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[802SEC] Response to 802.11 comments on P802.1Qcb PAR

EC Colleauges

We have received the following comments from 802.11:

802.11 comment#1:

Suggest Change to 7.1: 
“IEC 62439-3 defines high-availability mechanisms in automation networks, but it is restricted to ring topologies, whereas this amendment will work on all LAN topologies.”

802.1 response:

Accepted. We have used the suggested text.

802.11 comment#2:

7.1 It appears that PRP or RSTP in IEC 62439-3 are not limited to “ring topologies”. (See tutorial at
(a) Can you please explain why PRP and RSTP are not suitable solutions?
(b) Does the revision of 62439-3 make a difference?

802.1 response:

(a) PRP (like HSR described in IEC 62439-3) is a solution that provides seamless redundancy through completely doubling network topologies (which severely limits financial feasibility) and introduces a dual connection mechanism that is not compliant with IEEE 802.1 bridging.

RSTP and its specific application in a ring topology described in IEC 62439-1 still is a mechanism that relies on network reconfiguration and introduces communication outages to whole networks or parts of the network. This is in conflict with the main requirement of the proposed PAR, enabling seamless redundancy without any loss of communication.

(b) No, the IEC 62439-3:2012-07 spec revision does not change any of the fundamental concepts of the PRP and HSR protocol described in this document. It merely corrects mistakes e.g. in the MIB and adds additional material throughout the document (e.g. HSR to PRP connections) to clarify questions and ambiguities reported to the IEC SC65CWG15 group by implementers.

802.11 comment#3 (on the 5C):

Distinct Identity: Suggest change “provides fault tolerance” with “provides link or intermediate node failure tolerance”.
Suggest change in b: “fault tolerance” with “link or intermediate node failure tolerance”

Economic Feasibility:
Suggested replacement of c: “The installation cost of enhanced VLAN bridges and end stations is expected to be similar to existing implementations”. 

802.1 response:

These were considered to be helpful improvements to the text of the 5C and have been incorporated.


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