’s epoch
number after you have enabled the server:
ncl> change node splsys dtss epoch 0
Once you know that a server is starting up with the proper epoch number, do not
change the epoch, unless serious system or network problems corrupt all of the
server clock values. In the unlikely event that the majority of the server clocks
become faulty, use the change command and the epoch number characteristic to
isolate problem servers, so you can perform troubleshooting and maintenance
without affecting the rest of the DECdts application. See Chapter 3, Problem
Solving, for further information on setting epoch numbers to isolate, test, and
troubleshoot system clocks.
2.4.2.2 The Advertisement Interval and Check Interval Characteristics
Use the advertisement interval characteristic to specify how often you want
the servers on a LAN to broadcast their availability by advertisement messages.
The default setting of 90 minutes should be adequate. You can update the lists
of servers maintained in all the systems more frequently by lowering the setting,
but lower settings contribute to greater network overhead. The following example
shows how to set the advertisement interval value:
ncl> set node splsys dtss advertisement interval 00-00:30:00.00

2–18 Managing DECdts

Enter the check interval characteristic only for servers that are connected to
time-providers. The check interval function allows DECdts to periodically check
all the servers on a LAN to make sure they are remaining synchronized with
the time-provider. When the amount of time specified by the check interval
setting has elapsed, the server with the time-provider (the TP server) performs
the following procedure:
1. The TP server requests time values from all the other servers on the LAN.
2. The TP server starts the synchronization process.
3. The TP server identifies the server time intervals that do not intersect with
its own.
4. The TP server issues event messages for each nonintersecting server it
detects.
In the preceding sequence, note that the TP server does not actually modify the
system clock after it starts the synchronization process. The TP server runs the
process only to detect nonintersecting (potentially faulty) servers. The DECdts
software assumes that the time value at the TP server is the most accurate
available, so the TP server does not use the values it collects from other servers
to change its clock. The TP server instead functions as a reference timekeeper for
the other servers.
You can set the check interval to a lower value for a more rapid notification
of nonintersecting servers, but lower settings contribute to greater network
overhead. The following example shows how to set the check interval value:
ncl> set node splsys dtss check interval 00-00:30:00.00

2.4.3 Modifying the System Time
There are four ways you can modify a system’s time using DECdts commands.
1. Update the time monotonically
2. Change the time nonmonotonically
3. Force system synchronization
4. Set the system clock to local time
This section describes reasons for changing the system time, and shows examples
of the commands you can use to modify the time and change the system clock.
2.4.3.1 Updating the Time Monotonically
If your network does not use time-providers and the network systems have been
running for some time, you may want to update the time on several servers to
match UTC or another external reference. When time-providers are absent from
your network, the systems remain closely synchronized, but their clocks may drift
away from accepted time standards such as UTC.
Use the update command to modify the time on a server system to make it more
accurate. The DECdts synchronization process ensures that the new time you
supply with the update command is propagated to the other network systems. To
update the server clock to a new time, the interval determined by the new time
and inaccuracy must be within the bounds of the current interval.

Managing DECdts 2–19

To use the update command effectively, you must have temporary access to a
trusted time reference. Such references include the time signals that many
standards organizations disseminate by radio or telephone. You can also use a
clock that you have recently verified as accurate. See Appendix B for suppliers of
UTC time.
Because the update command is a manually entered command used to modify
an absolute time, it is not useful for small inaccuracy settings. The minimum
reliable inaccuracy you can achieve with the update command is approximately
1 second. Human error and processing delays combine to make lower settings
unreliable. For example, you type the command and new time and then begin
monitoring the reference. When you perceive that the reference has reached the
desired time, you press the Return key to initiate the command. Your perception
of the reference mark and your pressing of the Return key do not coincide exactly.
Furthermore, once the command is initiated, the system load increases and
DECdts takes time to interpret and execute the command.
The following example shows how to update the time on a system (and eventually
propagate the adjustment throughout the network):
ncl> update node splsys dtss time 1990-10-07-09:30:15.0I01.0
If your systems require synchronization closer than 1 second to a standard such
as UTC, consider purchasing one of the time-providers listed in Appendix B. All of
the time-providers described compensate for transmission and processing delays,
and can provide time references that are precise to the millisecond level.
2.4.3.2 Changing System Time Nonmonotonically
Use the change command when you want to immediately set the time for a
server system. The command immediately changes the system clock setting to
the specified time, rather than gradually adjusting the clock as with the update
command. Use caution when changing the time on a server; the command can
set the clock backwards and can affect other distributed applications. Use the
change command at system startup or when the system clock is faulty and you
have identified and corrected the problem. The epoch argument is required for
this command, and the epoch number you specify must be different from the
current epoch number before the command will execute and change the time. If
you change the epoch, then change the server’s time to a setting that falls outside
the time intervals of the previously known servers, and then change the epoch
number back to the original setting, DECdts will declare the local system faulty
at the next synchronization.
Because the change command is normally used to correct gross clock errors, it is
likely that the time you specify for a given system will not intersect with those
of the system’s known servers if the system and servers have the same epoch
number. You can prevent the systems whose times you are changing from being
declared faulty by using the time argument to set the new time for a system and
the epoch argument to isolate it from the other systems. You can then change
the epoch for the other systems until all the systems once again share the same
epoch. This process is useful in the extremely rare case when the majority of
servers in the network have become faulty.
To use the change command effectively, you must have temporary access to a
trusted time reference. Such references can include the time signals that many
standards organizations disseminate by radio or telephone. You can also use a
clock that you have recently verified as accurate. See Appendix B for a list of
time reference sources.

2–20 Managing DECdts

Like the update command, the change command is a manually entered command
used to modify an absolute time. It is not useful for small inaccuracy settings;
the minimum reliable inaccuracy you can achieve with the change command is
approximately 1 second.
The following example shows how to change both the time and epoch for a system.
The epoch argument is required when setting the time.
ncl> change dtss epoch 1 time 1990-10-07-09:30:15.0000I01.0000
2.4.3.3 Forcing System Synchronization
Once you have created and enabled DECdts on all the systems in your network,
they will synchronize without any further intervention. There are situations,
however, when you want to force a system to initiate a synchronization rather
than waiting for the amount of time specified by the synchronization hold
down and maximum inaccuracy characteristics. For example, you can synchronize
a system with a TP server that you have just added to the network. If you
enter the synchronize command, the narrow time interval contributed by the
time-provider is quickly propagated throughout the network.
The following example shows how to force a system to synchronize:
ncl> synchronize node splsys dtss set clock true
You can adjust the system clock gradually or set it immediately. By entering
the set clock argument and the value true, the system clock is set; use this
argument if you want faster results and are not running applications that depend
on monotonic time. If the system clock has a relatively small inaccuracy, and it is
not important for the clock to be set immediately, enter the set clock argument
and the value false; however, the clock adjustment takes longer to complete.
2.4.3.4 Setting the System Clock to Local Time
DECdts displays the local time by default. DECdts uses UTC as the standard
by which it monitors and adjusts time. All times that are displayed by DECdts
reflect the time zone rule that is selected at system installation. Normally, the
time displayed is a local time that is offset from UTC by a specified number
of hours and minutes. The offset used to determine the local time is called the
time differential factor (TDF). The time zone rules for each geographic location
also dictate seasonal changes to the TDF and the resulting local time display.
For further details on changing the TDF, see HP DECnet-Plus for OpenVMS
Installation and Configuration.
Some time zones specify periodic seasonal adjustments of 1 hour or less.
Depending on the time zone you select at the initial operating system or
DECnet-Plus configuration, your system may require periodic adjustment of
the local TDF.
If the time zone rule for your system specifies a periodic TDF change, you can use
either of the following methods to adjust the local TDF:
•

Allow the DECdts entity to change the local TDF (and displayed local time)
automatically by leaving the automatic tdf change characteristic set at its
default setting of true.

•

Adjust the local TDF manually by entering the set dtss auto tdf change
false command and then entering the set dtss auto tdf change true
command at the appropriate time of year. After the local time has changed,
you can disable automatic TDF changes again.

Managing DECdts 2–21

If you are running time-sensitive applications (applications that read the system
clock and require monotonically increased time) on a DECnet-Plus for OpenVMS
system, you should use the preceding manual procedure with additional steps as
follows:
1. Enter the NCL command set dtss automatic tdf change false after you
enable the DECdts software. You may want to add this command to the
DECdts startup script as described in Section 2.1.3.
2. When a seasonal time change is required, disable the time-sensitive
application.
3. Enter the NCL command set dtss automatic tdf change true.
4. Monitor the local time with the NCL command show dtss current time to
ensure that it has changed. If the seasonal time change for the system’s locale
has already passed, the local time is changed immediately.
5. Restart the time-sensitive application.

2–22 Managing DECdts

3
Problem Solving
This chapter describes the problems most commonly encountered when
implementing DECdts and recommends actions to solve the problems.

3.1 A Clerk System’s Clock is Incorrect
If you have just installed the clerk, the time may be incorrect unless you entered
the DTSS management command enable dtss set clock true. If you do not set
the clock when enabling the clerk, the time is updated gradually and may take a
long time to complete if the clock is grossly inaccurate.
If the clerk is not newly installed, complete the following steps:
1. Use NCL to check the values of the synchronization hold down and maximum
inaccuracy attributes:
ncl> show dtss synchronization hold down
ncl> show dtss maxi inac
The default values for these attributes are 10 minutes and 0.2 second,
respectively. If the current settings for either of these attributes are higher,
go to step 2. Otherwise, go to step 3.
2. Set the synchronization hold down and maximum inaccuracy attributes to
their default settings or less.
ncl> set dtss sync hold down
ncl> set dtss maxi inac
3. Enter the following command to force a synchronization and set the clock
(note that setting the clock can interfere with DECdns and other distributed
applications that depend on monotonically adjusted time):
ncl> synch dtss set clock true
After you enter the synchronize command, recheck the current time. If the
time is still incorrect, go to the next step.
4. Enable all DTSS events as follows:
ncl> pass event disp outb stream * glob filt ((dtss), all)
5. After you have enabled all DTSS events, enter the following NCL command:
ncl> synchronize dtss set clock true
If the Synchronization Completed event is displayed and the time is still
incorrect, one or more of the servers have incorrect times; see Section 3.2. If
a different event is displayed, see the following list of events and actions.
•

Insufficient Resources Detected: Allocate more virtual memory to the
system.

Problem Solving 3–1

•

System Errors Detected: Follow the recommended user action described
in the supplemental error message.

•

Too Few Servers Detected: Lower the servers required setting or add
servers to the network.

•

Server Not Responding: See Section 3.3 and Section 3.4.

3.2 A Server System’s Clock is Incorrect
If you have just installed the server, the time may be incorrect unless you entered
the DTSS management command enable dtss set clock true. If you do not set
the clock when enabling the server, the time is updated gradually and may take a
long time to complete if the clock is grossly inaccurate.
If the server is not newly installed, see the problem descriptions and solutions in
the following sections.

3.2.1 Large Inaccuracy On One Server
If the inaccuracy value is infinite or very large on the subject server, but relatively
small on other servers, follow these steps:
1. Enter the following NCL commands to determine if the server has
synchronized recently:
ncl> show dtss current time
ncl> show dtss last sync
If there is a large difference between the two times, go to Step 4. If the server
has synchronized recently, go to the next step.
2. Enter the following NCL commands to check the values of the
synchronization hold down and maximum inaccuracy attributes:
ncl> show dtss synchronization hold down
ncl> show dtss maxi inac
If the synchronization hold down setting is higher than 5 minutes, and/or
the maximum inaccuracy setting is higher than 0.2 second, go to step 3.
Otherwise, go to step 4.
3. Set the synchronization hold down and maximum inaccuracy attributes to
their default settings or less.
ncl> set dtss synchronization hold down
ncl> set dtss maxi inac
4. Enter the following command to force a synchronization and set the clock
(note that setting the clock can interfere with DECdns and other distributed
applications that depend on monotonically adjusted time):
ncl> synch dtss set clock true
After you enter the synchronize command, recheck the current time. If the
time is still incorrect, go to the next step.
5. Enable all DTSS events as follows:
ncl> pass event disp outb stream * glob filt ((dtss), all)
6. After you have enabled all DTSS events, enter the following NCL command:
ncl> synchronize dtss set clock true

3–2 Problem Solving

7. If the Synchronization Completed event is displayed, the time should be
correct. If a different event is displayed, see the following list of events and
actions.
•

Different Epoch Detected: Enter the NCL command show dtss epoch
number; note the epoch number of the correct servers and change the
epoch number of the differing server to match. At the same time, you can
specify a correct time with the change command. For example:
ncl> change dtss epoch number 1 time_ncl> 1991-03-21-16:07:46.479-05:00I01.00

•

Insufficient Resources Detected: Allocate more virtual memory to the
system.

•

System Errors Detected: Follow the recommended user action described
in the supplemental error message.

•

Too Few Servers Detected: Lower the servers required setting or add
servers to the network.

•

Server Times Not Intersecting: Correct the times of the incorrect servers
by entering the change command for each server as shown in the previous
example.

3.2.2 Large Inaccuracy On All Servers
If the inaccuracy value is infinite or very large on all servers, and you want to
adjust the clocks monotonically, enter the update command for any of the servers.
See the following example:
ncl> update dtss time 1996-03-21-16:07:45.000-05:00I02.00
To verify that the clock adjustment is occurring, enter several show dtss current
time commands (pause between each command). The inaccuracy value should
decrease and eventually stabilize on all servers.
If the inaccuracy value is infinite or very large on all servers, and you want to set
the clocks nonmonotonically, enter the change command for one of the servers,
specifying an epoch number (that is different from those of the other servers) and
the correct time. See the following example:
ncl> change dtss epoch 1 time 1996-03-21-16:07:45.000-05:00I0.50
Enter the show dtss current time command to make sure that the system has
the correct time and inaccuracy, and then enter the change command for each of
the other systems in the network, specifying a new epoch number for each. See
the following example:
ncl> change node jhmsys dtss epoch 1
As each server switches to the new epoch, its clock is synchronized with the
servers that already have that epoch.
If you have used the update or change command to correct the clocks on all
servers, and their times are not corrected, follow these steps:
1. Enable all DTSS events on each node as follows:
ncl> pass event disp outb stream * glob filt ((dtss), all)

Problem Solving 3–3

2. After you have enabled all DTSS events, enter the following NCL command
for each server:
ncl> synchronize dtss set clock true
3. If the Synchronization Completed event is displayed, the time should be
correct. If a different event is displayed, see the following list of events and
actions.
•

•

Insufficient Resources Detected: Allocate more virtual memory to the
system.

•

System Errors Detected: Follow the recommended user action described
in the supplemental error message.

•

Too Few Servers Detected: Lower the servers required setting or add
servers to the network.

3.3 Local Servers are Unavailable or Unresponsive
If the NCL command show dtss decnet local servers * all does not display
servers, or if some servers were not used for the last synchronization, there are
several possible reasons.
•

Servers not installed/created: Verify that the other servers have been
installed and the create dtss type server command has been entered for
each server; if not, install and create the servers.

•

Servers not enabled: Verify that all servers are enabled by entering the show
dtss state command for each server. The state value should be on. If the
state value is off, enter the enable dtss command for each server.

•

Server epochs differ: If a server cannot find other servers, it may have
a different epoch from the others. In this case, if a server attempts to
synchronize with a server in another epoch, the event Different Epochs
Detected is generated at the initiating server and the synchronization fails.
Use the show dtss epoch number command for several servers to learn which
epoch they are using, and then enter the change command with a new epoch
number for the nonmatching server.

•

Servers time out: Check the value of the lan timeout characteristic by
entering the following command:
ncl> show dtss lan timeout
If the value is less than 2 seconds, or you suspect that the LAN may have
high traffic volume, increase the value by entering the command set dtss lan
timeout n, where n is a higher value than previously shown. It should not be
necessary to set the value higher than 15 seconds.

3–4 Problem Solving

If increasing the lan timeout setting does not cause the servers to respond,
enter the following commands (disabling and enabling the entity forces it to
repopulate the server list):
ncl> disable dtss
ncl> enable dtss
•

Servers isolated from the LAN: If your network has an extended LAN
topology, and bridges connect the LAN segments, the bridges may be
preventing communications between servers. Program all bridges to pass the
DECdts multicast messages unfiltered. The DECdts multicast address (ID) is
09-00-2B-02-01-02.

3.4 Global Servers are Unavailable or Unresponsive
If the NCL command show dtss decnet global servers * all does not display
servers, or if some servers were not used at the last synchronization, there are
several possible reasons. See Section 3.3 for a preliminary list of reasons and
suggested actions; see the following list for WAN-related reasons and actions.
•

Servers do not respond in time: Check the value of the wan timeout
characteristic by entering the show dtss wan timeout command. If the value
is less than 15 seconds, or you suspect that the WAN may have high traffic
volume or routing delays, increase the value by entering the set dtss wan
timeout n command, where n is a higher value than previously shown.

•

Global directory not set or empty: To see if a global directory has been
set, enter the show dtss global directory command. If a full name is
not displayed, specify a global directory by entering the set dtss global
directory name command, where name is the full name of the global
directory. To show the objects in the global directory, use the DECdns
directory command or the DECdns browser (for further details, see the HP
DECnet-Plus for OpenVMS DECdns Management guide). If the directory
is empty, add global server names to the directory by entering the NCL
command advertise dtss server name name, where name is the simple name
of a global server system.

•

DECdns clerk not functioning: Enter the NCL command show dns clerk
status and verify that the state is on. If the state is not on, see the HP
DECnet-Plus for OpenVMS DECdns Management guide for recommended
actions.

•

Global servers do not respond: Enter the NCL command show dtss
servers not responding, wait for the amount of time specified by the
synchronization hold down attribute, and enter the command again. If the
counter value has increased, the WAN link may not be working or the timeout
value may be too low. Verify that the WAN link is functional.

3.5 The Advertise Command Fails
There are several reasons why the advertise command can fail. This section
contains possible causes and suggested actions.

Problem Solving 3–5

3.5.1 Global Directory Not Configured
If the advertise command fails, an incorrect or missing global server directory
is the most common cause. To check the accuracy of the global server directory,
follow these steps:
1. Display the global server directory by entering the following command:
ncl> show dtss global directory
2. Verify the directory name by entering a DECdns command as in the following
example:
dns> show directory WAK:.DTSS_GlobalTimeServers
If the DECdns command does not return the directory name and attributes,
the name is incorrect. See the next step.
3. Verify the global directory name by checking the directory name from other
systems or by checking the name recorded on the planning worksheets. Set
the correct global server directory by entering an NCL command as in the
following example:
ncl> set dtss global directory MAK:.DTSS_GlobalTimeServers

3.5.2 Access Violation Messages
When you enter the advertise command, an access violation (no privilege) or
unknown entry message may be returned. If an access violation message is
displayed, follow these steps:
1. Enter the following NCL command to display the global directory for the node
you are using:
ncl> show dtss global directory
2. Exit NCL, access the DECdns control program, and display the access rights
for the global server directory, as in the following example:
dns> show directory WAK:.DTSS_GlobalTimeServers
3. When the directory attributes are displayed, ensure that the DNS$ACS set
with the suffix system has read, write, delete, test, and control privileges. If
the root or system accounts do not have these privileges, add them as in the
following examples:
dns> add directory WAK:.DTSS_GlobalTimeServers_> access .mynode.system for r,w,d,t,c
4. Reaccess NCL and enter the advertise command again.
If you follow the preceding steps and the advertise command still returns an
access violation message, the problem may be due to session control access to the
DECdns directory. Follow these steps to change the access rights:
1. Access the DECdns control program and display the access rights for the
global server directory, as in the following example:
dns> show directory WAK:.DTSS_GlobalTimeServers

3–6 Problem Solving

2. When the directory attributes are displayed, ensure that the DNS$ACS set
with the suffix "DNA$SessCtrl" has read and write privileges. If the set does
not have these privileges, add them as in the following example:
DNS> add directory WAK:.DTSS_GlobalTimeServers _DNS> access wak:nodename.DNA$SessCtrl for r,w,t,c
DNS> add directory WAK:.DTSS_GlobalTimeServers _DNS> access wak:nodename.system for r,w,t,c
In these examples, nodename is the full name of your local system.
3. Complete the advertise command by entering a session control command as
in the following example:
ncl> update session control tower maintenance_ncl> WAK:.DTSS_GlobalTimeServers

Problem Solving 3–7

4
DECdts Command Dictionary
The DIGITAL Network Architecture (DNA) contains many modules that each
relate to a functional area or product. All DECdts management functions
are contained in the DTSS module. The DTSS module has several entities
that enable you to synchronize, adjust, and maintain the system clocks in a
distributed network. This chapter describes accessing the command interface
and the command format, and also describes the commands for the entities
that constitute the DTSS module. For a detailed explanation of system clock
synchronization and management, see Chapter 2, Managing DECdts. For further
information on the DIGITAL Network Architecture and its Network Command
Language (NCL), see HP DECnet-Plus for OpenVMS Network Control Language
Reference.
Figure 4–1 shows the hierarchical relationship of the entities that constitute the
DTSS module.
Figure 4–1 Hierarchy of DTSS Module Entities

dtss module

dtss

decnet
global
server

decnet
local
server

ZK−2629A−GE

4.1 The DTSS Entities
Each entity in the DTSS module is listed as follows, along with the commands
used to manage it. Note that the main entity in the DTSS module is named

dtss.

DECdts Command Dictionary 4–1

dtss advertise
change
create
delete
disable
enable
set
show
synchronize
update
dtss decnet global servers
show
dtss decnet local servers
show
The DTSS entities have the following functions:
•

The DTSS entity provides access to most of the management functions for the
DTSS module and the DECdts product, including creating and deleting the
software, enabling and disabling the software, setting attributes, adjusting
the clock, and forcing synchronizations.

•

The dtss decnet global servers entity provides information about a node’s
synchronization with one or more servers in the global set.

•

The dtss decnet local servers entity provides information about a node’s
synchronization with one or more servers in the local set.

The commands for each entity are described in reference pages that appear in
alphabetical order in this chapter.

4.2 Command Format
All of the entities in the DTSS module use the same NCL format for commands.
To enter a command, enter the name of the command and the name of the entity
to which the command applies. If you are trying to manage the entity at a remote
system, you must also enter node followed by the node ID. Some commands have
required arguments, and some commands have optional arguments, attributes,
or prepositional phrases. Arguments modify the way the command is executed;
attributes further define a general command such as set or show; prepositional
phrases filter or redirect the command output. A value is associated with each
argument and settable attribute, and most prepositional phrases. A command
example is shown in Figure 4–2.

4–2 DECdts Command Dictionary

Figure 4–2 Command Syntax

ncl> set node my_node dtss servers required 3
Command Node

Node−ID

Entity

[Attribute]

Value

[Argument]
ZK−2763A−GE

4.2.1 Attribute Groups
Each entity in the DTSS module has several types of attributes—pieces or sets
of data associated with the entity. Attributes describe the operational properties
of an entity and specify other information that regulates or monitors the entity’s
behavior. The DTSS module attributes are categorized as follows:
Characteristics

Display or affect the entity’s operation

Counters

Record the number of occurrences of an event since the entity
was last enabled

Identifiers

Distinguish the entity from other entities

Status

Describe the current operational state of the entity

Each entity has a show command that you can use to display attribute values;
you can specify attribute groups or individual attributes with these commands.
The dtss entity also has a set command that you can use to modify the values of
some attributes.

4.2.2 Prepositional Phrases
You can use prepositional phrases to affect the destination or content of command
output. The phrases are most useful with the show command. If you are
managing a remote system or managing the local system from a nonprivileged
account, you can use the by prepositional phrase to specify access control
information with a command. See Section 4.2.3 for further information on how to
use the by phrase.
You can combine several prepositional phrases in one command; precede each
phrase with a comma and a space. The following table summarizes the to and
with prepositional phrases and their uses:

, to file=filename

Redirects the output to filename. If the file exists, a
new version is created. If the file does not exist, it is
created.

, to extend file=filename

Appends the output to an existing file filename. If the
file does not exist, it is created.

, to terminal

Directs the output to the terminal. This is the default
prepositional phrase.

DECdts Command Dictionary 4–3

, with attribute [relop] value

Limits a directive only to those entities whose
attributes have certain values. If you do not specify
a relop (relational operator), the default is an equal
sign. Other valid relational operators are greater
than (>), less than (<), greater than or equal to (>=),
less than or equal to (<=), and not equal (<>). If you
specify multiple with phrases in a command, the
entity must meet all the conditions you specify before
the command executes. This phrase works only with
commands that can operate on multiple attributes
(such as show commands).

4.2.3 NCL Access Control
NCL access control allows you to manage entities on remote systems or
through various accounts on the local system (node 0). To supply access control
information in a command, use the by prepositional phrase or specify an access
control string in the node id. This section describes these methods.
Use the by prepositional phrase at the end of a command to execute the command
through an account or proxy account other than the one you are currently
using. The account and user must have the required permissions to execute the
command. The following example shows the by phrase format:
by user=username, password=password, account=account, proxy=[true/false]
The following example shows a command that uses access control:
ncl> set node 0 dtss serv req 4, by user=kosta, password=abc4th5zbn
You can also specify access control information as part of a node id you enter
with a command. The combined node-id/access control string contains a node
name, a user/account name, and an account password. In the following example,
systempasswd is the password of the system account on node farnod.
ncl> set node farnod"system systempasswd" dtss servers required 3
For more information about access control in NCL, see the HP DECnet-Plus for
OpenVMS Network Control Language Reference manual.

4.2.4 Wildcards
You can use wildcard characters in the last simple name that you specify in show
commands. Wildcards are especially useful with the show dtss decnet local
servers and show dtss decnet global servers commands for displaying all
known servers or a subset of the known servers. The following table describes the
valid wildcard characters you can use.
Table 4–1 Wildcard Characters
Symbol

Meaning

Matches zero (0) or more characters in the name that you specify in a
simple name

?
...

Matches exactly one character in the name that you specify
Searches any part of the directory hierarchy at or below this level for a
match

See the show command reference pages for examples of wildcard use.

4–4 DECdts Command Dictionary

4.3 Editing the Commands
You can cancel commands, edit command lines, continue a command beyond one
line, or recall commands within NCL.
Canceling a Command
Press Ctrl/C to cancel command processing during command entry or while the
command is being processed; you are returned to the system prompt.
Continuing a Command Line
To continue a long command line onto the next line, type a hyphen at the end of
the first line:
ncl> show node smrt_node dtss decnet local servers * all status, _ncl> with used in last synchronization=true
Recalling a Command
You can recall previously typed commands to avoid retyping them. The recall
buffer holds up to 20 commands entered during the current NCL session. Once a
command is redisplayed, you can reexecute or edit it.
To display the commands stored in the recall buffer, press Ctrl/B or the up arrow
and down arrow keys. Pressing Ctrl/B recalls the previous command. The up and
down arrow keys allow you move up and down through the stack of commands
in the buffer. When the desired command is displayed, press the Return key to
enter it.

4.4 Accessing and Exiting the Management Interface
You can use either of two methods to start the NCL command interface and
access the NCL prompt. The first method follows:
$ run sys$system:ncl
ncl>
You can also access the NCL command interface using a second method:
$ mcr ncl
ncl>
To exit the NCL command interface and return to the system prompt, enter the
exit command as follows:
ncl> exit
Alternatively, you can type Ctrl/Z to exit the interface.

4.5 Commands
This section describes the commands for managing the DTSS module entities.

DECdts Command Dictionary 4–5

advertise dtss

advertise dtss
Modifies the DECdns directory of DECdts global servers and adds the DECdts
server to the global set.

SYNOPSIS
advertise [node node-id] dtss argument

ARGUMENT
server name simple-name
Specifies the name of the server to be added to the DECdns list of global time
servers.

DESCRIPTION
The advertise command, including the server name argument, causes the
DECdts server entity to register the name of the server with DECdns, which adds
the name to the directory of global time servers. To delete a global server name
from the DECdns directory .DTSS_GlobalTimeServers and remove it from the
global set, use the following DECdns command, substituting the full name of the
node for object-name:
dnscp> delete object object-name
See HP DECnet-Plus for OpenVMS DECdns Management for information on how
to access and use the DECdns control program.
Note
This command is valid only for servers.
If your network uses the Local namespace instead of
DECdns, the advertise command fails and the error DNS_
NOCOMMUNICATION is displayed. See the site-specific configuration
file sys$common:[sysmgr]dtss$config_template.dat for information on
configuring global servers using the Local namespace.

EXCEPTIONS
System Error
The command failed because of an operating system error.
Wrong State
The entity is not in the on state.

EXAMPLE
The following example shows how to advertise a server.
ncl> advertise dtss server name yamsca

4–6 DECdts Command Dictionary

change dtss

change dtss
Alters the epoch number and time on the local node.

SYNOPSIS
change [node node-id] dtss epoch integer [, time absolute-time]

ARGUMENTS
epoch integer
Specifies the new epoch number; the new epoch number must be different from
the current epoch number and in the range 0–255. This argument is required.
time absolute-time
Specifies a new clock setting for the new epoch. If the argument is not supplied,
the current clock time is used for the new epoch. This argument is optional.

DESCRIPTION
Changes the epoch and (optionally) sets the time of the DECdts server on which
it is entered. Use this command to isolate a server from the rest of the servers in
the network and to change (set) the time.
Note
This command is valid only for servers.

EXCEPTIONS
Same Epoch
The new epoch must differ from the current epoch.
System Error
The command failed because of an operating system error.
Wrong State
The entity is not in the on state.

EXAMPLES
The following examples show uses of the change command.
1. This example shows how to change the epoch number.
ncl> change dtss epoch 1
2. This example shows how to change the epoch number and time.
ncl> change dtss epoch 1, time 1996-11-30-10:58:00.000-05:00I02.000

DECdts Command Dictionary 4–7

create dtss

create dtss
Creates the DECdts clerk or server process on the specified node.

SYNOPSIS
create [node node-id] dtss argument

ARGUMENT
type type
Specifies the type of DECdts process to be created on the specified node. This
argument is required.

clerk
server

The DECdts process is created as a clerk. The default setting is
clerk.
The DECdts process is created as a server.

DESCRIPTION
This command creates a DECdts server or DECdts clerk process on the specified
system.
Note
You cannot activate a DECdts process by interactively entering the
create command on DECnet-Plus for OpenVMS systems. The entity type
is determined by the NCL startup file that is created during the DECnetPlus software installation (as described in Section 2.1.3). To activate and
create the clerk or server process without running the entire net$startup
process, enter the following command at the system prompt:
$ @sys$startup:net$startup "network" "dtss" "startup"
As an alternate method, you can directly execute the DECdts startup file
sys$startup:dtss$startup.com to create the clerk or server process.

EXCEPTIONS
Already Exists
The command failed because the clerk or server is already created.
System Error
The command failed due to an operating system error.

EXAMPLE
The following example shows how to create a server:
ncl> create node sys4u2 dtss type server

4–8 DECdts Command Dictionary

delete dtss

delete dtss
Deletes the DECdts process.

SYNOPSIS
delete [node node-id] dtss

DESCRIPTION
This command removes the server or clerk process from the specified system.
Note
The delete command will not execute unless you have previously entered
the disable command, which causes the status attribute state to be set to
off.

EXCEPTION
Wrong State
The DTSS entity is not in the off state.

EXAMPLE
The following example shows how to enter the delete command:
ncl> delete node abnrml dtss

RELATED INFORMATION
disable command

DECdts Command Dictionary 4–9

disable dtss

disable dtss
Stops the DECdts process on the specified node.

SYNOPSIS
disable [node node-id] dtss

DESCRIPTION
This command turns off the DECdts process on the specified system. When the
command is executed, the status attribute state is set to off.
Note
The disable command will not execute unless you have previously
entered the enable command, which causes the status attribute state to
be set to on.

EXCEPTIONS
System Error
The command failed due to an operating system error.
Wrong State
The dtss entity is already in the off state.

EXAMPLE
The following example shows how to enter the disable command:
ncl> disable node slsmgr dtss

RELATED INFORMATION
enable command

4–10 DECdts Command Dictionary

enable dtss

enable dtss
Starts the DECdts process on the specified node.

SYNOPSIS
enable [node node-id] dtss [argument]

ARGUMENT
set clock boolean
Specifies whether the clock is abruptly set or gradually adjusted to the computed
time at the end of the first synchronization. This argument is optional.

false
true

The clock is gradually adjusted. This is the default condition.
The clock is abruptly set.

DESCRIPTION
This command activates the DECdts process entity on the specified system. When
the command is executed, the status attribute state is set to on.
Note
The enable command will not execute unless you have previously entered
the create command.

EXCEPTIONS
System Error
The command failed because of an operating system error.
Wrong State
The dtss entity is not in the off state.

EXAMPLES
The following examples show uses of the enable command.
1. This example shows how to enable the entity and adjust the clock gradually
to the computed time following the first synchronization.
ncl> enable node mysyst dtss
2. This example shows how to enable the entity and immediately set the clock to
the computed time following the first synchronization.
ncl> enable dtss set clock true

RELATED INFORMATION
disable command

DECdts Command Dictionary 4–11

set dtss

set dtss
Modifies characteristic attributes for the dtss entity.

SYNOPSIS
set [node node-id] dtss characteristic [,...]

ARGUMENT
characteristic
value
Specifies the name and value of the characteristic to be modified.
Specify one or more of the following for characteristic.

advertisement interval [relative-time]
automatic tdf change [Boolean]
check interval [relative-time]
courier role [role]
error tolerance [relative-time]
global directory [full-name]
lan timeout [relative-time]
maximum inaccuracy [relative-time]
query attempts [integer]
servers required [integer]
synchronization hold down [relative-time]
wan timeout [relative-time]

DESCRIPTION
This section describes each of the values for the characteristic argument.
advertisement interval
Specifies the amount of time between a server’s advertisement broadcasts.
Default: 0-01:30:00.000

Value: 0-00:00:30.000–99-99:99:99.999

automatic tdf change
Specifies whether the entity performs an unattended change to the local
time differential factor, according to the time zone rule selected at the initial
configuration.
Default: true

Value: true/false

check interval
Specifies the amount of time between checks for faulty servers. Applicable only
for servers that have external time-providers.
Default: 0-01:30:00.000

4–12 DECdts Command Dictionary

Value: 0-00:00:30.000–99-99:99:99.999

set dtss

courier role
Specifies a server’s interaction with the set of global servers.
Default: backup courier

backup courier
courier
noncourier

Value: See following description.
The local server may become a courier if it is not using a
time-provider and no couriers are available on the LAN.
The local server attempts to synchronize with at least
one global server.
The local server does not routinely synchronize with the
global set of servers.

error tolerance
Specifies the maximum separation allowed between the local clock and the
computed time before synchronizations become immediate rather than gradual
(monotonic).
Default: 0-00:10:00.000

Value: 0-00:00:00.500–99-99:99:99.999

global directory
Specifies the full name of the DECdns directory that contains the list of DECdts
servers that belong to the global set. The default example uses ns to denote the
default namespace.
Default: ns:.DTSS_
GlobalTimeServers

Value: See previous description.

lan timeout
Specifies the amount of time the node waits for a response to a synchronization
request before sending another request or declaring that a server is unavailable.
The node sends the number of requests determined by the query attempts
characteristic before declaring that a nonresponding server is unavailable.
Default: 0-00:00:02.000

Value: 0-00:00:00.000–0-00:05:00.000

maximum inaccuracy
Specifies the inaccuracy limit for the node. When the node exceeds the maximum
inaccuracy setting, it attempts to synchronize.
Default: 0-00:00:00.200

Value: 0-00:00:00.000–99-99:99:99.999

query attempts
Specifies the number of attempts that a node makes to contact a server before the
node considers the server unavailable.
Default: 3

Value: 1–10

servers required
Specifies the minimum number of servers the node must successfully query for
time values before it can synchronize. If more than the specified number of
servers are available, clerks query up to three servers and servers query all other
local servers.
Default: 3 (servers)
1 (clerks)

Value: 1–32

DECdts Command Dictionary 4–13

set dtss

synchronization hold down
Specifies the interval a node must wait to synchronize. Also specifies
synchronization frequency when a node reaches the value specified by the
maximum inaccuracy characteristic.
Default: 0-00:10:00.000 (clerks)
0-00:05:00.000 (servers)

Value: 0-00:00:30.000–01-00:00:00.000

wan timeout
Specifies the amount of time the node waits for a response to a WAN
synchronization request before declaring that a global server is unavailable.
Default: 0-00:00:15.000

Value: 0-00:00:00.000–0-00:10:00.000

EXAMPLES
The following examples show some uses of the set command.
1. This example shows how to set the advertisement interval.
ncl> set dtss advertisement interval 00-01:20:00.000
2. This example shows how to set the global directory name.
ncl> set dtss global directory co:.mktg.mont.bac
3. This example shows how to set the number of servers required before the
entity can synchronize.
ncl> set dtss servers required 4
4. This example shows how to set the courier role for a server.
ncl> set dtss courier role backup courier

RELATED INFORMATION
show command

4–14 DECdts Command Dictionary

show dtss

show dtss
Displays current information about the dtss entity.

SYNOPSIS
show [node node-id] dtss attribute-specifier [,...]

ARGUMENT
attribute-specifier
Specifies the name of an attribute group or individual attribute to be displayed.

DESCRIPTION
The show command displays the names and values of the attributes or attribute
groups named in attribute-specifier. You can use any combination of attribute
specifiers in any order in a single command; use a comma to separate specifiers.
If you do not supply an attribute specifier, the command displays all
characteristics and their values. The following are valid attribute specifiers:
•

all [characteristics]

•

all characteristics

•

all counters

•

all status

•

attribute-name

As shown in this list, attribute-name is the name of a specific attribute from one
of the listed groups. The following sections list names of attributes, categorized
by group (characteristics, counters, and status).
Characteristics

acting courier role
Specifies whether a backup courier is temporarily functioning as a courier. If the
role is courier, the node is attempting to contact at least one global server at
every synchronization. If the role is noncourier, then the node is not attempting
to synchronize with global servers.

automatic tdf change
Default: true

Value: true/false

Specifies whether the entity performs an unattended change to the local
time differential factor, according to the time zone rule selected at the initial
configuration.

advertisement interval
Default: 0-01:30:00.000

Value: 0-00:00:30.000–99-99:99:99.999

Specifies the amount of time between a server’s advertisement broadcasts.

DECdts Command Dictionary 4–15

show dtss

check interval
Default: 0-01:30:00.00

Value: 0-00:00:30.000–99-99:99:99.999

Specifies the amount of time between checks for faulty servers. Applicable only to
servers that have external time-providers.

clock adjustment rate
Specifies the rate at which the DECdts server or clerk entity adjusts the node’s
clock during a synchronization.

clock resolution
Specifies the amount of time, in nanoseconds, between system clock ticks. The
value is determined by the operating system.

courier role
Default: backup courier

Value: See following description.

Specifies a server’s interaction with the set of global servers.

backup courier
courier
noncourier

The local server may become a courier if none are
available on the LAN.
The local server attempts to synchronize with at least
one global server.
The local server does not routinely synchronize with the
global set of servers.

DNA Version
Specifies the DIGITAL Network Architecture (DNA) version to which the DECdts
software conforms.

DTSS Version
Specifies the DTSS module/DECdts software version installed on the node.

epoch number
Default: 0

Value: 0–255

Specifies the server’s epoch number. The change command modifies this
characteristic.

error tolerance
Default: 0-00:10:00.000

Value: 0-00:00:00.500–99-99:99:99.999

Specifies the maximum separation allowed between the local clock and the
computed time before synchronizations become immediate rather than gradual
(monotonic).

global directory
Default: ns:.DTSS_
GlobalTimeServers

Value: See following description

Specifies the full name of the DECdns directory that contains the list of DECdts
servers that belong to the global set. The default example uses ns to denote the
default namespace.

4–16 DECdts Command Dictionary

show dtss

lan timeout
Default: 0-00:00:02.000

Value: 0-00:00:00.000–0-00:05:00.000

Specifies the amount of time the node waits for a response to a synchronization
request before sending another request or declaring that a server is unavailable.
The node sends the number of requests determined by the query attempts
characteristic before declaring that a nonresponding server is unavailable.

local time differential factor
Specifies the time differential factor (TDF) for the node, which is the difference
between the node’s displayed local time and UTC (Coordinated Universal Time).

maximum clock drift rate
Specifies the worst case drift rate of the node’s clock, in nanoseconds per second,
as determined by the manufacturer’s specifications.

maximum inaccuracy
Default: 0-00:00:00.200

Value: 0-00:00:00.0–99 99:99:99.99

Specifies the inaccuracy limit for the node. When the node exceeds the maximum
inaccuracy setting, it attempts to synchronize.

next tdf change
Specifies the calendar date and time of the next scheduled adjustment of the local
time. The value is determined by the time zone rule selected during operating
system or DECnet configuration. The value of the characteristic auto tdf change
must be true for the change to become effective.

query attempts
Default: 3

Value: 1–10

Specifies the number of attempts that a node makes to contact a server before the
node considers the server unavailable.

servers required
Default: 3 (servers)
1 (clerks)

Value: 1–32

Specifies the minimum number of servers the specified node must successfully
query for time values before it can synchronize.

synchronization hold down
Default: 0-00:10:00.00 (clerks)
0-00:05.00.00 (servers)

Value: 0-00:00:30.0–01 00:00:00.00

Specifies the interval a node must wait to synchronize. Also specifies
synchronization frequency when a node reaches the value specified by the maximum
inaccuracy characteristic.

time provider present
Specifies whether or not the entity used an external time-provider at the last
successful synchronization. This attribute applies to servers only.

time representation version
Specifies the timestamp version (format) used by the installed DECdts software.

DECdts Command Dictionary 4–17

show dtss

type
Specifies whether the node is a DECdts server or clerk. The create command
modifies this characteristic.

wan timeout
Default: 0-00:00:15.000

Value: 0-00:00:00.000–0-00:10:00.000

Specifies the amount of time the node waits for a response to a WAN
synchronization request before declaring that a global server is unavailable.
If you set the value to 0-00:00:00.000, global servers are not queried.
Counters

clock settings
Specifies the number of times the node clock has been set nonmonotonically
(abruptly).

creation time
Specifies the time at which the DECdts entity was created and the counters were
initialized.

different epochs detected
Specifies the number of times the server received time response messages from
servers that had epoch numbers different from its own.

disable directives completed
Specifies the number of times DECdts has been disabled.

enable directives completed
Specifies the number of times DECdts has been enabled.

epoch changes completed
Specifies the number of times the server’s epoch has changed.

global responses sent
Specifies the number of times the node has responded to a synchronization
request from a node outside the LAN.

insufficient resources detected
Specifies the number of times the node has been unable to allocate virtual
memory.

invalid messages detected
Specifies the number of times the local node failed to process a received message
that had an unknown message type or incorrect length.

local responses sent
Specifies the number of times the node has responded to a synchronization
request from another node in the LAN.

local times not intersecting
Specifies the number of times the node’s time interval failed to intersect with the
computed interval of the servers.

no global servers detected
Specifies the number of times the server could not contact any global servers.

4–18 DECdts Command Dictionary

show dtss

protocol mismatches detected
Specifies the number of times the local node failed to process a received message
containing an incompatible protocol version.

server times not intersecting
Specifies the number of times a server has detected faulty servers (other than
itself).

servers not responding
Specifies the number of times the courier server could not contact a specific global
server.

synchronizations completed
Specifies the number of times the node has successfully synchronized.

system errors detected
Specifies the number of times a DECdts operation has detected a system error.

time provider failures detected
Specifies the number of times the external time-provider signaled a failure or the
node was unable to access the time-provider.

time representation mismatches detected
Specifies the number of times the local node failed to process a received message
containing an incompatible timestamp format.

too few servers detected
Specifies the number of times a node failed to synchronize because it could not
contact the required minimum number of servers.

too many servers detected
Specifies the number of times the responses to a synchronization request
overflowed the assigned system buffer.

updates initiated
Specifies the number of times a server has attempted to update its clock.
Status

current time
Specifies the current time on the node.

last synchronization
Specifies the computed time at the last synchronization.

state
Specifies the state of the DECdts software.
Off
On
Synchronizing
Updating

The DECdts process is disabled.
The DECdts process is enabled.
The DECdts process is synchronizing.
The DECdts process is updating the time.

uid
Specifies the entity’s unique identifier, which is generated when the entity is
created.

DECdts Command Dictionary 4–19

show dtss

EXAMPLES
The examples in this section list some uses of the show command.
1. The following command shows how to display the current time:
ncl> show dtss current time
Node 0:. DTSS
AT 1996-02-22-11:56:40.153-05:00I0.110
Status
Current Time

= 1996-02-22-11:56:40.153-05:00I0.110

2. The following command shows how to display all of the entity’s characteristic
attribute settings:
ncl> show dtss all char
Node 0 DTSS
AT 1996-02-05-16:44:17.312-05:00I0.107
Characteristics
Advertisement Interval
Check Interval
Epoch Number
Error Tolerance
Local Time Differential Factor
Maximum Inaccuracy
Servers Required
Query Attempts
LAN Timeout
WAN Timeout
Synchronization Hold Down
Type
Courier Role
Acting Courier Role
Clock Adjustment Rate
Maximum Clock Drift Rate
DNA Version
DTSS Version
Time Representation Version
Service Trace
Communication Trace
Global Directory
Time Provider Present
Automatic TDF Change
Next TDF Change
Clock Resolution

4–20 DECdts Command Dictionary

= +0-01:30:00.000Iinf
= +0-01:30:00.000Iinf
= 0
= +0-00:10:00.000Iinf
= -0-05:00:00.000Iinf
= +0-00:00:00.200Iinf
= 3
= 3
= +0-00:00:00.000Iinf
= +0-00:00:15.000Iinf
= +0-00:05:00.000Iinf
= Server
= Backup Courier
= NonCourier
= 10000000
= 50000
= V1.0.0
= V2.0.0
= V1.0.0
= True
= True
= LOCAL:.DTSS_GlobalTimeServers
= False
= True
= 1996-04-05-03:00:00.000-04:00I0.000
= 3970000

show dtss

3. The following command shows how to display the entity’s status:
ncl> show dtss all status
Node 0:. DTSS
AT 1996-02-21-16:35:15.077-05:00I0.099
Status
Current Time
Uid
Last Synchronization
State

= 1996-02-21-16:35:15.073-05:00I0.099
= 5F000004-D0D0-11C9-9006-08002B0DC030
= 1996-02-21-16:34:55.066-05:00I0.094
= On

RELATED INFORMATION
set command

DECdts Command Dictionary 4–21

show dtss decnet global servers

show dtss decnet global servers
Displays current information about the dtss DECnet global servers entity.

FORMAT
show [node node-id] dtss decnet global servers fullname-attribute-specifier [,...]

ARGUMENT
attribute-specifier
Specifies the name of an attribute group or individual attribute to be displayed.

all [characteristics]

•

all characteristics

•

all identifiers

•

all status

•

attribute-name

As shown in this list, attribute-name is the name of a specific attribute from one
of the listed groups. The following sections list names of attributes, categorized
by group.
Note that when you enter the show dtss decnet global servers command at
a DTSS global server, the list does not include the server itself. To verify what
DECdts role the current node is running, enter the following command:
ncl> show dtss type
Characteristics

transport
Specifies the transport protocol used to communicate with the global server.
Identifier

name
Specifies the full name of the global server, as registered in the namespace.
Status

last observed skew
Specifies the skew between the node’s clock and the time received from the
specified global server after the most recent synchronization.

last observed time
Specifies the time the node last received from the specified global server.

4–22 DECdts Command Dictionary

show dtss decnet global servers

last time polled
Specifies the time the node last solicited a time value from the specified global
server.

used in last synchronization
Specifies whether or not a time value from the specified global server was used in
the node’s last successful clock synchronization.

EXAMPLES
The examples in this section list some uses of the show command.
1. The following command shows how to display the transport used by a global
server known to the local node:
ncl> show dtss decnet global servers .DTSS_GlobalTimeServers.eng transport
Node 0:. DTSS Decnet Global Servers ABC:.DTSS_GlobalTimeServers.eng
AT 1996-02-21-17:26:09.073-05:00I0.096
Characteristics
Transport

= DECnet

2. The following command shows how to display all attributes of the global
servers known to the DECdts clerk or server on the local system:
ncl> show dtss decnet global servers * all
Node 0:. DTSS Decnet Global Servers ABC:.DTSS_GlobalTimeServers.sales
AT 1996-02-21-17:34:27.358-05:00I0.092
Identifiers
Name

= ABC:.DTSS_GlobalTimeServers.sales

Status
Last Time Polled
= 1996-02-21-16:54:45.114-05:00I0.101
Last Observed Time
= 1996-02-21-16:54:45.105-05:00I0.107
Last Observed Skew
= 0-00:00:00.009I0.000
Used In Last Synchronization = True
Characteristics
Transport

= DECnet

Node 0:. DTSS Decnet Global Servers ABC:.DTSS_GlobalTimeServers.small
AT 1996-02-21-17:34:27.365-05:00I0.092
Identifiers
Name

= ABC:.DTSS_GlobalTimeServers.small

Status
Last Time Polled
= 1996-02-21-16:54:45.114-05:00I0.101
Last Observed Time
= 1996-02-21-16:54:45.105-05:00I0.105
Last Observed Skew
= 0-00:00:00.005I0.000
Used In Last Synchronization = True
Characteristics
Transport

= DECnet

DECdts Command Dictionary 4–23

show dtss decnet global servers

RELATED INFORMATION
show dtss decnet local servers command

4–24 DECdts Command Dictionary

show dtss decnet local servers

show dtss decnet local servers
Displays current information about the dtss DECnet local servers entity.

FORMAT
show [node node-id] dtss decnet local servers fullname-attribute-specifier [,...]

ARGUMENT
attribute-specifier
Specifies the name of an attribute group or individual attribute to be displayed.

all [characteristics]

•

all characteristics

•

all identifiers

•

all status

•

attribute-name

As shown in this list, attribute-name is the name of a specific attribute from one
of the listed groups. The following sections list names of attributes, categorized
by group.
Note that when you enter the show dtss decnet local servers command at
a DTSS local server, the list does not include the server itself. To verify what
DECdts role the current node is running, enter the following command:
ncl> show dtss type
Characteristics

transport
Specifies the transport protocol used to communicate with the local server.
Identifier

address
Specifies the DECnet address of the server.
Status

last observed skew
Specifies the skew between the node’s clock and the time received from the
specified local server after the most recent synchronization.

last observed time
Specifies the time the node last received from the specified known server.

DECdts Command Dictionary 4–25

show dtss decnet local servers

last time polled
Specifies the time that the node last solicited a time value from the specified
known server.

used in last synchronization
Specifies whether or not a time value from the specified known server was used
in the node’s last successful clock synchronization.

EXAMPLES
The examples in this section describe some uses of the show command.
1. The following command shows how to display the transport for a local server
known to the local node:
ncl> show dtss decnet local servers 00-00-04-00-01-fc transport
Node 0:. DTSS Decnet Local Servers 00-00-04-00-01-fc (63.1)
AT 1996-02-21-17:19:50.645-05:00I0.097
Characteristics
Transport

= IEEE802.2

2. The following command shows how to display all the local servers known to
the clerk or server system, and lists all their attributes:
ncl> show dtss decnet local servers * all
Node 0:. DTSS Decnet Local Servers 10-00-04-00-02-fc (63.2)
AT 1996-02-21-16:56:05.151-05:00I0.098
Identifiers
ADDRESS

= 10-00-04-00-02-fc (63.2)

Status
Last Time Polled
= 1996-02-21-16:54:45.114-05:00I0.101
Last Observed Time
= 1996-02-21-16:54:45.105-05:00I0.105
Last Observed Skew
= 0-00:00:00.009I0.000
Used In Last Synchronization = True
Characteristics
Transport

= IEEE802.2

Node 0:. DTSS Decnet Local Servers 11-00-04-00-03-fc (63.3)
AT 1996-02-21-16:56:05.155-05:00I0.098
Identifiers
ADDRESS

= 11-00-04-00-03-fc (63.3)

Status
Last Time Polled
= 1996-02-21-16:54:45.114-05:00I0.101
Last Observed Time
= 1996-02-21-16:54:45.109-05:00I0.107
Last Observed Skew
= 0-00:00:00.005I0.000
Used In Last Synchronization = True
Characteristics
Transport

4–26 DECdts Command Dictionary

= IEEE802.2

show dtss decnet local servers

RELATED INFORMATION
show dtss decnet global servers command

DECdts Command Dictionary 4–27

synchronize dtss

synchronize dtss
Causes the DECdts server or clerk to initiate a synchronization.

SYNOPSIS
synchronize [node node-id] dtss [argument]

ARGUMENT
set clock Boolean
Specifies whether the clock is immediately set or gradually adjusted to the
computed time. This argument is optional.

false
true

The clock is gradually adjusted. This is the default
condition.
The clock is immediately set.

DESCRIPTION
This command causes the DECdts process to initiate a synchronization on the
specified system. If the synchronization is successfully completed, the system
clock is adjusted or set to the new computed time. This command overrides the
functions of the synchronization hold down characteristic.
Note
The synchronize command does not execute unless the entity is in the on
state.

EXCEPTIONS
System Error
The command failed due to an operating system error.
Wrong State
The dtss entity is not in the on state.

EXAMPLES
The following examples show some uses of the synchronize command.
1. This example shows how to initiate a synchronization for a remote node,
followed by a gradual adjustment (update) to the clock on that node.
ncl> synchronize node reback dtss
2. This example shows how to initiate a synchronization for the local system,
followed by an immediate reset of the clock.
ncl> synchronize dtss set clock true

4–28 DECdts Command Dictionary

update dtss

update dtss
Gradually adjusts the clock on the specified server node to a new time, beginning
at the time specified by the argument.

SYNOPSIS
update [node node-id] dtss argument

ARGUMENT
time absolute-time
Specifies the absolute time that begins clock adjustment. This argument is
required.

DESCRIPTION
Gradually adjusts the system clock to a new time, beginning at the time specified
in the argument. The difference between the current clock value and the absolute
time specified in the argument is used to adjust the clock. The update command
is valid only for servers.

EXCEPTIONS
Invalid Time
The specified time and inaccuracy must be within the interval formed by the
current time and inaccuracy.
System Error
The command failed because of an operating system error.
Wrong State
The dtss entity is not in the on state.

Example
The following example shows how to update the time for a server; the clock is
gradually adjusted to a new time, beginning at the specified time.
ncl> update dtss time 1996-12-30-11:24:00.000-05:00I02.000

DECdts Command Dictionary 4–29

A
Event Messages
This section alphabetically lists and describes all events for the dtss entity.
clock set
This event is generated each time a DECdts process sets its local clock.
Arguments:
new time

Specifies the corrected clock setting.

old time

Specifies the faulty time before the clock was set.

different epoch detected
This event is generated each time the local node receives a time value that has
an epoch number different from its own. This event normally occurs after a
node’s epoch has been changed.
Arguments:
local epoch
number

Specifies the local node’s epoch number.

server [id]

Specifies the known servers and their epoch numbers.

disable completed
This event is generated each time a disable command is executed to stop
DECdts.
enable completed
This event is generated each time an enable command is executed to start
DECdts.
epoch change completed
This event is generated each time the epoch is set for the local node.
Arguments:
new epoch

Specifies the epoch number after the epoch was declared.

old epoch

Specifies the epoch number before the epoch was declared.

insufficient resources detected
This event is generated each time the node’s virtual memory is full. The event is
displayed on all nodes and is usually followed by a system abort.
invalid message detected
This event is generated each time the local node receives a corrupted or incorrect
message. Invalid messages are normally retransmitted, but the hexadecimal
contents of the invalid message are supplied for troubleshooting.

Event Messages A–1

Arguments:
message

Specifies the hexadecimal contents of the invalid message.

node [id]

Specifies the full name of the node that generated the invalid
message.

local time does not intersect
This event is generated each time the time interval of the local node does not
intersect with the values received from other servers. If this event is generated
frequently, you can decrease the setting for the characteristic synchronization
hold down or increase the settings for the characteristics error tolerance or
maximum inaccuracy.
Arguments:
clock set

Specifies whether or not the clock was automatically set to correct
the time on the local system. If false, the clock was not set to
correct the time on the local system.

computed time

Specifies the intersection of the majority of server times.

local time

Specifies the local time interval that does not intersect with the
computed time.

no global server
This event is generated at a courier server when it cannot locate a global server.
protocol version mismatch detected
This event is generated each time the DECdts protocol version of a received
message does not match the protocol in force at the local node.
Argument:
node [id]

Specifies the full name of the node that generated the message with
the incompatible protocol version.

server not responding
This event is generated at a courier server when it attempts to synchronize
with the listed global server, but the server does not respond. The event may be
caused by a low characteristic setting for wan timeout.
Argument:
node [id]

Specifies the node name of the server not responding.

server time does not intersect
This event is generated each time the local node receives a faulty time value
from a server. If continuing faulty servers detected events are generated
for the same node, examine the node’s settings for these characteristics: error
tolerance, synchronization hold down, and maximum inaccuracy.
Argument:
server [id]

Specifies the list of servers used in the synchronization.

synchronization completed
This event is generated each time a synchronization is completed for the local
node.

A–2 Event Messages

Arguments:
clock adjustment

Specifies the relative time the local clock needs to be adjusted to
match the computed time.

computed time

Specifies the time computed from the intersection of all server time
intervals.

system error detected
This event is generated each time the operating system has a system error
relevant to DECdts operation. See the system documentation for an explanation
of the report text.
Argument:
error text

Specifies the system error report.

time provider failure detected
This event is generated each time an external time-provider returns an invalid
time or does not respond.
time representation version mismatch detected
This event is generated each time the local node receives a response indicating
that it is using an invalid time representation version.
Argument:
node [id]

Specifies the name of the node that is running the incompatible
time representation version.

too few servers detected
This event is generated each time the number of servers specified by the servers
required characteristic are not available for synchronization with the local node.
Arguments:
number detected

Specifies the number of servers that responded to the
synchronization request.

number required

Specifies the number of servers required for synchronization.

too many servers detected
This event is generated each time server responses overflow the synchronization
list buffer of the local node. The difference between the maximum delivered
and number accepted arguments is the number of responses that overflowed
the buffer.
Arguments:
number accepted

Specifies the number of server responses that were accepted by the
node.

number detected

Specifies the number of servers responding to a solicitation.

update initiated
This event confirms an attempt to change the system time resulting from the
update command.

Event Messages A–3

Arguments:
current time

Specifies the current system time.

update time

Specifies the new, updated system time.

A–4 Event Messages

B
Time-Providers and Time Services
This appendix explains the criteria to use when selecting a time-provider, and
describes time dissemination services, time-providers (hardware and/or software),
and their interaction with DECdts. The appendix also contains a world time zone
map.

B.1 Criteria for Selecting a Time Source
Before you select a time source for your network, ask the following questions:
•

How accurate is the time provided?
Accuracy is affected by the time source itself, as well as the transmission
media. As long as the inaccuracy is known, DECdts can compensate for it.

•

How reliable is the time source?
The time source should always be available. If the time source is not
available, the server connected to the time-provider uses times from other
servers and compensates for any time difference when the source again
becomes available.

•

What is the extent of coverage?
The time source must be available in the geographical area where the
time-provider server is located.

•

What is the level of known inaccuracy?
If this is known, DECdts can compensate for it. Most sources have known
inaccuracy levels.

•

What is the cost?

•

Does the source conform to the operating environment?
The available power supply and physical conditions must be compatible with
the source; consult the supplier for specifications.

Table B–1 summarizes the selection criteria for each type of time source.

Time-Providers and Time Services B–1

Table B–1 Time-Provider Selection Criteria
Selection Criteria
Type

Coverage

Inaccuracy

Regional

10 ms

MSF

Europe

10 ms

WWV

N. America

100 ms

WWVB

N. America
Europe

10 ms

WWVH

Eastern &
Central N.
Pacific

100 ms

GOES

W. Hemisphere

1 ms corrected

GPS

Worldwide

< 100 ns

TRANSIT

Worldwide

1 ms

Telephone
NIST
Radio

Satellite

B.2 Sources of Coordinated Universal Time
There are several sources of UTC time including telephone, radio, and satellite,
as described in the following sections.

B.2.1 Telephone Services
Telephone time-provider services require the time-provider software to dial a
centralized UTC time source through a modem. Modem speeds and line delays
can affect the accuracy of the time returned.
Telephone time-provider services are usually provided by standards agencies. For
example, in the United States this service is offered by the National Institute of
Standards and Technology (NIST) with their Automated Computer Time Service
(ACTS), and by the U.S. Naval Observatory with their Automated Data Service
(ADS). There is often a per-call fee for the service in addition to the cost of the
modem software.
Sample time-provider programs you can use with NIST’s ACTS are supplied with
the DECdts kit in the following file:
sys$common:[syshlp.examples.dtss]dtss$provider_acts.c
Comments in the programs explain their use.
For telephone time-provider services in other countries, contact the applicable
standards organization listed in Table B–2.

B–2 Time-Providers and Time Services

B.2.2 Radio Broadcasts
Commercial radio receivers that monitor time and frequency broadcasts can
return time values back through the time-provider interface (TPI) to a DECdts
server. Standards organizations usually operate radio stations that broadcast
time and frequency signals. In the United States, NIST operates the following
time and frequency stations:
•

WWV
Transmits at 2.5, 5, 10, 15 MHz to North America and South America.

•

WWVB
Transmits at 60 kHz primarily to the United States, providing high-quality
frequency information because atmospheric propagation effects are relatively
minor.

•

WWVH
Transmits at 2.5, 5, 10, 15 MHz to Alaska, Hawaii, Australia, New Zealand,
Japan, and Southeast Asia.

In addition to the stations listed above, more than 30 radio stations worldwide
provide UTC time. Use the partial list in Table B–2 and consult the national
standards organization in your country for further information.
Table B–2 UTC Radio Stations and Managing Authorities
Call Letters

Authority

ATA

National Physical Laboratory
Dr. K.S. Krishnan Rd.
New Delhi, - 110012, India

BPM

Shaanxi Astronomical Observatory
Chinese Academy of Sciences
P.O. Box 18 - Lintong
Shaanxi, China

BSF

Telecommunication Laboratories
Directorate General of Telecommunications
Ministry of Communications
P.O. Box 71 - Chung-Li
32099 Taiwan, R.O.C.

CHU

National Research Council
Institute for National Measurement Standards Time Standards
Ottawa, Ontario, Canada K1A OR6

DCF77

Physikalisch-Technische
Bundesanstalt, Lab. Zeiteinheit
Bundesallee 100
W - 3300 Braunschweig
Federal Republic of Germany

EBC

Real Instituto y Observatorio
de la Armada - San Fernando
Cadiz, Spain

HBG

Service horaire HBG
Observatoire Cantonal
CH - 2000 Neuchatel, Switzerland
(continued on next page)

Time-Providers and Time Services B–3

Table B–2 (Cont.) UTC Radio Stations and Managing Authorities
Call Letters

Authority

HLA

Time and Frequency Laboratory
Korea Standards Research Institute
P.O. Box 3, Taedok Science Town
Taejon 305-606, Republic of Korea

IBF

Istituto Elettrotecnico Nazionale
Galileo Ferraris
Strada delle Cacce, 91
10135 - Torino, Italy

JJY
JG2AS

Standards and Measurements Div.
Communications Research Laboratory
2-1, Nukui-kitamachi 4-chome
Koganei-shi, Tokyo
184 Japan

LOL

Director, Observatorio Naval
Av. Espana 2099
1107 - Buenos Aires, Republica Argentina

MSF

National Physical Laboratory
Division of Electrical Science
Teddington, Middlesex TW11 OLW
United Kingdom

PPE
PPR

Departemento Servico da hora
Observatorio Nacional (CNPq)
Rua General Bruce, 586
20921 Rio de Janeiro - RJ, Brazil

TDF

Centre National d’Etudes des
Telecommunications - PAB - STC
Etalons de frequence et de temps
196 Ave. Henri Ravera
92220 - Bagneux, France

WWV
WWVB
WWVH

Time and Frequency Division
National Institute of Standards and Technology
325 Broadway
Boulder, Colorado 80303, U.S.A

YVTO

Direccion de Hidrografia y Navegacion
Observatorio Cagigal
Apartado Postal No. 6745
Caracas, Venezuela

A sample time-provider program
(sys$common:[syshlp.examples.dtss]dtss$provider.c) you can use with
UTC radio receivers is supplied with the DECdts kit. Comments in the program
explain its use. For a list of supported radio receivers, see Table B–3. Neither
the listing nor the availability of the sample time-provider programs imply any
endorsement of the receivers by HP.

B–4 Time-Providers and Time Services

Table B–3 Radio Receiver Manufacturers
Model

Manufacturer

GC-100

Heathkit
Heath Company
Benton Harbor, MI 49022
U.S.A.
Tel. 616-982-3200

6020

Hopf Elektronik, Gmbh
Postfach 1847
D-5880 Luedenscheid
Federal Republic of Germany
Tel. 49-(0)2351-45038

OEM-10

PSTI (See Traconex)

Netclock/2

Spectracom Corp.
101 Despatch Drive
Rochester, NY 14445
U.S.A.
Tel. 716-381-4827

1020

Traconex Corp.
3510 Bassett St.
Santa Clara, CA 95054
U.S.A.
Tel. 408-727-0260

B.2.3 Network Time Protocol
Nodes that have Internet access can use the Network Time Protocol (NTP) as a
source of UTC time for DECdts. See Appendix C for an explanation of how to use
NTP as a time-provider.

B.2.4 Satellite
Satellites have worldwide availability; they can provide relatively precise times if
their delays are known and compensated for. See the following list for satellite
sources of UTC.
•

GOES
Geostationary Operational Environmental Satellite; a satellite network
operated by the U.S. National Oceanic and Atmospheric Administration
(NOAA). Coverage is limited to the Western Hemisphere.

•

GPS
Global Positioning System; a satellite system operated by the U.S.
Department of Defense. GPS is available worldwide.

•

TRANSIT
U.S. Navy satellite system; available worldwide.

B.3 World Time Zone Map
Figure B–1 shows a map of the world time zones, including the following:
•

UTC (GMT) reference zone

•

Odd- and even-numbered zones

Time-Providers and Time Services B–5

•

Half-hour zones

•

Countries and areas that have not adopted the zone system or in which time
differs less than 1 hour from the neighboring zone

Figure B–1 World Time Zone Map
90°

105°

120°

135°

150°

165°

180°

165°

150°

135°

120°

105°

90°

75°

60°

45°

30°

15°

0°

15°

30°

45°

60°

75°

90°

ARCTIC OCEAN

ARCTIC OCEAN
80°

80°

−3

ASIA
60°
NORTH AMERICA

ASIA
EUROPE

60°
−3h 30m

NORTH PACIFIC OCEAN

40°

+6h 30m

40°

NORTH ATLANTIC OCEAN

−1 DAY
+1 DAY

−4

20°
AFRICA

−3h 45m
−3h 30m

+7h 30m

−44m

INDIAN OCEAN

20°

0°

+5h 30m

SOUTH AMERICA

+6h 30m

0°

20°
AUSTRALIA

SOUTH PACIFIC OCEAN

+9h 30m
−3

40°

20°

SOUTH ATLANTIC OCEAN

40°
F

+10

+11

+12−

−11

−10

−9

−8

−7

−6

−5
−5

−4

−3

−2

−1

105°

120°

135°

150°

165°

180°

165°

150°

135°

120°

105°

90°

75°

60°

45°

30°

15°

0°

15°

30°

75°
45°

60°

75°

MIDNIGHT

NOON

60°

Even numbered zones

Odd numbered zones

Half hour zone

Countries and areas which have not adopted
zone system, or where time differs other than
half hour from neighboring zones.
ZK−2455A−GE

B–6 Time-Providers and Time Services

C
Interoperation with NTP
This chapter explains how to implement both DECdts and NTP in the same
DECnet-Plus network.
NTP is an Internet-recommended standard for synchronizing the time on Internet
nodes. The NTP synchronization subnetwork is represented by a tree-structured
graph with nodes representing time servers and edges representing the
transmission paths between them. The root nodes of the tree are designated
primary servers, which synchronize to a radio broadcast or calibrated atomic
clock. Remaining nodes are designated secondary servers, which synchronize to
other servers (primary and secondary).
The number of subnetwork hops between a particular server and a primary
server determines the stratum of that server (the smaller the number of hops,
the lower the stratum). A lower stratum server always has a higher accuracy
than a higher stratum server. All servers have identical functionality and can
operate simultaneously as clients of the next lower stratum and servers for the
next higher one.
Servers, both primary and secondary, typically run NTP with several other
servers at the same or lower strata. A selection algorithm attempts to select
the most accurate and reliable server or set of servers from which to actually
synchronize the local clock.
NTP and DECdts can both be used in large computer networks that have
embedded local networks (connected by routers, gateways, and bridges) and use
both broadcast and point-to-point transmission media. DECdts and NTP can run
simultaneously on the same LAN. The following sections describe giving time to
and getting time from local and remote NTP time sources, and preventing loops.

C.1 Getting the Time from Remote NTP Time Sources
The DECdts kit contains four NTP time-provider files (in the sys$examples:
directory) that allow DECdts to interoperate with NTP:

dtss$provider_ntp.c
dtss$provider_ntp.exe
run_ntp_tp.com
start_detached_ntp_tp.com

DECdts NTP Provider Program
DECdts NTP Provider Image
Procedure to run DTSS$PROVIDER_NTP
Procedure to run as a detached process

The dtss$provider_ntp program takes the time from a NTP server as it would
from a radio receiver. To use either program, you must specify the name of the
NTP server and the inaccuracy.
Run the DECdts server with the dtss$provider_ntp time-provider on a node with
access to a NTP server. Specify the inaccuracy in a manner that is consistent
with local NTP experience.

Interoperation with NTP C–1

The following advisories should be observed:
•

Advisory: If links to remote sources are distant, you may want one of the
subnetwork nodes to run NTP locally.

•

Advisory: The NTP time-provider will not accept time from a NTP node at
stratum 8 or higher.

•

Advisory: The NTP node should be as close to stratum 1 as possible.

Figure C–1 and Figure C–2 both show a DECdts server getting the time from a
remote NTP time source (a stratum 3 server). In the first scenario, however, all
of the recommendations made in Section C.1 are followed; in the second scenario,
one of the recommendations (running NTP locally on one of the subnetwork nodes
if the link to a remote source is distant) is ignored.
Figure C–1 Getting the Time from a Remote NTP Time Source (Scenario 1)

stratum 3

remote
NTP server

stratum 4

local
NTP server

DECdts
server
dtss$ntp_provider.c

DECdts
server

DECdts
client

ZK−2959A−GE

C–2 Interoperation with NTP

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

stratum 3

remote
NTP node

DECdts
server
dtss$ntp_provider.c

DECdts
server

DECdts
client

ZK−2960A−GE

C.2 Giving the Time to NTP Nodes
Any DECdts server or clerk that also runs the NTP software can be configured
as a NTP server. The tcpip$ntp.conf configuration file controls the NTP
configuration. See the section entitled ‘‘Using NTP with Another Time Service’’
in the HP TCP/IP Services for OpenVMS Management manual for information
about how to configure the NTP software as a server that gets its time from
DECdts.
In this configuration, NTP never sets the clock. NTP can, however, give the time
to other NTP clients. Note that loops between DECdts and NTP should not be
allowed to form; if NTP gives the time to DECdts, then DECdts gives the time
back to the same set of NTP servers, unexpected results can occur.
The NTP configuration file is set up to ensure that a NTP server which obtains
the time from DECdts is a stratum 8 node. In addition, the dtss$ntp_provider
is prohibited from accepting time from a node at stratum 8 or higher.
A DECdts (server) node can give time to a NTP node if the following rules and
advisories are observed:
•

Rule: The NTP server must be at stratum 8.

•

Advisory: Multiple nodes in the set can be running the NTP software
configured as an NTP server.

•

Advisory: If any DECdts-managed system has a local time source, that
system should be used as an NTP server.

Interoperation with NTP C–3

•

Advisory: Although this operation can occur on either a DECdts server or a
DECdts client node, a DECdts server is preferred.

Figure C–3 shows two DECdts server nodes running NTP servers providing time
to a NTP subnetwork. The tcpip$ntp.conf file defines these servers at stratum
8.
Figure C–3 Giving the Time to NTP

stratum 8

stratum 9

DECdts
server
NTP
server

NTP
server

NTP
client

DECdts
client

stratum 10
ZK−2961A−GE

C.3 Preventing Loops
Regardless of the circumstances, you must never allow loops, such as the
following, to form:
NTP

DECdts

NTP

Figure C–4 shows a configuration that HP does not recommend. This
configuration works only as long as the remote NTP stratum 2 node does
not fail.

C–4 Interoperation with NTP

Figure C–4 Configuration Before Stratum 2 Node Fails

stratum 2

remote
NTP server

DECdts
server

stratum 8

stratum 3

DECdts
server
NTP
server

NTP server

dtss$ntp_provider.c

ZK−2962A−GE

If the remote NTP stratum 2 node goes down, the stratum 3 node starts accepting
time from the stratum 8 node. Once this occurs, the stratum 3 node drops to
stratum 9, as shown in Figure C–5.

Interoperation with NTP C–5

Figure C–5 Configuration After Stratum 2 Node Fails

stratum 8

stratum 9

DECdts
server
NTP
server

NTP server

2
DECdts
server

dtss$ntp_provider.c

ZK−2963A−GE

This scenario shows the creation of a loop:
1
2

From the node labeled stratum 8, proceed to the NTP node labeled stratum 9.
From the NTP node labeled stratum 9, continue to the node running

dtss$ntp_provider.c.
3

The DECdts node running the time-provider then feeds the time back to the
NTP daemon in the node labeled stratum 8, creating a loop.

If this occurs, time in the NTP and DECdts subnetwork can arbitrarily drift
from UTC.

C–6 Interoperation with NTP

Glossary
The following terms are used in programming with DECdts.
absolute time
A point on a time scale. For DECdts, absolute times reference the UTC standard.
adjustment
The DECdts process of changing the system clock time by modifying the
incremental value that is added to the clock’s software register for a specified
duration.
advertisement
The process by which a server makes its address and attributes known to other
servers and clerks in a local area network.
binary timestamps
Opaque 128-bit (16 octet) binary sequences that represent time values.
clerk
A DECdts process that synchronizes the clock for its client system by requesting
time values from servers, computing a new time from the values, and supplying
the computed time to client applications, such as the operating system.
clock
The combined hardware interrupt timer and software register that maintain the
system time. The hardware timer sends interrupts to the operating system; at
each interrupt, the operating system adds an increment to a software register
that contains the time value.
computed time
The result of the synchronization process used to adjust the system clock time;
the time interval that the clerk or server process computes according to the
intersections of the server time values it receives.
Coordinated Universal Time (UTC)
An international time standard maintained by the International Time Bureau.
courier
A local server that requests a time value from a randomly selected global server
each time it synchronizes.
DECdts entity
DECdts server or clerk software on a system.

Glossary–1

drift
A clock’s constantly increasing error rate.
entity
A specific software implementation on a system.
entity type
The subgrouping of an entity that determines its relationship to other DECdts
components: clerk or server.
epoch number
An identifier that a server appends to the time values it sends to other servers.
Servers only use time values from other servers with whom they share epoch
numbers.
error
The difference between a system’s clock value and the computed time.
error tolerance
The amount of system clock error to which the DECdts entity responds by
abruptly setting the system clock to the computed time, rather than gradually
adjusting the clock.
global server
A DECdts server that frequently provides its clock value to courier servers on
other LANs, or infrequently provides its clock value to systems that have failed
to obtain the specified number of servers locally.
global set
All of the global servers in a network.
global server directory
The name service directory where DECdts servers are stored.
inaccuracy
The bounded uncertainty of a clock value as compared to a standard reference.
interval
The combination of a clock’s value and the inaccuracy associated with it. The
range of values contained in the clock value minus its inaccuracy and the clock
value plus its inaccuracy.
leap seconds
Infrequent adjustment to UTC to account for the irregularity of the earth’s
rotation.
local set
All of the servers in a particular local area network (LAN).
local server
A server that synchronizes with its peers and provides its clock value to other
servers and clerks on the same LAN.

Glossary–2

relative time
A discrete time interval that is usually added to or subtracted from an absolute
time.
server
A DECdts entity that synchronizes with its peers and provides its clock value to
clerks and their client applications.
skew
The time difference between two clocks or clock values.
synchronization
The process by which a DECdts entity requests clock values from other systems,
computes a new time from the values, and adjusts its system clock to the new
time.
synchronization list
The list of servers that a DECdts entity has discovered; the entity sends requests
for clock values to the servers on the list.
system time
The time value the operating system maintains according to its reading of the
system’s hardware clock.
tick
The clock timer interrupt that causes the operating system to increment the
system time.
time differential factor (TDF)
The difference between UTC and the time in a particular time zone.
time-provider
A hardware device that monitors UTC time and forwards it to a DECdts server.
TP server
A DECdts server system connected to a time-provider.
TDF
See time differential factor.
UTC
See Coordinated Universal Time.

Glossary–3

Index
A
Absolute time, 1–10, 2–2
representation of, 1–10, 2–2
Access control, 4–4
acting courier role characteristic, 4–15
Address
multicast, 1–14
Adjustment rate, 1–8
advertisement interval characteristic, 2–18, 4–12,
4–15
Attribute groups
defined, 4–3
listed, 4–3
Attributes, 4–3
automatic tdf change, 4–15
automatic tdf change characteristic, 2–21, 4–12

B
backup courier role characteristic, 4–15

C
check interval characteristic, 2–18, 4–12, 4–15
Clerks, 1–12
changing server to, 2–8
Clock
See system clock
clock adjustment rate characteristic, 4–15
Clock Error, 1–5
clock resolution characteristic, 4–15
Clock set event, A–1
clock settings counter, 4–18
Commands, 2–1
canceling, 4–5
continuing, 4–5
DECdts, 4–5
DTSS module, 4–5
dtss decnet global servers entity, 4–5
dtss decnet local servers entity, 4–5
dtss entity, 4–5
editing, 4–5
format, 4–2
management, 2–1
recalling, 4–5
specifying access control in, 4–4

Commands (cont’d)
specifying attributes in, 4–3
specifying prepositional phrases in, 4–3
specifying wildcards in, 4–4
syntax, 2–1, 4–2
Communications delay, 1–5
Computed time, 1–6
finding, 1–1, 1–6
Control program, 2–1
Coordinated Universal Time
See UTC
Correctness, 1–2
courier role characteristic, 2–3, 2–8, 4–13, 4–15
Couriers, 1–15, 2–8
backup, 1–15
creation time counter, 4–18
current time status, 4–19

D
DECdns
objects, 1–16
use by DECdts, 1–16
DECdts, 1–1
applications support, 1–2
basic concepts, 1–4
operation, 1–13
DECdts/NTP Interoperation in DECnet-Plus
Networks, C–1
different epoch detected event, A–1
different epochs detected counter, 4–18
disable completed event, A–1
disable directives completed counter, 4–18
DNA version characteristic, 4–15
Drift, 1–5
dtss decnet global servers entity, 2–3
attribute specifiers, listed
for show command, 4–22
characteristic, listed
for show command, 4–22
identifier, listed
for show command, 4–22
last observed skew status, 4–22
last observed time status, 4–22
last time polled status, 4–22
name identifier, 4–22
show command, 4–22

Index–1

dtss decnet global servers entity (cont’d)
status, listed
for show command, 4–22
transport characteristic, 4–22
used in last synchronization status, 4–22
dtss decnet local servers entity, 2–3
address identifier, 4–25
attribute specifiers, listed
for show command, 4–25
characteristics, listed
for show command, 4–25
identifier, listed
for show command, 4–25
last observed skew status, 4–25
last observed time status, 4–25
last time polled status, 4–25
show command, 4–25
status, listed
for show command, 4–25
transport characteristic, 4–25
used in last synchronization status, 4–25
DTSS entities, 4–1
dtss entity, 2–3
advertise command, 2–5, 4–6
attribute specifiers
show command, 4–15
change command, 2–20, 4–7
characteristics
settable, 2–11
show command, 4–15
counters, listed
for show command, 4–18
create command, 2–3, 4–8
critical commands and characteristics, 2–11
delete command, 4–9
disable command, 4–10
enable command, 2–3, 4–11
set command, 4–12
show command, 4–15
status, listed
for show command, 4–19
synchronize command, 2–21, 4–28
update command, 2–19, 4–29
DTSS module
commands
summary, 2–9
commands, listed, 4–1
entities, listed, 4–1
entity hierarchy (fig), 4–1

E
enable completed event, A–1
enable directives completed counter, 4–18
entity, 1–1
Epoch, 1–14, 2–18

Index–2

epoch change completed event, A–1
epoch changes completed counter, 4–18
Epoch number, 1–14, 2–18
epoch number characteristic, 4–15
error tolerance characteristic, 2–15, 4–13, 4–15
Event messages, A–1
Events, A–1
Exit command, 2–3

F
Faulty clocks
detecting, 1–7

G
Geostationary Operational Environmental
Satellite, B–5
global directory characteristic, 4–13, 4–15, 4–16
Global Positioning Satellite, B–5
global responses sent counter, 4–18
GOES, B–5
GPS, B–5

H
HP DECnet-Plus Distributed Name Service
See DECdns
HP DECnet-Plus Distributed Time Service, 1–1

I
Inaccuracy, 1–4, 1–5
insufficient resources detected counter, 4–18
insufficient resources detected event, A–1
Internet Network Time Protocol
See NTP
Interprocess communication, 1–12
Interval, 1–1, 1–5
nonintersecting, 1–7
invalid message detected event, A–1
invalid messages detected counter, 4–18

L
lan timeout characteristic, 2–17, 4–13, 4–15
last synchronization status, 4–19
Leap seconds, 1–6
local responses sent counter, 4–18
Local time
setting with time-sensitive applications, 2–22
local time differential factor characteristic, 4–15
local time does not intersect event, A–2
local times not intersecting counter, 4–18

M
Management, 1–4
routine tasks, 2–11
Management interface, 2–1
accessing and exiting, 2–3, 4–5
maximum clock drift rate characteristic, 4–15
maximum inaccuracy characteristic, 2–14, 4–13,
4–15
Monotonicity, 1–2

N
Namespace (DECdns), 1–16
National Institute of Standards and Technology
See NIST
NCL, 2–1, 2–3
access control information, 4–4
accessing and exiting, 2–3, 4–5
NET$DISABLE_DTSS, 2–9
Network Command Language
See NCL
Network Time Protocol
See NTP
next tdf change characteristic, 4–15
NIST, 1–1, B–2
no global server event, A–2
no global servers detected counter, 4–18
NTP, B–5, C–1
getting time from, C–1
giving time to, C–3
using the tcpip$ntp.conf configuration file,
C–3
preventing loops with, C–4

O
Objects (DECdns), 1–16

P
Prepositional phrases, 4–3
defined, 4–3
listed, 4–3
Problem solving, 3–1
advertise command fails
access violation, 3–6
unconfigured global directory, 3–6
advertise command failure, 3–5
clerk clock incorrect, 3–1
global servers unavailable, 3–5
global servers unresponsive, 3–5
large inaccuracy on all servers, 3–3
large inaccuracy on one server, 3–2
Local servers unavailable, 3–4
Local servers unresponsive, 3–4
server clock incorrect, 3–2

protocol mismatches detected counter, 4–18
protocol version mismatch detected event, A–2

Q
query attempts characteristic, 2–17, 4–13, 4–15

R
Radio broadcasts
UTC, B–3
Radio receivers
Heath, B–4
Hopf, B–4
manufacturers, B–4
addresses, B–4
PSTI, B–4
Spectracom, B–4
Traconex, B–4
Radio stations
UTC-broadcasting, B–3
Relative time, 1–11
representation of, 1–11
Rule
time zone, 2–21

S
Sample time-provider programs
dtss$ntp_provider.c, 1–3, C–1
dtss$provider.c, 1–3
dtss$provider_acts.c, 1–3
server not responding event, A–2
Servers, 1–14
changing clerk to, 2–8
courier, 1–15, 2–8
backup, 2–8
configuring, 2–8
global, 1–14, 2–5
configuring, 2–5
designating with site-specific template, 2–8
discovery of, 1–16
lists of on clerks, 1–12
lists of on servers, 1–14
local, 1–14
management, 2–18
matching epochs, 2–18
servers not responding counter, 4–18
servers required characteristic, 2–11, 4–13, 4–15
use with global servers, 2–13
use with systems on point-to-point lines, 2–13
server time does not intersect event, A–2
server times not intersecting counter, 4–18
Setting system clock, 1–9
Site-specific template, 2–8
Skew, 1–5

Index–3

Startup script, 2–2
contents, 2–2
DECnet-Plus, 2–2
state status, 4–19
Stratum, C–1
synchronization completed event, A–2
synchronization hold down characteristic, 2–14,
4–14, 4–15
Synchronization process, 1–6
computation of correct time, 1–6
synchronizations completed counter, 4–18
Synchronize, 1–6
System clock
adjustment, 1–8
changing, 2–20
definition, 1–8
forcing synchronization, 2–21
modifying, 2–19
updating, 2–19
system error detected event, A–3
system errors detected counter, 4–18
System time
changing, 2–20
modifying, 2–19
updating, 2–19

T
tcpip$ntp.conf, C–3
TDF, 1–10, 2–21
Template
site-specific, 1–15
Tick, 1–8
Time
display format, 1–10, 2–2
display format variants, 1–11
displays, 1–9, 2–21
local, 2–21
setting with time-sensitive applications,
2–22
local translation, 1–11
representation of, 1–9
seasonal adjustment of, 2–21
Time Differential Factor
See TDF
time interval, 1–1
Time measurement factors, 1–4
time provider failure detected event, A–3
time provider failures detected counter, 4–18
time-provider interface, 1–1
Time-provider programs
See Sample time-provider programs
Time-providers, 1–1, 1–3, B–1
radio receivers, B–3, B–4
support for, 1–3
telephone, B–2

Index–4

time representation mismatches detected counter,
4–18
time representation version characteristic, 4–15
time representation version mismatch detected
event, A–3
Time services, B–1
Time sources, B–1
criteria for selecting, B–1
Timestamp, 2–2
displays, 2–2
Time standards authorities, B–3
too few servers detected counter, 4–18
too few servers detected event, A–3
too many servers detected counter, 4–18
too many servers detected event, A–3
TPI, 1–1
TP server, 1–4
TRANSIT, B–5
Troubleshooting
See Problem solving
type characteristic, 4–15

U
uid status, 4–19
update initiated event, A–3
Updates
automatic local time, 1–2
updates initiated counter, 4–18
UTC, 1–6, 1–9
sources, B–2
dial-up, B–2
radio broadcasts, B–3
satellite, B–5

W
wan timeout characteristic, 2–17, 4–14, 4–15
Wildcards
described, 4–4
World Time Zone Map, B–5