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M&Ms: CS Freshmen Experience600.105Networks

DepartmentofComputerScienceTheJohnsHopkinsUniversity

YairAmir Spring2017/Week3 1

YairAmir Spring2017/Week3 2

Networks

Reading:

https://en.wikipedia.org/wiki/History_of_the_Internet

https://en.wikipedia.org/wiki/Routinghttps://en.wikipedia.org/wiki/Distance-vector_routing_protocolhttps://en.wikipedia.org/wiki/Link-state_routing_protocol

https://en.wikipedia.org/wiki/Internet_protocol_suitehttps://en.wikipedia.org/wiki/Berkeley_sockets

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TheInternetRevolutionATechnicalPerspective

Asingle,multi-purpose,IP-basednetwork• Theartofdesign– asuccessfulparadigm

– Keepitsimpleinthemiddle• Best-effortpacketswitching,routing(intranet,Internet)

– Smartattheedge• End-to-endreliability,naming

• Couldthereforeadaptandscale– Survivedfor4decadesandcounting– Sustainedatleast7ordersofmagnitudegrowth

• Standardizedandalotridesonit– Thebasicservicesarenotlikelytochange

3YairAmir Spring2017/Week3

Routing

• Distancevectorrouting• Linkstaterouting• Inter-networkrouting

4YairAmir Spring2017/Week3

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DistanceVectorRouting• Eachrouterknowstheidofeveryotherrouterinthenetwork.

• Eachroutermaintainsavectorwithanentryforeverydestinationthatcontains:– Thecosttoreachthedestinationfromthisrouter.– Thefirstlinkthatisonthatleast-costpath.

• Eachrouterperiodicallysendsitsvectortoitsdirectneighbors.

• Uponreceivingavector,arouterupdatesthelocalvectorbasedonthedirectlink’scostandthereceivedvector.

5YairAmir Spring2017/Week3

LinkStateRouting• Eachrouterknowstheidofeveryotherrouterinthenetwork.

• Eachroutermaintainsatopologymapofthewholenetwork.

• Eachrouterperiodicallyfloodsitsdirectlinksstate(withitsdirectconnectivityinformation).

• Uponreceivingavector,arouterupdatesthelocaltopologymapandre-calculatesshortestpaths.

6YairAmir Spring2017/Week3

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InternetRouting• RoutingInformationProtocol:

– Distancevectorprotocol.– Hopcountmetric– Exchangeisdoneevery30seconds,faultdetectionevery180seconds.

– Cheapandeasytoimplement,unstableinthepresenceoffaults.

• OpenShortestPathFirst:– Linkstateprotocol.– Internalhierarchyforbetterscaling.– OptimizationforbroadcastLANswithroutersonthem.(AdesignatedrouterrepresentsthewholeLAN)- Savescontrolmessagesandsize.

7YairAmir Spring2017/Week3

InternetRouting(cont)

• Ahierarchicalroutingprotocolthatconnectsnetworks,eachofwhichrunsaninternalroutingprotocol.

• OSPForRIParecommoninternalprotocols.• BGP- BorderGatewayProtocol-

– Apathvectorprotocolwithadditionalpolicyinformationforeachpath.Pathvectorprotocolshavethecompletepathineachentryandnotonlythenextdirectmember.

– Generallyusedasthehierarchicalroutingprotocol.

8YairAmir Spring2017/Week3

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Sockets:SimpleAPItoAccessItAll• Socket• Bind• Sendto• Recvfrom

• Listen• Connect• Accept• Send

9YairAmir Spring2017/Week3

NewApplicationsBringNewDemands

• Communicationpatterns– FromPoint-to-point– topoint-to-multipoint– tomany-to-many

• Highperformancereliability– “Fasterthanreal-time”filetransfers

• Lowlatencyinteractivity– 150mskeystrokemirroring– 100msforVoIP– 80-100msforinteractivegames(65msonewayforremotesurgery?)

• End-to-enddependability– From“Internet”dependability– to“phoneservice”dependability– to

“TVservice”dependability– to“remotesurgery”dependability• Systemresiliency

– FromE-mailfaulttolerance– tofinancialtransactionsecurity– tocriticalinfrastructure(SCADA)intrusiontolerance

10Fall2016/Week4YairAmir

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TheOverlayParadigm

• Overlay paradigm: – In contrast to “keep it simple in the middle and smart at the edge”– Move intelligence and resources to the middle

• Software-based overlay routers working on top of the internet• Overlay links translated to Internet paths

• Smaller overlay scale (# nodes) è smarter algorithms, better performance, and new services.

YairAmir Fall2016/Week4 11

TheLiveTimeNet Cloud

YairAmir 12Fall2016/Week4

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State-of-the-art:CombiningTimelinessandReliabilityovertheInternet

200msone-waylatencyrequirement,99.999%reliabilityguarantee40msone-waypropagationdelayacrossNorthAmerica 13

NewChallenges:CombiningTimelinessandReliability

130msround-triplatencyrequirement80msround-trippropagationdelayacrossNorthAmerica 14