For those like me who had no idea:
Fuzzball routers were the first modern routers on the Internet.
Six Fuzzball routers provided the routing backbone of the first 56 kbit/s NSFNET, allowing the testing of many of the Internet's first protocols. It allowed the development of the first TCP/IP routing protocols, and the Network Time Protocol. They were the first routers to implement key refinements to TCP/IP such as variable-length subnet masks.