计算机网络理论教学资料quiz4

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1、1.Whafsthekeynetwork-layerfunctions?❖forwarding:movepacketsfromrouter'sinputtoappropriaterouteroutput❖routing:determineroutetakenbypacketsfromsourcetodest.PPT4-52.Whatservicemodelfor"channel"transportingdatagramsfromsendertoreceiver?exampleservicesforindividualdatagrams:❖guaranteeddel

2、ivery❖guaranteeddeliverywithlessthan40msecdelayexampleservicesforaflowofdatagrams:❖in-orderdatagramdelivery❖guaranteedminimumbandwidthtoflow❖restrictionsonchangesininter-packetspacingPPT4-83.HowtosolvetheNATtraversalproblem?Give2solutions.❖solution1:staticallyconfigureNATtoforwardinco

3、mingconnectionrequestsatgivenporttoserver■e.g.,(138.76.29.7,port2500)alwaysforwardedto10.0.0.1port25000❖solution2:UniversalPlugandPlay(UPnP)InternetGatewayDevice(IGD)Protocol.AllowsNATedhostto:■learnpublicIPaddress(138.76.29.7)■add/removeportmappings(withleasetimes)i.e.,automatestatic

4、NATportmapconfigurationPPT4-61~4-634.Whafsthechanges(oradvantages)ofIPv6,comparetoIPv4?❖Initialmotivation:32-bitaddressspacesoontobecompletelyallocated.❖Checksum:removedentirelytoreduceprocessingtimeateachhop❖Options:allowed,butoutsideofheader,indicatedby"NextHeader"field❖ICMPv6:newve

5、rsionofICMP■additionalmessagetypes,e.g."PacketTooBig"■multicastgroupmanagementfunctions5.HowdoestheGraphtheoryapplytocomputernetworks?Pointout2graphexamplesincomputernetworks.Remark:Graphabstract!onisusefulinothernetworkcontextsExample:P2P,whereNissetofpeersandEissetofTCPconnectionsPP

6、T牛776.Whafsthedifferenceofnetworkandtransportlayerconnectionservice・PPT4-7,4-11❖networkvstransportlayerconnectionservice:■network:betweentwohosts(mayalsoinvolveinterveningroutersincaseof1.Whafsthekeynetwork-layerfunctions?❖forwarding:movepacketsfromrouter'sinputtoappropriaterouteroutp

7、ut❖routing:determineroutetakenbypacketsfromsourcetodest.PPT4-52.Whatservicemodelfor"channel"transportingdatagramsfromsendertoreceiver?exampleservicesforindividualdatagrams:❖guaranteeddelivery❖guaranteeddeliverywithlessthan40msecdelayexampleservicesforaflowofdatagrams:❖in-orderdatagram

8、deliv