I've prepared a more or less blind backport of the TCP SACK code which was recently introduced in -CURRENT. Didn't put the patch through lots of testing, but it just seems to work... The patch is available from the URL bellow and should apply cleanly against both 4.10-RELEASE and -STABLE. http://tel.fer.hr/zec/BSD/4.10-sack.diff Cheers, Marko