EN IEC 61158-6-2:2019

Industrial communication networks - Fieldbus specifications - Part 6-2: Application layer protocol specification - Type 2 elements

IEC 61158-6-2:2019 provides common elements for basic time-critical and non-time-critical messaging communications between application programs in an automation environment and material specific to Type 2 fieldbus. The term “time-critical” is used to represent the presence of a time-window, within which one or more specified actions are required to be completed with some defined level of certainty. Failure to complete specified actions within the time window risks failure of the applications requesting the actions, with attendant risk to equipment, plant and possibly human life. This International Standard specifies interactions between remote applications and defines the externally visible behavior provided by the Type 2 fieldbus application layer. The purpose of this document is to define the protocol provided to a) define the wire-representation of the service primitives defined in this document, and b) define the externally visible behavior associated with their transfer. This document specifies the protocol of the Type 2 fieldbus application layer, in conformance with the OSI Basic Reference Model (ISO/IEC 7498-1) and the OSI application layer structure (ISO/IEC 9545). This fourth edition includes the following significant technical changes with respect to the previous edition: - clarifications of response PDU formats in case of failure in 4.1.5; - clarifications of connection request priority definition and handling in 4.1.6.5 and 4.1.6.6; - clarification of connection remaining path in 4.1.6.12; - extensions of general syntax in 4.1.8.1; - extensions and clarifications of Identity object PDUs in 4.1.8.2; - updates of Assembly object PDUs in 4.1.8.4; - extensions and clarification of Time sync object PDUs in 4.1.8.6; - updates of Parameter object PDUs in 4.1.8.7; - extensions of Connection Manager object PDUs in 4.1.8.8; - clarifications of Connection object PDUs in 4.1.8.9; - extensions and clarifications of message and connection paths in 4.1.9; - updates of object and service class codes in 4.1.10 and error codes in 4.1.11; - updates of data types in 4.2.4, 5.1.3 and 5.2.3; - updates of the encapsulation abstract syntax in 4.3; - updates to the DLL mapping protocol machine 2 in Clause 11; - miscellaneous editorial corrections.

Industrielle Kommunikationsnetze - Feldbusse - Teil 6-2: Protokollspezifikation des Application Layer (Anwendungsschicht) - Typ 2-Elemente

Réseaux de communication industriels - Spécifications des bus de terrain - Partie 6-2: Spécification du protocole de la couche application - Éléments de type 2

L’IEC 61158-6-2:2019 fournit des éléments communs pour les communications à temps critique ou non entre des programmes d'application dans un environnement et avec un matériel d'automation spécifiques aux bus de terrain de type 2. Le terme "à temps critique" signale l'existence d'une fenêtre temporelle dans laquelle est exigée la réalisation d'une ou de plusieurs actions spécifiées, avec un niveau de certitude défini. La non-réalisation des actions spécifiées dans la fenêtre temporelle induit un risque de défaillance des applications qui demandent ces actions, avec les risques relatifs à l'équipement, les installations et éventuellement la vie humaine. Le présent document spécifie les interactions entre les applications distantes et définit le comportement, visible par un observateur externe, assuré par la couche application de bus de terrain de type 2, en termes a) de syntaxe abstraite formelle définissant les unités de données de protocole de couche application, acheminées entre les entités d'application en communication; b) de syntaxe de transfert définissant les règles de codage qui s'appliquent aux unités de données de protocole de couche application; c) du diagramme d'états de contexte application définissant le comportement de service application visible entre des entités d'application engagées dans une communication; d) de diagrammes d'états de relations d'applications définissant le comportement de communication visible entre les entités d'application en communication.

Industrijska komunikacijska omrežja - Specifikacije za procesna vodila - 6-2. del: Specifikacija protokola na aplikacijski ravni - Elementi tipa 2 (IEC 61158-6-2:2019)

Aplikacijski nivo procesnih vodil (FAL) uporabniškim programom omogoča dostop do komunikacijskega okolja procesnih vodil. Glede na to je mogoče aplikacijski nivo procesnih vodil šteti za »okno med ustreznimi aplikacijami«. Standard IEC 61158-6-2 določa skupne elemente za osnovne časovno kritične in časovno nekritične sporočilne komunikacije med aplikacijami v avtomatizacijskem okolju ter material, specifičen za procesna vodila tipa 2. Izraz »časovno kritičen« se uporablja za predstavitev prisotnosti časovnega okna, v okviru katerega se zahteva dokončanje enega ali več opredeljenih dejanj z določeno stopnjo gotovosti. Zaradi neuspešnega dokončanja opredeljenih dejanj v časovnem oknu je možna odpoved aplikacij, ki zahtevajo dejanja, pri čemer so ogroženi oprema, obrat in morda človeška življenja. Ta mednarodni standard opredeljuje interakcije med oddaljenimi aplikacijami in določa zunanje vidno vedenje, ki ga zagotavlja aplikacijski nivo procesnih vodil tipa 2 v zvezi s/z: a) formalno abstraktno sintakso, ki opredeljuje podatkovne enote protokola aplikacijskega nivoja, ki se prenašajo med aplikacijskimi osebki, ki komunicirajo, b) prenosno sintakso, ki opredeljuje pravila kodiranja, ki se uporabljajo za podatkovne enote protokola aplikacijskega nivoja, c) strojem stanj aplikacijskega konteksta, ki opredeljuje vedenje aplikacijskega opravila, vidnega med aplikacijskimi osebki, ki komunicirajo, in d) stroji stanj aplikacijskega razmerja, ki opredeljujejo komunikacijsko vedenje med aplikacijskimi osebki, ki komunicirajo. Namen tega standarda je opredeliti protokol za: a) določitev žične predstavitve primitivov opravil iz standarda IEC 61158-5-2 in b) določitev zunanje vidnega vedenja, povezanega z njihovim prenosom. Ta dokument določa protokol aplikacijskega nivoja procesnih vodil tipa 2 v skladu z osnovnim referenčnim modelom OSI (ISO/IEC 7498-1) in strukturo aplikacijskega nivoja OSI (ISO/IEC 9545).

General Information

• Status: Published
• Publication Date: 22-Aug-2019
• Withdrawal Date: 24-Jul-2022
• ICS: 25.040.40 - Industrial process measurement and control
• ICS: 35.100.70 - Application layer
• ICS: 35.110 - Networking
• Technical Committee: CLC/TC 65X - Industrial-process measurement, control and automation
• Drafting Committee: IEC/SC 65C - IEC_SC_65C
• Current Stage: 6060 - Document made available - Publishing
• Start Date: 23-Aug-2019
• Completion Date: 23-Aug-2019
• Ref Project: SIST EN IEC 61158-6-2:2019 - Industrial communication networks - Fieldbus specifications - Part 6-2: Application layer protocol specification - Type 2 elements (IEC 61158-6-2:2019)

Relations

• Replaces: EN 61158-6-2:2014 - Industrial communication networks - Fieldbus specifications - Part 6-2: Application layer protocol specification - Type 2 elements
• Effective Date: 07-Jun-2022
• Replaced By: EN IEC 61158-6-2:2023 - Industrial communication networks - Fieldbus specifications - Part 6-2: Application layer protocol specification - Type 2 elements
• Effective Date: 04-Apr-2023
• Revised: EN IEC 61158-6-26:2023 - Industrial communication networks - Fieldbus specifications - Part 6-26: Application layer protocol specification - Type 26 elements
• Effective Date: 01-Feb-2022

Overview

EN IEC 61158-6-2:2019 - "Industrial communication networks - Fieldbus specifications - Part 6-2: Application layer protocol specification - Type 2 elements" defines the application layer protocol for Type 2 fieldbus systems used in industrial automation. The standard specifies the wire representation of service primitives and the externally visible behavior of application-layer exchanges between remote applications. It covers both basic time‑critical and non‑time‑critical messaging, conforming to the OSI Basic Reference Model (ISO/IEC 7498-1) and OSI application layer structure (ISO/IEC 9545).

This fourth edition clarifies response PDU formats, connection request priority handling, connection path behavior, and extends object PDUs (Identity, Assembly, Time sync, Parameter, Connection Manager). It also updates data types, encapsulation syntax, and the DLL mapping protocol machine.

Key Topics and Requirements

• Application layer protocol definition: precise description of PDUs, service primitives and their transfer semantics for Type 2 fieldbus.
• Time‑critical messaging: requirements for operations that must complete within defined time windows to avoid application or safety failures.
• Abstract and transfer syntaxes: ASN.1-style abstract syntax, compact encoding rules, and data type dictionaries.
• Protocol elements and objects: Identity, Assembly, Time Sync, Parameter, Connection and Connection Manager object PDUs; message and connection path semantics.
• State machines and protocol machines: AP‑Context, FAL (FAL service protocol machine), ARPMs (connectionless UCMM and connection‑oriented transports) and mapping to the DLL.
• Encapsulation and transport: encapsulation abstract syntax, common packet formats and transport classes.
• Conformance and interoperability: specification of externally visible behavior to enable interoperable device implementations.

Applications

EN IEC 61158-6-2:2019 is applied in:

• Industrial automation and process control systems using Type 2 fieldbus networks.
• Systems requiring mixed time‑critical and non‑time‑critical messaging (e.g., I/O scanning, explicit messaging, time‑synchronization).
• Design and implementation of field devices, gateways, PLCs and real-time controllers that must interoperate at the application layer.
• Safety‑oriented systems where meeting time windows is essential to prevent equipment or human risk.

Who should use it

• Automation engineers and system integrators implementing fieldbus communication.
• Device manufacturers and firmware developers building Type 2 fieldbus-compliant products.
• Network architects and safety engineers responsible for deterministic messaging and time synchronization.
• Compliance and certification teams verifying interoperability and conformance.

Related Standards

• IEC 61158 series (Parts 1, 3-2, 4-2, 5-2)
• IEC 61784 (fieldbus profiles)
• IEC 61588 (precision clock sync)
• ISO/IEC 7498-1 and ISO/IEC 9545 (OSI model and application layer structure)

Keywords: EN IEC 61158-6-2:2019, fieldbus, application layer protocol, Type 2, industrial communication networks, time-critical messaging, automation, PDUs, OSI.

Standards Content (Sample)

SLOVENSKI STANDARD
01-november-2019
Nadomešča:
SIST EN 61158-6-2:2015
Industrijska komunikacijska omrežja - Specifikacije za procesna vodila - 6-2. del:
Specifikacija protokola na aplikacijski ravni - Elementi tipa 2 (IEC 61158-6-2:2019)
Industrial communication networks - Fieldbus specifications - Part 6-2: Application layer
protocol specification - Type 2 elements (IEC 61158-6-2:2019)
Industrielle Kommunikationsnetze - Feldbusse - Teil 6-2: Protokollspezifikation des
Application Layer (Anwendungsschicht) - Typ 2-Elemente (IEC 61158-6-2:2019)
Réseaux de communication industriels - Spécifications des bus de terrain - Partie 6-2:
Spécification du protocole de la couche application - Éléments de type 2 (IEC 61158-6-
2:2019)
Ta slovenski standard je istoveten z: EN IEC 61158-6-2:2019
ICS:
25.040.40 Merjenje in krmiljenje Industrial process
industrijskih postopkov measurement and control
35.100.70 Uporabniški sloj Application layer
35.110 Omreževanje Networking
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN IEC 61158-6-2

NORME EUROPÉENNE
EUROPÄISCHE NORM
August 2019
ICS 25.040.40; 35.100.70; 35.110 Supersedes EN 61158-6-2:2014 and all of its
amendments and corrigenda (if any)
English Version
Industrial communication networks - Fieldbus specifications -
Part 6-2: Application layer protocol specification - Type 2
elements
(IEC 61158-6-2:2019)
Réseaux de communication industriels - Spécifications des Industrielle Kommunikationsnetze - Feldbusse - Teil 6-2:
bus de terrain - Partie 6-2: Spécification du protocole de la Protokollspezifikation des Application Layer
couche application - Éléments de type 2 (Anwendungsschicht) - Typ 2-Elemente
(IEC 61158-6-2:2019) (IEC 61158-6-2:2019)
This European Standard was approved by CENELEC on 2019-07-25. 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 61158-6-2:2019 E

European foreword
The text of document 65C/948/FDIS, future edition 4 of IEC 61158-6-2, 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 61158-6-2:2019.
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2020-04-25
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2022-07-25
document have to be withdrawn
This document supersedes EN 61158-6-2:2014 and all of its amendments and corrigenda (if any).
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 61158-6-2:2019 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 61131-3 NOTE Harmonized as EN 61131-3
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)
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
IEC 61158-1 2019 Industrial communication networks - EN IEC 61158-1 2019
Fieldbus specifications - Part 1: Overview
and guidance for the IEC 61158 and IEC
61784 series
IEC 61158-3-2 2014 Industrial communication networks - EN 61158-3-2 2014
Fieldbus specifications - Part 3-2: Data-
lonk layer service definition - Type 2
elements
IEC 61158-3-2019  + A1 2019
2:2014/Amd 1
IEC 61158-4-2 2019 Industrial communication networks - EN IEC 61158-4-2 2019
Fieldbus specifications - Part 4-2: Data-link
layer protocol specification - Type 2
elements
IEC 61158-5-2 2019 Industrial communication networks - EN IEC 61158-5-2 2019
Fieldbus specifications - Part 5-2:
Application layer service definition - Type 2
elements
IEC 61588 2009 Precision clock synchronization protocol for - -
networked measurement and control
systems
IEC 61784-3-2 -  Industrial communication networks - - -
Profiles - Part 3-2: Functional safety
fieldbuses - Additional specifications for
CPF 2
IEC 61800-7-202 -  Adjustable speed electrical power drive EN 61800-7-202 -
systems - Part 7-202: Generic interface
and use of profiles for power drive systems
- Profile type 2 specification
IEC 62026-3 2014 Low-voltage switchgear and controlgear - - -
Controller-device interfaces (CDIs) - Part 3:
DeviceNet
ISO 639-2 -  Codes for the representation of names of - -
languages - Part-2: Alpha-3 code
ISO 11898 1993 Road vehicles - Interchange of digital - -
information - Controller area network
(CAN) for high-speed communication
ISO/IEC 7498-1 -  Information technology - Open Systems - -
Interconnection - Basic reference model:
The basic model
ISO/IEC 8824-1 -  Information technology - Abstract Syntax - -
Notation One (ASN.1): Specification of
basic notation
ISO/IEC 8825-1 -  Information technology - ASN.1 encoding - -
rules: Specification of Basic Encoding
Rules (BER), Canonical Encoding Rules
(CER) and Distinguished Encoding Rules
(DER)
ISO/IEC 9545 -  Information technology - Open Systems - -
Interconnection - Application layer
structure
ISO/IEC 10646 -  Information technology_- Universal Coded - -
Character Set (UCS)
ISO/IEC 10731 -  Information technology - Open Systems - -
Interconnection - Basic Reference Model -
Conventions for the definition of OSI
services
IEEE Std 802.1D 2004 IEEE standard for local and metropolitan
area networks – Media Access Control
(MAC) bridges
IEEE Std 802.1Q 2005 IEEE standard for local and metropolitan
area networks – Virtual bridged local area
networks
IEEE Std 802.3 2015 IEEE Standard for Ethernet - -
IETF RFC 1035 -  Domain Names - Implementation and - -
Specification
IETF RFC 1112 -  Host Extensions for IP Multicasting - -
IETF RFC 1117 -  Internet numbers - -
IETF RFC 1122 -  Requirements for Internet Hosts - - -
Communication Layers
IETF RFC 1759 -  Printer MIB - -
IETF RFC 2236 -  Internet Group Management Protocol, - -
Version 2
IETF RFC 2474 -  Definition of the Differentiated Services - -
Field (DS Field) in the IPv4 and IPv6
Headers
IETF RFC 2475 -  An Architecture for Differentiated Services - -
IETF RFC 2597 -  Assured Forwarding PHB Group - -
IETF RFC 2873 -  TCP Processing of the IPv4 Precedence - -
Field
IETF RFC 3140 -  Per Hop Behavior Identification Codes - -
IETF RFC 3246 -  An Expedited Forwarding PHB (Per-Hop - -
Behavior)
IETF RFC 3376 -  Internet Group Management Protocol, - -
Version 3
IETF RFC 4594 -  Configuration Guidelines for DiffServ - -
Service Classes
IETF RFC 791 -  Internet protocol darpa internet program - -
protocol specification
ISO/IEC/IEEE 8802--  Standard for Ethernet - -
IEC 61158-6-2 ®
Edition 4.0 2019-06
INTERNATIONAL
STANDARD
Industrial communication networks – Fieldbus specifications –

Part 6-2: Application layer protocol specification – Type 2 elements

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 25.040.40; 35.100.70; 35.110 ISBN 978-2-8322-7007-3

– 2 – IEC 61158-6-2:2019 © IEC 2019
CONTENTS
FOREWORD . 14
INTRODUCTION . 16
1 Scope . 17
1.1 General . 17
1.2 Specifications . 17
1.3 Conformance . 18
2 Normative references . 18
3 Terms, definitions, symbols, abbreviated terms and conventions . 20
3.1 Terms and definitions from other ISO/IEC standards . 20
3.1.1 Terms and definitions from ISO/IEC 7498-1 . 20
3.1.2 Terms and definitions from ISO/IEC 9545 . 21
3.1.3 Terms and definitions from ISO/IEC 8824-1 . 21
3.1.4 Terms and definitions from ISO/IEC 8825-1 . 22
3.2 Terms and definitions from IEC 61158-5-2 . 22
3.3 Additional terms and definitions . 22
3.4 Abbreviated terms and symbols . 29
3.5 Conventions . 29
3.5.1 General concept . 29
3.5.2 Attribute specification . 30
3.5.3 Common services . 30
3.5.4 State machine conventions . 34
4 Abstract syntax . 35
4.1 FAL PDU abstract syntax . 35
4.1.1 General . 35
4.1.2 PDU structure . 36
4.1.3 UCMM_PDUs . 38
4.1.4 Transport_Headers . 40
4.1.5 CM_PDUs . 43
4.1.6 CM PDU components . 57
4.1.7 MR headers . 66
4.1.8 OM_Service_PDU . 67
4.1.9 Message and connection paths . 122
4.1.10 Class, attribute and service codes . 137
4.1.11 Error codes . 143
4.2 Data abstract syntax specification . 157
4.2.1 Transport format specification . 157
4.2.2 Abstract syntax notation . 157
4.2.3 Control network data specification . 158
4.2.4 Data type specification / dictionaries . 160
4.3 Encapsulation abstract syntax . 162
4.3.1 Encapsulation protocol . 162
4.3.2 Command descriptions . 165
4.3.3 Common packet format . 177
5 Transfer syntax . 181
5.1 Compact encoding . 181
5.1.1 Encoding rules . 181

IEC 61158-6-2:2019 © IEC 2019 – 3 –
5.1.2 Encoding constraints . 182
5.1.3 Examples. 182
5.2 Data type reporting . 188
5.2.1 Object data representation. 188
5.2.2 Elementary data type reporting . 189
5.2.3 Constructed data type reporting . 190
6 Structure of FAL protocol state machines . 196
7 AP-Context state machine . 196
7.1 Overview. 196
7.2 Connection object state machine . 196
7.2.1 I/O Connection instance behavior . 196
7.2.2 Bridged Connection instance behavior . 200
7.2.3 Explicit Messaging Connection instance behavior . 201
8 FAL service protocol machine (FSPM) . 204
8.1 General . 204
8.2 Primitive definitions . 204
8.3 Parameters of primitives . 209
8.4 FSPM state machines . 209
9 Application relationship protocol machines (ARPMs) . 210
9.1 General . 210
9.2 Connection-less ARPM (UCMM) . 210
9.2.1 General . 210
9.2.2 Primitive definitions . 210
9.2.3 Parameters of primitives . 211
9.2.4 UCMM state machines . 212
9.2.5 Examples of UCMM sequences . 217
9.2.6 Management UCMM . 219
9.3 Connection-oriented ARPMs (transports) . 220
9.3.1 Transport PDU buffer . 220
9.3.2 Transport classes . 220
9.3.3 Common primitive definitions . 221
9.3.4 Parameters of common primitives . 222
9.3.5 Transport state machines – class 0 . 222
9.3.6 Transport state machines – class 1 . 226
9.3.7 Transport state machines – class 2 . 231
9.3.8 Transport state machines – class 3 . 239
9.3.9 Transport state machines – classes 4, 5, 6 . 249
9.3.10 Transport state machines – class 4 . 249
9.3.11 Transport state machines – class 5 . 249
9.3.12 Transport state machines – class 6 . 249
10 DLL mapping protocol machine 1 (DMPM 1) . 249
10.1 General . 249
10.2 Link producer . 250
10.3 Link consumer . 250
10.4 Primitive definitions . 250
10.4.1 Primitives exchanged between DMPM and ARPM . 250
10.4.2 Parameters of ARPM/DMPM primitives . 250
10.4.3 Primitives exchanged between data-link layer and DMPM . 251

– 4 – IEC 61158-6-2:2019 © IEC 2019
10.4.4 Parameters of DMPM/Data-link Layer primitives . 251
10.4.5 Network connection ID . 252
10.5 DMPM state machine . 253
10.5.1 DMPM states . 253
10.5.2 Functions used by DMPM . 254
10.6 Data-link Layer service selection. 254
11 DLL mapping protocol machine 2 (DMPM 2) . 254
11.1 General . 254
11.2 Mapping of UCMM PDUs . 255
11.2.1 General . 255
11.2.2 Common requirements for Connection Manager PDU’s . 256
11.2.3 Forward_open PDU for class 2 and class 3 connections . 258
11.2.4 Forward_open for class 0 and class 1 connections . 258
11.2.5 Forward_close . 262
11.3 Mapping of transport class 0 and class 1 PDUs. 263
11.3.1 Class 0 and class 1 PDUs. 263
11.3.2 No dependency on TCP connections . 263
11.3.3 Class 0 and class 1 packet ordering . 263
11.3.4 Screening incoming connected data . 264
11.4 Mapping of transport class 2 and class 3 PDU’s . 264
11.5 Mapping of transport classes 4 to 6. 265
11.6 IGMP Usage . 265
11.6.1 Background (informative) . 265
11.6.2 IGMP Membership Report messages . 266
11.6.3 IGMP Leave Group messages . 266
11.7 Quality of Service (QoS) for CP 2/2 messages . 267
11.7.1 Overview . 267
11.7.2 DSCP format . 267
11.7.3 IEEE 802.1D/IEEE 802.Q format . 268
11.7.4 Mapping CPF 2 traffic to DSCP and IEEE 802.1D . 268
11.7.5 CP 2/2 usage of DSCP . 269
11.7.6 CP 2/2 usage of IEEE 802.1D/IEEE 802.1Q . 269
11.7.7 User considerations with IEEE 802.1D/IEEE 802.1Q . 269
11.8 Management of an encapsulation session . 270
11.8.1 Phases of an encapsulation session . 270
11.8.2 Establishing a session . 270
11.8.3 Terminating a session . 270
11.8.4 Maintaining a session . 270
11.8.5 TCP connection management . 271
12 DLL mapping protocol machine 3 (DMPM 3) . 271
Bibliography . 272

Figure 1 – Attribute table format and terms . 30
Figure 2 – Service request/response parameter . 30
Figure 3 – Example of an STD . 34
Figure 4 – Network connection parameters . 58
Figure 5 – Priority/Tick_time bit definition . 61
Figure 6 – Member ID/EX description (WORD). 75

IEC 61158-6-2:2019 © IEC 2019 – 5 –
Figure 7 – Transport Class Trigger attribute . 110
Figure 8 – CP2/3_initial_comm_characteristics attribute format . 114
Figure 9 – Segment type . 123
Figure 10 – Port segment . 124
Figure 11 – Logical segment encoding . 126
Figure 12 – Extended network segment . 132
Figure 13 – Symbolic segment encoding . 133
Figure 14 – Encapsulation message . 162
Figure 15 – FixedLengthBitString compact encoding bit placement rules . 185
Figure 16 – Example compact encoding of a SWORD FixedLengthBitString . 186
Figure 17 – Example compact encoding of a WORD FixedLengthBitString . 186
Figure 18 – Example compact encoding of a DWORD FixedLengthBitString . 186
Figure 19 – Example compact encoding of a LWORD FixedLengthBitString . 186
Figure 20 – Example 1 of formal encoding of a structure type specification . 191
Figure 21 – Example 2 of formal encoding of a structure type specification . 191
Figure 22 – Example 3 of formal encoding of a handle structure type specification . 192
Figure 23 – Example 4 of formal encoding of a handle structure type specification . 192
Figure 24 – Example 5 of abbreviated encoding of a structure type specification . 193
Figure 25 – Example 1 of formal encoding of an array type specification. 194
Figure 26 – Example 2 of formal encoding of an array type specification. 194
Figure 27 – Example 1 of abbreviated encoding of an array type specification . 195
Figure 28 – Example 2 of abbreviated encoding of an array type specification . 195
Figure 29 – I/O Connection object state transition diagram . 196
Figure 30 – Bridged Connection object state transition diagram . 200
Figure 31 – Explicit Messaging Connection object state transition diagram . 202
Figure 32 – State transition diagram of UCMM client9 . 212
Figure 33 – State transition diagram of high–end UCMM server . 214
Figure 34 – State transition diagram of low–end UCMM server . 216
Figure 35 – Sequence diagram for a UCMM with one outstanding message . 218
Figure 36 – Sequence diagram for a UCMM with multiple outstanding messages . 219
Figure 37 – TPDU buffer . 220
Figure 38 – Data flow diagram using a client transport class 0 and server transport
class 0 . 223
Figure 39 – Sequence diagram of data transfer using transport class 0 . 223
Figure 40 – Class 0 client STD . 224
Figure 41 – Class 0 server STD . 225
Figure 42 – Data flow diagram using client transport class 1 and server transport

class 1 . 226
Figure 43 – Sequence diagram of data transfer using client transport class 1 and
server transport class 1 . 227
Figure 44 – Class 1 client STD . 229
Figure 45 – Class 1 server STD . 230
Figure 46 – Data flow diagram using client transport class 2 and server transport
class 2 . 232

– 6 – IEC 61158-6-2:2019 © IEC 2019
Figure 47 – Diagram of data transfer using client transport class 2 and server transport
class 2 without returned data . 233
Figure 48 – Sequence diagram of data transfer using client transport class 2 and

server transport class 2 with returned data . 234
Figure 49 – Class 2 client STD . 235
Figure 50 – Class 2 server STD . 237
Figure 51 – Data flow diagram using client transport class 3 and server transport
class 3 . 240
Figure 52 – Sequence diagram of data transfer using client transport class 3 and
server transport class 3 without returned data . 241
Figure 53 – Sequence diagram of data transfer using client transport class 3 and

server transport class 3 with returned data . 242
Figure 54 – Class 3 client STD . 244
Figure 55 – Class 3 server STD . 247
Figure 56 – Data flow diagram for a link producer and consumer . 249
Figure 57 – State transition diagram for a link producer . 253
Figure 58 – State transition diagram for a link consumer . 254
Figure 59 – DS field in the IP header . 268
Figure 60 – IEEE 802.1Q tagged frame . 268

Table 1 – Get_Attributes_All response service rules . 31
Table 2 – Example class level object/service specific response data of
Get_Attributes_All . 31
Table 3 – Example Get_Attributes_All data array method . 32
Table 4 – Set_Attributes_All request service rules . 33
Table 5 – Example Set_Attributes_All attribute ordering method . 33
Table 6 – Example Set_Attributes_All data array method . 33
Table 7 – State event matrix format . 35
Table 8 – Example state event matrix . 35
Table 9 – UCMM_PDU header format . 39
Table 10 – UCMM command codes . 39
Table 11 – Transport class 0 header . 40
Table 12 – Transport class 1 header . 40
Table 13 – Transport class 2 header . 40
Table 14 – Transport class 3 header . 40
Table 15 – Real-time data header – exclusive owner . 41
Table 16 – Real-time data header– redundant owner . 41
Table 17 – Forward_Open request format . 46
Table 18 – Forward_Open_Good response format . 46
Table 19 – Forward_Open_Bad response format . 47
Table 20 – Large_Forward_Open request format . 48
Table 21 – Large_Forward_Open_Good response format . 48
Table 22 – Large_Forward_Open_Bad response format . 49
Table 23 – Forward_Close request format. 50
Table 24 – Forward_Close_Good response format . 50

IEC 61158-6-2:2019 © IEC 2019 – 7 –
Table 25 – Forward_Close_Bad response format . 51
Table 26 – Unconnected_Send request format . 51
Table 27 – Unconnected_Send_Good response format . 52
Table 28 – Unconnected_Send_Bad response format . 53
Table 29 – Unconnected_Send request format (modified) . 54
Table 30 – Unconnected_Send_Good response format (modified) . 54
Table 31 – Unconnected_Send_Bad response format (modified) . 55
Table 32 – Get_Connection_Data request format . 55
Table 33 – Get_Connection_Data response format . 55
Table 34 – Search_Connection_Data request format . 56
Table 35 – Get_Connection_Owner request format . 57
Table 36 – Get_Connection_Owner response format . 57
Table 37 – Time-out multiplier . 60
Table 38 – Tick time units . 61
Table 39 – Encoded application path ordering. 65
Table 40 – Transport class, trigger and Is_Server format . 66
Table 41 – MR_Request_Header format . 66
Table 42 – MR_Response_Header format . 67
Table 43 – Structure of Get_Attributes_All_ResponsePDU body . 67
Table 44 – Structure of Set_Attributes_All_RequestPDU body . 68
Table 45 – Structure of Get_Attribute_List_RequestPDU body . 68
Table 46 – Structure of Get_Attribute_List_ResponsePDU body . 68
Table 47 – Structure of Set_Attribute_List_RequestPDU body . 68
Table 48 – Structure of Set_Attribute_List_ResponsePDU body . 69
Table 49 – Structure of Reset_RequestPDU body . 69
Table 50 – Structure of Reset_ResponsePDU body . 69
Table 51 – Structure of Start_RequestPDU body . 69
Table 52 – Structure of Start_ResponsePDU body . 69
Table 53 – Structure of Stop_RequestPDU body . 70
Table 54 – Structure of Stop_ResponsePDU body . 70
Table 55 – Structure of Create_RequestPDU body . 70
Table 56 – Structure of Create_ResponsePDU body . 70
Table 57 – Structure of Delete_RequestPDU body . 70
Table 58 – Structure of Delete_ResponsePDU body . 70
Table 59 – Structure of Get_Attribute_Single_ResponsePDU body . 71
Table 60 – Structure of Set_Attribute_Single_RequestPDU body . 71
Table 61 – Structure of Set_Attribute_Single_ResponsePDU body . 71
Table 62 – Structure of Find_Next_Object_Instance_RequestPDU body . 71
Table 63 – Structure of Find_Next_Object_Instance_ResponsePDU body . 72
Table 64 – Structure of Apply_Attributes_RequestPDU body . 72
Table 65 – Structure of Apply_Attributes_ResponsePDU body . 72
Table 66 – Structure of Save_RequestPDU body . 72
Table 67 – Structure of Save_ResponsePDU body . 72

– 8 – IEC 61158-6-2:2019 © IEC 2019
Table 68 – Structure of Restore_RequestPDU body . 73
Table 69 – Structure of Restore_ResponsePDU body . 73
Table 70 – Structure of Get_Member_ResponsePDU body . 73
Table 71 – Structure of Set_Member_RequestPDU body . 73
Table 72 – Structure of Set_Member_ResponsePDU body . 73
Table 73 – Structure of Insert_Member_RequestPDU body . 74
Table 74 – Structure of Insert_Member_ResponsePDU body . 74
Table 75 – Structure of Remove_Member_ResponsePDU body . 74
Table 76 – Common structure of _Member_RequestPDU body (basic format) . 75
Table 77 – Common structure of _Member_ResponsePDU body (basic format) . 75
Table 78 – Common structure of _Member_RequestPDU body (extended format) . 76
Table 79 – Common structure of _Member_ResponsePDU body (extended format) . 76
Table 80 – Extended Protocol ID. 76
Table 81 – Structure of _Member_RequestPDU body (Multiple Sequential Members) . 77
Table 82 – Structure of _Member_ResponsePDU body (Multiple Sequential Members) . 77
Table 83 – Structure of _Member_RequestPDU body (International String Selection) . 78
Table 84 – Structure of _Member_ResponsePDU body (International String Selection) . 78
Table 85 – Structure of Group_Sync_RequestPDU body . 78
Table 86 – Structure of Group_Sync_ResponsePDU body . 78
Table 87 – Structure of Multiple_Service_Packet_RequestPDU body . 79
Table 88 – Structure of Multiple_Service_Packet_ResponsePDU body . 79
Table 89 – Identity object class attributes . 80
Table 90 – Identity object instance attributes . 80
Table 91 – Identity object bit def
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