TCP SACK (RFCs 2883 3708 3517)
http://leaf.dragonflybsd.org/mailarchive/commits/2004-11/msg00142.html

TCP Appropriate Byte Counting (RFC 3465)
http://leaf.dragonflybsd.org/mailarchive/commits/2005-05/msg00207.html

Extensive rewrite of poorly written IP routing code.
(lots of commits over several months, but see
http://leaf.dragonflybsd.org/mailarchive/commits/2005-01/msg00103.html)

Specifically, compare FreeBSD rtalloc1() with DragonFlyBSD's _rtlookup():

http://leaf.dragonflybsd.org/~hsu/iprouting/rtalloc1
http://leaf.dragonflybsd.org/~hsu/iprouting/_rtlookup

Eifel Detection (RFC 3522)
http://leaf.dragonflybsd.org/mailarchive/commits/2003-08/msg00086.html
http://leaf.dragonflybsd.org/mailarchive/commits/2003-08/msg00097.html