IEC 62439-3:2021/COR1:2023

© IEC 2023
INTERNATIONAL ELECTROTECHNICAL COMMISSION
COMMISSION ÉLECTROTECHNIQUE INTERNATIONALE
____________
IEC 62439-3 IEC 62439-3
Edition 4.0  2021-12 Edition 4.0  2021-12

INDUSTRIAL COMMUNICATION NETWORKS – RÉSEAUX DE COMMUNICATION INDUSTRIELS –
HIGH AVAILABILITY AUTOMATION NETWORKS – RÉSEAUX DE HAUTE DISPONIBILITÉ POUR
Part 3: Parallel Redundancy Protocol (PRP) and L'AUTOMATISATION –
High-availability Seamless Redundancy (HSR) Partie 3: Protocole de redondance en parallèle
(PRP) et redondance transparente de haute
disponibilité (HSR)
CORRIGENDUM 1
Corrections to the French version appear after the English text. Please note that some
corrections are different for the English and French texts.
Les corrections à la version française sont données après le texte anglais. Veuillez noter que
certaines corrections sont différentes pour les textes anglais et français.

Corrections to the English version:

INTRODUCTION to Corrigendum 1
This Corrigendum 1 corrects errors and possible misinterpretations in IEC 62439-3:2021, which
were discovered during the first field implementations based on this International Standard. All
corrections are only intended to improve the consistency of implementations of the
specifications and do not introduce new features to the technology.
NOTE This Corrigendum 1 includes corrections for the MIBs in Clause 7 and Annex E. These MIBs are provided as
code components in companion documents, see https://www.iec.ch/sc65c/supportingdocuments. The corrections for
Clause 7 and Annex E are provided for convenience, while the versions in the companion documents IEC_62439-
3_2021B1.mib and IEC_62439-100_2021B1.mib contain the corrected code and prevail in case of discrepancies.
4 Parallel Redundancy Protocol (PRP)
4.2.7.2 NodesTable
Replace, in the last paragraph (two occurrences), “Supervision Frames” with “supervision
frames”.
IEC 62439-3:2021-12/COR1:2023-04(en-fr)

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© IEC 2023
4.2.7.5.5 Receiving and NodesTable
Replace, in the first row of the table, “If this frame is not a PRP_Supervision frame or an HSR
Supervision frame” with “If this frame is neither a PRP_Supervision frame nor an
HSR_Supervision frame”.
Replace, in the third row of the table, “Else if this frame is a PRP_Supervision frame” with “Else
(i.e. if this frame is a PRP_Supervision frame or an HSR_Supervision frame)”.
Replace, in the fifth row of the table, “Supervision Frame” with “supervision frame”.
Replace, in NOTE 1, “a well-formed RCT” with “a well-formed RCT on one port only”.
Replace, in NOTE 2, “Supervision Frames” with “supervision frames” and “Supervision Frame”
with “supervision frame”.
5 High-availability Seamless Redundancy (HSR)
5.2.2.3 HSR-PRP RedBox for ring connection to a PRP network
Add, at the beginning of subclause 5.2.2.3, the following new headline 5.2.2.3.1:
“5.2.2.3.1 Configuration and operation”
Add, at the end of subclause 5.2.2.3, the following new subclause 5.2.2.3.2:
5.2.2.3.2 Handling of supervision frames
5.2.2.3.2.1 Forwarding supervision frames between HSR and PRP networks
Special processing has to be applied to supervision frames received by the RedBox because
PRP_Supervision frames (see 4.3) and HSR_Supervision frames (see 5.7.2) have a slightly
different format, so DANPs could be unable to recognize HSR_Supervision frames, while
DANHs could be unable to recognize PRP_Supervision frames.
To resolve such potential incompatibility, an HSR-PRP RedBox shall perform a proxy translation
of supervision frames in both directions (HSR→PRP and PRP→HSR).
The translation shall include the following:
1) Translate TLV1.TYPE
a) If its value is 20 or 21 (PRP_Supervision frame), replace it with 23 before forwarding the
frame to the HSR network
b) If its value is 23 (HSR_Supervision frame), replace it with 20 (duplicate discard) before
forwarding the frame to the PRP network
2) If TLV2 is not present,
a) Insert TLV2
b) Replace the supervision frame’s sequence number with the RedBox’s local sequence
number
3) If TLV2 is present, leave it and the supervision frame’s sequence number unmodified
4) Replace the frame’s source MAC address with the MAC address of the RedBox and replace
the RedundancyTag sequence number with the RedBox’s local sequence number

© IEC 2023
In an HSR-PRP RedBox, it is mandatory to provide a configuration possibility to enable or
disable this translation process. The translation can be disabled if, in the particular network, all
DANPs accept a TLV1.TYPE equal to 23 and all DANHs accept a TLV1.TYPE equal to 20 and
21.
If the proxy translation is disabled, supervision frames shall still be forwarded, without
modification, between HSR and PRP networks in both directions.
5.2.2.3.2.2 Generating supervision frames
An HSR-PRP RedBox shall send its own supervision frames (see 4.3.3 and 5.7.2.1) both to the
HSR network (in the HSR_Supervision frame format) and to the PRP network (in the
PRP_Supervision frame format) with the same supervision frame sequence number and
RedundancyTag sequence number.
5.2.2.3.2.3 Clarification of supervision frames proxy-translation scenarios (informative)
Scenario 1: DANP sends PRP_Supervision frame:
• PRP_Supervision frame received by HSR-PRP-A RedBox
• HSR-PRP-A RedBox translates the frame to HSR_Supervision frame, also inserting TLV2
and replacing supervision sequence number, and sends it to HSR ring in both directions
• PRP_Supervision frame received by HSR-PRP-B RedBox
• HSR-PRP-B RedBox translates the frame to HSR_Supervision frame, also inserting TLV2
and replacing supervision sequence number, and sends it to HSR ring in both directions
• DANHs receive two copies of the HSR_Supervision frames from HSR-PRP-A RedBox
(DANP appears as VDANH behind HSR-RedBox A)
• DANHs receive two copies of the HSR_Supervision frames from HSR-PRP-B RedBox
(DANP appears as VDANH behind HSR-RedBox B)
Scenario 2: PRP-RedBox sends PRP_Supervision frame on behalf of VDANPs:
• PRP_Supervision frame received by HSR-PRP-A RedBox
• HSR-PRP-A RedBox translates the frame to HSR_Supervision frame, only modifying TLV1
and replacing source MAC address and RedundancyTag sequence number, and sends it to
HSR ring in both directions
• PRP_Supervision frame received by HSR-PRP-B RedBox
• HSR-PRP-B RedBox translates the frame to HSR_Supervision frame, only modifying TLV1
and replacing source MAC address and RedundancyTag sequence number, and sends it to
HSR ring in both directions
• DANHs receive two copies of the HSR_Supervision frame from HSR-PRP-A RedBox
(originating PRP-RedBox appears as HSR-RedBox; VDANPs appear as VDANHs behind
the HSR-RedBox)
• DANHs receive two copies of the HSR_Supervision frame from HSR-PRP-B RedBox
(originating PRP-RedBox appears as HSR-RedBox; VDANPs appear as VDANHs behind
the HSR-RedBox)
Scenario 3: DANH sends HSR_Supervision frame:
• HSR_Supervision frame (two copies) received by HSR-PRP-A RedBox
• HSR-PRP-A RedBox translates the frame to PRP_Supervision frame, also inserting TLV2
and replacing supervision sequence number, and sends it to PRP LAN-A
• HSR_Supervision frame (two copies) received by HSR-PRP-B RedBox
• HSR-PRP-B RedBox translates the frame to PRP_Supervision frame, also inserting TLV2
and replacing supervision sequence number, and sends it to PRP LAN-B

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© IEC 2023
• DANPs in LAN-A receive (potentially two copies of, depending on whether HSR-PRP-A
RedBox applies duplicate discard to supervision frames or not) the PRP_Supervision frame
from HSR-PRP-A RedBox (DANH appears as VDANP behind PRP-RedBox A)
• DANPs in LAN-B receive (potentially two copies of, depending on whether HSR-PRP-B
RedBox applies duplicate discard to supervision frames or not) the PRP_Supervision frame
from HSR-PRP-B RedBox (DANH appears as VDANP behind PRP-RedBox B)
Scenario 4: HSR-RedBox sends HSR_Supervision frame on behalf of VDANHs:
• HSR_Supervision frame (two copies) received by HSR-PRP-A RedBox
• HSR-PRP-A RedBox translates the frame to PRP_Supervision frame, only modifying TLV1
and replacing source MAC address and RedundancyTag sequence number, and sends it to
PRP LAN-A
• HSR_Supervision frame (two copies) received by HSR-PRP-B RedBox
• HSR-PRP-B RedBox translates the frame to PRP_Supervision frame, only modifying TLV1
and replacing source MAC address and RedundancyTag sequence number, and sends it to
PRP LAN-B
• DANPs in LAN-A receive (potentially two copies of, depending on whether HSR-PRP-A
RedBox applies duplicate discard to supervision frames or not) the PRP_Supervision frame
from HSR-PRP-A RedBox (originating HSR-RedBox appears as PRP-RedBox; VDANHs
appear as VDANPs behind the PRP-RedBox)
• DANPs in LAN-B receive (potentially two copies of, depending on whether HSR-PRP-B
RedBox applies duplicate discard to supervision frames or not) the PRP_Supervision frame
from HSR-PRP-B RedBox (originating HSR-RedBox appears as PRP-RedBox; VDANHs
appear as VDANPs behind the PRP-RedBox)
Scenario 5: HSR-PRP-A RedBox sends a supervision frame on behalf of VDANHs both to PRP
LAN-A and to HSR ring:
• HSR_Supervision frame (two copies) received by HSR-PRP-B RedBox
• HSR-PRP-B RedBox translates the frame to PRP_Supervision frame, only modifying TLV1
and replacing source MAC address and RedundancyTag sequence number, and sends it to
PRP LAN-B
• DANPs in LAN-B receive (potentially two copies of, depending on whether HSR-PRP-B
RedBox applies duplicate discard to supervision frames or not) the PRP_Supervision frame
from HSR-PRP-B RedBox (originating HSR-PRP-A RedBox appears as PRP-RedBox;
VDANHs appear as VDANPs behind the PRP-RedBox)
• DANHs receive two copies of the HSR_Supervision frame from HSR-PRP-A RedBox – same
as from a regular HSR-RedBox
• DANPs in LAN-A receive one copy of the PRP_Supervision frame from HSR-PRP-A RedBox
(HSR-PRP-A RedBox appears as PRP-RedBox; VDANHs appear as VDANPs behind the
PRP-RedBox)
Scenario 6: HSR-PRP-B RedBox sends a supervision frame – everything is symmetrical to
Scenario 5.
Scenario 7: HSR-PRP-A RedBox does not have VDANHs connected and acts as a DANH itself.
It sends a supervision frame to both PRP LAN-A and HSR ring:
• HSR_Supervision frame (two copies) received by HSR-PRP-B RedBox
• HSR-PRP-B RedBox translates the frame to PRP_Supervision frame, also inserting TLV2
and replacing supervision sequence number, and sends it to PRP LAN-B
• DANPs in LAN-B receive (potentially two copies of, depending on whether HSR-PRP-B
RedBox applies duplicate discard to supervision frames or not) the PRP_Supervision frame
from HSR-PRP-B RedBox (HSR-PRP-A RedBox appears as VDANP behind PRP-RedBox
B)
© IEC 2023
• DANHs receive two copies of the HSR_Supervision frame from HSR-PRP-A RedBox – same
as from a regular DANH
• DANPs in LAN-A receive one copy of the PRP_Supervision frame from HSR-PRP-A RedBox
(HSR-PRP-A RedBox appears as VDANP)
Scenario 8: HSR-PRP-B RedBox acts a DANH and sends a supervision frame – everything is
symmetrical to Scenario 7.
5.4.1 RedBox properties
Replace, in NOTE 1, “A RedBox sends Supervision frames” with “A RedBox sends supervision
frames”.
5.4.3 RedBox receiving from port A or port B (HSR ring)
Delete, in the first sentence of the first paragraph, the word “valid”.
Replace the complete pseudo-code table with the following new table:
If this frame is not HSR-tagged:
If the frame carries a non-forwardable address (IEEE 802.1Q Table 8-1 & 8-2)

consume the frame and do not forward it.

Else if the node is in Mode M
enqueue the unchanged frame to port C.

forward to the other HSR port in accordance with IEEE 802.1Q forwarding
rules
Else if the node is in Mode T
enqueue the unchanged frame for passing to its link layer interface.

enqueue the unmodified frame for sending over the second port.
Else
enqueue the unchanged frame for passing to its link layer interface.

do not forward this frame to the other HSR port
Else (frame is HSR-tagged):
If the node is in Mode T (transparent)

remove the HSR tag
send the modified frame over the second port
send the modified frame to its link layer interface
Else (node is not in transparent mode)

If this node is a destination:

If this is the first occurrence of the frame:

remove the HSR tag and pass the modified frame to its link layer

interface.
Else (this is not the first occurrence of the frame over the link

layer interface):
do not pass the frame to the link layer interface.

Else (if this node is not a destination):

do not pass the frame to the link layer interface.

If this node is not the unique destination or the node is in Mode U:

If the destination is in the ProxyNodeTable and the node is not in

Mode U:
do not enqueue the unchanged frame to the other HSR port.

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© IEC 2023
If this is the first occurrence of the frame and the node is not in

Mode N:
enqueue the unmodified frame for sending over the other HSR

port(s).
Else (this is not the first occurrence of the frame or the node is in

Mode N):
do not enqueue the unchanged frame to the other HSR port.

If this is the first occurrence of the frame in direction of port C:

If the destination is registered in the NodesTable and the node

is not in Mode U:
discard the frame
If the RedBox is in HSR-SAN mode:

remove the HSR tag;
If the source is registered in the ProxyNodeTable:

discard the frame
Else
validate and enqueue frame for passing to port C.

Else if the RedBox is in HSR-PRP mode (RedBox A or RedBox B):

If the NetId matches that of the RedBox

discard the frame
Else
remove the HSR tag and append the PRP RCT with PathId

“1010” (RedBox A) or “1011” (RedBox B), reusing the HSR
sequence number.
validate and enqueue frame for passing to the port C.

Else (if the RedBox is in HSR-HSR mode)

do not modify the frame.
enqueue frame for passing to port C.

Else (If this is not the first occurrence of the frame in direction

of port C:
discard the frame
Else (If this node is the only (unicast) destination and the node is not

in Mode U:
discard the frame.
Delete the two paragraphs and the NOTE at the end of the subclause, after the pseudo code
table.
5.7.2.1 Sending
Insert, between NOTE 1 and Table 9, the following new paragraph:
A RedB
...