[Idr] Re: Gorry Fairhurst's No Objection on draft-ietf-idr-link-bandwidth-19: (with COMMENT)

[Reshma Das <[e-mail]>]

Hi Gory,

Thank you for reviewing the document. Please find my reply inline:

RD>

Thanks & Regards,
Reshma Das

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From: Gorry Fairhurst via Datatracker <[e-mail]>
Date: Monday, October 20, 2025 at 7:16 AM
To: The IESG <[e-mail]>
Cc: [e-mail] <[e-mail]>, [e-mail] <[e-mail]>, [e-mail] <[e-mail]>, [e-mail] <[e-mail]>, [e-mail] <[e-mail]>
Subject: Gorry Fairhurst's No Objection on draft-ietf-idr-link-bandwidth-19: (with COMMENT)
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Gorry Fairhurst has entered the following ballot position for
draft-ietf-idr-link-bandwidth-19: No Objection

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COMMENT:
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Thank you for the effort put into completing this specification. I have adopted
the position of "No Objection", because I think my transport-related comments
are likely easily addressed.

I have two substantial comments with the text, that were also echoed by one of
the review team:

1. "The bandwidth value is encoded as a 4-octet value representing bytes per
second. What if there were cases where a 100Gbps (or higher) path exists, but
the maximum value that could be encoded is 8x2^32 = ~34Gbps?"

- Is there still a possibility that it be worth using Kbps as the unit rather
than bytes?

RD> The bandwidth value format is an IEEE 754 32-bit floating point number.  Its maximum range is roughly 3.4 x 10^38.


2. I don't understand this text: "carries the bandwidth information of a
router", to me it announces bandwidth information of a "link "(aka hop). Is it
really about router forwarding capability?
RD> The Link Bandwidth Extended Community provides a mechanism for routers to advertise the bandwidth of their downstream path that may either be a directly connected link or multi-hop/multipath nexthop.


3. I was unsure what actually this means, is it really a requirement?:
" If any of the paths lack a valid Link Bandwidth Extended Community,
   ECMP (Equal-Cost Multi-Path) MUST be used instead."
- Maybe this could mean something like, if there is no Link Bandwidth Extended
Community then ECMP can (MAY) be used?

RD> If all paths don’t have a valid LBWC that it is not possible to do accurate WECMP. Hence this is a MUST.

Some other comments are:

The current abstract is too terse to be useful:
- It does not mention 'link bandwidth', please explain this.
- It does not say that this describes both the format of the type and the
processing rules for the type.

This text appears mangled: /doesn't matter for purpose/does not matter for the
purpose/

RD> Please review the suggested text :
“This document defines a BGP Extended Community, the Link Bandwidth Extended Community, which carries link bandwidth information to enable weighted load-balancing in multipath scenarios. It specifies the format and processing rules for this community type”