CS6250/l CSl 6250l Examl 2l (Latestl 2025/l 2026l Update)l Guidel Q/Al |l Gradel A|l 100%l Correctl (Verifiedl Answers)
Q:l Whatl isl thel relationshipl betweenl forwardingl andl routing?
Answer:
Traditionall approachl -l thel routingl algorithmsl (controll plane)l andl forwardingl functionl (datal plane)l arel closelyl coupled.Thel routerl runsl andl participatesl inl thel routingl algorithms.l Froml there,l itl isl ablel tol constructl thel forwardingl tablel whichl itl consultsl forl thel forwarding.
SDNl approachl -l al remotel controllerl thatl computesl andl distributesl thel forwardingl tablesl tol bel usedl byl everyl router.l Thisl controllerl isl physicallyl separatel froml thel router.l Therel isl al clearl separationl ofl thel functionalities.l Thel routersl arel solelyl responsiblel forl forwarding,l andl thel remotel controllersl arel solelyl responsiblel forl computingl andl distributingl thel forwardingl tables.
Q:l Forwardingl vsl Routingl Expanded
Answer:
Forwarding -l Isl thel processl insidel al routerl ofl determiningl throughl whichl outputl linkl tol sendl thel packetl itl receivedl atl itsl inputl link.-l Itl couldl actuallyl blockl thel packetl froml exitingl thel router,l ifl itl isl suspectedl tol havel beenl sentl byl al maliciousl router.-l Itl couldl alsol duplicatel thel packetl andl sendl itl alongl multiplel outputl links.-l Forwardingl usuallyl takesl placel inl nanosecondsl andl isl implementedl inl thel hardware.-l Forwardingl isl al functionl ofl thel datal plane.-l Al routerl looksl atl thel headerl ofl anl incomingl packetl andl consultsl thel forwardingl table,l tol determinel thel outgoingl linkl tol sendl thel packetl to.Routing -l Involvesl determiningl thel pathl froml thel senderl tol thel receiverl acrossl thel network. 1 / 4
-l Routersl relyl onl routingl algorithmsl forl thisl purpose.-l Itl isl anl end-to-endl processl forl networks.-l Itl usuallyl takesl placel inl secondsl andl isl implementedl inl software.-l Routingl isl al functionl ofl thel controll plane.
Q:l Whatl isl thel differencel betweenl al traditionall andl SDNl approachl inl termsl ofl couplingl ofl controll andl datal plane?
Answer:
Inl thel traditionall approach,l thel routingl algorithmsl (controll plane)l andl forwardingl functionl (datal plane)l arel closelyl coupled.l Thel routerl runsl andl participatesl inl thel routingl algorithms.l Froml therel itl isl ablel tol constructl thel forwardingl tablel whichl consultsl itl forl thel forwardingl function.
Inl thel SDNl approach,l therel isl al remotel controllerl thatl computesl andl distributesl thel forwardingl tablesl tol bel usedl byl everyl router.l Thisl controllerl isl physicallyl separatel froml thel router.l Wel havel al separationl ofl thel functionalities.l Thel routersl arel solelyl responsiblel forl forwarding,l andl thel remotel controllersl arel solelyl responsiblel forl computingl andl distributingl thel forwardingl tables.l Thel controllerl isl implementedl inl software,l andl thereforel wel sayl thel networkl isl software-defined.
Q:l Whatl arel thel mainl componentsl ofl SDNl networkl andl theirl responsibilities?
Answer:
SDN-controlledl networkl elements >l Forwardsl networkl trafficl basedl onl rulesl computedl byl thel SDNl controll plane.
SDNl controller >l Actsl asl anl interfacel betweenl otherl two
Network-controll applications >l Programsl thatl managel underlyingl networkl byl collectingl infol onl elementsl withl helpl ofl thel controller.
Q:l Whatl arel thel fourl definingl featuresl inl anl SDNl architecture?
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Answer:
1)l Flow-basedl forwarding:l Thel rulesl forl forwardingl packetsl inl thel SDN-controlledl switchesl canl bel computedl basedl onl anyl numberl ofl headerl fieldl valuesl inl variousl layersl suchl asl thel transport-layer,l network-layerl andl link-layer.l Thisl differsl froml thel traditionall approachl wherel onlyl thel destinationl IPl addressl determinesl thel forwardingl ofl al packet.2)l Separationl ofl datal planel andl controll plane:l Thel SDN-controlledl switchesl operatel onl thel datal planel andl theyl onlyl executel thel rulesl inl thel flowl tables.l Thosel rulesl arel computed,l installed,l andl managedl byl softwarel thatl runsl onl separatel servers.3)l Networkl controll functions:l Thel SDNl controll plane,l (runningl onl multiplel serversl forl increasedl performancel andl availability)l consistsl ofl twol components:l thel controllerl andl thel networkl applications.l Thel controllerl maintainsl up-to-datel networkl statel informationl aboutl thel networkl devicesl andl elementsl (forl example,l hosts,l switches,l links)l andl providesl itl tol thel network-controll applications.l Thisl information,l inl turn,l isl usedl byl thel applicationsl tol monitorl andl controll thel networkl devices.4)l Al programmablel network:l Thel network-controll applicationsl actl asl thel "brain"l ofl thel SDNl controll planel byl managingl thel network.l Examplel applicationsl canl includel networkl management,l trafficl engineering,l security,l automation,l analytics,l etc.l Forl example,l wel canl havel anl applicationl thatl determinesl thel end-to-endl pathl betweenl sourcesl andl destinationsl inl thel networkl usingl Dijkstra'sl algorithm.
Q:l Whatl arel thel threel layersl ofl SDNl controller?
Answer:
Thel SDNl controllerl isl al partl ofl thel SDNl controll planel andl actsl asl anl interfacel betweenl thel networkl elementsl andl thel network-controll applications.Thel SDNl controller,l althoughl viewedl asl al monolithicl servicel byl externall devicesl andl applications,l isl implementedl byl distributedl serversl tol achievel faultl tolerance,l highl availabilityl andl efficiency.l Despitel thel issuesl ofl synchronizationl acrossl servers,l manyl modernl controllersl suchl asl OpenDayLightl andl ONOSl havel solvedl itl andl preferl distributedl controllersl tol providel highlyl scalablel services.
Anl SDNl controllerl canl bel broadlyl splitl intol threel layers:
Communicationl layer:
communicatingl betweenl thel controllerl andl thel networkl elements Controller'sl "southbound"l interface OpenFlowl isl anl examplel ofl thisl protocol
Network-widel state-managementl layer:
storesl informationl ofl network-statel (hosts,l links,l switches,l flowl tablesl ofl thel switches,l etc.) 3 / 4
Interfacel tol thel network-controll applicationl layer:
communicatingl betweenl controllerl andl applications Controller'sl "northbound"l interface Network-controll applicationsl canl read/writel networkl statel andl flowl tablesl inl thel controller'sl state-managementl layer.
Q:l SDNl Intro,l thel 3l planes
Answer:
Traditionallyl viewed,l computerl networksl havel threel planesl ofl functionality,l whichl arel
alll abstractl logicall concepts:
Datal plane:l Thesel arel functionsl andl processesl thatl forwardl datal inl thel forml ofl packetsl orl frames.Controll plane:l Thesel referl tol functionsl andl processesl thatl determinel whichl pathl tol usel byl usingl protocolsl tol populatel forwardingl tablesl ofl datal planel elements.Managementl plane:l Thesel arel servicesl thatl arel usedl tol monitorl andl configurel thel controll functionality,l e.g.l SNMP-basedl tools.Inl short,l sayl ifl al networkl policyl isl definedl inl thel managementl plane,l thel controll planel enforcesl thel policyl andl thel datal planel executesl thel policyl byl forwardingl thel datal accordingly.
Q:l Describel thel threel perspectivesl ofl thel SDNl landscape.
Answer:
1.l Al planel orientedl view >l Managementl plane,l controll plane,l datal plane
2.l Thel SDNl layers >l Networkl apps,l PL,l language-basedl virtualization,l northboundl interface,l networkl OS,l networkl hypervisor,l southboundl interface,l andl networkl infrastructure
3.l Al systeml design >l Networkl applications,l networkl OSl andl networkl hypervisors,l andl hardware
Q:l Describel thel responsibilityl ofl eachl layerl inl thel SDNl layerl perspective.
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