Review of Last LectureOrganizing Network FunctionalityNetworking ApplicationOne Level of In-DirectionISO OSI Reference ModelISO OSI Reference ModelInternet Protocol ArchitectureInternet Protocol ArchitectureKey ConceptsFunctions of the LayersEncapsulationExample: Sending Video Over InternetA TFTP UDP / IP / 802.3 PacketPhysical LayerHistorical PerspectiveFrequency, Bandwith of SignalBandwidth of Transmission ChannelsMultiplexingBaseband versus Carrier ModulationAmplitude Carrier ModulationFrequency Division Multiplexing:Multiple ChannelsAnalog vs. DigitalData Encoding: Mapping Data Into SignalAnalog vs. Digital TransmissionNon-Ideal ChannelDigitalization of Analog VoiceDigital Transmission/Multiplexing HierarchyData over Telephone NetworkModulationAmplitude and FrequencyModulationChannel Bandwidth and Capacity For Digital SignalCapacity of Noisy ChannelCopper WireDS-3 Coax Connectors and UsageAge of Fiber and OpticsRay PropagationLight Transmission in FiberFiber and Optical Source TypesFiber ConnectorsGigabit Ethernet:Physical Layer ComparisonSONETSynchronous Data TransferSONET FramingKnow Your Signal Line RatesTransport OverheadSection and LineUsing SONET in NetworksSelf-Healing SONET RingsOptical AmplicationWavelength Division MultiplexingWDM: A Winner in Long HaulPutting It All Together2x4 Network ArchitectureSome Observations115-441 Computer NetworksLecture 4Layered Architecture Physical LayerProfessor Hui [email protected] ZhangReview of Last Lecture Many types of networks Switching architectures Other concepts Timing graph Conversion among transmission rate (bps), time (second), distance (meter)3Hui ZhangOrganizing Network Functionality Many kinds of networking functionality e.g., encoding, framing, routing, addressing, reliability, etc. How should they be organized? How should they interact? Layering is one answer to these questions4Hui ZhangNetworking ApplicationSMTP SSH FTPPacketradioCoaxial cableFiberopticHTTPApplicationTransmissionMedia new application has to interface to all existing media adding new application requires O(m) work, m = number of media new media requires all existing applications be modified adding new media requires O(a) work, a = number of applications total work in system O(ma) → eventually too much work to add apps/media Application end points may not be on the same media!5Hui ZhangOne Level of In-Direction Solution: introduce an intermediate layer that provides a singleabstraction for various network technologies O(1) work to add app/media variation on “add another level of indirection”SMTP SSH NFS802.11LANCoaxial cableFiberopticHTTPApplicationIntermediate layerTransmissionMedia6Hui ZhangISO OSI Reference Model ISO – International Standard Organization OSI – Open System Interconnection Goal: a general open standard allow vendors to enter the market by using their own implementation and protocols7Hui ZhangISO OSI Reference ModelApplicationPresentationSessionTransportNetworkDatalinkPhysicalApplicationPresentationSessionTransportNetworkDatalinkPhysicalNetworkDatalinkPhysicalPhysical medium Physical medium Seven layers Lower two layers are peer-to-peer Network layer involves multiple switches Next four layers are end-to-end8Hui ZhangInternet Protocol ArchitectureFTPprogramTCPIPEthernetDriverEthernetDriverATMDriverIPFTPprogramTCPIPATMDriverFTP protocolTCP protocolIP protocol IP protocolEthernetprotocolATMprotocol9Hui ZhangInternet Protocol ArchitectureMPEG ServierprogramUDPIPEthernetDriverEthernetDriverATMDriverIPMPEG PlayerprogramUDPIPATMDriverRTP protocolUDP protocolIP protocol IP protocolEthernetprotocolATMprotocol10Hui ZhangKey Concepts Service – says what a layer does Ethernet: unreliable subnet unicast/multicast/broadcast datagramservice IP: unreliable end-to-end unicast datagram service TCP: reliable end-to-end bi-directional byte stream service UDP: what service do you use in your project? Interface – says how to access the service E.g. socket interface Protocol – says how is the service implemented a set of rules and formats that govern the communication between two peers Syntax, semantics, timing11Hui ZhangFunctions of the Layers Service: Handles details of application programs. Functions: Service: Controls delivery of data between hosts. Functions: Connection establishment/termination, error control, flow control. Service: Moves packets inside the network. Functions: Routing, addressing, switching, congestion control. Service: Reliable transfer of frames over a link. Functions: Synchronization, error control, flow controltelnet, ftp, emailwww, AFSTCP, UDPIP, ICMP, OSPFRIP, BGPEthernet, WiFiPoS, T1ApplicationLayerTransportLayerNetworkLayer(Data) LinkLayer12Hui ZhangEncapsulation As data is moving down the protocol stack, each protocol is adding layer-specific control information.ApplicationTCPIPEthernetDriverUser dataUser dataApplicationHeaderApplication dataTCP HeaderApplication dataTCP HeaderIP HeaderApplication dataTCP HeaderIP HeaderEthernetHeaderEthernetTrailerIP datagramTCP segmentEthernet frame13Hui ZhangExample: Sending Video Over InternetRTPHeaderRTPHeaderVideo FrameVideo FrameApplicationApplicationPresentationPresentationSessionSessionTransportTransportNetworkNetworkData linkData linkPhysicalPhysicalUDP/IP headerUDP/IP header. . .ApplicationpayloadApplicationpayload14Hui ZhangA TFTP UDP / IP / 802.3 PacketEthernet preambleEthernet preambleMAC headerMAC headerLLC / SNAP headerLLC / SNAP headerIP headerIP headerUDP headerUDP headerDataDataTFTP headerTFTP header15Physical Layer16Hui ZhangHistorical Perspective Independent developments of telecommunication network and local area data networks (LAN) Telecommunication network Analog signal with analog transmission Digital transmission of voice over long distance Long distance digital circuit for data transmission service Access modem for data transmission Introduction of optical transmission17Hui ZhangFrequency, Bandwith of Signal A signal can be viewed as a sum of sine waves of different strengths. Corresponds to energy at a certain frequency Every signal has an equivalent representation in the frequency domain Frequency: how fast a period signal changes, measured in HZ Bandwidth: width of the frequency range E.g. human voice: 100~3300 HZ, with a bandwidth of
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