I am the assigned Gen-ART reviewer for this draft. The General Area
Review Team (Gen-ART) reviews all IETF documents being processed
by the IESG for the IETF Chair. Please treat these comments just
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Document: draft-ietf-ippm-qoo
Title: Quality of Outcome (QoO)
Reviewer: Paul Kyzivat
Review Date: 2026-02-09
IETF LC End Date: 2026-02-13
IESG Telechat date: ?
Summary: This draft is on the right track but has open issues, described
in the review.
Note: This reviewer has no experience in, or knowledge of, network
performance measurement. Hence I'm unqualified to comment on the
semantics of this draft. In such cases I usually fall back to reviewing
the form and syntax. Even that is hard here, since there is little in
the way of formal specification.
Issue:
My impression is that for QoO values to be composable, they must be
based on the same measurement percentiles. Achieving that across the
managers of connected networks seems difficult. Is it realistic?
Issue:
I had difficulty understanding the notation used in the formula in
section 7:
QoO_latency = min_{i}(min(
max((1 - ((ML_i - ROP_i) / (CPUP_i - ROP_i))) * 100, 0), 100))
Fortunately, Martin Thompson has posted an alternative rendition for
this formula, that I find much more understandable:
for i in ROP:
m = (ML[i] - ROP[i]) / (CPUP[i] - ROP[i])
metrics[i] = clamp(0, m, 1)
QoO_latency = find_min(metrics) * 100
(It is in his followup message to his ArtArt review of this document.
<https://mailarchive.ietf.org/arch/msg/art/BC-qxC6pD_63lfHfLd1R4n_KA8c/>)
Martin considers this a nit, but I consider it to be a significant
issue. It is the closest thing this document has to a normative
requirement, so it is essential that all readers understand it
consistently. I recommend reworking the rendition of this formula into a
form that will be clear to all who need to understand it.
I found Martin's full ArtArt review insightful. While it goes beyond my
understanding of the subject material, I agree with it to the extent of
my understanding.
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