Louis Pouzin

Datagrams. Pouzin led France's CYCLADES network from 1971, which made the network itself simple and unreliable and gave the computers at each end the job of checking and reassembling data. That datagram approach was far easier to scale than the ARPANET's managed links, and Cerf and Kahn built it into TCP/IP. CYCLADES lost its funding in the late 1970s, but the internet runs on its central idea.