Greetings,
After reading a mail about ECN support under NetBSD mailing lists I 
found SACK, RH (Rate-Halving) and ECN implementations at the Pittsburgh 
Supercomputer Center (Advanced Networking group). Despite the fact that 
they are really OLD, I think we can use them and incorporate them in
the tree if it's worth. 

http://www.psc.edu/networking/projects/tcp/

Regards.

-- 
Rui Paulo                          "Simplicity is the ultimate sophistication."
                                      -- Leonardo da Vinci