[pim] Re: Gorry Fairhurst's Discuss on draft-ietf-pim-zero conf-mcast-addr-alloc-ps-07: (with DISCUSS and COMMENT)

Gorry,

Thanks for your review! We uploaded draft-ietf-pim-zeroconf-mcast-addr-alloc-ps-08 and made changes based on your feedback:

> there are no formal requirements based on RFC-2119 keywords derived

You are right. We updated section 3 to use requirements language.

> I expect the declaration of keywords can also be removed

I see your point – this document, being informational, does not impose any requirements. It does document requirements for other protocols, but this is different than imposing its own requirements. I’m not sure if we should remove the reference to RFC 2119 et al. It is useful in interpreting the language in section 3. It may be most appropriate to move these references to the list of informational references?

> From the TSV_ART review…

We’ve incorporated updates from this review.

Best Regards,

Nate

From: Gorry Fairhurst via Datatracker <[email protected]>
Sent: Monday, October 20, 2025 07:19
To: The IESG <[email protected]>
Cc: [email protected]; [email protected]; [email protected]
Subject: [pim] Gorry Fairhurst's Discuss on draft-ietf-pim-zeroconf-mcast-addr-alloc-ps-07: (with DISCUSS and COMMENT)

Gorry Fairhurst has entered the following ballot position for draft-ietf-pim-zeroconf-mcast-addr-alloc-ps-07: Discuss When responding, please keep the subject line intact and reply to all email addresses included in the To and CC lines. (Feel


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DISCUSS:

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(1) The documents says it defines requirements.

I saw in the abstract this statement:

"The document presents explicit requirements covering discovery", but yet from

a standards perspective it does not - there are no formal requirements based on

RFC-2119 keywords derived. That may well be suitable for an Informational

document, and I expect the declaration of keywords can also be removed, and

this sentence could be rewritten as guidance for future work rather than

requirements?



(2) From the TSV_ART review:

The document appears to be about selecting multicast IP addresses to avoid link

address collisions, rather than IP address collisions. That should be made more

clear in the title, abstract, intro, and throughout. The current text is easily

misread as focusing on IP address collisions until section 2.



Can this be clarified in the document?



(3) The TSV_ART review suggested:

The document jumps between link and network issues without enough context for

the reader to distinguish between the two. Collisions should be referred to

throughout as link address collisions, not just address collisions, and address

assignment should be referred to as IP address assignment.



Sec 5 should more clearly relate the way 32 IP addresses could map to the same

MAC address, i.e., this is because only the lower 23 bits are used of the 28

bits in the IP multicast address range. It would be very useful if the reason

for this mapping were discussed in this doc – i.e., why did we not just use all

28 bits?



Can this be clarified in the document?





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COMMENT:

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Thank you Joe Touch for his TSV-ART review, I'd like to pick-up on the issues

discussed there, so include them here:



(i) It also appears that the limited number of (host) hardware address filters

has been overlooked; i.e., if a device is capable of filtering only 4 multicast

addresses in hardware, the device would more efficiently support 7 addresses if

at least 3 DID collide, rather than ensuring that none collide.  When no

addresses collide and the number of filters is exceeded, the network interface

is driven into promiscuous mode that requires software filtering – i.e., it

completely undermines the goal of this doc.



(ii) The protocol requirements need some refinement. Resistance to failure is

NOT the same as robustness to a single point of failure; the tag phrase and the

definition need to be adjusted to align. Item 3 is “multicast self-assignment

protocol coexistence”, i.e., this isn’t about interoperation with other

protocols in general. Item 7 (collision detection and resolution) is not a

requirement; it is an approach to satisfying other requirements, such as 1, 2,

and 5. It would help if the tag phrases were similar (they seem to be phrases

defining properties, except for #6, which should be “supports host-level

multiplexing” – check this throughout for all lists).



(iii) The Note needs revision; the collisions arise after *rejoining

disconnected networks caused by* a temporary network partition. I.e., it is the

rejoining that causes the problem, not the partitioning. The second list should

describe goals of a design; it seems odd to include “cross-platform

availability”, as this seems to conflate deployment with OS capabilities; it is

difficult to appreciate what OS properties could ever interfere with these

mechanisms. An example would help as would rephrasing this as “OS independence”.



... Please see additional comments in the review that may also be helpful.







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