2022/10/29TCP/IPProtocolSuite1Chapter3UnderlyingTechnologiesTransmissionmediaLANWANConnectingdevice2022/10/29TCP/IPProtocolSuite2InternetModelInternet不是一種新的網(wǎng)絡(luò)建立在底層網(wǎng)絡(luò)上的網(wǎng)際網(wǎng)底層網(wǎng)絡(luò)——“物理網(wǎng)”網(wǎng)際網(wǎng)——“互聯(lián)網(wǎng)”物理網(wǎng)為上層提供通信支持TCP/IP將物理網(wǎng)絡(luò)視為是互聯(lián)網(wǎng)的“信道”或“接口”LocalISPLAN2022/10/29TCP/IPProtocolSuite3TransmissionMediaWiredGuided/Conductedmedia，導(dǎo)向介質(zhì)UseawireorcableconductorTwisted-pair（雙絞線）、Coaxialcable（同軸電纜）Fiber-opticcable（光纖）WirelessUnguided/Radiatedmedia，非導(dǎo)向介質(zhì)Useradiowavesofdifferentfrequencies2022/10/29TCP/IPProtocolSuite4WiredMedia10Base5Twisted-pairFiberOptics2022/10/29TCP/IPProtocolSuite5TheElectromagneticSpectrumRadio,microwave,infrared,andvisiblelightportionsofthespectrumcanallbeusedfortransmittinginformationbymodulatingtheamplitude,frequency,orphaseofthewaves.Ultravioletlight,X-rays,andgammaraysarehardtoproduceandmodulate,donotpropagatewellthroughbuildings,andaredangeroustolivingthings.2022/10/29TCP/IPProtocolSuite6Chapter3UnderlyingTechnologiesTransmissionmediaLANWANConnectingdevice2022/10/29TCP/IPProtocolSuite7LANLocalAreaNetwork，局域網(wǎng)Transmissiontechnology：Broadcastlinks

MultiplesystemsattachedtoasharedmediaFeaturesBroadcastcapabilityHightotalbandwidth,lowdelay,lowerrorrateLimitedgeography,limitednumbersofstationsTechnologiesEthernet,TokenRing,FDDI,WLAN2022/10/29TCP/IPProtocolSuite8IEEE802ArchitectureLLCMAC實現(xiàn)鏈路層的流量控制和差錯控制2022/10/29TCP/IPProtocolSuite9Collision（沖突）ABCDEABCDENormaltransmissionCollisionoccurscollisiondomain（沖突域）2022/10/29TCP/IPProtocolSuite10CSMA/CDCSMA/CD最小幀長度幀的最小長度≥2τc2τ:網(wǎng)絡(luò)的往返傳播延遲c:信道容量（數(shù)據(jù)率）傳統(tǒng)以太網(wǎng)：已知信道長度為2500m時，2τ＝51.2us，c＝10Mbps，那么最小幀長度是：512bit＝64Byte2022/10/29TCP/IPProtocolSuite11EthernetVSIEEE802.3DIX標準：DEC/Intel/Xerox早期標準，便于使用但權(quán)威性不足EthernetⅠ(1980)、EthernetⅡ(1982)IEEE標準當(dāng)今標準，由IEEE802.3工作組負責(zé)1982年12月：802.3標準草案宣布Xerox將4件專利轉(zhuǎn)交IEEE802.3得到ANSI/ISO的認可，成為以太網(wǎng)的同義詞IEEE802.3-1985：標準的第一個版本必須與LLC子層一起使用IEEE802.3-2002：正式標準第二版（現(xiàn)行）可以直接通過MAC向高層提供服務(wù)（可不需LLC）2022/10/29TCP/IPProtocolSuite12EthernetFrameFormatRFC894:IPpacketsoverEthernetnetworks,1984RFC1042:IPpacketsoverIEEE802networks,1988IP/ARPPacket802.2LLC802.2SNAPIP/ARPPacket3538~1492PreambleSFDDestinationAddressSourceAddressTypeFCSData7166246~15004bytePreambleSFDDestinationAddressSourceAddressLenFCSData7166246~15004byte2022/10/29TCP/IPProtocolSuite13IEEE802.3FrameFormat（cont.）IEEEstd802.3-2002Length/TypefieldThemeaningdependsonitsnumericvalueLength：if<=1500Type：if>=1536（0x0600）PreambleSFDDestinationAddressSourceAddressLen/TypeFCSData7166246~15004byte2022/10/29TCP/IPProtocolSuite14雙地址：目的地址（6Byte），源地址（6Byte）地址類型Broadcast（廣播）地址：toallstationsallbitis‘1’Multicast（組播）地址:toagroupofstations第一個字節(jié)的最低位＝1Unicast（單播）地址:toaspecificstation第一個字節(jié)的最低位＝0例如00-16-76-07-D7-F601-16-76-07-D7-F6全局地址空間：2(48-2)=246=7×1013個地址全局地址唯一byte 1 2 3 4 5 6 IEEE802.3Address網(wǎng)絡(luò)發(fā)送順序：逐字節(jié)“從左至右”每個字節(jié)“先低位、再高位”2022/10/29TCP/IPProtocolSuite15補充：LAN發(fā)展中的變化高速化、光纖傳輸日益成熟10Mbps/100Mbps/1000Mbps/10Gbps80年代/1995年/1998年/2002年光纖傳輸日益成熟，使之進入主干網(wǎng)領(lǐng)域從共享到交換：以太網(wǎng)交換機產(chǎn)生并大量應(yīng)用網(wǎng)絡(luò)總體性能急劇提高CSMA/CD協(xié)議開始只具有象征意義幾乎不使用共享信道（而采用點對點信道），MAC協(xié)議不是必須以太幀結(jié)構(gòu)的重大改進擺脫LLC，面向多協(xié)議擴展幀結(jié)構(gòu)，支持VLAN等多種用途2022/10/29TCP/IPProtocolSuite16Chapter3UnderlyingTechnologiesTransmissionmediaLANWANConnectingdevice2022/10/29TCP/IPProtocolSuite17WANWideAreaNetwork，廣域網(wǎng)FeaturesLong-distancetransmissionofdata,voiceandvideoinformationoverlargegeographicalareasUtilizepublic,leased,orprivatecommunicationfacilities,usuallyincombination2022/10/29TCP/IPProtocolSuite18WANTechnologiesPoint-to-pointWAN:Toconnecttworemotedevices

（使用從公用網(wǎng)得到的鏈路來連接2個遠地設(shè)備）Physicallayer:V.90modem,ADSL,Tline,SONETDataLinkLayer:PPP,PPPoE…SwitchedWAN:（Internet）Backbone

networksFrameRelay,ATM…2022/10/29TCP/IPProtocolSuite19WANPSTNADSLDialingAccessnetwork區(qū)域ISP網(wǎng)絡(luò)骨干網(wǎng)絡(luò)網(wǎng)絡(luò)接入點（NAP）骨干網(wǎng)絡(luò)2022/10/29TCP/IPProtocolSuite20Switching（交換）CircuitSwitching（電路交換）PacketSwitching（分組交換）Datagram（數(shù)據(jù)報）VirtualCircuit（VC，虛電路）MessageSwitching（報文交換）Store-and-Forward2022/10/29TCP/IPProtocolSuite21CircuitSwitchingConnectionsetupDatatransferConnectionrelease2022/10/29TCP/IPProtocolSuite22PacketSwitchingDatagramSubnet（數(shù)據(jù)報子網(wǎng)）VirtualCircuitSubnet（虛電路子網(wǎng)）ABYXIIIIIIIV12321ABYXIIIIIIIV2312022/10/29TCP/IPProtocolSuite23異步（統(tǒng)計）時分復(fù)用2022/10/29TCP/IPProtocolSuite24Chapter3UnderlyingTechnologiesTransmissionmediaLANWANConnectingdevice2022/10/29TCP/IPProtocolSuite25ConnectingDeviceRepeater轉(zhuǎn)發(fā)器/Hub集線器Bridge網(wǎng)橋/L2switch二層交換機Router路由器/L3switch三層交換機Gateway網(wǎng)關(guān)GatewayRouterBridgeAPSTNDLPhAPSTNDLPhRepeater2022/10/29TCP/IPProtocolSuite26Repeater/HubAPSTNDLPhAPSTNDLPhPhABCDEFAtoDSD2022/10/29TCP/IPProtocolSuite27RepeaterToextendthephysicallengthofnetwork把一個局域網(wǎng)的兩個網(wǎng)段連接起來Forwardseverypacket(everybit)——Nofilteringcapacity是一個“再生器”，而非放大器2022/10/29TCP/IPProtocolSuite28Bridge/L2SwitchAPSTNDLPhABCDEFGHAtoDAtoGAPSTNDLPhDLPhPhXSD1D2過濾：檢查幀的目的地址，然后決定是轉(zhuǎn)發(fā)還是丟棄2022/10/29TCP/IPProtocolSuite29Bridge/L2SwitchBridgeTable過濾依據(jù)：網(wǎng)橋轉(zhuǎn)發(fā)表2022/10/29TCP/IPProtocolSuite30Learningbridge2022/10/29TCP/IPProtocolSuite31Bridge/L2SwitchRegeneratereceivedsignalFilterbycheckingdestinationphysicaladdresscontainedinthepacketAtable

thatmapsaddresstointerfaceNophysicaladdressDonotchangethephysicaladdresscontainedinaframeL2switch是一種多端口的網(wǎng)橋，可以為每個主機分配一個端口——無競爭2022/10/29TCP/IPProtocolSuite32Router/L3SwitchInternetworkingdevice(toconnectindependentLANsandWANs)cf.HuborBridgetoconnectsegmentsofaLANFunctions:Regeneratesignalatphysicall