计算机网络自定向下设计课件第二章.pptx

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计算机网络自定向下设计课件第二章.pptx

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PacketswitchingversuscircuitswitchingGreatforburstydataresourcesharingnocallsetupExcessivecongestion:packetdelayandlossprotocolsneededforreliabledatatransfer,congestioncontrolQ:Howtoprovidecircuit-likebehavior?bandwidthguaranteesneededforaudio/videoappsstillanunsolvedproblem(chapter6)Ispacketswitchinga“slamdunkwinner?”1

Packet-switchednetworks:routingGoal:movepacketsamongroutersfromsourcetodestinationwe’llstudyseveralpathselectionalgorithms(chapter4)datagramnetwork:destinationaddressdeterminesnexthoproutesmaychangeduringsession(分时系统用)对话期间analogy:driving,askingdirectionsvirtualcircuitnetwork:eachpacketcarriestag(virtualcircuitID),tagdeterminesnexthopfixedpathdeterminedatcallsetuptime,remainsfixedthrucallroutersmaintainper-callstate2

AccessnetworksandphysicalmediaQ:Howtoconnectendsystemstoedgerouter?residentialaccessnetsinstitutionalaccessnetworks(school,company)mobileaccessnetworksKeepinmind:bandwidth(bitspersecond)ofaccessnetwork?sharedordedicated?3

Residentialaccess:pointtopointaccessDialupviamodemupto56Kbpsdirectaccesstorouter(conceptually)ISDN:integratedservicesdigitalnetwork:128Kbpsall-digitalconnectiontorouterADSL:asymmetricdigitalsubscriberlineupto1Mbpshome-to-routerupto8Mbpsrouter-to-homeADSLdeployment-2millionlinesinU.S.andCanada4

Residentialaccess:cablemodemsHFC:hybridfibercoaxasymmetric:upto10Mbpsdownstream,1MbpsupstreamnetworkofcableandfiberattacheshomestoISProutersharedaccesstorouteramonghomesissues:congestion,dimensioningdeployment:availableviacablecompanies,e.g.,MediaOne5

Institutionalaccess:localareanetworkscompany/univlocalareanetwork(LAN)connectsendsystemtoedgerouterEthernet:sharedordedicatedcableconnectsendsystemandrouter10Mbs,100Mbps,GigabitEthernetDeployment（配置）:institutions,homeLANssoonLANs:chapter56