Bachelor of Science, Swarthmore College, 1966. Doctor of Philosophy, Massachusetts Institute of Technology, 1973.
Research scientist Massachusetts Institute of Technology, Cambridge, Massachusetts, 1973—1980, principal research scientist, 1980—1984, senior research scientist, since 1984. Chairman Computer Science and Telecommunications Board, National Academies, Washington, 1996—2004.
Fellow: Association for Computing Machinery (ACM) (Hamming award 1998, SigComm award 1990), Institute of Electrical and Electronics Engineers (award Public Service Telecommunications 2000), American Academy Arts and Sciences. Member: National Academy of Engineering.
Married Susan Butts; children: Dana, Robin.