Selective Acks

[Max]

I am dual booting Windows & Knoppix Linux HDD install. While running
Windows & doing the TweakTest at: http://www.dslreports.com/tweaks
everything looks good but running the same test under Linux I get this:

Selective Acks: OFF
Notes and recommendations:
Turn on Selective Acks (FAQ #578)

I know how to adjust this under Windows (DRTCP) but how would I do that
under Linux? TIA
Max