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On Wed, May 11, 2005 at 06:08:32PM +0200, Hubert Feyrer wrote:
> TCP ABC is ``... a small modification to the way TCP increases
>    its congestion window.  Rather than the traditional method of
>    increasing the congestion window by a constant amount for each
>    arriving acknowledgment, the document suggests basing the increase on
>    the number of previously unacknowledged bytes each ACK covers.  This
>    change improves the performance of TCP, as well as closes a security
>    hole TCP receivers can use to induce the sender into increasing the
>    sending rate too rapidly.''[1]

Intresting.

According to a 2004 paper[0] ~50% of the webservers they surveyed had
ABC implemented, though looking at the test they used, I think that
those are Linux boxes with the "simple" solution to ACK division attacks.

"The second, perhaps simpler, solution is to only increment cwnd by one
SMSS when a valid ACK arrives that covers the entire data segment sent."[1]

> I wonder if the code from DragonflyBSD[2] would be of interest for NetBSD?

Didn't most of Jeff Hsu's stuff have a bit of a quirky licence?

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

[0]: http://www.cis.udel.edu/~ladha/2004.TbitExtensions.pdf
[1]: http://www.cs.washington.edu/homes/djw/papers/CCR99.pdf

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