Review of Lecture 1Time Travel: Let’s Build a NetworkEarly Communication over Long DistanceTelegraph: Communication Using ElectronsTelegraph EngineeringTelephonyTelephony MilestonesTelephony MilestonesTelephony MilestonesTelephony MilestonesSummaryData or Computer NetworksWhat is a Communication Network?(from end-system point of view)What is a Communication Network?Infrastructure Centric ViewTypes of NetworksTypes of NetworksA Taxonomy of Communication NetworksBroadcast vs. Switched Communication NetworksA Taxonomy of Communication NetworksCircuit SwitchingTiming in Circuit SwitchingCircuit SwitchingCircuit Switching: Multiplexing/DemultiplexingA Taxonomy of Communication NetworksPacket SwitchingPacket SwitchingPacket Switching: Multiplexing/DemultiplexingA Taxonomy of Communication NetworksDatagram Packet SwitchingTiming of Datagram Packet SwitchingDatagram Packet SwitchingA Taxonomy of Communication NetworksVirtual-Circuit Packet SwitchingVirtual-Circuit Packet SwitchingTiming of Virtual-Circuit Packet SwitchingDatagram Packet SwitchingPacket-Switching vs. Circuit-SwitchingWhat Does Router Look Like?115-441 Computer NetworksLecture 3Professor Hui ZhangWean Hall [email protected] of Lecture 1 How long does it take to move 1GB data from campus to your home? 56Kbps modem 2Mbps DSL Other possibilities?33333Time Travel: Let’s Build a Network 1870 Alexander Bell 1970 Dave Boggs, Bob Metcalfe 1970 Larry Roberts, Bob Kahn, Vint Cerf 1995 Network architect of UUNET Director of Campus Computing, CMU 2004 Network architecture of Reliance Network architecture of General Motor44444Early Communication over Long Distance Between human beings Letter and messenger Information carried by physical objects Speed limited by transportation means: horse, bird, train, car Bandwidth? distance? security? Fire Early optical communication Speed of light Bandwidth? distance? security?55555Telegraph: Communication Using Electrons Between human beings Major milestones: 1827: Ohm’s Law 1837: “workable” telegraph invented by Samuel Morse 1838: demonstration over 10 miles at 10 w.p.m 1844: Capitol Hill to Baltimore 1851: Western Union founded 1868: transatlantic cable laid 1985: last telegraph circuit closed down Other important dates 1869: transcontinental railway 1876: Alexander Bell invented telephone66666Telegraph Engineering Technical issues How to encode information? How to feed/input information to the system? How to output information? How to improve the distance? How to improve the speed? Common issues faced by all telecommunication systems77777Telephony Interactive telecommunication between people Analog voice vs. digital information Transmitter/receiver continuously contact with electronic circuit Electric current varies with acoustic pressureAnalog/Continuous SignalDigital/Discrete Signal88888Telephony Milestones 1876: Alaxendar Bell invented telephone 1878: Public switches installed at New Haven and San Francisco, public switched telephone network is born– People can talk without being on the same wire !Without Switch With Switch99999Telephony Milestones 1878: First telephone directory; white house line 1881: Insulated, balanced twisted pair as local loop 1885: AT&T formed 1892: First automatic commercial telephone switch 1903: 3 million telephones in U.S. 1915: First transcontinental telephone line 1927: First commercial transatlantic commercial service1010101010Telephony Milestones 1937: Multiplexing introduced for inter-city callsWith MultiplexingWithout Multiplexing1111111111Telephony Milestones 1939: Pulse Code Modulation (PCM) invented 1948: Transistor invented by Bell scientists 1951: Direct dialing for long-distance demonstrated 1963: Digital transmission introduced 1965 1ESS central office switch introduced Stored Program Control (computerized) 1976 4ESS: first digital electronic switch 1982 Bell System split into ATT and 7 RBOCs 1983 First fiber-optic cable in ATT long distance network 1989 SONET standard published by CCITT 1999 Last 4ESS switch installed in ATT network1212121212Summary Communication long before computer Evolutions of modern communication and computer intertwined Important concepts Switching Multiplexing Analog vs. Digital Bandwidth Latency1313131313Data or Computer Networks Networks designed for computers to computers or devices vs. communication between human beings Digital information vs. analog voice1414141414What is a Communication Network?(from end-system point of view) Network offers a service: move information Bird, fire, messenger, truck, telegraph, telephone, Internet … Another example, transportation service: move objects– Horse, train, truck, airplane ... What distinguish different types of networks? The services they provide What distinguish the services? Latency Bandwidth Loss rate Number of end systems Service interface Other details– Reliability, unicast vs. multicast, real-time, message vs. byte ...1515151515What is a Communication Network?Infrastructure Centric View Electrons and photons as communication medium Links: fiber, copper, satellite, … Switches: electronic/optic, crossbar/Banyan Protocols: TCP/IP, ATM, MPLS, SONET, Ethernet, X.25, FrameRelay, AppleTalk, IPX, SNA Functionalities: routing, error control, flow control, congestion control, Quality of Service (QoS) Applications: telephony, FTP, WEB, X windows, ...1616161616Types of Networks Geographical distance Local Area Networks (LAN): Ethernet, Token ring, FDDI Metropolitan Area Networks (MAN): DQDB, SMDS Wide Area Networks (WAN): X.25, ATM, frame relay Information type Data networks vs. telecommunication networks Application type Special purpose networks: airline reservation network, banking network, credit card network, telephony General purpose network: Internet1717171717Types of Networks Right to use Private: enterprise networks Public: telephony network, Internet Ownership of protocols Proprietary: SNA Open: IP Technologies Terrestrial vs. satellite Wired vs. wireless Protocols IP, AppleTalk, SNA1818181818A Taxonomy of Communication Networks Communication networks can be
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