SIST EN IEC 61158-4-4:2019

Industrial communication networks - Fieldbus specifications - Part 4-4: Data-link layer protocol specification - Type 4 elements (IEC 61158-4-4:2019)

The data-link layer provides basic time-critical messaging communications between devices in an automation environment. This protocol provides a means of connecting devices through a partial mesh network, such that most failures of an interconnection between two devices can be circumvented. In common practice the devices are interconnected in a non-redundant hierarchical manner reflecting application needs.

Industrielle Kommunikationsnetze - Feldbusse - Teil 4-4: Protokollspezifikation des Data Link Layer (Sicherungsschicht) - Typ 4-Elemente (IEC 61158-4-4:2019)

Réseaux de communication industriels - Spécifications des bus de terrain - Partie 4-4: Spécification du protocole de la couche liaison de données - Eléments de type 4 (IEC 61158-4-4:2019)

IEC 61158-4-4:2019 La couche de liaison de données assure les communications de messagerie à contrainte de temps de base entre les appareils d'un environnement d'automatisation.
Ce protocole fournit un moyen de connecter des appareils par le biais d'un réseau maillé partiel, de sorte que la plupart des défaillances d'une interconnexion entre deux appareils peuvent être contournées. Les appareils sont généralement interconnectés d'une manière hiérarchique non redondante qui reflète les besoins de l'application.

Industrijska komunikacijska omrežja - Specifikacije za procesna vodila - 4-4. del: Specifikacija protokola na ravni podatkovnih povezav - Elementi tipa 4 (IEC 61158-4-4:2019)

Nivo podatkovnih povezav omogoča osnovne časovno kritične sporočilne komunikacije med napravami v avtomatizacijskem okolju. Ta protokol omogoča način za povezovanje naprav prek delnega zankastega omrežja, tako da se je mogoče izogniti večini napak v medsebojnem povezovanju med napravama. Pri običajni praksi so naprave medsebojno povezane na neredundanten hierarhičen način, ki odraža potrebe aplikacije.

General Information

• Status: Published
• Publication Date: 07-Oct-2019
• ICS: 25.040.40 - Industrial process measurement and control
• ICS: 35.100.20 - Data link layer
• ICS: 35.110 - Networking
• Technical Committee: MOV - Measuring equipment for electromagnetic quantities
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 01-Jul-2019
• Due Date: 05-Sep-2019
• Completion Date: 08-Oct-2019
• Ref Project: EN IEC 61158-4-4:2019 - Industrial communication networks - Fieldbus specifications - Part 4-4: Data-link layer protocol specification - Type 4 elements

Relations

• Replaces: SIST EN 61158-4-4:2015 - Industrial communication networks - Fieldbus specifications - Part 4-4: Data-link layer protocol specification - Type 4 elements (IEC 61158-4-4:2014)
• Effective Date: 25-Jun-2019

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN IEC 61158-4-4:2019
01-november-2019
Nadomešča:
SIST EN 61158-4-4:2015
Industrijska komunikacijska omrežja - Specifikacije za procesna vodila - 4-4. del:
Specifikacija protokola na ravni podatkovnih povezav - Elementi tipa 4 (IEC 61158-
4-4:2019)
Industrial communication networks - Fieldbus specifications - Part 4-4: Data-link layer
protocol specification - Type 4 elements (IEC 61158-4-4:2019)
Industrielle Kommunikationsnetze - Feldbusse - Teil 4-4: Protokollspezifikation des Data
Link Layer (Sicherungsschicht) - Typ 4-Elemente (IEC 61158-4-4:2019)
Réseaux de communication industriels - Spécifications des bus de terrain - Partie 4-4:
Spécification du protocole de la couche liaison de données - Eléments de type 4 (IEC
61158-4-4:2019)
Ta slovenski standard je istoveten z: EN IEC 61158-4-4:2019
ICS:
25.040.40 Merjenje in krmiljenje Industrial process
industrijskih postopkov measurement and control
35.100.20 Podatkovni povezovalni sloj Data link layer
35.110 Omreževanje Networking
SIST EN IEC 61158-4-4:2019 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN IEC 61158-4-4:2019


EUROPEAN STANDARD EN IEC 61158-4-4

NORME EUROPÉENNE

EUROPÄISCHE NORM
June 2019
Supersedes EN 61158-4-4:2014
ICS 25.040.40; 35.100.20; 35.110
English Version
Industrial communication networks - Fieldbus specifications -
Part 4-4: Data-link layer protocol specification - Type 4 elements
(IEC 61158-4-4:2019)
Réseaux de communication industriels - Spécifications des Industrielle Kommunikationsnetze - Feldbusse - Teil 4-4:
bus de terrain - Partie 4-4: Spécification du protocole de la Protokollspezifikation des Data Link Layer
couche liaison de données - Eléments de type 4 (Sicherungsschicht) - Typ 4-Elemente
(IEC 61158-4-4:2019) (IEC 61158-4-4:2019)
This European Standard was approved by CENELEC on 2019-05-23. 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 CEN-CENELEC
Management Centre 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 CEN-CENELEC Management Centre 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, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.



European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2019 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
 Ref. No. EN IEC 61158-4-4:2019 E

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SIST EN IEC 61158-4-4:2019
EN IEC 61158-4-4:2019 (E)
European foreword
The text of document 65C/946/FDIS, future edition 3 of IEC 61158-4-4, 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 approved by CENELEC as EN IEC 61158-4-4:2019.
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2020-02-23
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2022-05-23
document have to be withdrawn

This document supersedes EN 61158-4-4:2014.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.

Endorsement notice
The text of the International Standard IEC 61158-4-4:2019 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 61158-1:2019 NOTE Harmonized as EN IEC 61158-1:2019 (not modified)
IEC 61158-2:2014 NOTE Harmonized as EN 61158-2:2014 (not modified)
IEC 61158-3-4:2019 NOTE Harmonized as EN IEC 61158-3-4:2019 (not modified)
IEC 61158-5-4:2019 NOTE Harmonized as EN IEC 61158-5-4:2019 (not modified)
IEC 61784-1:2019 NOTE Harmonized as EN IEC 61784-1:2019 (not modified)
IEC 61784-2:2019 NOTE Harmonized as EN IEC 61784-2:2019 (not modified)
2

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SIST EN IEC 61158-4-4:2019
EN IEC 61158-4-4:2019 (E)
Annex ZA
(normative)

Normative references to international publications
with their corresponding European publications
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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 1  Where an International Publication has been modified by common modifications, indicated by (mod), the relevant
EN/HD applies.
NOTE 2  Up-to-date information on the latest versions of the European Standards listed in this annex is available here:
www.cenelec.eu.

Publication Year Title EN/HD Year
ISO/IEC 7498-1 -  Information technology - Open Systems - -
Interconnection - Basic reference model:
The basic model
ISO/IEC 7498-3 -  Information technology - Open Systems - -
Interconnection - Basic reference model:
Naming and addressing
ISO/IEC 10731 -  Information technology - Open Systems - -
Interconnection - Basic Reference Model -
Conventions for the definition of OSI
services

3

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SIST EN IEC 61158-4-4:2019



IEC 61158-4-4

®


Edition 3.0 2019-04




INTERNATIONAL



STANDARD



















Industrial communication networks – Fieldbus specifications –

Part 4-4: Data-link layer protocol specification – Type 4 elements



























INTERNATIONAL

ELECTROTECHNICAL


COMMISSION





ICS 25.040.40; 35.100.20; 35.110 ISBN 978-2-8322-6774-5




  Warning! Make sure that you obtained this publication from an authorized distributor.


® Registered trademark of the International Electrotechnical Commission

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CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
1.1 General . 7
1.2 Specifications . 7
1.3 Procedures . 7
1.4 Applicability . 7
1.5 Conformance . 7
2 Normative references . 8
3 Terms, definitions, symbols and abbreviations . 8
3.1 Reference model terms and definitions . 8
3.2 Service convention terms and definitions . 10
3.3 Terms and definitions. 11
3.4 Symbols and abbreviations . 14
4 Data Link Protocol Definition . 14
4.1 Overview of the DL-protocol . 14
4.2 General structure and encoding of PhIDUs and DLPDUs, and related
elements of procedure . 26
4.3 DLPDU-specific structure, encoding and elements of procedure . 33
4.4 DL-service elements of procedure . 37
4.5 Route mechanism . 40
4.6 Link-access system . 43
4.7 Local variables, counters and queues . 44
Bibliography . 46

Figure 1 – Relationship of PhE, DLE and DLS-user . 15
Figure 2 – DLE state diagram for confirmed and unconfirmed, unacknowledged
DLPDUs . 17
Figure 3 – DLE state diagram for confirmed acknowledged DLPDUs . 18
Figure 4 – DLE state diagram for unconfirmed acknowledged DLPDUs . 19
Figure 5 – Full duplex DLE receive state diagram . 20
Figure 6 – Full duplex DLE transmit state diagram . 20
Figure 7 – Link access example . 23
Figure 8 – Simple Type 4-route format . 29
Figure 9 – Extended Type 4-route format . 29
Figure 10 – Complex Type 4-route format . 30
Figure 11 – Immediate Type 4-route format . 30
Figure 12 – IP Type 4-route format . 31
Figure 13 – Control-status format. 32
Figure 14 – Data-field-format . 32
Figure 15 – Source / destination designator . 41
Figure 16 – Simple Type 4-route generation . 41
Figure 17 – Extended Type 4-route generation . 41
Figure 18 – Complex and IP Type 4-route generation . 42
Figure 19 – Simple DL-route generation . 42

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Figure 20 – Extended DL-route generation . 43
Figure 21 – Complex and IP DL-route generation . 43

Table 1 – Summary structure of DLPDUs . 33
Table 2 – Structure of confirmed DLPDUs . 34
Table 3 – Structure of unconfirmed DLPDUs . 35
Table 4 – Structure of acknowledge DLPDU . 36
Table 5 – Structure of immediate-reply DLPDU . 36

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INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

INDUSTRIAL COMMUNICATION NETWORKS –
FIELDBUS SPECIFICATIONS –

Part 4-4: Data-link layer protocol specification –
Type 4 elements

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.
Attention is drawn to the fact that the use of the associated protocol type is restricted by its
intellectual-property-right holders. In all cases, the commitment to limited release of
intellectual-property-rights made by the holders of those rights permits a layer protocol type to
be used with other layer protocols of the same type, or in other type combinations explicitly
authorized by its intellectual-property-right holders.
NOTE Combinations of protocol types are specified in IEC 61784-1 and IEC 61784-2.
International Standard IEC 61158-4-4 has been prepared by subcommittee 65C: Industrial
networks, of IEC technical committee 65: Industrial-process measurement, control and
automation.
This third edition cancels and replaces the second edition published in 2014. This edition
constitutes a technical revision.

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IEC 61158-4-4:2019 © IEC 2019 – 5 –
This edition includes the following significant technical changes with respect to the previous
edition:
a) additional user parameters to services;
b) additional services to support distributed objects;
c) additional secure services;
The text of this International Standard is based on the following documents:
FDIS Report on voting
65C/946/FDIS 65C/955/RVD

Full information on the voting for the approval of this International standard can be found in
the report on voting indicated in the above table.
This publication has been drafted in accordance with ISO/IEC Directives, Part 2.
A list of all the parts of the IEC 61158 series, published under the general title Industrial
communication networks – Fieldbus specifications, can be found on the IEC website.
The committee has decided that the contents of this 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 publication may be issued at a later date.

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INTRODUCTION
This document is one of a series produced to facilitate the interconnection of automation
system components. It is related to other standards in the set as defined by the “three-layer”
fieldbus reference model described in IEC 61158-1.
The data-link protocol provides the data-link service by making use of the services available
from the physical layer. The primary aim of this document is to provide a set of rules for
communication expressed in terms of the procedures to be carried out by peer data-link
entities (DLEs) at the time of communication. These rules for communication are intended to
provide a sound basis for development in order to serve a variety of purposes:
a) as a guide for implementors and designers;
b) for use in the testing and procurement of equipment;
c) as part of an agreement for the admittance of systems into the open systems environment;
d) as a refinement to the understanding of time-critical communications within OSI.
This document is concerned, in particular, with the communication and interworking of
sensors, effectors and other automation devices. By using this document together with other
standards positioned within the OSI or fieldbus reference models, otherwise incompatible
systems may work together in any combination.

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IEC 61158-4-4:2019 © IEC 2019 – 7 –
INDUSTRIAL COMMUNICATION NETWORKS –
FIELDBUS SPECIFICATIONS –

Part 4-4: Data-link layer protocol specification –
Type 4 elements



1 Scope
1.1 General
The data-link layer provides basic time-critical messaging communications between devices in
an automation environment.
This protocol provides a means of connecting devices through a partial mesh network, such
that most failures of an interconnection between two devices can be circumvented. In
common practice the devices are interconnected in a non-redundant hierarchical manner
reflecting application needs
1.2 Specifications
This document specifies
a) procedures for the timely transfer of data and control information from one data-link user
entity to a peer user entity, and among the data-link entities forming the distributed data-
link service provider;
b) the structure of the fieldbus DLPDUs used for the transfer of data and control information
by the protocol of this document, and their representation as physical interface data units.
1.3 Procedures
The procedures are defined in terms of
a) the interactions between peer DL-entities (DLEs) through the exchange of fieldbus
DLPDUs;
b) the interactions between a DL-service (DLS) provider and a DLS-user in the same system
through the exchange of DLS primitives;
c) the interactions between a DLS-provider and a Ph-service provider in the same system
through the exchange of Ph-service primitives.
1.4 Applicability
These procedures are applicable to instances of communication between systems which
support time-critical communications services within the data-link layer of the OSI or fieldbus
reference models, and which require the ability to interconnect in an open systems
interconnection environment.
Profiles provide a simple multi-attribute means of summarizing an implementation’s
capabilities, and thus its applicability to various time-critical communications needs.
1.5 Conformance
This document also specifies conformance requirements for systems implementing these
procedures. This document does not contain tests to demonstrate compliance with such
requirements.

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2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements 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 All parts of the IEC 61158 series, as well as IEC 61784-1 and IEC 61784-2 are maintained simultaneously.
Cross-references to these documents within the text therefore refer to the editions as dated in this list of normative
references.
ISO/IEC 7498-1, Information technology – Open Systems Interconnection – Basic Reference
Model: The Basic Model
ISO/IEC 7498-3, Information technology – Open Systems Interconnection – Basic Reference
Model: Naming and addressing
ISO/IEC 10731, Information technology – Open Systems Interconnection – Basic Reference
Model – Conventions for the definition of OSI services
3 Terms, definitions, symbols and abbreviations
For the purposes of this document, the following terms, definitions, symbols and abbreviations
apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1 Reference model terms and definitions
This document is based in part on the concepts developed in ISO/IEC 7498-1 and
ISO/IEC 7498-3, and makes use of the following terms defined therein.
3.1.1 called-DL-address [7498-3]
3.1.2 calling-DL-address [7498-3]
3.1.3 centralized multi-end-point-connection [7498-1]
3.1.4 correspondent (N)-entities [7498-1]
correspondent DL-entities  (N=2)
correspondent Ph-entities  (N=1)
3.1.5 demultiplexing [7498-1]
3.1.6 DL-address [7498-3]
3.1.7 DL-address-mapping [7498-1]
3.1.8 DL-connection [7498-1]
3.1.9 DL-connection-end-point [7498-1]
3.1.10 DL-connection-end-point-identifier [7498-1]
3.1.11 DL-connection-mode transmission [7498-1]

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3.1.12 DL-connectionless-mode transmission [7498-1]
3.1.13 DL-data-sink [7498-1]
3.1.14 DL-data-source [7498-1]
3.1.15 DL-duplex-transmission [7498-1]
3.1.16 DL-facility [7498-1]
3.1.17 DL-local-view [7498-3]
3.1.18 DL-name [7498-3]
3.1.19 DL-protocol [7498-1]
3.1.20 DL-protocol-connection-identifier [7498-1]
3.1.21 DL-protocol-control-information [7498-1]
3.1.22 DL-protocol-data-unit [7498-1]
3.1.23 DL-protocol-version-identifier [7498-1]
3.1.24 DL-relay [7498-1]
3.1.25 DL-service-connection-identifier [7498-1]
3.1.26 DL-service-data-unit [7498-1]
3.1.27 DL-simplex-transmission [7498-1]
3.1.28 DL-subsystem [7498-1]
3.1.29 DL-user-data [7498-1]
3.1.30 flow control [7498-1]
3.1.31 layer-management [7498-1]
3.1.32 multiplexing [7498-3]
3.1.33 naming-(addressing)-authority [7498-3]
3.1.34 naming-(addressing)-domain [7498-3]
3.1.35 naming-(addressing)-subdomain [7498-3]
3.1.36 (N)-entity [7498-1]
DL-entity
Ph-entity
3.1.37 (N)-interface-data-unit [7498-1]
DL-service-data-unit  (N=2)
Ph-interface-data-unit  (N=1)
3.1.38 (N)-layer [7498-1]
DL-layer  (N=2)
Ph-layer  (N=1)
3.1.39 (N)-service
[7498-1]
DL-service  (N=2)
Ph-service  (N=1)

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3.1.40 (N)-service-access-point [7498-1]
DL-service-access-point  (N=2)
Ph-service-access-point  (N=1)
3.1.41 (N)-service-access-point-address
[7498-1]
DL-service-access-point-address  (N=2)
Ph-service-access-point-address  (N=1)
3.1.42 peer-entities
[7498-1]
3.1.43 Ph-interface-control-information [7498-1]
3.1.44 Ph-interface-data [7498-1]
3.1.45 primitive name [7498-3]
3.1.46 reassembling [7498-1]
3.1.47 recombining [7498-1]
3.1.48 reset [7498-1]
3.1.49 responding-DL-address [7498-3]
3.1.50 routing [7498-1]
3.1.51 segmenting [7498-1]
3.1.52 sequencing [7498-1]
3.1.53 splitting [7498-1]
3.1.54 synonymous name [7498-3]
3.1.55 systems-management [7498-1]
3.2 Service convention terms and definitions
This document also makes use of the following terms defined in ISO/IEC 10731 as they apply
to the data-link layer:
3.2.1 acceptor
3.2.2 asymmetrical service
3.2.3 confirm (primitive);
requestor.deliver (primitive)
3.2.4 deliver (primitive)
3.2.5 DL-confirmed-facility
3.2.6 DL-facility
3.2.7 DL-local-view
3.2.8 DL-mandatory-facility
3.2.9 DL-non-confirmed-facility
3.2.10 DL-provider-initiated-facility
3.2.11 DL-provider-optional-facility
3.2.12 DL-service-primitive;
primitive

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3.2.13 DL-service-provider
3.2.14 DL-service-user
3.2.15 DL-user-optional-facility
3.2.16 indication (primitive)
acceptor.deliver (primitive)
3.2.17 multi-peer
3.2.18 request (primitive);
requestor.submit (primitive)
3.2.19 requestor
3.2.20 response (primitive);
acceptor.submit (primitive)
3.2.21 submit (primitive)
3.2.22 symmetrical service
3.3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.3.1
broadcast-Node-address
address used to send broadcasts to all DLEs on a Link
Note 1 to entry: All DLEs on a Link receive all DLPDUs where the first Node-address is equal to the Broadcast-
Node-Address. Such DLPDUs are always Unconfirmed, and their receipt is never acknowledged. The value of a
Broadcast-Node-address is 126.
3.3.2
destination-DL-route
holds a sequence of DL-route-elements, describing the complete route to the destination
Note 1 to entry: This includes both the destination DLSAP and a local component meaningful to the destination
DLS-user.
3.3.3
DL-route
combination of a Destination-DL-route and a Source-DL-route
3.3.4
DL-route-element
octet holding a Node-address or an address used by the DLS-user
3.3.5
DLSAP
distinctive point at which DL-services are provided by a single DL-entity to a single higher-
layer entity.
Note 1 to entry: This definition, derived from ISO/IEC 7498-1, is repeated here to facilitate understanding of the
critical distinction between DLSAPs and their DL-addresses.
3.3.6
DL(SAP)-address
an individual DLSAP-address, designating a single DLSAP of a single DLS-user

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SIST EN IEC 61158-4-4:2019
– 12 – IEC 61158-4-4:2019 © IEC 2019
3.3.7
(individual) DLSAP-address
DL-address that designates only one DLSAP within the extended link
Note 1 to entry: A single DL-entity may have multiple DLSAP-addresses associated with a single DLSAP.
3.3.8
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