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Network Working Group                                            V. CerfRequest for Comments: 829                                          DARPA                                                           November 1982PACKET SATELLITE TECHNOLOGY REFERENCE SOURCES                             Vinton G. Cerf               Defense Advanced Research Projects AgencyABSTRACTThis paper describes briefly the packet satellite technology developedby the Defense Advanced Research Projects Agency and several otherparticipating organizations in the U.K. and Norway and provides abiblography of relevant papers for researchers interested inexperimental and operational experience with this dynamicsatellite-sharing technique.INTRODUCTIONPacket Satellite technology was an outgrowth of early work in packetswitching on multiaccess radio channels carried out at the University ofHawaii with the support of the Defense Advanced Research Projects Agency(DARPA).  The primary difference between the earlier packet-switchedARPANET [1, 2] and the ALOHA system developed at the University ofHawaii [3] was the concept of multiple transmitters dynamically sharinga common and directly-accessible radio channel.  In the ARPANET, sourcesof traffic inserted packets of data into the network through packetswitches called Interface Message Processors (IMPs).  The IMPs used highspeed point-to-point full-duplex telephone circuits [4] on astore-and-forward basis.  All packet traffic for a given telephonecircuit was queued, if necessary, in the IMP and transmitted as soon asthe packet reached the head of the queue.  On such full duplex circuitsthere is exactly one transmitter and one receiver in each direction.The ALOHA system, on the other hand, assigned a common transmit channelfrequency to ALL radio terminals.  A computer at the University ofHawaii received packet bursts from the remote terminals which shared the"multi-access" channel.  Under the control of a small processor, eachterminal would transmit whenever it had traffic, and would await anacknowledgement, on another frequency, dedicated to the service host. Ifno acknowledgement was received, the terminal processor would transmitagain at a randomly chosen time.  The system operated on the assumptionthat no store-and-forward or radio relay was needed.  The University ofHawaii researchers later demonstrated that the ALOHA concept worked on asatellite channel linking Hawaii and Nasa-Ames via NASA's ATS-1satellite [5, 6].  A variety of more elaborate satellite channelassignment strategies were developed and analyzed in the early 1970's[7-13, 31].Cerf                                                            [Page 1]

RFC 829                                                    November 1982                                              Remote User Telnet ServiceTHE ATLANTIC PACKET SATELLITE EXPERIMENT (SATNET)In 1973, DARPA began the development of a packet satellite system whichwould support the sharing of a common, high speed channel among manyground stations.  Using an INTELSAT-IV satellite, the Atlantic PacketSatellite experiment was carried out with the cooperation and support ofthe British Post Office, COMSAT Corporation, Linkabit Corporation, andBolt Beranek and Newman Corporation, later joined by the NorwegianTelecommunication Administration and the Norwegian Defense ResearchEstablishment (NDRE).  Along with University College London and COMSATLaboratories, NDRE became one of the major users of the SATNET system.During 1975-1978, SATNET underwent a broad range of performanceevaluations and tests.  Since 1979, it has served as a stable supportfor international experiments and demonstrations of command and controltechnology of interest to DARPA, NDRE and the U.K. Royal Signals andRadar Establishment (RSRE).  Late in 1982, a ground station was added toconnect the German Aeronautics and Space Research Establishment (DFVLR)into the system.The early development of SATNET is outlined in [14].  The system designis documented in [15-22].  Experience with the operation of the SATNETis reported in [23-24] and experimental results in [25-26].  Potentialservices which might be supported by this technology are discussed in[27].The integration of the packet satellite technology into a larger,multiple packet network context is discussed in [28-29].  The system isexpected to continue in use to support joint research by DARPA, RSRE,NDRE, DFVLR and UCL.  DARPA and the U.S. Defense Communications Agencyare experimenting with a 3 megabit/second domestic packet satellitesystem to determine whether packetized voice and data services can beintegrated economically using this technology.  DARPA and the U.S. NavalElectronic Systems Command recently demonstrated a Mobile AccessTerminal Network (MATNET) which uses packet satellite techniques tosupport ship-ship and ship-shore communication over a shared FLTSATCOMsatellite channel [30].ACKNOWLEDGEMENTSThe development of Packet Satellite technology has involved manyinstitutions and individuals, but special credit for the successfulrealization of the SATNET and its successor systems must be given to Dr.Robert E. Kahn, Director, Information Processing Techniques Office,DARPA, for his continuous support and technical contributions throughoutthe development and maturation of this technology.Cerf                                                            [Page 2]

RFC 829                                                    November 1982                                              Remote User Telnet ServiceREFERENCES1.  L.G. Roberts and B.D. Wessler, "Computer Network Development toAchieve Resource Sharing," Spring Joint Computer Conference, AFIPSProceedings, Vol. 36, 1970, pp. 543-549.2.  R.E. Kahn, "Resource Sharing Computer Networks," Proceedings of theIEEE, Vol. 60, No. 11, November 1972, pp. 1397-1407.3.  N. Abramson, "The Aloha System - Another Alternative for ComputerCommunications," AFIPS Conference Proceedings, Vol. 36, 1970, pp.295-298.4.  F.E. Heart, et al, "The Interface Message Processor of the ARPAComputer Network, Spring Joint Computer Conference, AFIPS Proceedings,1970, pp. 551-567.5.  R. Binder, et al, "Aloha Packet Broadcasting--a retrospect," AFIPSConference Proceedings, National Computer Conference, 1975, pp. 203-215.6.  N. Abramson and F. Kuo, Editors, Computer Communication Networks,Prentice Hall, Englewood Cliffs, N.J., 1973.7.  L. Kleinrock and S. Lam, "Packet Switching in a Slotted SatelliteChannel," AFIPS Conference Proceedings, NCC, 1973, pp. 703-710.8.  L. Kleinrock and F. Tobagi, "Random Access Techniques for DataTransmission over Packet Switched Radio Channels," AFIPS ConferenceProceedings, NCC, 1975, pp. 187-201.9.  L. Kleinrock and S.S. Lam, "Packet Switching in a MultiaccessBroadcast Channel:  Performance Evaluation," IEEE Transactions onCommunication, Vol. COM-23, 1975, pp. 410-423.10.  L.G. Roberts, "Aloha Packet System with and without Slots andCapture," ACM SIGCOMM, Computer Communication Review, Vol 5, No. 2,April 1975.11.  S.S. Lam and L. Kleinrock, "Packet Switching in a Multi-accessBroadcast Channel:  Dynamic Control Procedures," IEEE Transactions onCommunication, Vol Com-23, September, 1975.12.  L.G. Roberts, "Dynamic Allocation of Satellite Capacity throughPacket Reservation," AFIPS Conference Proceedings, NCC, 1973, pp.711-716.13.  N. Abramson, "Packet Switching with Satellites," AFIPS ConferenceProceedings, NCC, 1973, pp. 695-702.Cerf                                                            [Page 3]

RFC 829                                                    November 1982                                              Remote User Telnet Service14.  R.E. Kahn, "The Introduction of Packet Satellite Communications,"National Telecommunications Conference, Nov. 1979, p. 45.1.1-45.1.8.15.  I.M. Jacobs, et al, "CPODA - A Demand Assignment Protocol forSATNET," Fifth Data Communications Symposium, Snowbird, Utah, 1977.16.  I.M. Jacobs, et.al, "General Purpose Satellite Networks,"Proceedings IEEE, Vol 66, No. 11, November 1978, pp. 1448-1467.17.  I.M. Jacobs, et al, "Packet Satellite Network Design Issues,"Proceedings, NTC, November 1979.18.  L. Palmer, J. Kaiser, S. Rothschild and D. Mills, "SATNET PacketData Transmission," COMSAT Technical Review, Volume 12, No. 1, Spring1982, pp. 181-212.19.  Weissler, et al, "Synchronization and Multiple Access Protocol inthe Initial Satellite IMP," COMPCON, September 1978.20.  Hsu and Lee, "Channel Scheduling Snychronization for the PODAProtocol," ICC, June 1978.21.  E. Killian and R. Binder, "Control Issues in a PODA Voice/DataSatellite Network," ICC, June 1980.22.  C. Heegaard, J. Heller and A. Viterbi, "A Microprocessor-based PSKModem for Packet Transmission over Satellite Channels," IEEETransactions on Communications, COM-26, No. 5, May 1978, pp. 552-564.23.  P. Cudhea, D. McNeill, D. Mills, "SATNET Operations," AIAA 9thCommunications Satellite Systems Conference, Collection of TechnicalPapers, 1982, pp. 100-105.24.  D.A. McNeill, et al, "SATNET Monitoring and Control," Proceedingsof the NTC, November 1979.25.  P.T. Kirstein, et al, "SATNET Applications Activities," Proceedingsof the NTC, November 1979.26.  W.W. Chu, et al, "Experimental Results on the Packet SatelliteNetwork," Proceedings of the NTC, November 1979.27.  E.V. Hoversten and H. L. Van Trees, "International Broadcast PacketSatellite Services," ICCC Conference Proceedings, Kyoto, Japan,September 1978.28.  V.G. Cerf and R.E. Kahn, "A Protocol for Packet NetworkIntercommunication," IEEE Trans. on Comm., Vol. COM-23, May 1974, pp.637-648.Cerf                                                            [Page 4]

RFC 829                                                    November 1982                                              Remote User Telnet Service29.  V.G. Cerf and P.T. Kirstein, "Issues in Packet NetworkInterconnection," IEEE Proceedings, Vol. 66, No. 11, Nov 1978, pp.1386-1408.30.  L. Evenchik, D. McNeill, R.P. Rice, F. Deckelman, et al, "MATNET,an Experimental Navy Shipboard Satellite Communications Network, "IEEEINFOCOM 82 Proceedings, March, 1982.31.  M.L. Molle and L. Kleinrock, "Analysis of Concentrated ALOHASatellite Links," Sixth Data Communications Symposium, Nov 27-29, 1979,pp. 87-95.Cerf                                                            [Page 5]