SACK retransmits multiple segments respond to single dupack

[Daikichi Osuga]

Hello,

I had experiments with FreeBSD SACK implementation.
FreeBSD SACK retransmits multiple segments respond to single dupack.
It breaks "packet conservation principle".

In OpenBSD SACK implementation,
retransmission from SACK hole is limited to single segment.
"sack_rxmit" and "sendalot" are exclusive. 

I think solution is introducing mechanism to estimate amount of outstanding segments.
For example, "pipe" alogorithm is well known.
http://www.icir.org/floyd/talks/sf-sacks-96.pdf

Regards,
--
Daikichi Osuga