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tcp: shift PRR sending cadence left to prevent long runs of ACKs not clocking out a segment
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Authored by rscheff on Dec 5 2023, 10:47 PM.
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Details

Summary

PRR currently can start by waiting a short run of ACKs
without sending any segments - partially due to limited
transmit.

This change pulls the transmission opportunities slightly
leftward, preventing long runs of ACKs (initially up to 4)
before a segment is allowed for transmit. Depending on
the expected cwnd reduction, and if ACK compression is
happening, at most every other ACK should now elicit a
new segment.

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rG FreeBSD src repository
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Buildable 54808
Build 51697: arc lint + arc unit