SATNET was the experimental satellite network that linked early Internet research sites in the 1970s.
Also called the Atlantic Packet Satellite Network, SATNET was developed under ARPA direction and implemented by BBN Technologies. It used satellite communication to connect geographically separated research networks, extending the reach of the ARPANET across the Atlantic. By the late 1970s, it connected sites in the United States, the United Kingdom, Norway, Germany, and Italy.
SATNET was important because it was not simply a long-distance link between two computers. It helped researchers test internetworking: making different networks communicate despite differences in packet formats, interfaces, addressing, and transmission speeds. Those challenges influenced the work of Bob Kahn and Vint Cerf on the Transmission Control Program.
On November 22, 1977, a major demonstration linked SATNET, the ARPANET, and the packet-radio network PRNET. That experiment showed that a single communication system could span satellite, wired, and radio networks—the basic idea behind an Internet. NSFNET later became a major academic backbone, while CSNET and BITNET were separate research or academic networking projects.