IEC 61158-4-3:2014

IEC 61158-4-3 ®
Edition 3.0 2014-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Industrial communication networks – Fieldbus specifications –
Part 4-3: Data-link layer protocol specification – Type 3 elements

Réseaux de communication industriels – Spécifications des bus de terrain –
Partie 4-3: Spécification du protocole de la couche liaison de données –
Éléments de type 3
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IEC 61158-4-3 ®
Edition 3.0 2014-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Industrial communication networks – Fieldbus specifications –

Part 4-3: Data-link layer protocol specification – Type 3 elements

Réseaux de communication industriels – Spécifications des bus de terrain –

Partie 4-3: Spécification du protocole de la couche liaison de données – Éléments

de type 3
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX XH
ICS 25.04.40; 35.100.20; 35.110 ISBN 978-2-8322-1721-4

– 2 – IEC 61158-4-3:2014 © IEC 2014

CONTENTS
FOREWORD . 6

INTRODUCTION . 8

1 Scope . 9

1.1 General . 9

1.2 Specifications . 9

1.3 Procedures . 9

1.4 Applicability . 9

1.5 Conformance . 10
2 Normative references . 10
3 Terms, definitions, symbols and abbreviations . 10
3.1 Reference model terms and definitions . 10
3.2 Service convention terms and definitions . 12
3.3 Common terms and definitions . 13
3.4 Additional Type 3 definitions. 15
3.5 Common symbols and abbreviations . 17
3.6 Type 3 symbols and abbreviations . 18
4 Common DL-protocol elements . 22
4.1 Frame check sequence . 22
5 Overview of the DL-protocol . 25
5.1 General . 25
5.2 Overview of the medium access control and transmission protocol . 25
5.3 Transmission modes and DL-entity . 26
5.4 Service assumed from the PhL . 31
5.5 Operational elements . 35
5.6 Cycle and system reaction times . 50
6 General structure and encoding of DLPDUs, and related elements of procedure . 53
6.1 DLPDU granularity . 53
6.2 Length octet (LE, LEr) . 54
6.3 Address octet . 54
6.4 Control octet (FC) . 57
6.5 DLPDU content error detection . 61
6.6 DATA_UNIT . 61

6.7 Error control procedures . 62
7 DLPDU-specific structure, encoding and elements of procedure . 63
7.1 DLPDUs of fixed length with no data field . 63
7.2 DLPDUs of fixed length with data field . 65
7.3 DLPDUs with variable data field length . 67
7.4 Token DLPDU . 68
7.5 ASP DLPDU . 69
7.6 SYNCH DLPDU . 69
7.7 Time Event (TE) DLPDU . 69
7.8 Clock Value (CV) DLPDU . 70
7.9 Transmission procedures . 70
8 Other DLE elements of procedure. 73
8.1 DL-entity initialization . 73
8.2 States of the media access control of the DL-entity . 74

8.3 Clock synchronization protocol . 80

Annex A (normative) DL-Protocol state machines . 85

A.1 Overall structure . 85

A.2 Variation of state machines in different devices . 86

A.3 DL Data Resource . 87

A.4 FLC / DLM . 91

A.4.1 Primitive definitions . 91

A.4.2 State machine description . 96

A.5 MAC . 115

A.5.1 Primitive definitions . 115
A.5.2 State machine description . 115
A.6 SRU . 141
A.6.1 Overview . 141
A.6.2 Character send SM(CTX) . 142
A.6.3 Character receive SM (CRX) . 143
A.6.4 Timer-SM (TIM) . 143
A.6.5 Primitive definition of SRC . 144
A.6.6 State machine description . 145
Annex B (informative) Type 3 (synchronous): exemplary FCS implementations . 160
Annex C (informative) Type 3: Exemplary token procedure and message transfer
periods . 162
C.1 Procedure of token passing . 162
C.2 Examples for token passing procedure . 163
C.3 Examples for message transfer periods – asynchronous transmission . 168
Bibliography . 170

Figure 1 – Relationships of DLSAPs, DLSAP-addresses and group DL-addresses . 14
Figure 2 – Logical token-passing ring . 28
Figure 3 – PhL data service for asynchronous transmission . 32
Figure 4 – Idle time T . 37
ID1
Figure 5 – Idle time T (SDN, CS) . 38
ID2
Figure 6 – Idle time T (MSRD) . 38
ID2
Figure 7 – Slot time T . 39
SL1
Figure 8 – Slot time T . 39
SL2
Figure 9 – Slot time T . 44
SL1
Figure 10 – Slot time T . 44
SL2
Figure 11 – Token transfer period . 50
Figure 12 – Message transfer period . 51
Figure 13 – UART character . 53
Figure 14 – Octet structure . 54
Figure 15 – Length octet coding . 54
Figure 16 – Address octet coding . 55
Figure 17 – DAE/SAE octet in the DLPDU . 56
Figure 18 – Address extension octet . 56
Figure 19 – FC octet coding for send/request DLPDUs . 58
Figure 20 – FC octet coding for acknowledgement or response DLPDUs . 58

– 4 – IEC 61158-4-3:2014 © IEC 2014

Figure 21 – FCS octet coding. 61

Figure 22 – Data field . 62

Figure 23 – Ident user data . 62

Figure 24 – DLPDUs of fixed length with no data field . 64

Figure 25 – DLPDUs of fixed length with no data field . 65

Figure 26 – DLPDUs of fixed length with data field . 66

Figure 27 – DLPDUs of fixed length with data field . 66

Figure 28 – DLPDUs with variable data field length . 67

Figure 29 – DLPDUs with variable data field length . 68
Figure 30 – Token DLPDU . 68
Figure 31 – Token DLPDU . 69
Figure 32 – Send/request DLPDU of fixed length with no data . 70
Figure 33 – Token DLPDU and send/request DLPDU of fixed length with data . 71
Figure 34 – Send/request DLPDU with variable data field length . 71
Figure 35 – Send/request DLPDU of fixed length with no data . 72
Figure 36 – Token DLPDU and send/request DLPDU of fixed length with data . 72
Figure 37 – Send/request DLPDU with variable data field length . 73
Figure 38 – DL-state-diagram . 75
Figure 39 – Overview of clock synchronization . 81
Figure 40 – Time master state machine . 82
Figure 41 – Time receiver state machine . 83
Figure 42 – Clock synchronization . 84
Figure A.1 – Structuring of the protocol machines . 86
Figure A.2 – Structure of the SRU Machine . 142
Figure B.1 – Example of FCS generation for Type 3 (synchronous) . 160
Figure B.2 – Example of FCS syndrome checking on reception for Type 3
(synchronous) . 160
Figure C.1 – Derivation of the token holding time (T ) . 163
TH
Figure C.2 – No usage of token holding time (T ) . 164
TH
Figure C.3 – Usage of token holding time (T ) for message transfer (equivalence
TH
between T of each Master station) . 165
TH
Figure C.4 – Usage of token holding time (T ) in different working load situations . 167
TH
Table 1 – FCS length, polynomials and constants by Type 3 synchronous . 23
Table 2 – Characteristic features of the fieldbus data-link protocol . 25
Table 3 – Transmission function code . 59
Table 4 – FCB, FCV in responder . 60
Table 5 – Operating parameters . 73
Table A.1 – Assignment of state machines . 87
Table A.2 – Data resource . 88
Table A.3 – Primitives issued by DL-User to FLC . 91
Table A.4 – Primitives issued by FLC to DL-User . 92
Table A.5 – Primitives issued by DL-User to DLM . 94
Table A.6 – Primitives issued by DLM to DL-User . 94

Table A.7 – Parameters used with primitives exchanged between DL-User and FLC . 95

Table A.8 – Parameters used with primitives exchanged between DL-User and DLM . 95

Table A.9 – FLC/DLM state table . 96

Table A.10 – FLC / DLM function table . 108

Table A.11 – Primitives issued by DLM to MAC. 115

Table A.12 – Primitives issued by MAC to DLM. 115

Table A.13 – Parameters used with primitives exchanged between DLM and MAC . 115

Table A.14 – Local MAC variables . 116

Table A.15 – MAC state table . 117
Table A.16 – MAC function table . 137
Table A.17 – Primitives issued by DLM to SRC . 144
Table A.18 – Primitives issued by SRC to DLM . 144
Table A.19 – Primitives issued by MAC to SRC. 144
Table A.20 – Primitives issued by SRC to MAC. 145
Table A.21 – Parameters used with primitives exchanged between MAC and SRC . 145
Table A.22 – FC structure . 145
Table A.23 – Local variables of SRC . 146
Table A.24 – SRC state table . 147
Table A.25 – SRC functions . 159

– 6 – IEC 61158-4-3:2014 © IEC 2014

INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________
INDUSTRIAL COMMUNICATION NETWORKS –

FIELDBUS SPECIFICATIONS –
Part 4-3: Data-link layer protocol specification –

Type 3 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.
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 61158-4-3 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 2010. This edition
constitutes a technical revision.

The changes with respect to the previous edition are listed below:

• Corrections in Table A.15 and Table A.16;

• Expired patent removed and added new patents.

The text of this standard is based on the following documents:

FDIS Report on voting
65C/762/FDIS 65C/772/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 the ISO/IEC Directives, Part 2.
A list of all parts of the IEC 61158 series, published under the general title Industrial
communication networks – Fieldbus specifications, can be found on the IEC web site
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.
– 8 – IEC 61158-4-3:2014 © IEC 2014

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 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.
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 its profile parts. Use of the various protocol types in other combinations may
require permission from their respective intellectual-property-right holders.
The International Electrotechnical Commission (IEC) draws attention to the fact that it is
claimed that compliance with this document may involve the use of a patent concerning Type
3 elements and possibly other types given in the normative elements of this standard.
The following patent rights for Type 3 have been announced by [SI]:
Publication Title
EP 1253494 Control device with fieldbus

IEC takes no position concerning the evidence, validity and scope of these patent rights.
The holder of these patent rights has assured IEC that he/she is willing to negotiate licenses

either free of charge or under reasonable and non-discriminatory terms and conditions with
applicants throughout the world. In this respect, the statement of the holder of these patent
rights is registered with IEC. Information may be obtained from:
[SI]: Siemens AG
CT IP M&A
Otto-Hahn-Ring 6
D-81739 Munich
Germany
Attention is drawn to the possibility that some of the elements of this document may be the
subject of patent rights other than those identified above. IEC shall not be held responsible for
identifying any or all such patent rights.
ISO (www.iso.org/patents) and IEC (http://patents.iec.ch) maintain on-line databases of
patents relevant to their standards. Users are encouraged to consult the databases for the
most up to date information concerning patents.

INDUSTRIAL COMMUNICATION NETWORKS –

FIELDBUS SPECIFICATIONS –
Part 4-3: Data-link layer protocol specification –

Type 3 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 communication opportunities to a pre-selected “master” subset of data-
link entities in a cyclic asynchronous manner, sequentially to each of those data-link entities.
Other data-link entities communicate only as permitted and delegated by those master data-
link entities.
For a given master, its communications with other data-link entities can be cyclic, or acyclic
with prioritized access, or a combination of the two.
This protocol provides a means of sharing the available communication resources in a fair
manner. There are provisions for time synchronization and for isochronous operation.
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.

– 10 – IEC 61158-4-3:2014 © IEC 2014

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.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and

are indispensable for its application. 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.
IEC 61131-3, Programmable controllers – Part 3: Programming languages
IEC 61158-2:2014, Industrial communication networks – Fieldbus specifications – Part 2:
Physical layer specification and service definition
IEC 61158-3-3, Industrial communication networks – Fieldbus specifications – Part 3-3: Data
link service definition – Type 3 elements
ISO/IEC 2022, Information technology – Character code structure and extension techniques
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
ISO 1177, Information processing – Character structure for start/stop and synchronous
character oriented transmission
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 [ISO/IEC 7498-3]
3.1.2 calling-DL-address [ISO/IEC 7498-3]
3.1.3 centralized multi-end-point-connection [ISO/IEC 7498-3]

3.1.4 correspondent (N)-entities [ISO/IEC 7498-3]
correspondent DL-entities  (N=2)

correspondent Ph-entities  (N=1)

3.1.5 demultiplexing [ISO/IEC 7498-3]

3.1.6 DL-address [ISO/IEC 7498-3]

3.1.7 DL-address-mapping [ISO/IEC 7498-3]

3.1.8 DL-connection [ISO/IEC 7498-3]

3.1.9 DL-connection-end-point [ISO/IEC 7498-3]
3.1.10 DL-connection-end-point-identifier [ISO/IEC 7498-3]
3.1.11 DL-connection-mode transmission [ISO/IEC 7498-3]
3.1.12 DL-connectionless-mode transmission [ISO/IEC 7498-3]
3.1.13 DL-data-sink [ISO/IEC 7498-3]
3.1.14 DL-data-source [ISO/IEC 7498-3]
3.1.15 DL-duplex-transmission [ISO/IEC 7498-3]
3.1.16 DL-facility [ISO/IEC 7498-3]
3.1.17 DL-local-view [ISO/IEC 7498-3]
3.1.18 DL-name [ISO/IEC 7498-3]
3.1.19 DL-protocol [ISO/IEC 7498-3]
3.1.20 DL-protocol-connection-identifier [ISO/IEC 7498-3]
3.1.21 DL-protocol-control-information [ISO/IEC 7498-3]
3.1.22 DL-protocol-data-unit [ISO/IEC 7498-3]
3.1.23 DL-protocol-version-identifier [ISO/IEC 7498-3]
3.1.24 DL-relay [ISO/IEC 7498-3]
3.1.25 DL-service-connection-identifier [ISO/IEC 7498-3]
3.1.26 DL-service-data-unit [ISO/IEC 7498-3]
3.1.27 DL-simplex-transmission [ISO/IEC 7498-3]
3.1.28 DL-subsystem [ISO/IEC 7498-3]
3.1.29 DL-user-data [ISO/IEC 7498-3]
3.1.30 flow control [ISO/IEC 7498-3]
3.1.31 layer-management [ISO/IEC 7498-3]
3.1.32 multiplexing [ISO/IEC 7498-3]
3.1.33 naming-(addressing)-authority [ISO/IEC 7498-3]
3.1.34 naming-(addressing)-domain [ISO/IEC 7498-3]

– 12 – IEC 61158-4-3:2014 © IEC 2014

3.1.35 naming-(addressing)-subdomain [ISO/IEC 7498-3]

3.1.36 (N)-entity [ISO/IEC 7498-3]

DL-entity
Ph-entity
3.1.37 (N)-interface-data-unit [ISO/IEC 7498-3]

DL-service-data-unit  (N=2)
Ph-interface-data-unit  (N=1)

3.1.38 (N)-layer [ISO/IEC 7498-3]

DL-layer  (N=2)
Ph-layer  (N=1)
3.1.39 (N)-service [ISO/IEC 7498-3]
DL-service  (N=2)
Ph-service  (N=1)
3.1.40 (N)-service-access-point [ISO/IEC 7498-3]
DL-service-access-point  (N=2)
Ph-service-access-point  (N=1)
3.1.41 (N)-service-access-point-address [ISO/IEC 7498-3]
DL-service-access-point-address  (N=2)
Ph-service-access-point-address  (N=1)
3.1.42 peer-entities [ISO/IEC 7498-3]
3.1.43 Ph-interface-control-information [ISO/IEC 7498-3]
3.1.44 Ph-interface-data [ISO/IEC 7498-3]
3.1.45 primitive name [ISO/IEC 7498-3]
3.1.46 reassembling [ISO/IEC 7498-3]
3.1.47 recombining [ISO/IEC 7498-3]
3.1.48 reset
[ISO/IEC 7498-3]
3.1.49 responding-DL-address [ISO/IEC 7498-3]
3.1.50 routing [ISO/IEC 7498-3]
3.1.51 segmenting [ISO/IEC 7498-3]

3.1.52 sequencing [ISO/IEC 7498-3]
3.1.53 splitting [ISO/IEC 7498-3]
3.1.54 synonymous name [ISO/IEC 7498-3]
3.1.55 systems-management [ISO/IEC 7498-3]

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
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 Common terms and definitions

For the purposes of this document, the following terms and definitions apply.
NOTE Many definitions are common to more than one protocol Type; they are not necessarily used by all protocol
Types.
3.3.1
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 period(s) of
attempted communication
– 14 – IEC 61158-4-3:2014 © IEC 2014

3.3.2
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. (See Figure 1.)

DLS-user-entity
DLS-user-entity
DLS-users
DLSAP DLSAP DLSAP
DLSAP-
address DLSAP-
DLSAP-
group DL-
address
addresses
address
DL-layer
DL-entity
PhSA P PhSA P
Ph-layer
NOTE 1 DLSAPs and PhSAPs are depicted as ovals spanning the boundary between two adjacent layers.
NOTE 2 DL-addresses are depicted as designating small gaps (points of access) in the DLL portion of a DLSAP.
NOTE 3 A single DL-entity may have multiple DLSAP-addresses and group DL-addresses associated with a
single DLSAP.
Figure 1 – Relationships of DLSAPs, DLSAP-addresses and group DL-addresses
3.3.3
DL(SAP)-address
either an individual DLSAP-address, designating a single DLSAP of a single DLS-user, or a
group DL-address potentially designating multiple DLSAPs, each of a single DLS-user
Note 1 to entry: This terminology is chosen because ISO/IEC 7498-3 does
...