EN 62439-7:2012

SLOVENSKI STANDARD
01-maj-2012
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Industrial communication networks - High availability automation networks - Part 7: Ring-
based Redundancy Protocol (RRP) (IEC 62439-7:2011)
Industrielle Kommunikationsnetze - Hochverfügbare Automatisierungsnetze - Teil 7:
Protokoll für ringbasierte Redundanz (RRP) (IEC 62439-7:2011)
Réseaux de communication industriels - Réseau de haute disponibilité pour l'automation
- Partie 7: Protocole de redondance pour réseau en anneau (RRP) (CEI 62439-7:2011)
Ta slovenski standard je istoveten z: EN 62439-7:2012
ICS:
25.040.01 Sistemi za avtomatizacijo v Industrial automation
industriji na splošno systems in general
35.110 Omreževanje Networking
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN 62439-7
NORME EUROPÉENNE
March 2012
EUROPÄISCHE NORM
ICS 25.040; 35.040
English version
Industrial communication networks -
High availability automation networks -
Part 7: Ring-based Redundancy Protocol (RRP)
(IEC 62439-7:2011)
Réseaux de communication industriels -  Industrielle Kommunikationsnetze -
Réseau de haute disponibilité pour Hochverfügbare Automatisierungsnetze -
l'automation - Teil 7: Protokoll für ringbasierte
Partie 7: Protocole de redondance pour Redundanz (RRP)
réseau en anneau (RRP) (IEC 62439-7:2011)
(CEI 62439-7:2011)
This European Standard was approved by CENELEC on 2012-01-20. 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, Romania, Slovakia, Slovenia,
Spain, Sweden, Switzerland, Turkey and the United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Management Centre: Avenue Marnix 17, B - 1000 Brussels

© 2012 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 62439-7:2012 E
Foreword
The text of document 65C/668/FDIS, future edition 1 of IEC 62439-7, 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 62439-7:2012.

The following dates are fixed:
(dop) 2012-10-20
• latest date by which the document has
to be implemented at national level by
publication of an identical national
standard or by endorsement
(dow) 2015-01-20
• latest date by which the national
standards conflicting with the
document have to be withdrawn
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC [and/or CEN] shall not be held responsible for identifying any or all such patent
rights.
Endorsement notice
The text of the International Standard IEC 62439-7:2011 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following note has to be added for the standard indicated:
IEC 61158 series NOTE  Harmonized in EN 61158 series.

- 3 - EN 62439-7:2012
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

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  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 60050-191 - International Electrotechnical Vocabulary - -
(IEV) -
Chapter 191: Dependability and quality of
service
IEC 62439-1 2010 Industrial communication networks - High EN 62439-1 2010
availability automation networks -
Part 1: General concepts and calculation
methods
ISO/IEC 8802-3 2000 Information technology - Telecommunications - -
and information exchange between systems -
Local and metropolitan area networks -
Specific requirements -
Part 3: Carrier sense multiple access with
collision detection (CSMA/CD) access method
and physical layer specifications

IEC 62439-7 ®
Edition 1.0 2011-12
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Industrial communication networks – High availability automation networks –
Part 7: Ring-based Redundancy Protocol (RRP)

Réseaux de communication industriels – Réseaux de haute disponibilite pour
l'automation –
Partie 7: Protocole de redondance pour réseau en anneau (RRP)

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX XC
ICS 25.040; 35.040 ISBN 978-2-88912-838-9

– 2 – 62439-7 © IEC:2011
CONTENTS
FOREWORD . 6
INTRODUCTION . 8
1 Scope . 9
2 Normative references . 9
3 Terms, definitions, abbreviations, acronyms, and conventions . 9
3.1 Terms and definitions . 9
3.2 Abbreviations and acronyms . 10
3.3 Conventions . 10
4 RRP overview . 11
4.1 General . 11
4.2 Frame forwarding and receiving control . 11
4.2.1 General . 11
4.2.2 Normal Device (ND) and Gateway Device (GWD) . 11
4.2.3 Behaviours of the General Device (GD) . 12
4.2.4 Behaviours of the Line Network Manager (LNM) . 13
4.2.5 Behaviours of the Ring Network Managers (RNMs) . 13
4.3 Link status monitoring . 14
4.4 Error detection . 14
4.5 Plug and play . 14
4.6 Network management information base (NMIB) management . 14
4.7 Network recovery . 15
4.8 Automatic network configuration . 15
4.9 RRP basic operating principle . 15
5 RRP redundancy behaviours . 17
5.1 Network topology. 17
5.2 Network recovery in ring network . 18
5.2.1 General . 18
5.2.2 Link fault between neighbouring devices . 20
5.2.3 Link fault of remote device . 21
5.2.4 Device fault on a RNM . 22
5.3 Automatic Ring Network Manager (RNM) election procedure . 23
5.3.1 General . 23
5.3.2 Primary RNM (RNMP). 23
5.3.3 Secondary RNM (RNMS) . 24
5.4 Path management . 24
5.4.1 General . 24
5.4.2 Path in a line topology network . 24
5.4.3 Path in a ring topology network . 25
5.5 Device address collision . 26
6 RRP class specification . 27
6.1 General . 27
6.2 Template . 27
6.3 Attributes. 29
7 RRP services specification . 34
7.1 Set device information . 34
7.2 Get device information . 36

62439-7 © IEC:2011 – 3 –
7.3 Get network information . 38
7.4 Get path table information . 40
8 RRP protocol specification. 42
8.1 General . 42
8.2 Ethernet header . 43
8.2.1 Preamble . 43
8.2.2 Start frame delimiter . 43
8.2.3 Destination MAC address . 43
8.2.4 Source MAC address . 43
8.2.5 Length/Type . 43
8.3 Encoding of RRP_FrameHDR . 43
8.3.1 Version and length . 43
8.3.2 DST_addr . 44
8.3.3 SRC_addr. 45
8.3.4 Frame Control (FC) . 45
8.4 Encoding of data and pad . 47
8.4.1 General . 47
8.4.2 Encoding of FamilyReq . 47
8.4.3 Encoding of FamilyRes . 48
8.4.4 Encoding of MediaLinked . 48
8.4.5 Encoding of AdvThis . 49
8.4.6 Encoding of LineStart . 49
8.4.7 Encoding of RingStart . 50
8.4.8 Encoding of AckRNMS . 51
8.4.9 Encoding of CheckRNMS . 52
8.5 Frame Check Sequence (FCS) . 52
9 RRP protocol machine . 52
9.1 Protocol state machine description . 52
9.2 Local parameters and variables for protocol state . 54
9.2.1 General . 54
9.2.2 Variables to support local device information management . 54
9.2.3 Variables to support network information management . 55
9.2.4 Variables to support device path information management . 55
9.2.5 Variables of Received RRP Frame . 55
9.2.6 Local variables for protocol state . 56
9.2.7 Constants for protocol state . 56
9.3 State transitions . 57
9.4 Function descriptions . 70
10 RRP Management Information Base (MIB) . 75
Bibliography . 81

Figure 1 – Forwarding and receiving Ethernet frames . 11
Figure 2 – Structures of ND and GWD . 12
Figure 3 – LNM forwarding control . 13
Figure 4 – RNM forwarding control . 13
Figure 5 – Link status information . 14
Figure 6 – A device operation in initialization phase . 15

– 4 – 62439-7 © IEC:2011
Figure 7 – Devices operation in line network establishing phase . 16
Figure 8 – Extension of line network operation . 16
Figure 9 – Ring network establishment operation . 17
Figure 10 – Ring to line network change operation . 17
Figure 11 – Ring topology . 18
Figure 12 – Link fault between neighbouring devices . 21
Figure 13 – Link fault of remote device . 22
Figure 14 – Device fault on a RNM . 22
Figure 15 – Path management in a line topology network. 24
Figure 16 – Path management in a ring topology network . 25
Figure 17 – RRP device address collision in a ring network . 26
Figure 18 – Common MAC frame format for RRP DLPDU . 43
Figure 19 – RRP protocol state machine . 53

Table 1 – RRP network recovery parameter . 19
Table 2 – Parameters for calculation . 19
Table 3 – Path table of Device1 in a line topology network . 24
Table 4 – Path table of Device4 in a line topology network . 25
Table 5 – Path table of Device1 in a ring topology network . 25
Table 6 – Path table of Device3 in a ring topology network . 26
Table 7 – Device address collision information. 27
Table 8 – Parameters of set device information service . 34
Table 9 – Parameters of get device information service . 36
Table 10 – Parameters of get network information service . 38
Table 11 – Parameters of get path table information service . 40
Table 12 – RRP Length/Type field . 43
Table 13 – Version . 44
Table 14 – DST_addr . 44
Table 15 – SRC_addr . 45
Table 16 – Network control message type . 45
Table 17 – Type of service . 45
Table 18 – Priority . 46
Table 19 – Validation of extension code . 46
Table 20 – Encoding of FamilyReq frame . 47
Table 21 – Encoding of FamilyRes frame . 48
Table 22 – Encoding of MediaLinked frame . 48
Table 23 – Encoding of AdvThis frame . 49
Table 24 – Encoding of LineStart frame . 49
Table 25 – Encoding of RingStart frame . 50
Table 26 – Encoding of AckRNMS frame . 51
Table 27 – Encoding of CheckRNMS frame . 52
Table 28 – Variables to support device information management . 54
Table 29 – Variables to support managing network information . 55

62439-7 © IEC:2011 – 5 –
Table 30 – Variables to support device path information management . 55
Table 31 – Variables of Received RRP Frame . 55
Table 32 – Local variables for protocol state . 56
Table 33 – Constants for protocol state . 56
Table 34 – RRP State transitions . 57
Table 35 – RRP Function descriptions . 70

– 6 – 62439-7 © IEC:2011
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
INDUSTRIAL COMMUNICATION NETWORKS –
HIGH AVAILABILITY AUTOMATION NETWORKS –

Part 7: Ring-based Redundancy Protocol (RRP)

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
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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
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3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
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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
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6) All users should ensure that they have the latest edition of this publication.
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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.
International Standard IEC 62439-7 has been prepared by subcommittee 65C: Industrial
Networks, of IEC technical committee 65: Industrial-process measurement, control and
automation.
The text of this standard is based on the following documents:
FDIS Report on voting
65C/668/FDIS 65C/673/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 International Standard is to be read in conjunction with IEC 62439-1:2010, Industrial
communication networks – High availability automation networks – Part 1: General concepts
and calculation methods.
62439-7 © IEC:2011 – 7 –
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all the parts of the IEC 62439 series, under the general title Industrial communication
networks – High availability automation networks, 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.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
– 8 – 62439-7 © IEC:2011
INTRODUCTION
The IEC 62439 series specifies relevant principles for high availability networks that meet the
requirements for industrial automation networks.
In the fault-free state of the network, the protocols of the IEC 62439 series provide
ISO/IEC 8802-3:2000 (IEEE 802.3) with compatible, reliable data communications, and
preserve determinism in real-time data communications. In cases of fault, removal, and
insertion of a component, they provide deterministic recovery times.
These protocols retain fully the Ethernet communication capabilities typically used in the
office world, to ensure that software that relies on these protocols will remain applicable.
The market is in need of several network solutions, each with different performance
characteristics and functional capabilities, meeting diverse application requirements. These
solutions support different redundancy topologies and mechanisms, which are introduced in
IEC 62439-1 and specified in the companion International Standards. IEC 62439-1 also
distinguishes between these different solutions, providing guidance for the user.
The IEC 62439 series follows the general structure and terms of IEC 61158 series.
The International Electrotechnical Commission (IEC) draws attention to the fact that it is
claimed that compliance with this document may involve the use of patents concerning
IEC 61158-4-21 given in Clause 4 and Clause 5.
Patent Number KR 0789444 “COMMUNICATION PACKET PROCESSING APPARATUS AND METHOD FOR RING
TOPOLOGY ETHERNET NETWORK CAPABLE OF PREVENTING PERMANENT PACKET LOOPING,” owned by LS
INDUSTRIAL SYSTEMS CO., LTD., Anyang, Korea
Patent Number KR 0732510 “NETWORK SYSTEM” owned by LS INDUSTRIAL SYSTEMS CO., LTD., Anyang,
Korea
Patent Number KR 0870670 “Method For Determining a Ring Manager Node”， owned by LS INDUSTRIAL
SYSTEMS CO., LTD., Anyang, Korea
IEC takes no position concerning the evidence, validity and scope of these patent rights.
The holder of these patent rights has assured the IEC that he/she is willing to negotiate
licences 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:
LSIS Co Ltd
LS Tower
1026-6, Hogye-Dong
Dongan-Gu
Anyang, Gyeonggi-Do, 431-848
South Korea
Phone +82 2 2034 4917
Fax +82 2 2034 4648
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 data bases of
patents relevant to their standards. Users are encouraged to consult the data bases for the
most up to date information concerning patents.

62439-7 © IEC:2011 – 9 –
INDUSTRIAL COMMUNICATION NETWORKS –
HIGH AVAILABILITY AUTOMATION NETWORKS –

Part 7: Ring-based Redundancy Protocol (RRP)

1 Scope
The IEC 62439 series of standards is applicable to high-availability automation networks
based on the ISO/IEC 8802-3:2000 (Ethernet) technology.
This part of the IEC 62439 series specifies a redundancy protocol that is based on a ring
topology, in which the redundancy protocol is executed at the end nodes, as opposed to being
built into the switches. Each node detects link failure and link establishment using media-
sensing technologies, and shares the link information with the other nodes, to guarantee fast
connectivity recovery times. The nodes have equal RRP network management functions.
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.
IEC 60050-191, International Electrotechnical Vocabulary – Chapter 191 : Dependability and
quality of service
IEC 62439-1:2010, Industrial communication networks – High availability automation networks
– Part 1: General concepts and calculation methods
ISO/IEC 8802-3:2000, Information technology – Telecommunications and information
exchange between systems – Local and metropolitan area networks – Specific requirements –
Part 3: Carrier sense multiple access with collision detection (CSMA/CD) access method and
physical layer specifications
3 Terms, definitions, abbreviations, acronyms, and conventions
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60050-191 as well
as in IEC 62439-1, and the following apply.
3.1.1
R-port
port in a communication device that is part of a line or ring structure
3.1.2
device address
2 octet address that designates the device associated with a single device on a specific local
link
– 10 – 62439-7 © IEC:2011
3.1.3
Gateway Device
GWD
RRP device that has more than 3 Ethernet ports on it. At least 2 ports have to support RRP
protocol
3.1.4
Normal Device
ND
normal RRP device which has two RRP ports on it
3.1.5
Unique Identification
UID
Unique 8 octet identification used to identify a RRP device within a network segment. UID is
combines a 2 octet device address and a 6 octet MAC address, so that it has a unique value
in a network
3.2 Abbreviations and acronyms
For the purposes of this document, the abbreviations and acronyms given in IEC 62439-1 as
well as the following, apply.
ASE Application Service Element
DLE Data Link layer Entity
FC Frame Control
FCS Frame Check Sequence
GD General Device
GWD Gateway Device
LNM Line Network Manager
MAC Media Access Control
MIB Management Information Base
NCM Network Control Message
NCMT Network Control Message Type
ND Normal Device
NMIB Network Management Information Base
PHY Physical Interface Transceiver
PO Power On
PRI Priority
RES Reserved
RNM Ring Network Manager
RRP Ring based Redundancy Protocol
SA Stand Alone
ToS Type of Service
VoE Validation of Extension code
3.3 Conventions
This part of the IEC 62439 series follows the conventions defined in IEC 62439-1.

62439-7 © IEC:2011 – 11 –
4 RRP overview
4.1 General
The RRP specifies a recovery protocol, based on a ring topology. All links in an RRP network
shall be full duplex through the use of an internal hardware Ethernet switch. Thus, RRP
provides a collision-free transmission mechanism between two nodes. Every RRP device
detects link failure and link establishment using the rules specified in ISO/IEC 8802-3:2000
and shares this information with other RRP devices so that fast connectivity recovery time is
also guaranteed in the ring network.
A RRP device is a dual-port switching device that receives and transmits standard
ISO/IEC 8802-3:2000 Ethernet frames. It is intelligent and can control directional frame
forwarding between its dual ports according to the network status and device status. RRP
uses a special network management scheme specified in this standard. RRP also uses a
network control based on device address and MAC address, and thus general bridge hub or
switch might not be suitable for RRP network. However, when connecting a general Ethernet
device to RRP network, Gateway Device (GWD) should be used.
4.2 Frame forwarding and receiving control
4.2.1 General
RRP provides a collision-free transmission mechanism with an internal full-duplex hardware
switch with switching queue and dual MACs in a device. The switching priority method
between Tx and Forwarding can be Round-Robin, Tx-First or Forwarding-First scheme.
However RRP does not specify the switching method.
Thus, a RRP device transmits frames without the restriction of medium access, as soon as
they appear in the transmit queue for each MAC. Figure 1 shows the forwarding and receiving
control of the RRP device.
Data link layer entity (DLE)
Rx Tx Rx Tx
RRP
Forwarding
Device
Control
MAC1 MAC2
PHY1 PHY2
ISO/IEC 8802-3 Ethernet Frame
ISO/IEC 8802-3 Ethernet Frame
ISO/IEC 8802-3 Ethernet Frame
ISO/IEC 8802-3 Ethernet Frame
IEC  2661/11
Figure 1 – Forwarding and receiving Ethernet frames
4.2.2 Normal Device (ND) and Gateway Device (GWD)
RRP is operated in a dual-port ring topology. A general Ethernet device can send standard
Ethernet frames through RRP ring network with GWD. Multi-ring network can also be
established using GWD.
GWD is responsible for switching Ethernet frames between RRP network and external
Ethernet networks through application layer using a dynamic table. The dynamic table maps
addresses to external Ethernet ports automatically. The dynamic table is automatically made
by learning frame movements in the network. The GWD inspects both the destination and the
source addresses. The destination address is used for the forwarding decision; the source
address is used for adding entries to the table and for updating purposes. When an Ethernet

– 12 – 62439-7 © IEC:2011
frame is received at the media access control (MAC) layer through the physical interface
transceiver (PHY), a GWD handles the received frame by taking one of the following actions,
depending on the destination MAC address and the source MAC addresses in the received
frame:
• for a broadcast or multicast frame, accept and deliver the frame to the data link layer
entity (DLE), and forward the frame to the other RRP port and external Ethernet ports;
• for a frame designated for the device itself, accept and deliver the frame to the DLE
without forwarding;
• for a frame designated for another device, accept the frame to its application layer and
inspect both the destination and the source addresses. When the destination address of
the frame is in the dynamic table, the GWD delivers the frame to the corresponding port in
the dynamic table without forwarding to other ports. Otherwise, the GWD delivers the
frame to all other ports. The GWD adds this entry to the dynamic table with source MAC
address and port number information.
NOTE Dynamic table entries are automatically removed after the Ageing Time which is specified in IEEE 802.1D.
Figure 2 shows different structures of ND and GWD. In GWD, external Ethernet connection is
connected to RRP ring network through MAC_E and PHY_E.
RRP ND (Normal Device) RRP GWD(Gateway Device)
Dynamic Table
MAC addr.
Port 1
MAC addr.
Application Any other    Application Port 2
Any other
Apps.
Apps.
MAC addr.
Port n
Non-RRP
RRP type
RRP type Non-RRP type
type
MAC1 MAC2 MAC1 MAC2 MAC_E1 MAC_En
PHY1 PHY2 PHY1 PHY2 PHY_E1 PHY_En

IEC  2662/11
Figure 2 – Structures of ND and GWD
4.2.3 Behaviours of the General Device (GD)
When an Ethernet frame is received at the MAC layer through the PHY, a RRP general device
other than the ring network manager (RNM) or the line network manager (LNM), handles the
received frame by taking one of the following actions, depending on the destination MAC
address and the device address in the received frame:
• for a broadcast or multicast frame, accept and deliver the frame to the DLE, and forward
the frame to the other port;
• for a frame designated for the device itself, accept and deliver the frame to the DLE
without forwarding;
• for a frame designated for another device, do not accept the received frame, but forward
the frame to the other port.
This frame forwarding procedure is processed by the internal hardware switch, so that it has
little impact on the performance of the RRP protocol.

62439-7 © IEC:2011 – 13 –
4.2.4 Behaviours of the Line Network Manager (LNM)
As shown in Figure 3, the LNM disables the frame forward functions in both directions, so that
frames are not forwarded to another port. In RRP networks, a LNM is automatically configured.
When a device senses that only one port is connected, the device takes this to indicate that it
is at the end of the line network. The LNM also becomes a control point of the hop count to
other devices in a line network.
Data link layer entity (DLE)
Rx Tx Rx Tx
MAC1 MAC2
PHY1 PHY2
IEC  2663/11
Figure 3 – LNM forwarding control
4.2.5 Behaviours of the Ring Network Managers (RNMs)
A frame in a ring network can be continuously circulated when the designated device is not
found or when the frame is broadcast on the network. In a RRP ring network, two RNMs are
automatically selected, and each RNM enables only one directional frame forward function to
prevent infinite frame circulation, as shown in Figure 4.
The dual RNM structure is used to avoid message duplication. A primary RNM (RNMP) is
selected with the highest UID device first, and then one of its neighbouring nodes is selected
as a secondary RNM (RNMS). The RNMP and RNMS send Network Control Message Type
(NCMT) messages to each other, to monitor network integrity.
Data link layer entity (DLE) Data link layer entity (DLE)
Rx Rx Rx Rx
Tx Tx Tx Tx
MAC1 MAC2 MAC1 MAC2
PHY1 PHY2 PHY1 PHY2
IEC  2664/11
Figure 4 – RNM forwarding control

– 14 – 62439-7 © IEC:2011
4.3 Link status monitoring
The RRP manages the network dynamically. When a link between two devices is established
or released, it is automatically detected in the physical layer, as specified in
ISO/IEC 8802-3:2000, Clause 24. This link status information is distributed and shared with
every device on the network using NCMT messages, so that the network topology can be
managed dynamically. The link status information is either “PHY_LINK_UP” or
“PHY_LINK_DOWN” and the link status detection process is initiated by the sublayer of PHY
service. A status of “PHY_LINK_UP” means that a RRP communication link is connected
between two devices and it is possible to send frames through the link. A status of
“PHY_LINK_DOWN” means that a RRP communication link is not established through an
Ethernet MAC port and it is not possible to send frames through the port. By sharing all the
link information on the network, all RRP devices on the network can determine the online
network connectivity status. Figure 5 shows the intrinsic link status monitoring procedure of
the RRP device.
Data link layer entity (DLE)
RRP
Rx Tx Rx Tx
Device
Forwarding
MAC1 MAC2
Indicates the link
Indicates the link
PHY1 PHY2
status of
status of
“PHY_LINK_DOWN”
“PHY_LINK_UP”
Fault!
IEC  2665/11
Figure 5 – Link status information
4.4 Error detection
A RRP device examines both frame validation and physical link status. Frame validation is
examined using the frame check sequence (FCS) of ISO/IEC 8802-3:2000, Clause 3. The
physical link status can be validated by a PHY link monitoring function. RRP uses a service of
PHY sublayer to monitor link status.
4.5 Plug and play
When a new device joins an existing network, the new link information is broadcast via a
NCMT message to every device on the network. The new device also collects existing link
information from each device so that it can communicate to the other nodes on the network
without manual configuration.
4.6 Network management information base (NMIB) management
A RRP device automatically manages network information and a path table. Network
information and the path table are stored in the device’s NMIB. All RRP devices in a network
share link information via NCMT messages. Every device updates its network information and
path table when it receives
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