He graduated from Cornell University in 1973 with a B.A. in Mathematics.
After graduating from Cornell, Chapin spent the next two years writing time-sharing applications in COBOL for Systems & Programs Ltd. In 1977 he joined the newly-formed Networking Group at Data General Corporation, where he was responsible for creating software for distributed resources, distributed database management, and routing functions for DG’s open-system hardware and software products. He joined BBN (then Bolt, Beranek & Newman) in 1990 as Chief Network Architect in the Communications Division.
Lyman is a Fellow of the IEEE, and has served as the USA (ACM) representative to the International Federation for Information Processing (IFIP) Technical Committee on Communication Systems (TC6), and as the USA representative to the NATO Science Committee’s networking panel.
He been the chairman of the Internet Architecture Board (IAB), SIGCOMM, ANSI and ISO standards groups responsible for Network and Transport protocols. He was also the founding trustee of the Internet Society.