SIST EN 62439-1:2010

Industrial communication networks - High availability automation networks - Part 1: General concepts and calculation methods (IEC 62439-1:2010 )

The IEC 62439 series is applicable to high-availability automation networks based on the ISO/IEC 8802-3 (IEEE 802.3) (Ethernet) technology.
This part of the IEC 62439 series specifies the common elements and definitions for other parts of the IEC 62439 series; the conformance test specification (normative); a classification scheme for network characteristics (informative); a methodology for estimating network availability (informative); the configuration rules, calculation and measurement method for a deterministic recovery time in RSTP.

Industrielle Kommunikationsnetze - Hochverfügbare Automatisierungsnetze - Teil 1: Grundlagen und Berechnungsmethoden (IEC 62439-1:2010 )

Réseaux de communication industrielle - Réseaux d’automatisme à haute disponibilité - Partie 1 : Concepts généraux et méthodes de calcul (CEI 62439-1:2010 )

La CEI 62439-1:2010 s'applique aux réseaux de haute disponibilité pour l'automatisation reposant sur la technologie 8802-3 (IEEE 802.3) (Ethernet) de l'ISO/CEI. Elle spécifie:
- les éléments communs et les définitions pour d'autres parties de la série CEI 62439;
- la spécification d'essai de conformité (normative);
- un système de classification pour les caractéristiques de réseau (informative);
- une méthodologie pour l'estimation de la disponibilité du réseau (informative);
- les règles de configuration, la méthode de calcul et de mesure pour un temps de reprise déterministe dans le protocole RSTP. Elle annule et remplace la CEI 62439 publiée en 2008. Elle constitue une révision technique. Cette édition inclut les modifications suivantes:
- ajout d'une méthode de calcul pour le protocole RSTP (Rapid Spanning Tree Protocol, IEEE 802.1Q),
- ajout de deux nouveaux protocoles de redondance: HSR (High-availability Seamless Redundancy) et DRP (Distributed Redundancy Protocol),
- ajout d'une méthode de calcul du temps de reprise maximal du protocole RSTP dans une configuration restreinte (anneau) dans la CEI 62439-1 (Article 8),
- ajout de spécifications du protocole HSR (High-availability Seamless Redundancy), qui partage les principes du protocole PRP dans la CEI 62439-3 (Article 5), et introduction du protocole DRP (CEI 62439-6). La présente version bilingue (2013-07) correspond à la version anglaise monolingue publiée en 2010-02.

Industrijska komunikacijska omrežja za avtomatizacijo z visoko razpoložljivostjo - 1. del: Splošni koncept in metode izračunavanja (IEC 62439-1:2010 )

Serija IEC 62439 velja za omrežja za avtomatizacijo z visoko razpoložljivostjo, osnovana na ISO/IEC 8802-3 (IEEE 802.3) (eternet) tehnologiji.
Ta del serije IEC 62439 določa splošne elemente in definicije za druge dele serije IEC 62439; tehnično zahtevo (normativno) za preskušanje skladnosti;
klasifikacijska shemo za omrežne lastnosti (informativno); metodologijo za ocenjevanje omrežne razpoložljivosti (informativno); konfiguracijska pravila, metode izračunavanja in merjenja za ocenjeno obnovitvenega časa v RSTP.

General Information

• Status: Published
• Publication Date: 13-Apr-2010
• ICS: 25.040.01 - Industrial automation systems in general
• ICS: 35.110 - Networking
• Technical Committee: MOV - Measuring equipment for electromagnetic quantities
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 08-Apr-2010
• Due Date: 13-Jun-2010
• Completion Date: 14-Apr-2010
• Ref Project: EN 62439-1:2010 - Industrial communication networks - High availability automation networks - Part 1: General concepts and calculation methods

Relations

• Replaces: SIST EN 62439:2008 - High availability automation networks
• Effective Date: 01-May-2010
• Amended By: SIST EN 62439-1:2010/A1:2012 - Industrial communication networks - High availability automation networks - Part 1: General concepts and calculation methods (IEC 62439-1:2010/A1:2012)
• Effective Date: 07-Jun-2022
• Replaces: SIST EN 62439:2008 - High availability automation networks
• Effective Date: 29-Jan-2023
• Amended By: SIST EN 62439-1:2010/A1:2012 - Industrial communication networks - High availability automation networks - Part 1: General concepts and calculation methods (IEC 62439-1:2010/A1:2012)
• Effective Date: 29-Jan-2023
• Revised: SIST EN 62439:2008 - High availability automation networks
• Effective Date: 05-Mar-2013
• Revised: SIST EN 62439:2008 - High availability automation networks
• Effective Date: 07-Jun-2022

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN 62439-1:2010
01-maj-2010
1DGRPHãþD
SIST EN 62439:2008
,QGXVWULMVNDNRPXQLNDFLMVNDRPUHåMD]DDYWRPDWL]DFLMR]YLVRNRUD]SRORåOMLYRVWMR
GHO6SORãQLNRQFHSWLQPHWRGHL]UDþXQDYDQMD,(&
Industrial communication networks - High availability automation networks - Part 1:
General concepts and calculation methods (IEC 62439-1:2010 )
Industrielle Kommunikationsnetze - Hochverfügbare Automatisierungsnetze - Teil 1:
Grundlagen und Berechnungsmethoden (IEC 62439-1:2010 )
Réseaux de communication industrielle - Réseaux d’automatisme à haute disponibilité -
Partie 1 : Concepts généraux et méthodes de calcul (CEI 62439-1:2010 )
Ta slovenski standard je istoveten z: EN 62439-1:2010
ICS:
25.040.01 Sistemi za avtomatizacijo v Industrial automation
industriji na splošno systems in general
35.110 Omreževanje Networking
SIST EN 62439-1:2010 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 62439-1:2010

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SIST EN 62439-1:2010

EUROPEAN STANDARD
EN 62439-1

NORME EUROPÉENNE
March 2010
EUROPÄISCHE NORM

ICS 25.040; 35.040 Supersedes EN 62439:2008 (partially)


English version


Industrial communication networks -
High availability automation networks -
Part 1: General concepts and calculation methods
(IEC 62439-1:2010)


Réseaux de communication industrielle – Industrielle Kommunikationsnetze -
Réseaux d’automatisme à haute Hochverfügbare Automatisierungsnetze -
disponibilité – Teil 1: Grundlagen
Partie 1 : Concepts généraux et méthodes und Berechnungsmethoden
de calcul (IEC 62439-1:2010)
(CEI 62439-1:2010)




This European Standard was approved by CENELEC on 2010-03-01. CENELEC members are bound to comply
with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard
the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and notified
to the Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus,
the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy,
Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia,
Spain, Sweden, Switzerland and the United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Central Secretariat: Avenue Marnix 17, B - 1000 Brussels


© 2010 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 62439-1:2010 E

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SIST EN 62439-1:2010
EN 62439-1:2010 - 2 -
Foreword
The text of document 65C/583/FDIS, future edition 1 of IEC 662439-1, prepared by SC 65C, Industrial
networks, of IEC TC 65, Industrial-process measurement, control and automation, was submitted to the
IEC-CENELEC parallel vote and was approved by CENELEC as EN 62439-1 on 2010-03-01.
This EN 62439-1 together with EN 62439-2, EN 62439-3, EN 62439-4, EN 62439-5 and EN 62439-6
supersedes EN 62439:2008.
This EN 62439-1:2010 includes the following significant technical changes with respect to
EN 62439:2008:
– adding a calculation method for RSTP (rapid spanning tree protocol, IEEE 802.1Q),
– adding two new redundancy protocols: HSR (High-availability Seamless Redundancy) and DRP
(Distributed Redundancy Protocol),
– moving former Clauses 1 to 4 (introduction, definitions, general aspects) and the Annexes (taxonomy,
availability calculation) to EN 62439-1, which serves now as a base for the other documents,
– moving Clause 5 (MRP) to EN 62439-2 with minor editorial changes,
– moving Clause 6 (PRP) was to EN 62439-3 with minor editorial changes,
– moving Clause 7 (CRP) was to EN 62439-4 with minor editorial changes, and
– moving Clause 8 (BRP) was to EN 62439-5 with minor editorial changes,
– adding a method to calculate the maximum recovery time of RSTP in a restricted configuration (ring)
to EN 62439-1 as Clause 8,
– adding specifications of the HSR (High-availability Seamless Redundancy) protocol, which shares the
principles of PRP to EN 62439-3 as Clause 5, and
– introducing the DRP protocol as EN 62439-6.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN and CENELEC shall not be held responsible for identifying any or all such patent
rights.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
(dop) 2010-12-01
national standard or by endorsement
– latest date by which the national standards conflicting
(dow) 2013-03-01
with the EN have to be withdrawn
Annex ZA has been added by CENELEC.
__________

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SIST EN 62439-1:2010
- 3 - EN 62439-1:2010
Endorsement notice
The text of the International Standard IEC 62439-1:2010 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standards indicated:
IEC 61158 series NOTE  Harmonized in EN 61158 series (not modified).
IEC/TR 61158-1 NOTE  Harmonized as CLC/TR 61158-1.
IEC/TR 61158-6 series NOTE  Harmonized in EN 61158-6 series (not modified).
IEC 61784-2:2007 NOTE  Harmonized as EN 61784-2:2008 (not modified).
IEC 62439-2 NOTE  Harmonized as EN 62439-2.
IEC 62439-3 NOTE  Harmonized as EN 62439-3.
IEC 62439-4 NOTE  Harmonized as EN 62439-4.
IEC 62439-5 NOTE  Harmonized as EN 62439-5.
IEC 62439-6 NOTE  Harmonized as EN 62439-6.
IEC 61918:2007 NOTE  Harmonized as EN 61918:2008 (modified).
__________

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SIST EN 62439-1:2010
EN 62439-1:2010 - 4 -
Annex ZA
(normative)

Normative references to international publications
with their corresponding European publications

The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.

NOTE  When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD
applies.

Publication Year Title EN/HD Year

IEC 60050-191 1990 International Electrotechnical Vocabulary - -
(IEV) - Chapter 191: Dependability and quality
of service



IEC 61158 Series Fieldbus standard for use in industrial control EN 61158 Series
systems


IEC 61158-6-10 - Industrial communication networks - Fieldbus EN 61158-6-10 -
specifications -
Part 6-10: Application layer protocol
specification - Type 10 elements


ISO/IEC 8802-3 2000 Information technology - Telecommunications - -
and information exchange between systems -
Local and metropolitan area networks -
Specific requirements -
Part 3: Carrier sense multiple access with
collision detection (CSMA/CD) access method
and physical layer specifications


IEEE 802.1D 2004 IEEE Standard for Local and Metropoitan - -
Area Networks - Media Access Control (MAC)
Bridges


IEEE 802.1Q - IEEE Standard for Local and Metropolitan - -
Area Networks - Virtual Bridged Local Area
Networks


IETF RFC 791 - Internet Protocol - DARPA Internet Program - -
Protocol Specification

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SIST EN 62439-1:2010

IEC 62439-1
®
Edition 1.0 2010-02
INTERNATIONAL
STANDARD

colour
inside

Industrial communication networks – High availability automation networks –
Part 1: General concepts and calculation methods


INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
XA
ICS 25.040, 35.040 ISBN 2-8318-1081-1
® Registered trademark of the International Electrotechnical Commission

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SIST EN 62439-1:2010
– 2 – 62439-1 © IEC:2010(E)
CONTENTS
FOREWORD.5
INTRODUCTION.7
1 Scope.8
2 Normative references .8
3 Terms, definitions, abbreviations, acronyms, and conventions.9
3.1 Terms and definitions .9
3.2 Abbreviations and acronyms.16
3.3 Conventions .17
3.3.1 General conventions.17
3.3.2 Conventions for state machine definitions.17
3.3.3 Conventions for PDU specification.17
3.4 Reserved network addresses .18
4 Conformance requirements (normative) .18
4.1 Conformance to redundancy protocols.18
4.2 Conformance tests .19
4.2.1 Concept.19
4.2.2 Methodology.19
4.2.3 Test conditions and test cases.20
4.2.4 Test procedure and measuring .20
4.2.5 Test report.20
5 Concepts for high availability automation networks (informative) .21
5.1 Characteristics of application of automation networks.21
5.1.1 Resilience in case of failure.21
5.1.2 Classes of network redundancy .22
5.1.3 Redundancy maintenance .22
5.1.4 Comparison and indicators .23
5.2 Generic network system .24
5.2.1 Network elements.24
5.2.2 Topologies.26
5.2.3 Redundancy handling .32
5.2.4 Network recovery time .32
5.2.5 Diagnosis coverage .32
5.2.6 Failures .32
5.3 Safety .34
5.4 Security.34
6 Classification of networks (informative) .34
6.1 Notation .34
6.2 Classification of robustness.35
7 Availability calculations for selected networks (informative) .35
7.1 Definitions .35
7.2 Reliability models .36
7.2.1 Generic symmetrical reliability model.36
7.2.2 Simplified symmetrical reliability model.38
7.2.3 Asymmetric reliability model .38
7.3 Availability of selected structures .39
7.3.1 Single LAN without redundant leaves .39

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SIST EN 62439-1:2010
62439-1 © IEC:2010(E) – 3 –
7.3.2 Network without redundant leaves .40
7.3.3 Single LAN with redundant leaves .41
7.3.4 Network with redundant leaves .41
7.3.5 Considering second failures .42
7.4 Caveat .44
8 RSTP for High Availability Networks: configuration rules, calculation and
measurement method for deterministic recovery time in a ring topology .44
8.1 General .44
8.2 Deployment and configuration rules for the ring topology .44
8.3 Calculations for fault recovery time in a ring .45
8.3.1 Dependencies and failure modes.45
8.3.2 Calculations for non-considered failure modes.45
8.3.3 Calculations for the considered failure modes.45
8.4 Timing measurement method .46
8.4.1 Measurement of T .46
PA
8.4.2 Measurement of T .47
L
8.4.3 Measurement of (T + T ).48
TC F
8.4.4 System test example .50
Bibliography.52

Figure 1 – Conformance test overview .19
Figure 2 – General network elements (tree topology) .24
Figure 3 – Link Redundancy Entity in a Doubly Attached Node (DAN).26
Figure 4 – Example of tree topology.27
Figure 5 – Example of linear topology.28
Figure 6 – Example of ring topology.28
Figure 7 – Example of a partially meshed topology .29
Figure 8 – Example of fully meshed topology .30
Figure 9 – Single LAN structure without redundant leaf links.30
Figure 10 – Single LAN structure with redundant leaf links.31
Figure 11 – Redundant LAN structure without redundant leaf links.31
Figure 12 – Redundant LAN structure with redundant leaf links .31
Figure 13 – General symmetrical fault model .37
Figure 14 – Simplified fault model.38
Figure 15 – Asymmetric fault model .39
Figure 16 – Network with no redundancy .40
Figure 17 – Network with no single point of failure .41
Figure 18 – Network with resiliency to second failure.43
Figure 19 –Test rig for T measurement.47
PA
Figure 20 –Test rig for T measurement.48
L
Figure 21 –Test rig for (T + T ) measurement .49
TC F
Figure 22 –Test rig for system test.50

Table 1 – Examples of application grace time .21
Table 2 – Examples of redundancy protocols .23

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SIST EN 62439-1:2010
– 4 – 62439-1 © IEC:2010(E)
Table 3 – Code assignment for the field .34
Table 4 – Code assignment for the field .34
Table 5 – Code assignment for the field.35
Table 6 – Code assignment for the field .35

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SIST EN 62439-1:2010
62439-1 © IEC:2010(E) – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

INDUSTRIAL COMMUNICATION NETWORKS –
HIGH AVAILABILITY AUTOMATION NETWORKS –

Part 1: General concepts and calculation methods


FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard 62439-1 has been prepared by subcommittee 65C: Industrial Networks,
of IEC technical committee 65: Industrial-process measurement, control and automation.
This standard cancels and replaces IEC 62439 published in 2008. This first edition constitutes
a technical revision.
This edition includes the following significant technical changes with respect to IEC 62439
(2008):
– adding a calculation method for RSTP (rapid spanning tree protocol, IEEE 802.1Q),
– adding two new redundancy protocols: HSR (High-availability Seamless Redundancy)
and DRP (Distributed Redundancy Protocol),
– moving former Clauses 1 to 4 (introduction, definitions, general aspects) and the
Annexes (taxonomy, availability calculation) to IEC 62439-1, which serves now as a
base for the other documents,
– moving Clause 5 (MRP) to IEC 62439-2 with minor editorial changes,

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SIST EN 62439-1:2010
– 6 – 62439-1 © IEC:2010(E)
– moving Clause 6 (PRP) was to IEC 62439-3 with minor editorial changes,
– moving Clause 7 (CRP) was to IEC 62439-4 with minor editorial changes, and
– moving Clause 8 (BRP) was to IEC 62439-5 with minor editorial changes,
– adding a method to calculate the maximum recovery time of RSTP in a restricted
configuration (ring) to IEC 62439-1 as Clause 8,
– adding specifications of the HSR (High-availability Seamless Redundancy) protocol,
which shares the principles of PRP to IEC 62439-3 as Clause 5, and
– introducing the DRP protocol as IEC 62439-6.
The text of this standard is based on the following documents:
FDIS Report on voting
65C/583/FDIS 65C/589/RVD

Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
A list of the IEC 62439 series can be found, under the general title Industrial communication
networks – High availability automation networks, on the IEC website.
This publication has been drafted in accordance with ISO/IEC Directives, Part 2.
The committee has decided that the contents of this amendment and the base publication will
remain unchanged until the stability date indicated on the IEC web site under
"http://webstore.iec.ch" in the data related to the specific publication. At this date, the
publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this standard may be issued at a later date.

IMPORTANT – The “colour inside” logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct understanding
of its contents. Users should therefore print this publication using a colour printer.

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SIST EN 62439-1:2010
62439-1 © IEC:2010(E) – 7 –
INTRODUCTION
The IEC 62439 series specifies relevant principles for high availability networks that meet the
requirements for industrial automation networks.
In the fault-free state of the network, the protocols of the IEC 62439 series provide
ISO/IEC 8802-3 (IEEE 802.3) compatible, reliable data communication, and preserve
determinism of real-time data communication. In cases of fault, removal, and insertion of a
component, they provide deterministic recovery times.
These protocols retain fully the typical Ethernet communication capabilities as used in the
office world, so that the software involved remains applicable.
The market is in need of several network solutions, each with different performance
characteristics and functional capabilities, matching diverse application requirements. These
solutions support different redundancy topologies and mechanisms which are introduced in
IEC 62439-1 and specified in the other Parts of the IEC 62439 series. IEC 62439-1 also
distinguishes between the different solutions, giving guidance to the user.
The IEC 62439 series follows the general structure and terms of IEC 61158 series.

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SIST EN 62439-1:2010
– 8 – 62439-1 © IEC:2010(E)
INDUSTRIAL COMMUNICATION NETWORKS –
HIGH AVAILABILITY AUTOMATION NETWORKS –

Part 1: General concepts and calculation methods



1 Scope
The IEC 62439 series is applicable to high-availability automation networks based on the
ISO/IEC 8802-3 (IEEE 802.3) (Ethernet) technology.
This part of the IEC 62439 series specifies
• the common elements and definitions for other parts of the IEC 62439 series;
• the conformance test specification (normative);
• a classification scheme for network characteristics (informative);
• a methodology for estimating network availability (informative);
• the configuration rules, calculation and measurement method for a deterministic recovery
time in RSTP.
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
IEC 60050-191:1990, International Electrotechnical Vocabulary – Chapter 191: Dependability
and quality of service
IEC 61158 (all parts), Industrial communication networks – Fieldbus specifications
IEC 61158-6-10, Industrial communication networks – Fieldbus specifications – Part 6-10:
Application layer protocol specification – Type 10 elements
ISO/IEC 8802-3:2000, Information technology – Telecommunications and information
exchange between systems – Local and metropolitan area networks – Specific requirements –
Part 3: Carrier sense multiple access with collision detection (CSMA/CD) access method and
physical layer specifications
IEEE 802.1Q, IEEE standards for local and metropolitan area network. Virtual bridged local
area networks
IEEE 802.1D:2004, IEEE standard for local Local and metropolitan area networks Media
Access Control (MAC) Bridges
http://www.ietf.org>
IETF RFC 791, Internet Protocol; available at <

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SIST EN 62439-1:2010
62439-1 © IEC:2010(E) – 9 –
3 Terms, definitions, abbreviations, acronyms, and conventions
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60050-191, as well
as the following, apply
3.1.1
availability (performance)
ability of an item to be in a state to perform a required function under given conditions at a
given instant of time or over a given time interval, assuming that the required external
resources are provided
NOTE 1 This ability depends on the combined aspects of the reliability performance, the maintainability
performance, and the maintenance su
...