Vinton G. Cerf
Defense Advanced Research Projects Agency
- ABSTRACT
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- This paper describes briefly the packet satellite technology developed
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- by the Defense Advanced Research Projects Agency and several other
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- participating organizations in the U.K. and Norway and provides a
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- biblography of relevant papers for researchers interested in
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- experimental and operational experience with this dynamic
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- satellite-sharing technique.
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- INTRODUCTION
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- Packet Satellite technology was an outgrowth of early work in packet
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- switching on multiaccess radio channels carried out at the University of
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- Hawaii with the support of the Defense Advanced Research Projects Agency
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- (DARPA). The primary difference between the earlier packet-switched
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- ARPANET [1, 2] and the ALOHA system developed at the University of
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- Hawaii [3] was the concept of multiple transmitters dynamically sharing
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- a common and directly-accessible radio channel. In the ARPANET, sources
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- of traffic inserted packets of data into the network through packet
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- switches called Interface Message Processors (IMPs). The IMPs used high
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- speed point-to-point full-duplex telephone circuits [4] on a
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- store-and-forward basis. All packet traffic for a given telephone
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- circuit was queued, if necessary, in the IMP and transmitted as soon as
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- the packet reached the head of the queue. On such full duplex circuits
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- there is exactly one transmitter and one receiver in each direction.
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- The ALOHA system, on the other hand, assigned a common transmit channel
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- frequency to ALL radio terminals. A computer at the University of
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- Hawaii received packet bursts from the remote terminals which shared the
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- "multi-access" channel. Under the control of a small processor, each
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- terminal would transmit whenever it had traffic, and would await an
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- acknowledgement, on another frequency, dedicated to the service host. If
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- no acknowledgement was received, the terminal processor would transmit
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- again at a randomly chosen time. The system operated on the assumption
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- that no store-and-forward or radio relay was needed. The University of
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- Hawaii researchers later demonstrated that the ALOHA concept worked on a
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- satellite channel linking Hawaii and Nasa-Ames via NASA's ATS-1
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- satellite [5, 6]. A variety of more elaborate satellite channel
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- assignment strategies were developed and analyzed in the early 1970's
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- [7-13, 31].
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- THE ATLANTIC PACKET SATELLITE EXPERIMENT (SATNET)
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- In 1973, DARPA began the development of a packet satellite system which
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- would support the sharing of a common, high speed channel among many
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- ground stations. Using an INTELSAT-IV satellite, the Atlantic Packet
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- Satellite experiment was carried out with the cooperation and support of
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- the British Post Office, COMSAT Corporation, Linkabit Corporation, and
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- Bolt Beranek and Newman Corporation, later joined by the Norwegian
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- Telecommunication Administration and the Norwegian Defense Research
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- Establishment (NDRE). Along with University College London and COMSAT
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- Laboratories, NDRE became one of the major users of the SATNET system.
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- During 1975-1978, SATNET underwent a broad range of performance
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- evaluations and tests. Since 1979, it has served as a stable support
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- for international experiments and demonstrations of command and control
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- technology of interest to DARPA, NDRE and the U.K. Royal Signals and
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- Radar Establishment (RSRE). Late in 1982, a ground station was added to
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- connect the German Aeronautics and Space Research Establishment (DFVLR)
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- into the system.
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- The early development of SATNET is outlined in [14]. The system design
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- is documented in [15-22]. Experience with the operation of the SATNET
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- is reported in [23-24] and experimental results in [25-26]. Potential
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- services which might be supported by this technology are discussed in
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- [27].
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- The integration of the packet satellite technology into a larger,
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- multiple packet network context is discussed in [28-29]. The system is
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- expected to continue in use to support joint research by DARPA, RSRE,
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- NDRE, DFVLR and UCL. DARPA and the U.S. Defense Communications Agency
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- are experimenting with a 3 megabit/second domestic packet satellite
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- system to determine whether packetized voice and data services can be
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- integrated economically using this technology. DARPA and the U.S. Naval
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- Electronic Systems Command recently demonstrated a Mobile Access
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- Terminal Network (MATNET) which uses packet satellite techniques to
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- support ship-ship and ship-shore communication over a shared FLTSATCOM
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- satellite channel [30].
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- ACKNOWLEDGEMENTS
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- The development of Packet Satellite technology has involved many
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- institutions and individuals, but special credit for the successful
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- realization of the SATNET and its successor systems must be given to Dr.
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- Robert E. Kahn, Director, Information Processing Techniques Office,
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- DARPA, for his continuous support and technical contributions throughout
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- the development and maturation of this technology.
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- REFERENCES
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- 1. L.G. Roberts and B.D. Wessler, "Computer Network Development to
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- Achieve Resource Sharing," Spring Joint Computer Conference, AFIPS
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- Proceedings, Vol. 36, 1970, pp. 543-549.
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- 2. R.E. Kahn, "Resource Sharing Computer Networks," Proceedings of the
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- IEEE, Vol. 60, No. 11, November 1972, pp. 1397-1407.
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- 3. N. Abramson, "The Aloha System - Another Alternative for Computer
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- Communications," AFIPS Conference Proceedings, Vol. 36, 1970, pp.
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- 295-298.
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- 4. F.E. Heart, et al, "The Interface Message Processor of the ARPA
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- Computer Network, Spring Joint Computer Conference, AFIPS Proceedings,
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- 1970, pp. 551-567.
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- 5. R. Binder, et al, "Aloha Packet Broadcasting--a retrospect," AFIPS
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- Conference Proceedings, National Computer Conference, 1975, pp. 203-215.
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- 6. N. Abramson and F. Kuo, Editors, Computer Communication Networks,
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- Prentice Hall, Englewood Cliffs, N.J., 1973.
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- 7. L. Kleinrock and S. Lam, "Packet Switching in a Slotted Satellite
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- Channel," AFIPS Conference Proceedings, NCC, 1973, pp. 703-710.
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- 8. L. Kleinrock and F. Tobagi, "Random Access Techniques for Data
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- Transmission over Packet Switched Radio Channels," AFIPS Conference
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- Proceedings, NCC, 1975, pp. 187-201.
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- 9. L. Kleinrock and S.S. Lam, "Packet Switching in a Multiaccess
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- Broadcast Channel: Performance Evaluation," IEEE Transactions on
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- Communication, Vol. COM-23, 1975, pp. 410-423.
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- 10. L.G. Roberts, "Aloha Packet System with and without Slots and
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- Capture," ACM SIGCOMM, Computer Communication Review, Vol 5, No. 2,
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- April 1975.
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- 11. S.S. Lam and L. Kleinrock, "Packet Switching in a Multi-access
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- Broadcast Channel: Dynamic Control Procedures," IEEE Transactions on
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- Communication, Vol Com-23, September, 1975.
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- 12. L.G. Roberts, "Dynamic Allocation of Satellite Capacity through
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- Packet Reservation," AFIPS Conference Proceedings, NCC, 1973, pp.
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- 711-716.
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- 13. N. Abramson, "Packet Switching with Satellites," AFIPS Conference
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- Proceedings, NCC, 1973, pp. 695-702.
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- 14. R.E. Kahn, "The Introduction of Packet Satellite Communications,"
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- National Telecommunications Conference, Nov. 1979, p. 45.1.1-45.1.8.
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- 15. I.M. Jacobs, et al, "CPODA - A Demand Assignment Protocol for
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- SATNET," Fifth Data Communications Symposium, Snowbird, Utah, 1977.
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- 16. I.M. Jacobs, et.al, "General Purpose Satellite Networks,"
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- Proceedings IEEE, Vol 66, No. 11, November 1978, pp. 1448-1467.
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- 17. I.M. Jacobs, et al, "Packet Satellite Network Design Issues,"
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- Proceedings, NTC, November 1979.
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- 18. L. Palmer, J. Kaiser, S. Rothschild and D. Mills, "SATNET Packet
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- Data Transmission," COMSAT Technical Review, Volume 12, No. 1, Spring
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- 1982, pp. 181-212.
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- 19. Weissler, et al, "Synchronization and Multiple Access Protocol in
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- the Initial Satellite IMP," COMPCON, September 1978.
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- 20. Hsu and Lee, "Channel Scheduling Snychronization for the PODA
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- Protocol," ICC, June 1978.
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- 21. E. Killian and R. Binder, "Control Issues in a PODA Voice/Data
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- Satellite Network," ICC, June 1980.
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- 22. C. Heegaard, J. Heller and A. Viterbi, "A Microprocessor-based PSK
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- Modem for Packet Transmission over Satellite Channels," IEEE
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- Transactions on Communications, COM-26, No. 5, May 1978, pp. 552-564.
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- 23. P. Cudhea, D. McNeill, D. Mills, "SATNET Operations," AIAA 9th
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- Communications Satellite Systems Conference, Collection of Technical
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- Papers, 1982, pp. 100-105.
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- 24. D.A. McNeill, et al, "SATNET Monitoring and Control," Proceedings
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- of the NTC, November 1979.
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- 25. P.T. Kirstein, et al, "SATNET Applications Activities," Proceedings
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- of the NTC, November 1979.
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- 26. W.W. Chu, et al, "Experimental Results on the Packet Satellite
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- Network," Proceedings of the NTC, November 1979.
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- 27. E.V. Hoversten and H. L. Van Trees, "International Broadcast Packet
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- Satellite Services," ICCC Conference Proceedings, Kyoto, Japan,
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- September 1978.
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- 28. V.G. Cerf and R.E. Kahn, "A Protocol for Packet Network
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- Intercommunication," IEEE Trans. on Comm., Vol. COM-23, May 1974, pp.
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- 637-648.
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- 29. V.G. Cerf and P.T. Kirstein, "Issues in Packet Network
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- Interconnection," IEEE Proceedings, Vol. 66, No. 11, Nov 1978, pp.
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- 1386-1408.
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- 30. L. Evenchik, D. McNeill, R.P. Rice, F. Deckelman, et al, "MATNET,
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- an Experimental Navy Shipboard Satellite Communications Network, "IEEE
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- INFOCOM 82 Proceedings, March, 1982.
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- 31. M.L. Molle and L. Kleinrock, "Analysis of Concentrated ALOHA
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- Satellite Links," Sixth Data Communications Symposium, Nov 27-29, 1979,
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- pp. 87-95.
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