IEC 61784-2-18:2023

IEC 61784-2-18 ®
Edition 1.0 2023-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Industrial networks – Profiles –
Part 2-18: Additional real-time fieldbus profiles based on ISO/IEC/IEEE 8802-3 –
CPF 18
Réseaux industriels – Profils –
Partie 2-18: Profils de bus de terrain supplémentaires pour les réseaux en temps
réel fondés sur l’ISO/IEC/IEEE 8802-3 – CPF 18

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IEC 61784-2-18 ®
Edition 1.0 2023-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Industrial networks – Profiles –

Part 2-18: Additional real-time fieldbus profiles based on ISO/IEC/IEEE 8802-3 –

CPF 18
Réseaux industriels – Profils –

Partie 2-18: Profils de bus de terrain supplémentaires pour les réseaux en

temps réel fondés sur l’ISO/IEC/IEEE 8802-3 – CPF 18

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 35.100.20; 35.240.50 ISBN 978-2-8322-6907-7

– 2 – IEC 61784-2-18:2023 © IEC 2023

CONTENTS
FOREWORD . 3

INTRODUCTION . 5

1 Scope . 6

2 Normative references . 6

3 Terms, definitions, abbreviated terms, acronyms, and conventions . 7

3.1 Terms and definitions . 7

3.2 Abbreviated terms and acronyms . 8

3.3 Symbols . 8
3.4 Conventions . 8
4 CPF 18 (SafetyNET p) – RTE communication profiles . 9
4.1 General overview . 9
4.2 CP 18/1 . 9
4.2.1 Physical layer . 9
4.2.2 Data link layer . 9
4.2.3 Application layer . 12
4.2.4 Performance indicator selection . 14
4.3 CP 18/2 . 17
4.3.1 Physical layer . 17
4.3.2 Data link layer . 17
4.3.3 Application layer . 20
4.3.4 Performance indicator selection . 21
Bibliography . 24

Table 1 – CPF 18 symbols . 8
Table 2 – CP 18/1: DLL service selection . 9
Table 3 – CP 18/1: DLL protocol selection . 11
Table 4 – CP 18/1: AL service selection . 13
Table 5 – CP 18/1: AL protocol selection . 14
Table 6 – CP 18/1: PI overview . 14
Table 7 – CP 18/1: PI dependency matrix . 15
Table 8 – CP 18/2: DLL service selection . 17

Table 9 – CP 18/2: DLL protocol selection . 18
Table 10 – CP 18/2: AL service selection . 20
Table 11 – CP 18/2: AL protocol selection . 21
Table 12 – CP 18/2: PI overview . 22
Table 13 – CP 18/2: PI dependency matrix . 22

INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________
INDUSTRIAL NETWORKS –
PROFILES –
Part 2-18: Additional real-time fieldbus profiles

based on ISO/IEC/IEEE 8802-3 –

CPF 18
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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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
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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 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 layer protocol type to
be used with other layer protocols of the same type, or in other type combinations explicitly
authorized by their respective intellectual property right holders.
NOTE Combinations of protocol types are specified in the IEC 61784-1 series and the IEC 61784-2 series.
IEC 61784-2-18 has been prepared by subcommittee 65C: Industrial networks, of IEC technical
committee 65: Industrial-process measurement, control and automation. It is an International
Standard.
This first edition, together with the other parts of the same series, cancels and replaces the
fourth edition of IEC 61784-2 published in 2019. This first edition constitutes a technical revision.

– 4 – IEC 61784-2-18:2023 © IEC 2023

This edition includes the following significant technical changes with respect to

IEC 61784-2:2019:
a) split of the original IEC 61784-2 into several subparts, one subpart for the material of a

generic nature, and one subpart for each Communication Profile Family specified in the

original document.
The text of this International Standard is based on the following documents:

Draft Report on voting
65C/1209/FDIS 65C/1237/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
A list of all parts of the IEC 61784-2 series, published under the general title
Industrial networks – Profiles – Part 2: Additional real-time fieldbus profiles based on
ISO/IEC/IEEE 8802-3, can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
INTRODUCTION
The IEC 61784-2 series provides additional Communication Profiles (CP) to the existing

Communication Profile Families (CPF) of the IEC 61784-1 series and additional CPFs with one

or more CPs. These profiles meet the industrial automation market objective of identifying Real-

Time Ethernet (RTE) communication networks coexisting with ISO/IEC/IEEE 8802-3 –

commonly known as Ethernet. These RTE communication networks use provisions of

ISO/IEC/IEEE 8802-3 for the lower communication stack layers and additionally provide more

predictable and reliable real-time data transfer and means for support of precise

synchronization of automation equipment.

More specifically, these profiles help to correctly state the compliance of RTE communication
networks with ISO/IEC/IEEE 8802-3, and to avoid the spreading of divergent implementations.
Adoption of Ethernet technology for industrial communication between controllers and even for
communication with field devices promotes the use of Internet technologies in the field area.
This availability would be unacceptable if it causes the loss of features required in the field area
for industrial communication automation networks, such as:
• real-time,
• synchronized actions between field devices like drives,
• efficient, frequent exchange of very small data records.
These new RTE profiles can take advantage of the improvements of Ethernet networks in terms
of transmission bandwidth and network span.
Another implicit but essential requirement is that the typical Ethernet communication
capabilities, as used in the office world, are fully retained, so that the software involved remains
applicable.
The market is in need of several network solutions, each with different performance
characteristics and functional capabilities, matching the diverse application requirements. RTE
performance indicators, whose values will be provided with RTE devices based on
communication profiles specified in the IEC 61784-2 series, enable the user to match network
devices with application-dependent performance requirements of an RTE network.

– 6 – IEC 61784-2-18:2023 © IEC 2023

INDUSTRIAL NETWORKS –
PROFILES –
Part 2-18: Additional real-time fieldbus profiles

based on ISO/IEC/IEEE 8802-3 –

CPF 18
1 Scope
This part of IEC 61784-2 defines Communication Profile Family 18 (CPF 18). CPF 18 specifies
a set of Real-Time Ethernet (RTE) communication profiles (CPs) and related network
components based on the IEC 61158 series (Type 22), ISO/IEC/IEEE 8802-3 and other
standards.
For each RTE communication profile, this document also specifies the relevant RTE
performance indicators and the dependencies between these RTE performance indicators.
NOTE 1 All CPs are based on standards or draft standards or International Standards published by the IEC or on
standards or International Standards established by other standards bodies or open standards processes.
NOTE 2 The RTE communication profile(s) use ISO/IEC/IEEE 8802-3 communication networks and its related
network components or IEC 61588 and in some cases amend those standards to obtain RTE features.
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 the IEC 61784-1 series and the IEC 61784-2 series, 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 61158 (all parts), Industrial communication networks – Fieldbus specifications
IEC 61158-3-22:2014, Industrial communication networks – Fieldbus specifications – Part 3-22:
Data-link layer service definition – Type 22 elements

IEC 61158-4-22:2014, Industrial communication networks – Fieldbus specifications – Part 4-22:
Data-link layer protocol specification – Type 22 elements
IEC 61158-5-22:2014, Industrial communication networks – Fieldbus specifications – Part 5-22:
Application layer service definition – Type 22 elements
IEC 61158-6-22:2014, Industrial communication networks – Fieldbus specifications – Part 6-22:
Application layer protocol specification – Type 22 elements
IEC 61588, Precision clock synchronization protocol for networked measurement and control
systems
IEC 61784-2-0:2023, Industrial networks – Profiles – Part 2-0: Additional real-time fieldbus
profiles based on ISO/IEC/IEEE 8802-3 – General concepts and terminology

ISO/IEC/IEEE 8802-3, Telecommunications and exchange between information technology

systems – Requirements for local and metropolitan area networks – Part 3: Standard for

Ethernet
IEEE Std 802-2014, IEEE Standard for Local and Metropolitan Area Networks: Overview and

Architecture
IEEE Std 802.1AB-2016, IEEE Standard for Local and metropolitan area networks – Station and

Media Access Control Connectivity Discovery

IEEE Std 802.1AS-2020, IEEE Standard for Local and Metropolitan Area Networks – Timing

and Synchronization for Time-Sensitive Applications
IEEE Std 802.1Q-2018, IEEE Standard for Local and Metropolitan Area Networks – Bridges and
Bridged Networks
IETF RFC 768, J. Postel, User Datagram Protocol, August 1980, available at
https://www.rfc-editor.org/info/rfc768 [viewed 2022-02-18]
IETF RFC 791, J. Postel, Internet Protocol, September 1981, available at
https://www.rfc-editor.org/info/rfc791 [viewed 2022-02-18]
IETF RFC 792, J. Postel, Internet Control Message Protocol, September 1981, available at
https://www.rfc-editor.org/info/rfc792 [viewed 2022-02-18]
IETF RFC 793, J. Postel, Transmission Control Protocol, September 1981, available at
https://www.rfc-editor.org/info/rfc793 [viewed 2022-02-18]
3 Terms, definitions, abbreviated terms, acronyms, and conventions
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 61784-2-0,
ISO/IEC/IEEE 8802-3, IEEE Std 802-2014, IEEE Std 802.1AB-2016, IEEE Std 802.1AS-2020,
IEEE Std 802.1Q-2018 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at https://www.electropedia.org/

• ISO Online browsing platform: available at https://www.iso.org/obp
3.1.1
logical double line
sequence of root device and all ordinary devices processing the DLPDU in forward and
backward direction
3.1.2
real time frame line
RTFL
communication model with devices communicating in a logical double line
3.1.3
real time frame network
RTFN
communication model with devices communicating in a switched network

– 8 – IEC 61784-2-18:2023 © IEC 2023

3.2 Abbreviated terms and acronyms

For the purposes of this document, abbreviated terms and acronyms defined in IEC 61784-2-0

and the following apply.
CP Communication Profile [according to IEC 61784-1-0]

CPF Communication Profile Family [according to IEC 61784-1-0]

ICMP Internet Control Message Protocol (see IETF RFC 792)

IETF Internet Engineering Task Force

IP Internet Protocol (see IETF RFC 791)

LLDP Link Layer Discovery Protocol (see IEEE Std 802.1AB-2016)
NoS Number of Switches
PI Performance indicator
PTP Precision Time Protocol (see IEC 61588)
RSTP Rapid Spanning Tree Algorithm and Protocol (see IEEE Std 802.1Q-2018)
RTFL Real time frame line
RTFN Real time frame network
TCP Transmission Control Protocol (see IETF RFC 793)
UDP User Datagram Protocol (see IETF RFC 768)
3.3 Symbols
For the purposes of this document, symbols defined in IEC 61784-2-0 and Table 1 apply.
NOTE Definitions of symbols in this Subclause 3.3 do not use the italic font, as they are already identified as
symbols.
Table 1 – CPF 18 symbols
Symbol Definition Unit
l Distance along the cable in backward direction m
B
l Cable length m
C
l Distance along the cable in forward direction m
F
NoDoB Number of devices in backward direction –
NoDoF Number of devices in forward direction –
NoS Number of switching devices –

t Cable delay ns/m
CD
t Cycle time of communication system/relation µs
cyc
t Delivery time µs
D
t Transmit time of DLPDUs µs
data
t Propagation delay µs
pd
t Sink stack traversal time µs
STsink
t Source stack traversal time µs
STsrc
t Delay time of a switch µs
SW
3.4 Conventions
For the purposes of this document, the conventions defined in IEC 61784-2-0 apply.

4 CPF 18 (SafetyNET p ) – RTE communication profiles

4.1 General overview
Communication Profile Family 18 defines profiles based on IEC 61158-3-22, IEC 61158-4-22,

IEC 61158-5-22 and IEC 61158-6-22.

In this document, the following communication profiles are specified for CPF 18.

– Profile 18/1
This profile defines protocol and service selection for devices which utilize the

communication model real time frame line (RTFL).
– Profile 18/2
This profile defines protocol and service selection for devices which utilize the
communication model real time frame network (RTFN).
4.2 CP 18/1
4.2.1 Physical layer
The physical layer shall be based on standard Ethernet hardware according to
ISO/IEC/IEEE 8802-3.
CP 18/1 devices shall use a data rate of 100 Mbit/s and full-duplex transmission mode.
A combination of full-duplex and 100Base-TX with auto crossover function (wire, 2 twisted pairs)
should be used.
When using cables, they shall be rated Cat5e or better, and shielded in an appropriate way
(FTP, STP or SFTP) depending upon EMC constraints.
4.2.2 Data link layer
Data link layer is described in IEC 61158-3-22 and IEC 61158-4-22. Table 2 specifies the use
of the services included in this profile. Table 3 specifies the use of the protocol included in this
profile.
Table 2 – CP 18/1: DLL service selection
Clause Header Presence Constraints
1 Scope YES —
2 Normative references YES —
3 Terms, definitions, abbreviations and Partial If applicable
conventions
4 Data-link layer services and concepts — —
4.1 Operating principle YES —
4.2 Communication models — —
4.2.1 Overview YES —
4.2.2 RTFL device reference model YES —
4.2.3 RTFN device reference model NO —
4.3 Topology — —
___________
SafetyNET p is a trade name of the Pilz GmbH & Co. KG. This information is given for the convenience of users
of this document and does not constitute an endorsement by IEC of the trade name holder or any of its products.
Compliance with this profile does not require use of the trade name SafetyNET p. Use of the trade name
SafetyNET p requires permission of the trade name holder.

– 10 – IEC 61784-2-18:2023 © IEC 2023

Clause Header Presence Constraints

4.3.1 RTFL topology YES —
4.3.2 RTFN topology NO —
4.4 Addressing — —
4.4.1 Overview YES —
4.4.2 RTFL device addressing YES —

4.4.3 RTFN device addressing NO —

4.5 Gateway YES —
4.6 Interaction models — —
4.6.1 Overview YES —
4.6.2 Producer-consumer YES —
4.6.3 Publisher-subscriber NO —
4.7 Synchronization concept YES —
5 Communication services — —
5.1 Overview Partial Only services selected by this CP
5.2 Communication management services — —
5.2.1 Overview YES —
5.2.2 RTFL-network verification — —
5.2.2.1 DL-Network verification service (NV) YES —
5.2.2.2 DL-RTFN scan network read service NO —
(RTFNSNR)
5.2.3 Communication management — —
5.2.3.1 DL-RTFN connection establishment service NO —
(RTFNCE)
5.2.3.2 DL-RTFN connection release service NO —
(RTFNCR)
5.2.3.3 DL-RTFL control service (RTFLCTL) YES —
5.2.3.4 DL-RTFL configuration service (RTFLCFG) YES —
5.2.3.5 DL-Read configuration data service (RDCD) YES —
5.2.3.6 DL-RTFL configuration service 2 (RTFLCFG2) YES —
5.2.3.7 DL-Read configuration data service 2 (RDCD2) YES —
5.3 Cyclic data channel service (CDC) YES —
5.4 Message channel services (MSC) YES —
5.5 Time synchronization — —
5.5.1 DL-DelayMeasurement start service (DMS) YES —
5.5.2 DL-DelayMeasurement read service (DMR) YES —
5.5.3 DL-PCS configuration service (PCSC) YES —
5.5.4 DL-Sync master configuration service YES —
(SYNC_MC)
5.5.5 DL-Sync start service (SYNC_START) YES —
5.5.6 DL-Sync stop service (SYNC_STOP) YES —
5.6 Media independent interface (MII) YES —
management services
Table 3 – CP 18/1: DLL protocol selection

Clause Header Presence Constraints

1 Scope YES —
2 Normative references YES —
3 Terms, definitions, abbreviations and Partial If applicable
conventions
4 Overview of the DL-protocol — —

4.1 Operating principle YES —
4.2 Communication model — —
4.2.1 Overview YES —
4.2.2 RTFL device reference model YES —
4.2.3 RTFN device reference model NO —
4.3 Topology — —
4.3.1 RTFL topology YES —
4.3.2 RTFN topology NO —
4.4 DLPDU processing — —
4.4.1 Communication model RTFL YES —
4.4.2 Communication model RTFN NO —
4.5 General communication mechanisms YES —
4.6 Gateway YES —
4.7 Interaction models — —
4.7.1 Overview YES —
4.7.2 Producer-consumer YES —
4.7.3 Publisher-subscriber NO —
5 DLPDU structure — —
5.1 Overview YES —
5.2 Data types and encoding rules YES —
5.3 DLPDU identification YES —
5.4 General DLPDU structure — —
5.4.1 Type 22 DLPDU inside an ISO/IEC/IEEE 8802-3 YES —
DLPDU
5.4.2 Type 22 DLPDU inside a VLAN tagged NO —
ISO/IEC/IEEE 8802-3 DLPDU
5.4.3 Type 22 DLPDU inside an UDP DLPDU NO —
5.4.3 Type 22 DLPDU structure YES —
5.5 Communication management DLPDUs — —
5.5.1 RTFL-network verification DLPDUs YES —
5.5.2 RTFN scan network DLPDUs NO —
5.5.3 Identification data YES —
5.5.4 RTFN connection management DLPDU NO —
5.5.5 ID data NO —
5.5.6 RTFL control DLPDU YES —
5.5.7 RTFL configuration DLPDU YES —
5.6 Cyclic data channel (CDC) DLPDUs — —
5.6.1 Cyclic data channel line (CDCL) DLPDU YES —
5.6.2 Cyclic data channel network (CDCN) DLPDU NO —

– 12 – IEC 61784-2-18:2023 © IEC 2023

Clause Header Presence Constraints

5.7 Cyclic data channel (CDC) DLPDU data YES —

5.8 Message channel (MSC) DLPDUs — —

5.8.1 Message channel line (MSCL) DLPDU YES —

5.8.2 Message channel network (MSCN) DLPDU NO —

5.9 Message channel DLPDU data – MSC message YES —

transfer protocol (MSC-MTP)
5.10 Time synchronization YES —

6 Telegram timing and DLPDU handling — —

6.1 Communication mechanism — —
6.1.1 Communication model RTFL YES —
6.1.2 Communication model RTFN NO —
6.2 Device synchronization — —
6.2.1 Communication model RTFL – precise clock YES —
synchronization
6.2.2 Communication model RTFN NO —
7 Type 22 protocol machines — —
7.1 RTFL device protocol machines YES —
7.2 RTFN device protocol machines NO —
7.3 Message channel – message transfer protocol YES —
(MSC-MTP)
4.2.3 Application layer
Application layer is described in IEC 61158-5-22 and IEC 61158-6-22. Table 4 specifies the use
of the services included in this profile. Table 5 specifies the use of the protocol included in this
profile.
Table 4 – CP 18/1: AL service selection

Clause Header Presence Constraints

1 Scope YES —
2 Normative references YES —
3 Terms, definitions, abbreviations and conventions Partial If applicable

4 Concepts — —
4.1 Common concepts YES —
4.2 Type specific concepts — —

4.2.1 Operating principle YES —
4.2.2 Communication model overview — —
4.2.2.1 Overview YES —
4.2.2.2 Communication model RTFL YES —
4.2.2.3 Communication model RTFN NO —
4.2.3 Application layer element description YES —
4.2.4 Producer-consumer interaction YES —
4.2.5 Device reference models — —
4.2.5.1 RTFL device reference model YES —
4.2.5.2 RTFN device reference model NO —
5 Data type ASE YES —
6 Communication model specification — —
6.1 Application service elements (ASEs) — —
6.1.1 CeS ASE YES —
6.1.2 ISO/IEC/IEEE 8802-3 DLPDU communication YES —
ASE
6.1.3 Management ASE YES —
6.2 Application relationships (ARs) — —
6.2.1 Overview YES —
6.2.2 Point-to-point network-scheduled unconfirmed YES —
producer-consumer AREP
6.2.3 Point-to-multipoint network-scheduled YES —
unconfirmed producer-consumer AREP
6.2.4 Point-to-point network-scheduled confirmed YES —
client/server AREP
6.2.5 Point-to-point user-triggered confirmed NO —

client/server AREP
6.2.6 AR classes Partial According to the present ARs
6.2.7 FAL services by AREP class Partial According to the present ARs
6.2.8 Permitted FAL services by AREP role According to the present ARs
Partial
– 14 – IEC 61784-2-18:2023 © IEC 2023

Table 5 – CP 18/1: AL protocol selection

Clause Header Presence Constraints

1 Scope YES —
2 Normative references YES —
3 Terms, definitions, abbreviations and conventions Partial If applicable

4 Application layer protocol specification — —

4.1 Operating principle YES —
4.2 Device reference models — —

4.2.1 RTFL device reference model YES —
4.2.2 RTFN device reference model NO —
4.3 Application layer structure YES —
5 FAL syntax description YES —
6 FAL protocol state machines YES —
7 AP-context state machine YES —
8 FAL service protocol machine (FSPM) YES —
9 Application layer state machine (ALSM) YES —
10 DLL mapping protocol machine (DMPM) YES —

4.2.4 Performance indicator selection
4.2.4.1 Performance indicator overview
Table 6 gives an overview of the performance indicator usage.
Table 6 – CP 18/1: PI overview
Performance indicator Applicable Constraints
Delivery time YES None
Number of RTE end-stations YES None
Basic network topology YES Hierarchical star and linear topology
Number of switches between RTE end-stations YES For highest performance usage of
switches shall be omitted
Throughput RTE YES None
Non-RTE bandwidth YES None
Time synchronization accuracy YES None
Non-time-based synchronization accuracy NO —
Redundancy recovery time NO —
4.2.4.2 Performance indicator dependencies
Table 7 specifies the dependencies of the performance indicators (row) from the performance
indicators (column).
Table 7 – CP 18/1: PI dependency matrix

Influencing PI
Dependent PI
YES YES YES YES NO NO
Delivery time
4.2.4.5 4.2.4.6 4.2.4.7 4.2.4.8

Number NO NO NO NO NO YES
of end-stations 4.2.4.9
Basic network NO NO YES NO NO YES
topology 4.2.4.10 4.2.4.11
Number of switches NO NO YES NO NO YES
between 4.2.4.10 4.2.4.13
RTE end-stations
NO NO NO NO YES NO
Throughput RTE
4.2.4.14
NO NO NO NO YES NO
Non-RTE bandwidth
4.2.4.14
Time synchronization NO YES YES YES NO NO
accuracy 4.2.4.9 4.2.4.11 4.2.4.13

4.2.4.3 Delivery time calculation
The performance indicator delivery time for a linear topology and a star topology can be
calculated by Formula (1).
NoDoF NoDoB
t=t+t +t +t× l+l+ t ()i++t ()i t ()i++t ()i t
( ) (1)
∑∑( ) ( )
D cyc STsrc data CD F B pd SW pd SW ST sink
ii11
where
t is the delivery time;
D
t is the cycle time of the communication system (t ≥ t );
cyc cycle data
t is the stack traversal time including data-link layer and physical layer of the source;
STsrc
t is the time to transmit all Real-time DLPDU for one cycle;
data
t is the cable delay (4,5 ns/m to 5 ns/m);
CD
l is the distance along the cable in meters which is passed by the packed from source
F
to last device of the logical line;
l is the distance along the cable in meters which is passed by the packed from last
B
device of the logical line to sink;
t is the propagation delay of a device in forward or backward direction;
pd
t is the delay caused by switching procedure;
SW
NoDoF is the number of succeeding devices on forward direction from the source to the last
device of the logical line;
Delivery time
Number of
end-stations
Basic
network
topology
Number of
switches
between RTE
end-stations
Throughput
RTE
Non-RTE
bandwidth
Time
synchronizati
on accuracy
==
– 16 – IEC 61784-2-18:2023 © IEC 2023

NoDoB is the number of succeeding devices on backward direction from the last device of the

logical line to the sink;
t is the stack traversal time including data-link layer and physical layer of the sink.

STsink
NOTE 1 In the case of a linear topology, the time factor t has the value 0.
SW
NOTE 2 The distance in each direction is affected by the number of switching devices within the network topology.

4.2.4.4 Basic network topology

The basic network topologies supported by this profile are hierarchical star or linear topology.

It is highly recommended to use linear topology to reach highest performance. For both basic

network topologies, this profile establishes a logical line topology by appropriate addressing
within devices. For detailed information, refer to IEC 61158-4-22.
4.2.4.5 Delivery time dependency on number of end-stations
The number of end-stations typically influences the amount of data, thus the time to transmit
the data DLPDU as well as the sum of propagation delays. Furthermore, the number of devices
on forward and backward direction is influenced and hence the delivery time as described in
Formula (1).
4.2.4.6 Delivery time dependency on basic network topology
The delivery time depends on the amount of signal propagation delays within a network which
are introduced by a given network topology. The network topology dependent parameters in
terms of additional delay times are considered in Formula (1).
4.2.4.7 Delivery time dependency on number of switches between RTE end-stations
The delivery time depends on the amount of signal propagation delays within a network which
are introduced by switches between RTE end-stations. The switch dependent parameters in
terms of additional delay times are considered in Formula (1).
4.2.4.8 Delivery time dependency on throughput RTE
The delivery time depends on throughput RTE via data amount and cycle time. Throughput RTE
can be adapted by changing the parameters data amount and cycle time, whereas the minimal
reachable cycle time depends highly on the amount of data to be transferred. If throughput RTE
is increased by increasing the amount of data transferred within one cycle, the delivery time is
increased. An increase of throughput RTE by reducing the cycle time decreases the delivery
time. Throughput RTE can be increased by an adequate adjustment of both parameters without
influencing the delivery time as described in Formula (1).

4.2.4.9 Relation between number of end-stations and time synchronization accuracy
The number of end-stations influences the accuracy of time synchronization and vice versa.
4.2.4.10 Relation between basic network topology and number of switches between
RTE end-stations
The usage of switches is restricted to hierarchical star topology.
4.2.4.11 Relation between basic network topology and time synchronization accuracy
The usage of switches (for example to build up a hierarchical star topology) reduces the
reachable accuracy of time synchronization of devices.

4.2.4.12 Relation between number of end-stations and time synchronization accuracy

The number of end-stations influences the accuracy of time synchronization and vice versa.

4.2.4.13 Relation between number of switches between RTE end-stations and time

synchronization accuracy
Accuracy of time synchronization is the maximum jitter between device clocks. The usage of
switches reduces the reachable accuracy of time synchronization of devices.

4.2.4.14 Relation between throughput RTE and non-RTE bandwidth

The non-RTE bandwidth is the difference between overall bandwidth and the RTE throughput
(RTE overhead included), hence both values influence each other.
4.3 CP 18/2
4.3.1 Physical layer
The physical layer shall be based on standard Ethernet hardware according to
ISO/IEC/IEEE 8802-3.
4.3.2 Data link layer
Data link layer is described in IEC 61158-3-22 and IEC 61158-4-22. Table 8 specifies the use
of the services included in this profile. Table 9 specifies the use of the protocol included in this
profile.
Table 8 – CP 18/2: DLL service selection
Clause Header Presence Constraints
1 Scope YES —
2 Normative references YES —
3 Terms, definitions, abbreviations and Partial If applicable
conventions
4 Data-link layer services and concepts — —
4.1 Operating principle YES —
4.2 Communication models — —
4.2.1 Overview YES —
4.2.2 RTFL device reference model NO —

4.2.3 RTFN device reference model YES —
4.3 Topology — —
4.3.1 RTFL topology NO —
4.3.2 RTFN topology YES —
4.4 Addressing — —
4.4.1 Overview YES —
4.4.2 RTFL device addressing NO —
4.4.3 RTFN device addressing YES —
4.5 Gateway YES —
4.6 Interaction models — —
4.6.1 Overview YES —
4.6.2 Producer-consumer NO —
4.6.3 Publisher-subscriber YES —

– 18 – IEC 61784-2-18:2023 © IEC 2023

Clause Header Presence Constraints

4.7 Synchronization concept YES —

5 Communication services — —
5.1 Overview Partial Only services selected by this CP

5.2 Communication management services — —

5.2.1 Overview YES —
5.2.2 RTFL-network verification — —

5.2.2.1 DL-Network verification service (NV) NO —

5.2.2.2 DL-RTFN scan network read service YES —

(RTFNSNR)
5.2.3 Communication management — —
5.2.3.1 DL-RTFN connection establishment service YES —
(RTFNCE)
5.2.3.2 DL-RTFN connection release service YES —
(RTFNCR)
5.2.3.3 DL-RTFL control service (RTFLCTL) NO —
5.2.3.4 DL-RTFL configuration service (RTFLCFG) NO —
5.2.3.5 DL-Read configuration data service (RDCD) NO —
5.2.3.6 DL-RTFL configuration service 2 (RTFLCFG2) NO —
5.2.3.7 DL-Read configuration data service 2 (RDCD2) NO —
5.3 Cyclic data channel service (CDC) YES —
5.4 MSC services YES —
5.5 Time synchronization — —
5.5.1 DL-DelayMeasurement start service (DMS) NO —
5.5.2 DL-DelayMeasurement read service (DMR) NO —
5.5.3 DL-PCS configuration service (PCSC) NO —
5.5.4 DL-Sync master configuration service YES —
(SYNC_MC)
5.5.5 DL-Sync start service (SYNC_START) YES —
5.5.6 DL-Sync stop service (SYNC_STOP) YES —
5.6 Media independent interface (MII) NO —
management services
Table 9 – CP 18/2: DLL protocol selection

Clause Header Presence Constraints
1 Scope YES —
2 Normative references YES —
3 Terms, definitions, abbreviations and Partial If applicable
conventions
4 DL-protocol overview — —
4.1 Operating principle YES —
4.2 Communication model — —
4.2.1 Overview YES —
4.2.2 RTFL device reference model NO —
4.2.3 RTFN device reference model YES —
4.3 Topology — —
4.3.1 RTFL topology NO —
Clause Header Presence Constraints

4.3.2 RTFN topology YES —
4.4 DLPDU processing — —
4.4.1 Communication model RTFL NO —

4.4.2 Communicatio
...