現(xiàn)代通信網(wǎng)絡(luò)4課件

現(xiàn)代通信網(wǎng)絡(luò)

ModernTelecommunicationNetworkLecture4PS分組交換與IP互聯(lián)網(wǎng)電話：現(xiàn)代通信網(wǎng)絡(luò)4CommunicationNetworks【通信網(wǎng)絡(luò)的分類】CommunicationNetworkSwitched

CommunicationNetworkVirtualCircuitNetwork:MPLSBroadcast

CommunicationNetwork廣播，電視，衛(wèi)星PacketSwitch(PS)-分組交換DatagramNetwork:InternetCircuit-Switched(CS)-電話現(xiàn)代通信網(wǎng)絡(luò)4PS:PacketSwitch

分組交換網(wǎng)原理現(xiàn)代通信網(wǎng)絡(luò)4SimpleSwitchedNetwork現(xiàn)代通信網(wǎng)絡(luò)4PacketSwitching(PS)PrinciplesCircuitswitchingdesignedforvoice

Resourcesdedicatedtoaparticularcall

Muchofthetimeadataconnectionisidle

DatarateisfixedBothendsmustoperateatthesamerate現(xiàn)代通信網(wǎng)絡(luò)4PS：BasicOperation【基本操作原理】DatatransmittedinsmallpacketsTypically1000octetsLongermessagessplitintoseriesofpacketsEachpacketcontainsaportionofuserdataplussomecontrolinfoControlinfo【控制信息】

Routing(addressing)infoPacketsarereceived,storedbriefly(buffered)

andpastontothenextnode

Storeandforward現(xiàn)代通信網(wǎng)絡(luò)4PS：UsingPackets現(xiàn)代通信網(wǎng)絡(luò)4PS：Advantages【優(yōu)點】LineefficiencySinglenodetonodelinkcanbesharedbymanypacketsovertimePacketsqueuedandtransmittedasfastaspossibleDatarateconversionEachstationconnectstothelocalnodeatitsownspeedNodesbufferdataifrequiredtoequalizeratesPacketsareacceptedevenwhennetworkisbusyDeliverymayslowdownPrioritiescanbeused現(xiàn)代通信網(wǎng)絡(luò)4PS：SwitchingTechnique【交換技術(shù)】StationbreakslongmessageintopacketsPacketssentoneatatimetothenetworkPacketshandledintwowaysDatagram【數(shù)據(jù)報】VirtualCircuit【虛電路】

PVC:PermanentVirtualCircuit【永久虛電路】

SVC:SwitchVirtualCircuit【交換虛電路】現(xiàn)代通信網(wǎng)絡(luò)4PS：Datagram【數(shù)據(jù)報】EachpackettreatedindependentlyPacketscantakeanypracticalroutePacketsmayarriveoutoforderPacketsmaygomissingUptoreceivertore-orderpacketsandrecoverfrommissingpackets現(xiàn)代通信網(wǎng)絡(luò)4PS：DatagramApproach現(xiàn)代通信網(wǎng)絡(luò)4PS：VirtualCircuit【虛電路】PreplannedrouteestablishedbeforeanypacketssentCallrequestandcallacceptpacketsestablishconnection(handshake)EachpacketcontainsavirtualcircuitidentifierinsteadofdestinationaddressNoroutingdecisionsrequiredforeachpacketClearrequesttodropcircuitNotadedicatedpath現(xiàn)代通信網(wǎng)絡(luò)4SVC：SwitchVirtualCircuit–連接建立【可交換的虛電路】現(xiàn)代通信網(wǎng)絡(luò)4SVC：SwitchedVirtualCircuit–數(shù)據(jù)傳輸【可交換的虛電路】現(xiàn)代通信網(wǎng)絡(luò)4SVC：SwitchedVirtualCircuit–連接釋放【可交換的虛電路】現(xiàn)代通信網(wǎng)絡(luò)4VirtualCircuitsvDatagramVirtualcircuitsNetworkcanprovidesequencinganderrorcontrolPacketsareforwardedmorequicklyNoroutingdecisionstomakeLessreliableLossofanodeloosesallcircuitsthroughthatnodeDatagramNocallsetupphaseBetteriffewpacketsMoreflexibleRoutingcanbeusedtoavoidcongestedpartsofthenetwork現(xiàn)代通信網(wǎng)絡(luò)4虛電路舉例：FrameRelay【幀中繼】DLCI(DataLinkConnectionIdentifier)-identificationofavirtualcircuit【虛電路】DLCI-oflocal(foragivenport)meaningtherecanbemax.976VCsonaninterfaceuser-networkDLCIvalues:0-LMIchannel,1-15-reserved,16-991-availableforVCs,992-1007-layer2managementofFRservice,1008-1022-reserved,1023-inchannellayermanagementABCToA:DLCI121ToB:DLCI243ToA:DLCI182ToC:DLCI121現(xiàn)代通信網(wǎng)絡(luò)4TimingofDatagramPacketSwitchingPacket3Packet3Packet1Packet2Packet1Packet2Packet1Packet2Packet3processing

delayofPacket1atNode2Host1Host2Node1Node2propagationdelaybetweenHost1andNode2transmissiontimeofPacket1atHost1現(xiàn)代通信網(wǎng)絡(luò)4三種交換的比較

P1P2P3P4P1P2P3P4P3P4報文報文報文ABCDABCDABCD報文交換電路交換分組交換t連接建立數(shù)據(jù)傳送報文P2P1連接釋放數(shù)據(jù)傳送的特點比特流直達(dá)終點報文報文報文分組分組分組存儲轉(zhuǎn)發(fā)存儲轉(zhuǎn)發(fā)存儲轉(zhuǎn)發(fā)存儲轉(zhuǎn)發(fā)現(xiàn)代通信網(wǎng)絡(luò)4【獨享】–【共享】

虛電路概念在

TD-SCDMA網(wǎng)絡(luò)：空間接口的應(yīng)用現(xiàn)代通信網(wǎng)絡(luò)43GPP-HSDPA概述為了更好地發(fā)展數(shù)據(jù)業(yè)務(wù)，3GPP對空中接口作了改進(jìn)，在R5版本中引入高速下行分組接入（HSDPA）技術(shù);HSDPA(高速下行分組接入，HighSpeedDownlinkPackagesAccess)技術(shù)，是3GPP在R5協(xié)議中為了滿足上下行數(shù)據(jù)業(yè)務(wù)不對稱的需求提出來的，它可以在不改變已經(jīng)建設(shè)的系統(tǒng)網(wǎng)絡(luò)結(jié)構(gòu)的基礎(chǔ)上，大大提高用戶下行數(shù)據(jù)業(yè)務(wù)速率(理論上單載波最大值可達(dá)2.8Mbps)現(xiàn)代通信網(wǎng)絡(luò)4基站側(cè)物理資源有限，HSDPA資源不可以同時分配給R4業(yè)務(wù)使用，比如，當(dāng)系統(tǒng)為3個上行時隙與3個下行時隙的比例配置時，其中2個下行時隙分配給HSDPA使用，則下行業(yè)務(wù)時隙就剩下1個時隙，此時如果大量用戶的業(yè)務(wù)需求是普通R4業(yè)務(wù)，則系統(tǒng)會受限于資源而決絕新用戶的接入所以當(dāng)業(yè)務(wù)小區(qū)內(nèi)普通R4業(yè)務(wù)較多時，可以減少或者取消HSDPA資源配置，將大部分時隙資源分配給普通R4業(yè)務(wù)使用；當(dāng)業(yè)務(wù)小區(qū)內(nèi)大部分用戶需要使用高速下載的數(shù)據(jù)業(yè)務(wù)，則可以將大部分業(yè)務(wù)時隙分配給HSDPA使用靈活的載波配置可以滿足運營商網(wǎng)絡(luò)規(guī)劃中的不同的需求

HSDPA載波配置現(xiàn)代通信網(wǎng)絡(luò)4TD-SCDMA無線幀結(jié)構(gòu)

現(xiàn)代通信網(wǎng)絡(luò)4物理層復(fù)用與調(diào)度算法用戶被調(diào)度是HSDPA業(yè)務(wù)區(qū)別于普通R4業(yè)務(wù)的一個主要特征普通R4用戶會【“獨享”】一部分物理資源，直到其業(yè)務(wù)被釋放掉，即使此時并沒有在進(jìn)行數(shù)據(jù)傳輸，資源也是被占用的，形成了一種浪費（類似：電路交換中的實電路）而HSDPA業(yè)務(wù)，可以讓多用戶【共享】整個HSDPA資源，采取的方式是分時分碼復(fù)用，也就是在每一個TTI內(nèi)部分或者全部資源為一個用戶而用，下一個TTI，資源又給另一個用戶使用，這樣數(shù)據(jù)需求量大的用戶就可以獲得較高的被調(diào)用的幾率，從而獲得較高速率，節(jié)省了資源。靈活的調(diào)度算法也可以滿足運營商不同的需求?，F(xiàn)代通信網(wǎng)絡(luò)4PS應(yīng)用：IP-Internet

分組交換網(wǎng)-IP因特網(wǎng)現(xiàn)代通信網(wǎng)絡(luò)47.1IP互聯(lián)網(wǎng)結(jié)構(gòu)現(xiàn)代通信網(wǎng)絡(luò)4InternetworkingTerms(1)CommunicationsNetworkFacilitythatprovidesdatatransferserviceThe

Internet【因特網(wǎng)】-noteuppercaseITheglobalcollectionofthousandsofindividualmachinesandnetworksIntranet【內(nèi)聯(lián)網(wǎng)

】CorporateinternetoperatingwithintheorganizationUsesInternet(TCP/IPandhttp)technologytodeliverdocumentsandresources現(xiàn)代通信網(wǎng)絡(luò)4TelecommuterResidentialCableInternetBackbonexDSL,FTTH,DialAggregationISP’sEnterpriseEnterpriseIP-InternetArchitectureTransportControlProtocol(TCP)InternetProtocol(IP)現(xiàn)代通信網(wǎng)絡(luò)4InternetworkingTerms-2EndSystem(ES)DeviceattachedtooneofthenetworksofaninternetSupportsend-userapplicationsorservicesIntermediateSystem(IS)DeviceusedtoconnecttwonetworksPermitscommunicationbetweenendsystemsattachedtodifferentnetworks現(xiàn)代通信網(wǎng)絡(luò)4InternetworkingTerms-3BridgeISusedtoconnecttwoLANsusingsimilarLANprotocolsAddressfilterpassingonpacketstotherequirednetworkonlyOSIlayer2(DataLink)RouterConnectstwo(possiblydissimilar)networksUsesinternetprotocolpresentineachrouterandendsystemOSILayer3(Network)現(xiàn)代通信網(wǎng)絡(luò)4USA-InternetInfrastructure現(xiàn)代通信網(wǎng)絡(luò)4InternetInfrastructureTheinfrastructureoftheInternetconsistsofafederationofconnectednetworksthatareeachindependentlymanaged(“autonomoussystem”)Note:Each“autonomoussystemmayconsistofmultipleIPnetworksAutonomoussystemshaveanumber(ASnumber)Hierarchyofnetworkserviceproviders(NSPs)Tier-1:nationorworldwidenetwork(US:lessthan20)Tier-2:regionalnetworks(inUS:lessthan100)Tier-3:localInternetserviceprovider(inUS:severalthousand)現(xiàn)代通信網(wǎng)絡(luò)4InternetInfrastructure-2Locationwhereanetwork(ISP,corporatenetwork,orregionalnetwork)getsaccesstotheInternetiscalledaPoint-of-Presence(POP).

Locations(Tier-1orTier-2)networksareconnectedforthepurposeofexchangingtrafficarecalledpeeringpoints.Publicpeering:Trafficissinaspecificlocation,calledInternetexchangepoints(IXPs)Privatepeering:Twonetworksestablishadirectlinktoeachother.現(xiàn)代通信網(wǎng)絡(luò)4Internetstructure:

roughlyhierarchicalatcenter:“tier-1”ISPs(e.g.,UUNet,BBN/Genuity,Sprint,AT&T),national/internationalcoveragetreateachotherasequalsTier1ISPTier1ISPTier1ISPTier-1providersinterconnect(peer)privatelyNAPTier-1providersalsointerconnectatpublicnetworkaccesspoints(NAPs)Interconnect–互聯(lián)互通（不同公司，不同國家，等）

現(xiàn)代通信網(wǎng)絡(luò)4【美國】Tier-1ISP:e.g.,SprintSprintUSbackbonenetworkSeattleAtlantaChicagoRoachdaleStocktonSanJoseAnaheimFortWorthOrlandoKansasCityCheyenneNewYorkPennsaukenRelayWash.DCTacomaDS3(45Mbps)OC3(155Mbps)OC12(622Mbps)OC48(2.4Gbps)…to/fromcustomerspeering

to/frombackbone….………POP:point-of-presence現(xiàn)代通信網(wǎng)絡(luò)4CERNET【中國教育網(wǎng)-AS：4538】

徐聞長春哈爾濱烏魯木齊拉薩西寧蘭州銀川呼和浩特臺北沈陽南昌西安徐州武漢合肥鄭州石家莊北京南寧廣州福州杭州上海南京天津貴陽海口三亞湛江無錫大連太原濟(jì)南煙臺成都長沙重慶黃梅九江昆明青島汕頭唐山漢中宜昌珠海深圳惠州柳州百色廈門BackboneRegionalGigaPopPop桂林深圳現(xiàn)代通信網(wǎng)絡(luò)4

五類線核心層業(yè)務(wù)層匯聚層接入層城域骨干網(wǎng)BRASMANSRDSLAM樓道交換機(jī)銅纜匯聚交換機(jī)/MSTP/RPR(可級連）CN2SRCN2骨干網(wǎng)ChinaNet骨干網(wǎng)寬帶接入網(wǎng)核心路由器（可級連）骨干網(wǎng)園區(qū)交換機(jī)CPE終端城域網(wǎng)IP：國家骨干網(wǎng)-城域網(wǎng)：網(wǎng)絡(luò)結(jié)構(gòu)

現(xiàn)代通信網(wǎng)絡(luò)47.2IP網(wǎng)協(xié)議的體系結(jié)構(gòu)和協(xié)議地址7.2.1IP網(wǎng)協(xié)議的體系結(jié)構(gòu)現(xiàn)代通信網(wǎng)絡(luò)4IP網(wǎng)絡(luò):地址結(jié)構(gòu)

現(xiàn)代通信網(wǎng)絡(luò)4TCP/IPConcepts現(xiàn)代通信網(wǎng)絡(luò)4TCP/IP地址系統(tǒng)現(xiàn)代通信網(wǎng)絡(luò)4IPv4PacketFormat：地址格式現(xiàn)代通信網(wǎng)絡(luò)4HeaderFields(20Bytes)VersionCurrently4：【IPv6：6】IPv6-seelaterInternetheaderlengthIn32bitwordsIncludingoptionsTotallengthOfdatagram,inoctetsProtocolNexthigherlayertoreceivedatafieldatdestination現(xiàn)代通信網(wǎng)絡(luò)4InternetAddress：地址概念層次Internet：地址結(jié)構(gòu)Internet網(wǎng)絡(luò)1網(wǎng)絡(luò)nIP地址網(wǎng)絡(luò)號主機(jī)號2.編址方式

IPaddress=(netid+hostid）3.表示方法:

二進(jìn)制表示、點分十進(jìn)制IPaddress=

1000001001Thenetworknumberpart【netid】oftheIPaddressiscentrallyadministeredbytheInternetNetworkInformationCenter(theInterNIC)andisuniquethroughouttheInternet.現(xiàn)代通信網(wǎng)絡(luò)4ClassesofInternetAddresses:【分類IP地址】現(xiàn)代通信網(wǎng)絡(luò)47.2.2.互聯(lián)網(wǎng)的協(xié)議地址

地址類型A類：0-8位網(wǎng)絡(luò)號首字節(jié)1–126B類：10-16位網(wǎng)絡(luò)號首字節(jié)128–191C類：110-24位網(wǎng)絡(luò)號首字節(jié)192–223D類：1110-組播地址首字節(jié)224–239E類：11110-（保留未用）首字節(jié)240-247特殊IP地址廣播地址：主機(jī)號全‘1’有限廣播地址：32位全‘1’；回送地址：127.*.*.*，網(wǎng)絡(luò)軟件測試及本機(jī)進(jìn)程間的通信。IP地址的實質(zhì)：IP地址標(biāo)識的不一定是一臺主機(jī)，實質(zhì)上標(biāo)識的是到一個網(wǎng)絡(luò)的一條連接。現(xiàn)代通信網(wǎng)絡(luò)4Broadcastaddress現(xiàn)代通信網(wǎng)絡(luò)4LimitedBroadcastAddress現(xiàn)代通信網(wǎng)絡(luò)4All0Address現(xiàn)代通信網(wǎng)絡(luò)4IPAddressSpace【IP地址空間問題】Originally,3ClassesA,B,CProblem【問題所在】Classestoorigid(剛性的)(Ctoosmall,Atoobig)ClassAwasoverkillwithmorethan16millionhostsClassChadtoofewhostspernetworkClassBisafairbalancebetweenthenumberofnetworksandthenumberofhostsSolution【解決方案】

Subnetting【子網(wǎng)】ClasslessInterdomainRouting(CIDR)：【無分類IP地址】現(xiàn)代通信網(wǎng)絡(luò)43.子網(wǎng)的劃分－SubnetclassificationAllowarbitrarycomplexityofinternetworkedLANswithinorganizationHostportionofaddresspartitionedintosubnetnumberandhostnumber【IP地址的主機(jī)地址部分劃分為：子網(wǎng)碼：主機(jī)碼】現(xiàn)代通信網(wǎng)絡(luò)4SubnetsandSubnetMasks【子網(wǎng)掩碼】Insulate【隔離】overallinternetfromgrowthofnetworknumbersandroutingcomplexitySitelookstorestofinternetlikesinglenetworkEachLANassignedsubnetnumber【子網(wǎng)號碼】LocalroutersroutewithinsubnettednetworkSubnetmask【子網(wǎng)掩碼】indicateswhichbitsaresubnetnumberandwhicharehostnumber現(xiàn)代通信網(wǎng)絡(luò)4IP地址的各字段和子網(wǎng)掩碼

145.13.3.10兩級IP地址子網(wǎng)號為3的網(wǎng)絡(luò)的網(wǎng)絡(luò)號三級IP地址主機(jī)號子網(wǎng)掩碼net-idhost-id子網(wǎng)的網(wǎng)絡(luò)地址1111111111111111

11111111000000000net-idsubnet-idhost-id145.13.145.13.33.10現(xiàn)代通信網(wǎng)絡(luò)40目的網(wǎng)絡(luò)地址子網(wǎng)掩碼下一跳282828接口0接口1R23H1子網(wǎng)1：網(wǎng)絡(luò)地址

子網(wǎng)掩碼2830R1

的路由表（未給出默認(rèn)路由器）R11R2子網(wǎng)2：網(wǎng)絡(luò)地址28

子網(wǎng)掩碼28H2380129H3子網(wǎng)3：網(wǎng)絡(luò)地址

子網(wǎng)掩碼2【例】已知互聯(lián)網(wǎng)和路由器R1

中的路由表。主機(jī)H1向H2發(fā)送分組。試討論R1收到H1

向H2發(fā)送的分組后查找路由表的過程?，F(xiàn)代通信網(wǎng)絡(luò)40目的網(wǎng)絡(luò)地址子網(wǎng)掩碼下一跳282828接口0接口1R2H1子網(wǎng)1：網(wǎng)絡(luò)地址

子網(wǎng)掩碼2830R11R2子網(wǎng)2：網(wǎng)絡(luò)地址28

子網(wǎng)掩碼28H23380129H3子網(wǎng)3：網(wǎng)絡(luò)地址

子網(wǎng)掩碼2主機(jī)H1

首先將本子網(wǎng)的子網(wǎng)掩碼28

與【toH2】分組的

IP

地址38逐比特相“與”(AND

操作)

28AND38的計算255就是二進(jìn)制的全1，因此255ANDxyz=xyz，這里只需計算最后的128AND138即可。128→10000000138→10001010逐比特AND

操作后：10000000→12828128.30.33.138128.30.33.128逐比特AND

操作

H1

的網(wǎng)絡(luò)地址現(xiàn)代通信網(wǎng)絡(luò)4路由器R1再用路由表中第2個項目的

子網(wǎng)掩碼和38逐比特AND

操作0目的網(wǎng)絡(luò)地址子網(wǎng)掩碼下一跳282828接口0接口1R2R1

的路由表（未給出默認(rèn)路由器）3H1子網(wǎng)1：網(wǎng)絡(luò)地址

子網(wǎng)掩碼2830R11R2子網(wǎng)2：網(wǎng)絡(luò)地址28

子網(wǎng)掩碼28H2380129H3子網(wǎng)3：網(wǎng)絡(luò)地址

子網(wǎng)掩碼228AND38=28匹配!這表明子網(wǎng)2就是收到的分組所要尋找的目的網(wǎng)絡(luò)R1

收到的分組的目的IP地址：38一致!現(xiàn)代通信網(wǎng)絡(luò)4

CIDP-ClasslessInter-DomainRouting

【無分類IP地址】CIDRisintroducedtoovercomethefollowingproblemsexhaustingofclassBnetworkexplosionofinternetroutingtable【路由表爆炸增長】CIDRallowsanylengthofsubRouterssummarizednetmaske.g.ChinaTelecom.canassign2classCnetworks(subnetmasklength=23)toacompanyifhehasonly300hosts=>efficientforIPaddressallocationRoutercanaggregateseveralroutestoabigroutewithlessmasklength=>reducecorerouter’sroutingtablesize現(xiàn)代通信網(wǎng)絡(luò)4LookupsMustbeFast

【路由表搜索必須快】12540Gb/s200331.2510Gb/s20017.812.5Gb/s19991.94622Mb/s199740Bpackets(Mpkt/s)LineRateYearlookupmechanismmustbesimple,easytoimplementmemoryaccesstimelong-termbottleneck現(xiàn)代通信網(wǎng)絡(luò)4RouteAggregationbyCIDRCIDRpermitsrouteaggregation

reducetheInternetroutingtable現(xiàn)代通信網(wǎng)絡(luò)4IPAddressLookup：【IP地址搜索】

CIDRandLongestPrefixMatchingroutingtablescontain(prefix,nexthop)pairsaddressinpacketcomparedtostoredprefixes,startingatleftprefixthatmatcheslargestnumberofaddressbitsisdesiredmatchpacketforwardedtospecifiednexthop01*5110*31011*50001*010*700010*1001100*21011001*31011010*501011*701001100*410110011*810011000*1001011001*90100110*6prefixnext

hoproutingtableaddress:101100101000Problem-largeroutermayhave

100,000prefixesinitslist現(xiàn)代通信網(wǎng)絡(luò)4NAT/PAT

NAT–NetworkAddressTranslation

PAT–PortAddressTranslation現(xiàn)代通信網(wǎng)絡(luò)4IPPrivateAddressesNotwomachinesthatconnecttoapublicnetworkcanhavethesameIPaddressbecausepublicIPaddressesareglobalandstandardizedPrivateIPaddressesareasolutiontotheproblemoftheexhaustionofpublicIPaddresses.AddressesthatfallwithintheserangesarenotroutedontheInternetbackbone:ConnectinganetworkusingprivateaddressestotheInternetrequirestheusageofNAT現(xiàn)代通信網(wǎng)絡(luò)4現(xiàn)代通信網(wǎng)絡(luò)42.IP地址與物理地址ARP-TheAddressResolutionProtocolisresponsibleforconvertingthehigher-levelprotocoladdresses(IPaddresses)tophysicalnetworkaddresses.SuchasEthernetAddress(MAC)現(xiàn)代通信網(wǎng)絡(luò)4ARP協(xié)議ARP的協(xié)議過程XYABARP請求IP=PA=?IP=PA=XXXIP=PA=YYYIP=PA=AAAIP=PA=BBBARP應(yīng)答PA=YYY現(xiàn)代通信網(wǎng)絡(luò)4C:\>arp-aInterface:06---0x2InternetAddressPhysicalAddressType2900-01-30-bd-e9-a0dynamic3200-04-96-05-47-0adynamic3300-04-96-05-47-15dynamic3400-04-96-05-34-f7dynamic3500-04-96-05-47-0edynamic3600-04-96-05-35-11dynamic3700-04-96-05-47-d6dynamic3800-04-96-05-34-ecdynamic3900-04-96-05-48-96dynamic4000-04-96-05-34-70dynamicC:\>現(xiàn)代通信網(wǎng)絡(luò)4IP（internet）網(wǎng)絡(luò)

工作原理現(xiàn)代通信網(wǎng)絡(luò)4RouterandtheOSIModel現(xiàn)代通信網(wǎng)絡(luò)4IPNetwork:DesignIssues【設(shè)計因素】Routing【IP路由選擇】Datagramlifetime【生命周期】Fragmentationandre-assemblyErrorcontrolFlowcontrol現(xiàn)代通信網(wǎng)絡(luò)4IPRouting【IP選路原理】Endsystemsandroutersmaintainroutingtables路由表IndicatenextroutertowhichdatagramshouldbesentStatic【靜態(tài)：路由表】MaycontainalternativeroutesDynamic【動態(tài)：路由表】FlexibleresponsetocongestionanderrorsSourcerouting【發(fā)端路由器選路】SourcespecifiesrouteassequentiallistofrouterstobefollowedSecurityPriorityRouterecording現(xiàn)代通信網(wǎng)絡(luò)4H1H2R1R5R2R3R4IP路由表設(shè)計原理

路徑：H1-R1-R2-R4-H2設(shè)計需要考慮到問題(4個)：路由器（Routers）的路由表如何獲取？為什么選擇這條路徑？假設(shè)R2與R4的連接斷掉，如何通知R1？在Internet中，是否每個路由器都必須了解其它路由器的情況？現(xiàn)代通信網(wǎng)絡(luò)4IP網(wǎng)絡(luò)：

路由器（Routers）的路由表如何獲?。?/p>

現(xiàn)代通信網(wǎng)絡(luò)4IP路由表的建立和維護(hù)-靜態(tài)配置靜態(tài)配置：管理員手工配置和更新路由表適用環(huán)境：拓?fù)湎鄬Ψ€(wěn)定，路由器個數(shù)較少優(yōu)點：節(jié)省路由器的處理時間、存儲空間以及網(wǎng)絡(luò)帶寬缺陷：對于鏈路故障及拓?fù)浣Y(jié)構(gòu)變化的響應(yīng)速度慢H1H2R1R5R2R3R4現(xiàn)代通信網(wǎng)絡(luò)4H1H2R1R5R2R3R4IP路由表的建立和維護(hù)–

動態(tài)配置動態(tài)配置：利用路由協(xié)議交換路由信息，并根據(jù)拓?fù)浣Y(jié)構(gòu)的變化動態(tài)更新路由表適用環(huán)境：路由器較多的大規(guī)模網(wǎng)絡(luò)優(yōu)點：自動適應(yīng)鏈路故障及拓?fù)浣Y(jié)構(gòu)的變化缺陷：耗費路由器的處理時間、存儲空間以及網(wǎng)絡(luò)帶寬現(xiàn)代通信網(wǎng)絡(luò)47.3IP路由表：選路原理1、選路方式：

表驅(qū)動：每個主機(jī)和路由器都有一張路由表，指明去往某信宿應(yīng)該走哪條路徑。選路時，查詢路由表。2、路由表格式【IPDestination:信宿】信宿地址去往信宿的路徑不是主機(jī)地址，而是網(wǎng)絡(luò)地址不是完整路徑，而是(nexthop)下一跳地址目標(biāo)網(wǎng)絡(luò)1的網(wǎng)絡(luò)號到達(dá)網(wǎng)絡(luò)1的下一跳路由器IP目標(biāo)網(wǎng)絡(luò)2的網(wǎng)絡(luò)號到達(dá)網(wǎng)絡(luò)2的下一跳路由器IP………現(xiàn)代通信網(wǎng)絡(luò)4網(wǎng)

1網(wǎng)

4網(wǎng)

3網(wǎng)

2目的主機(jī)所在的網(wǎng)絡(luò)下一跳地址直接交付，接口1直接交付，接口0路由器R2

的路由表鏈路

4鏈路

3鏈路

2鏈路

1R2R3R101R2R3R1在路由表中，對每一條路由，最主要的是（目的網(wǎng)絡(luò)地址，下一跳地址）現(xiàn)代通信網(wǎng)絡(luò)4IP網(wǎng)絡(luò)結(jié)構(gòu)：AS系統(tǒng)設(shè)置

AS-AutonomousSystems

自治系統(tǒng)現(xiàn)代通信網(wǎng)絡(luò)4WhatisAutonomousSystems(AS)GroupofroutersExchangeinformationCommonroutingprotocolSetofroutersandnetworksmanagedbysingleorganizationAconnectednetworkThereisatleastoneroutebetweenanypairofnodes現(xiàn)代通信網(wǎng)絡(luò)4現(xiàn)代通信網(wǎng)絡(luò)4InteriorRouterProtocol(IRP)PassesroutinginformationbetweenrouterswithinASMaybemorethanoneASininternetRoutingalgorithmsandtablesmaydifferbetweendifferentASIRPneedsdetailedmodel現(xiàn)代通信網(wǎng)絡(luò)4ExteriorRoutingProtocol(ERP)RoutersneedsomeinfoaboutnetworksoutsidetheirASUsedexteriorrouterprotocol(ERP)ERPsupportssummaryinformationonreachability(網(wǎng)絡(luò)可達(dá)性)現(xiàn)代通信網(wǎng)絡(luò)4ApplicationofIRPandERP現(xiàn)代通信網(wǎng)絡(luò)4CERNET【中國教育網(wǎng)-AS：4538】

徐聞長春哈爾濱烏魯木齊拉薩西寧蘭州銀川呼和浩特臺北沈陽南昌西安徐州武漢合肥鄭州石家莊北京南寧廣州福州杭州上海南京天津貴陽海口三亞湛江無錫大連太原濟(jì)南煙臺成都長沙重慶黃梅九江昆明青島汕頭唐山漢中宜昌珠海深圳惠州柳州百色廈門BackboneRegionalGigaPopPop桂林深圳現(xiàn)代通信網(wǎng)絡(luò)4IPRoutingAlgorithms【路由算法】RoutingalgorithmsareusedtobuildandmaintaintheIProutingtableonadevice.Therearetwoprimarymethodsusedtobuildtheroutingtable:Staticrouting:Staticroutingusepreprogrammeddefinitionsrepresentingpathsthroughthenetwork.Dynamicrouting:Dynamicroutingalgorithmsallowrouterstoautomaticallydiscover(learn)andmaintainawarenessofthepathsthroughthenetwork.Thisautomaticdiscoverycanuseanumberofcurrentlyavailabledynamicroutingprotocols.現(xiàn)代通信網(wǎng)絡(luò)4IP路由表原理

Dynamicrouting:【動態(tài)路由】現(xiàn)代通信網(wǎng)絡(luò)4DynamicRouting【算法原理】Distancevectorrouting矢量-距離算法：以跳數(shù)（hop）作為度量值，通過交換路由表，計算出所有已知的最短路由，更新路由表。Linkstaterouting【鏈路狀態(tài)算法】通過交換鏈路狀態(tài)，讓AS中的每個路由器都有一張該AS的網(wǎng)絡(luò)拓?fù)浣Y(jié)構(gòu)圖。使用Dijkstra算法求最短路徑，計算該路由器到其它目的站的最短路徑，然后更新路由表?，F(xiàn)代通信網(wǎng)絡(luò)4DistanceVectorRouting

矢量-距離算法現(xiàn)代通信網(wǎng)絡(luò)4Whatis【DistanceVectorRouting]】Theprinciplebehinddistancevectorroutingissimple.Eachrouterintheinternetworkmaintainsthedistanceorcost

fromitselftoeveryknowndestination.Thisvaluerepresentstheoveralldesirabilityofthepath.Pathsassociatedwithasmallercostvaluearemoreattractivetousethanpathsassociatedwithalargervalue.Thepathrepresentedbythesmallestcostbecomesthepreferredpathtoreachthedestination.現(xiàn)代通信網(wǎng)絡(luò)4WhatisDistanceVectorRoutingThisinformationismaintainedinadistancevectortable.Thetableisperiodicallyadvertisedtoeachneighboringrouter.Eachrouterprocessestheseadvertisementstodeterminethebestpathsthroughthenetwork.RIPandBGParetwopopularexamplesofdistancevectorroutingprotocols.現(xiàn)代通信網(wǎng)絡(luò)4DistanceVectorRouting【矢量-距離算法】Eachrouterperiodicallysharesitsknowledgeabouttheentirenetworkwithitsneighbors.Knowledgeaboutthewholenetwork.Routingonlytoneighbors.Informationsharingatregularintervals.Basedonhopcount現(xiàn)代通信網(wǎng)絡(luò)4ExampleofanInternet現(xiàn)代通信網(wǎng)絡(luò)4ConceptofDistanceVectorRouting現(xiàn)代通信網(wǎng)絡(luò)4DistanceVectorRoutingTable路由表Aroutercandiscovertowhichnetworksitisconnectedbyexaminingitsownlogicaladdresses現(xiàn)代通信網(wǎng)絡(luò)4OriginalRoutingTableDistribution現(xiàn)代通信網(wǎng)絡(luò)4UpdatingRoutingTableforRouterA現(xiàn)代通信網(wǎng)絡(luò)4UpdatingRoutingTableforRouterC現(xiàn)代通信網(wǎng)絡(luò)4UpdatedRoutingTables現(xiàn)代通信網(wǎng)絡(luò)4UpdatingRoutingTableforRouterF1-1-4B78

1-+ONEHOP=2A2A5A782A2A2A5A1-921-555A現(xiàn)代通信網(wǎng)絡(luò)4NewUpdatedRoutingTables現(xiàn)代通信網(wǎng)絡(luò)4FinalRoutingTables現(xiàn)代通信網(wǎng)絡(luò)4Linkstaterouting

【鏈路狀態(tài)算法】

使用Dijkstra算法求最短路徑現(xiàn)代通信網(wǎng)絡(luò)4Whatis【Linkstaterouting】Thealgorithmsareusedintheprincipleofalinkstateistodeterminenetworktopology.Alinkstateisthedescriptionofaninterfaceonarouter(forexample,IPaddress,subnetmask,typeofnetwork)anditsrelationshiptoneighboringrouters.Thecollectionoftheselinkstatesformsalinkstatedatabase.Eachrouteridentifiesallotherroutingdevicesonthedirectlyconnectednetworks.Eachrouteradvertisesalistofalldirectlyconnectednetworklinksandtheassociatedcostofeachlink.Thisisperformedthroughtheexchangeoflinkstateadvertisements(LSAs)withotherroutersinthenetwork.LSAs-linkstateadvertisements現(xiàn)代通信網(wǎng)絡(luò)4Usingtheseadvertisements,eachroutercreatesadatabasedetailingthecurrentnetworktopology.Thetopologydatabaseineachrouterisidentical.Eachrouterusestheinformationinthetopologydatabasetocomputethemostdesirableroutestoeachdestinationnetwork.ThisinformationisusedtoupdatetheIProutingtable.

TheSPFalgorithmisusedtoprocesstheinformationinthetopologydatabase.Itprovidesatree-representationofthenetwork.ThedevicerunningtheSPFalgorithmistherootofthetree.Theoutputofthealgorithmisthelistofshortest-pathstoeachdestinationnetwork.

TheOSPFprotocolisapopularexampleofalinkstateroutingprotocol.Whatis【Linkstaterouting】-2現(xiàn)代通信網(wǎng)絡(luò)4LinkStateRoutingSendknowledgeabouttheneighborhoodonlyToallrouters(flooding：泛洪)Informationsharingwhenthereisachange.現(xiàn)代通信網(wǎng)絡(luò)4ConceptofLinkStateRouting現(xiàn)代通信網(wǎng)絡(luò)4PacketCostCostisaweightedvaluebasedonavarietyoffactorssuchassecuritylevels,traffic,orthestateofthelink.Costisappliedonlybyroutersandnotbyanyotherstationsonanetwork.Costisappliedasapacketleavestherouterratherthanasitenters.現(xiàn)代通信網(wǎng)絡(luò)4CostsinLinkStateRouting現(xiàn)代通信網(wǎng)絡(luò)4LinkStatePacket(LSP)Whenarouterfloodsthenetworkwithinformationaboutitsneighborhood,itissaidtobeadvertising.Aroutergetsitsinformationaboutitsneighborsbyperiodicallysendingthemashortgreetingpacket.現(xiàn)代通信網(wǎng)絡(luò)4Flooding【泛洪】ofA’sLSP現(xiàn)代通信網(wǎng)絡(luò)4FloodingofB’sLSP現(xiàn)代通信網(wǎng)絡(luò)4LinkStateDatabase現(xiàn)代通信網(wǎng)絡(luò)4最短路由選擇算法–byE.DijkstraD(u)isthedistanceofsourcenode1toanynodeu.現(xiàn)代通信網(wǎng)絡(luò)4Dijkstra’sAlgorithmDefinitionsFindshortestpathsfromgivensourcenodetoallothernodes,bydevelopingpathsinorderofincreasingpathlengthN

= setofnodesinthenetworks= sourcenodeT

= setofnodessofarincorporatedbythealgorithmw(i,j)

= linkcostfromnodeitonodejw(i,i)=0w(i,j)=

ifthetwonodesarenotdirectlyconnectedw(i,j)

0ifthetwonodesaredirectlyconnectedL(n)

=

costofleast-costpathfromnodestonodencurrentlyknownAttermination,L(n)iscostofleast-costpathfromston現(xiàn)代通信網(wǎng)絡(luò)4現(xiàn)代通信網(wǎng)絡(luò)4Dijkstra’sAlgorithm：分析Step5：{1,2,3,4,5,6}Node1Node2:距離D：2，直連；Node1Node3:距離D：3，經(jīng)由節(jié)點：{4,5}現(xiàn)代通信網(wǎng)絡(luò)4CostsinDijkstraAlgorithm現(xiàn)代通信網(wǎng)絡(luò)4FourstepstodiscovertheshortestpathtreeThealgorithmbeginstobuildthetreebyidentifyingitsroot.Nodesandarcsaretemporary.Thealgorithmcomparesthetree’stemporaryarcsandidentifiesthearc(弧)withthelowestcumulativecost.Thealgorithmexaminesthedatabaseandidentifieseverynodethatcanbereachedfromitschosennode.Thelasttwostepsarerepeateduntileverynodeinthenetworkhasbecomeapermanentpartofthetree.現(xiàn)代通信網(wǎng)絡(luò)4ShortestPathCalculation現(xiàn)代通信網(wǎng)絡(luò)4ShortestPathCalculation現(xiàn)代通信網(wǎng)絡(luò)4ShortestPathCalculation現(xiàn)代通信網(wǎng)絡(luò)4ShortestPathCalculation現(xiàn)代通信網(wǎng)絡(luò)4ShortestPathCalculation現(xiàn)代通信網(wǎng)絡(luò)4ShortestPathCalculation現(xiàn)代通