Just go pull up his bibliography. Chord, the Click Modular Router (super big deal to me), RON (also a big deal to me), Vivaldi (which made its way into the Hashi products). He had a hand in a lot of stuff. His pre-CSAIL work was very much like that of the LBL Network Research Group (that's Van Jacobsen, Vern Paxson, Steve McCanne) --- he's in that league.