2. How to read this report

Every performance measurement carries a limited_by field recording what ran
out first. Without it a reader cannot tell a product measurement from a
measurement of our test rig.

`limited_by`	Means	Treat as a product figure?
`bng`	The platform was the constraint	Yes
`generator`	Our load generators ran out first	It depends — see below
`rss`	Receive-side distribution capped it	No — RSS is the limit
`none`	Neither side saturated	No — a latency or shape result
`controller`	The controller was the constraint	Yes, but name the component
`serial-by-design`	One operation in flight on purpose	No — latency, not throughput

A generator label alone is not enough to judge a forwarding cell, because it
covers two different situations. If the generators had the link essentially full
and the box forwarded everything with zero loss, that is a wire-speed result
and a legitimate product figure. If the generators never filled the link, the
cell is a floor that understates the platform. The forwarding matrix in §5.7
separates these explicitly and this report never promotes a floor into a claim.

Two further conventions used throughout:

offered_headroom > 1 means work arrived faster than the box drained it,
so the measured rate is the box's own. Below 1, the figure measures our
request rather than the platform.
completion_rate is preferred over mean_rate. Mean rate divides by
wall clock including ramp, and understates the platform.

A skip is not a pass. Each of the four is named in §6.2 with its reason.