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There was some discussion a while back regarding Appropriate Byte
Counting (RFC 3465).  As part of poking at HSTCP, I found a compelling
reason to implement this mechanism:

When a connection is in congestion avoidance, we currently grow the
window like thus:
  u_int cw =3D tp->snd_cwnd;
  u_int incr =3D tp->t_segsz;

  incr =3D incr * incr / cw;

The problem occurs when the congestion window grows past t_segsz
segments, since the increment is under a byte, the congestion window
won't be opened further.

Diff:
http://www.sigusr1.org/~kurahone/misc-hacks/tcp-abc-netbsd-3.99.20.diff.gz

The diff implements straight forward per-RFC ABC, with the "L" parameter
set at "1*SMSS".  As an additional bonus, I changed the header prediction
code to execute even when the connection is congestion window bound,
which should help overall performance.

Questions/Comments?

--=20
Kentaro A. Kurahone
SIGUSR1 Research and Development

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