数据教程课件chapter1introdu

Chapter OneIntroduction to Communications,Standards and Protocols1IntroductionWho today has not used a computer network?Mass transit,interstate highways,24-hour bankers,grocery stores,cable television,cell phones,businesses and schools,and retail outlets support some form of computer networkChapter One-Introduction to Communications,Standards,And Protocol2The Language of Computer NetworksComputer network an interconnection of computers and computing equipment using either wires or radio waves over small or large geographic areasLocal area network networks that are small in geographic size spanning a room,floor,building,or campusChapter One-Introduction to Communications,Standards,And Protocol3The Language of Computer NetworksMetropolitan area network networks that serve an area of 1 to 30 miles,approximately the size of a typical cityWide area network a large network that encompasses parts of states,multiple states,countries,and the worldChapter One-Introduction to Communications,Standards,And Protocol4The Language of Computer NetworksPersonal area network a network of a few meters,between wireless devices such as PDAs,laptops,and similar devicesVoice network a network that transmits telephone signalsData network a network that transmits computer dataChapter One-Introduction to Communications,Standards,And Protocol5The Language of Computer NetworksData communications the transfer of digital or analog data using digital or analog signalsTelecommunications the study of telephones and the systems that transmit telephone signalsNetwork management the design,installation,and support of a network,including its hardware and softwareChapter One-Introduction to Communications,Standards,And Protocol6The Big PictureNetworks are composed of many devices,including:Workstations(computers,telephones)ServersNetwork hubs and switches(bridges)Routers(LAN to WAN and WAN to WAN)Telephone switching gearChapter One-Introduction to Communications,Standards,And Protocol7Chapter One-Introduction to Communications,Standards,And Protocol8TopologiesCommon Bus TopologyStar TopologyRing TopologyFully Connected TopologyCombined TopologiesChapter One-Introduction to Communications,Standards,And Protocol9LAN Topologies10Common Bus Topology Multipoint medium:contentionTransmission propagates throughout medium Heard by all stationsNeed to identify target stationEach station has unique addressFull duplex connection between station and tapAllows for transmission and receptionNeed to regulate transmissionTo avoid collisionsTerminator absorbs frames at end of medium11Frame Transmissionon Bus LAN12Star TopologyEach station connected directly to central nodeUsually via two point to point linksCentral node can broadcastPhysical star,logical busOnly one station can transmit at a timeCentral node can act as frame switch13Ring TopologyRepeaters joined by point to point links in closed loopReceive data on one link and retransmit on anotherLinks unidirectional or bidirectionalStations attach to repeatersData in framesCirculate past all stationsDestination recognizes address and copies frameFrame circulates back to source where it is removedMedia access control determines when station can insert frame(token passing for example)14Frame TransmissionRing LAN15Ring and Star UsageRingVery high speed links over long distancesSingle link or repeater failure disables networkStarBest for short distancesHigh data rates for small number of devices16 Combined Topology Fully Connected Topology17Need For StandardsTask broken into subtasksImplemented separately in layers in stackFunctions needed in both systemsPeer layers communicateTypes of StandardsDe facto standardsFormally recognized and adopted by a standards organization18Key Elements of a ProtocolSyntaxData formatsSignal levelsSemanticsControl informationError handlingTimingSpeed matching19Standards OrganizationsIETF:Internet Engineering Task ForceIEEE:Institute of Electrical and Electronic Engineer,the largest professional organizationThree models to learn OSI model,Internet layers and TCP/IP protocol suite20Organization of air travela series of stepsticket(purchase)baggage(check)gates(load)runway takeoffairplane routingticket(complain)baggage(claim)gates(unload)runway landingairplane routingairplane routingWHY LAYERING？21ticket(purchase)baggage(check)gates(load)runway(takeoff)airplane routingdepartureairportarrivalairportintermediate air-trafficcontrol centersairplane routingairplane routingticket(complain)baggage(claimgates(unload)runway(land)airplane routingticketbaggagegatetakeoff/landingairplane routingLayering of airline functionalityLayers:each layer implements a servicevia its own internal-layer actionsrelying on services provided by layer below22Dealing with complex systems:explicit structure allows identification,relationship of complex systems pieceslayered reference model for discussionmodularization eases maintenance,updating of systemWHY LAYERING？23Overview of the OSI model:Chapter One-Introduction to Communications,Standards,And Protocol24Application layer where the application using the network resides.Common network applications include web browsing,e-mail,file transfers,and remote loginsPresentation layer performs a series of miscellaneous functions necessary for presenting the data package properly to the sender or receiverChapter One-Introduction to Communications,Standards,And Protocol25Network Architectures-OSISession layer responsible for establishing sessions between usersTransport layer provides an end-to-end error-free network connection.Makes sure the data arrives at the destination exactly as it left the source.Network layer responsible for creating,maintaining and ending network connections.Transfers a data packet from node to node within the network.Chapter One-Introduction to Communications,Standards,And Protocol26Network Architectures-OSIData link layer responsible for taking the data and transforming it into a frame with header,control and address information,and error detection codePhysical layer handles the transmission of bits over a communications channel.Includes voltage levels,connectors,media choice,modulation techniquesChapter One-Introduction to Communications,Standards,And Protocol27Logical and physical connectionsChapter One-Introduction to Communications,Standards,And Protocol28Network ArchitecturesLogical and physical connections A logical connection is one that exists only in the software,while a physical connection is one that exists in the hardwareNote that in a network architecture,only the lowest layer contains the physical connection,while are higher layers contain logical connectionsChapter One-Introduction to Communications,Standards,And Protocol29Chapter One-Introduction to Communications,Standards,And Protocol30The OSI Environment31Connection Strategies:Circuit Switching:phonesMessage Switching:store and forward networksPacket Switching:DatagramVirtual CircuitChapter One-Introduction to Communications,Standards,And Protocol32OSI Layers(1)Physical LayerPhysical interface between devicesMechanicalElectricalFunctionalProcedural33OSI Layers(2)Data Link LayerError detection and correctionParity Bit(even/odd)Media Access ControlCSMA/CDToken PassingToken RingToken BusFlow Control34OSI Layers(3)Network LayerTransport LayerFollow ControlConnection ManagementExchange of data between end systemsSessionControl of dialogues between applicationsDifference from the transport layer connection35OSI Layers(4)Presentation LayerCode ConversionData CompressionEncryption Application LayerFile Transfer ProtocolWeb BrowingE-mail 36Internet Layersapplication:supporting network applicationsFTP,SMTP,STTPtransport:host-host data transferTCP,UDPnetwork:routing of datagrams from source to destinationIP,routing protocolslink:data transfer between neighboring network elementsPPP,Ethernetphysical:bits“on the wire”applicationtransportnetworklinkphysical37messagesegmentdatagramframesourceapplicationtransportnetworklinkphysicalHtHnHlMHtHnMHtMMdestinationapplicationtransportnetworklinkphysicalHtHnHlMHtHnMHtMMnetworklinkphysicallinkphysicalHtHnHlMHtHnMHtHnHlMHtHnMHtHnHlMHtHnHlMrouterswitchDecapsulationEncapsulation38The TCP/IP Layers:Chapter One-Introduction to Communications,Standards,And Protocol39Network Architectures TCP/IPApplication layer equivalent to OSIs application and presentation layersTransport layer equivalent to OSIs transport layerNetwork(Internet or internetwork)layer equivalent to OSIs network layerNetwork access(data link/physical)layer equivalent to OSIs data link and physical layersChapter One-Introduction to Communications,Standards,And Protocol40Review Questions：2，8，16Exercises:4，5，13Chapter One-Introduction to Communications,Standards,And Protocol41