Industrial communication networks - Fieldbus specifications -- Part 4-4: Data-link layer protocol specification - Type 4 elements

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

Réseaux de communication industriels - Spécifications des bus de terrain - Partie 4-4: Spécification des protocoles des couches de liaison de données - Eléments de type 4

Industrijska komunikacijska omrežja - Specifikacije za procesna vodila - 4-4. del: Specifikacija protokola na nivoju podatkovnih povezav - Elementi tipa 4 (IEC 61158-4-4:2007)

General Information

Status
Withdrawn
Publication Date
09-Apr-2008
Withdrawal Date
25-Oct-2016
Current Stage
9900 - Withdrawal (Adopted Project)
Start Date
25-Oct-2016
Due Date
17-Nov-2016
Completion Date
26-Oct-2016

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SLOVENSKI STANDARD
SIST EN 61158-4-4:2008
01-junij-2008
1DGRPHãþD
SIST EN 61158-4:2004
Industrijska komunikacijska omrežja - Specifikacije za procesna vodila - 4-4. del:
Specifikacija protokola na nivoju podatkovnih povezav - Elementi tipa 4 (IEC 61158
-4-4:2007)
Industrial communication networks - Fieldbus specifications -- Part 4-4: Data-link layer
protocol specification - Type 4 elements
Industrielle Kommunikationsnetze - Feldbusse - Teil 4-4: Protokollspezifikation des Data
Link Layer (Sicherungsschicht) - Typ 4-Elemente
Réseaux de communication industriels - Spécifications des bus de terrain - Partie 4-4:
Spécification des protocoles des couches de liaison de données - Eléments de type 4
Ta slovenski standard je istoveten z: EN 61158-4-4:2008
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 61158-4-4:2008 en,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 61158-4-4:2008

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SIST EN 61158-4-4:2008


EUROPEAN STANDARD
EN 61158-4-4

NORME EUROPÉENNE
February 2008
EUROPÄISCHE NORM

ICS 35.100.20; 25.040.40 Partially supersedes EN 61158-4:2004


English version


Industrial communication networks -
Fieldbus specifications -
Part 4-4: Data-link layer protocol specification -
Type 4 elements
(IEC 61158-4-4:2007)


Réseaux de communication industriels -  Industrielle Kommunikationsnetze -
Spécifications des bus de terrain - Feldbusse -
Partie 4-4: Spécification des protocoles Teil 4-4: Protokollspezifikation des
des couches de liaison de données - Data Link Layer (Sicherungsschicht) -
Eléments de type 4 Typ 4-Elemente
(CEI 61158-4-4:2007) (IEC 61158-4-4:2007)




This European Standard was approved by CENELEC on 2008-02-01. 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, 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: rue de Stassart 35, B - 1050 Brussels


© 2008 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 61158-4-4:2008 E

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SIST EN 61158-4-4:2008
EN 61158-4-4:2008 - 2 -
Foreword
The text of document 65C/474/FDIS, future edition 1 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 was approved by CENELEC as EN 61158-4-4 on 2008-02-01.
This and the other parts of the EN 61158-4 series supersede EN 61158-4:2004.
With respect to EN 61158-4:2004 the following changes were made:
– deletion of Type 6 fieldbus, and the placeholder for a Type 5 fieldbus data-link layer, for lack of market
relevance;
– addition of new fieldbus types;
– partition into multiple parts numbered 4-1, 4-2, …, 4-19.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2008-11-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2011-02-01
NOTE  Use of some of the associated protocol types is restricted by their 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 particular data-link layer
protocol type to be used with physical layer and application layer protocols in type combinations as specified explicitly in the
EN 61784 series. Use of the various protocol types in other combinations may require permission from their respective
intellectual-property-right holders.
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 61158-4-4:2007 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 60870-5-1 NOTE  Harmonized as EN 60870-5-1:1993 (not modified).
IEC 61131-2 NOTE  Harmonized as EN 61131-2:2007 (not modified).
IEC 61131-3 NOTE  Harmonized as EN 61131-3:2003 (not modified).
IEC 61158-5-4 NOTE  Harmonized as EN 61158-5-4:2008 (not modified).
IEC 61158-6-4 NOTE  Harmonized as EN 61158-6-4:2008 (not modified).
IEC 61784-1 NOTE  Harmonized as EN 61784-1:2008 (not modified).
IEC 61784-2 NOTE  Harmonized as EN 61784-2:2008 (not modified).
ISO/IEC 9646-1 NOTE  Harmonized as EN ISO/IEC 9646-1:1996 (not modified).
ISO/IEC 9646-2 NOTE  Harmonized as EN ISO/IEC 9646-2:1996 (not modified).
ISO 9314-2 NOTE  Harmonized as EN 29314-2:1993 (not modified).
__________

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SIST EN 61158-4-4:2008
- 3 - EN 61158-4-4:2008
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 61158-2 2007 Industrial communication networks - EN 61158-2 2008
Fieldbus specifications -
Part 2: Physical layer specification and service
definition


1) 2)
IEC 61158-3-4 - Industrial communication networks - EN 61158-3-4 2008
Fieldbus specifications -
Part 3-4: Data-link layer service definition -
Type 4 elements


1) 2)
ISO/IEC 7498-1 - Information technology - Open Systems EN ISO/IEC 7498-1 1995
Interconnection - Basic Reference Model:
The Basic Model


1)
ISO/IEC 7498-3 - Information technology - Open Systems - -
Interconnection - Basic Reference Model:
Naming and addressing


1)
ISO/IEC 10731 - Information technology - Open Systems - -
Interconnection - Basic reference model -
Conventions for the definition of OSI services




1)
Undated reference.
2)
Valid edition at date of issue.

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SIST EN 61158-4-4:2008

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SIST EN 61158-4-4:2008
IEC 61158-4-4
Edition 1.0 2007-12
INTERNATIONAL
STANDARD

Industrial communication networks – Fieldbus specifications –
Part 4-4: Data-link layer protocol specification – Type 4 elements


INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
X
ICS 35.100.20; 25.040.40 ISBN 2-8318-9432-8

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SIST EN 61158-4-4:2008
– 2 – 61158-4-4 © IEC:2007(E)
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 .42
Figure 18 – Complex and IP Type 4-route generation .42

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SIST EN 61158-4-4:2008
61158-4-4 © IEC:2007(E) – 3 –
Figure 19 – Simple DL-route generation.43
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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SIST EN 61158-4-4:2008
– 4 – 61158-4-4 © IEC:2007(E)
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 provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
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.
NOTE  Use of some of the associated protocol types is restricted by their 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 particular data-link layer protocol type to be used with physical layer and application layer protocols in Type
combinations as specified explicitly in the IEC 61784 series. Use of the various protocol types in other
combinations may require permission from their respective intellectual-property-right holders.
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 first edition and its companion parts of the IEC 61158-4 subseries cancel and replace
IEC 61158-4:2003. This edition of this part constitutes a minor revision. This part and its
companion Type 4 parts also cancel and replace IEC PAS 62412, published in 2005.
This edition of IEC 61158-4 includes the following significant changes from the previous
edition:
a) deletion of the former Type 6 fieldbus, and the placeholder for a Type 5 fieldbus data link
layer, for lack of market relevance;

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SIST EN 61158-4-4:2008
61158-4-4 © IEC:2007(E) – 5 –
b) addition of new types of fieldbuses;
c) division of this part into multiple parts numbered -4-1, -4-2, …, -4-19.
The text of this standard is based on the following documents:
FDIS Report on voting
65C/474/FDIS 65C/485/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.
This publication has been drafted in accordance with ISO/IEC Directives, Part 2.
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result 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.
NOTE  The revision of this standard will be synchronized with the other parts of the IEC 61158 series.
The list of all the parts of the IEC 61158 series, under the general title Industrial
communication networks – Fieldbus specifications, can be found on the IEC web site.

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SIST EN 61158-4-4:2008
– 6 – 61158-4-4 © IEC:2007(E)
INTRODUCTION
This part of IEC 61158 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/TR 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 standard 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 standard is concerned, in particular, with the communication and interworking of sensors,
effectors and other automation devices. By using this standard 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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SIST EN 61158-4-4:2008
61158-4-4 © IEC:2007(E) – 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 standard 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 standard, 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 standard also specifies conformance requirements for systems implementing these
procedures. This standard does not contain tests to demonstrate compliance with such
requirements.

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SIST EN 61158-4-4:2008
– 8 – 61158-4-4 © IEC:2007(E)
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 61158-2 (Ed.4.0), Industrial communication networks – Fieldbus specifications – Part 2:
Physical layer specification and service definition
IEC 61158-3-4, Industrial communication networks – Fieldbus specifications – Part 3-4: Data-
link layer service definition – Type 4 elements
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.
3.1 Reference model terms and definitions
This standard 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]
3.1.12 DL-connectionless-mode transmission [7498-1]
3.1.13 DL-data-sink [7498-1]

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SIST EN 61158-4-4:2008
61158-4-4 © IEC:2007(E) – 9 –
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)
3.1.40 (N)-service-access-point [7498-1]
DL-service-access-point  (N=2)
Ph-service-access-point  (N=1)

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SIST EN 61158-4-4:2008
– 10 – 61158-4-4 © IEC:2007(E)
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 standard 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
3.2.13 DL-service-provider

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SIST EN 61158-4-4:2008
61158-4-4 © IEC:2007(E) – 11 –
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
3.3.1
broadcast-Node-address
address used to send broadcasts to all DLEs on a Link
NOTE  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  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
DL-segment, link, local link
single DL-subnetwork in which any of the connected DLEs may communicate directly, without
any intervening DL-relaying, whenever all of those DLEs that are participating in an instance
of communication are simultaneously attentive to the DL-subnetwork during the
...

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