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Trans-Atlantic link to NORSAR and University College London in September 1973 (prior to SATNET)
SATNET, from the Peter T. Kirstein report to DARPA, 1977
First Internet demonstration, linking the ARPANET, PRNET, and SATNET on November 22, 1977
SATNET diagram, mid 1979

SATNET, also known as the Atlantic Packet Satellite Network, was an early satellite network that formed an initial segment of the Internet. It was implemented by BBN Technologies under the direction of the Advanced Research Projects Agency.

SATNET had its origins in a proposed linkage between the ARPANET and the National Physical Laboratory (NPL) network, via ARPA's existing 2.4 kilobit/second NORSAR link to Norway (used for seismic research). The NORSAR link crossed the Atlantic via a satellite link to London, then continued via cable to Norway. In 1970, ARPA's Larry Roberts proposed to NPL's Donald Davies that the two organizations connect their networks via the satellite linkage. This original proposal proved infeasible, but in 1971 Peter T. Kirstein agreed to connect his university, University College London (UCL), instead. Funding was finally approved in 1973, by which time the trans-Atlantic connectivity had changed: two ARPANET Terminal Interface Processors (TIPs) were installed in Norway and connected to the ARPANET via satellite in June and September 1973. The TIP for UCL also arrived in September 1973, and its connection through Norway became operational in 1973 at 9.6 kilobits/second. At this point, UCL was connected to the ARPANET.

In that same year, Larry Roberts proposed that it would be possible to use a satellite's 64 kilobit/second link as a medium shared by multiple satellite earth stations within the beam's footprint. This proposal was implemented by Bob Kahn, and resulted in SATNET. Key participants included BBN Technologies, COMSAT, the Linkabit Corporation, UCLA, University College London, and the Norwegian Defence Research Establishment. By the late 1970s, SATNET connected research sites in the US, UK, Norway, Germany, and Italy.

SATNET played a central role in the creation of the Internet protocol suite. In 1973, Bob Kahn designed the interconnection of the ARPANET with other networks. He enlisted Vint Cerf, who was teaching at Stanford. The problem is that the ARPANET, radio-based PRNET, and SATNET all had different interfaces, packet sizes, labeling, conventions and transmission rates. Linking them together was very difficult. In response, Kahn and Cerf set about designing a net-to-net connection protocol. Cerf led the newly formed International Network Working Group. In September 1973, the two gave their first paper on the new Transmission Control Protocol (TCP) at an INWG meeting at the University of Sussex in England. In the end, SATNET was assigned a /8 IPv4 address range in the List of assigned /8 IPv4 address blocks.


  • L.G. Roberts, "Dynamic Allocation of Satellite Capacity through Packet Reservation", Proc. NCCC, Vol. 42, pages 695-702, 1973.
  • University College London ARPANET Project, Annual Report 1977, by Professor Peter T. Kirstein, April 1978.
  • Bolt Beranek and Newman Inc., "Combined Quarterly Technical Report No. 29", May 1983, Prepared for the Defense Advanced Research Projects Agency.
  • Peter T. Kirstein, "Early Experiences With the Arpanet and Internet in the United Kingdom", IEEE Annals of the History of Computing, Vol. 21, No. 1, 1999, pages 38-44.
  • Pål Spilling, "The Internet Development Process: Observations and Reflections", History of Nordic Computing 3: Third IFIP WG 9.7 Conference, HiNC3, Stockholm, Sweden, October 18-20, 2010, Revised Selected Papers.
  • Katie Hafner, Matthew Lyon, Where Wizards Stay Up Late: The Origins Of The Internet, Simon and Schuster, 1998, pages 221-226. ISBN 9780684832678.