Sdn和传统网络的区别.docx

Sdn和传统网络的区别.docx

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Sdn和传统网络的区别

SDNandtraditionalnetworkthemaindifferenceliesintheirdifferentnetworkarchitectures.

Intraditionalnetworkarchitecturediagram,themostimportantthingistocontrollayeranddatalayerseparation.Eachlevelhasdifferenttasks,layerwithlayerprovidesthedataforwarding,routingfunctions.Here,thecontrollayerisresponsiblefortheequipmentconfigurationoftheroutinganddataflowprocedures.Whenyoumanageaswitch,youareactuallyinthedealandswitchescontrollayer.Likearoutingtable,spanningtreeprotocolandallthesethingsarecalculatedbythecontrollayer.ThesetablesbuiltfromsuchasBPDU（bridgeprotocoldataunit,usedtoruntheSTPswitchestoexchangeinformationbetweentrue）,theHellomessagesuchasframerelay,accordingtothesenewsframe,switchestodeterminetheavailableforwardpath.Oncethepacketforwardingpath,thepathinformationwillbesenttothedatalayerdown,usuallystoredonhardware.Datalevelusuallychoosethelatestbythecontrollevelformessageforwardingpathinformationtransmissiontocomeover.Thismodelisveryefficientintraditionally,thedecision-makingprocessofhardwareisveryfast,theoveralldelaycontrollableandcontrolplanecanhandleheavyconfigurationrequirements.

Therearenoproblemswiththisapproach,wefocusonscalability.Inordertoprovethescalabilityproblem,withourqualityofservice（QoS）asanexample.QoSallowedaccordingtothecharacteristicsoftheframe,accordingtotherequirementsofthescheduling,priorityforwardspecificdataframes.Thistosomeextentreducedthespecifictrafficcongestioninthenetworkdatatransmissiondelay.Delay-sensitive,forexample,voiceandvideotrafficisclassifiedashighpriorityandforwardedtoensurethattheuserexperience.Trafficpriorityisusuallybasedonthelevelofservice（CoS）ofadataframeordistinguishservicecodepoint（DSCP）tag.Theframemustbeunifiedinthedataframeintothenetwork,thenthecorrespondingrulesmustalsobesetinthenetwork,thedemandinthetraditionalmultipleexchangenetworkbecomesawkward,becauseeachdeviceneedstohavethesameconfigurationinformation.

Toillustratethecurrentnetworkmanagementchallenges,weconsiderthateachportoneachdevicenodeinthenetwork,theadministratorneedstobeconfiguredindividually,suchworkisverytime-consuminganderror-proneandawkward.

Inaddition,inthedataclassificationandappropriateroutingnetworkchallengesstillexist.Forexample,nowwehavetwokindsofcompletelydifferentdatatraffic,isakindofiSCSItraffic,isakindofvoicetraffic.ISCSIasthestorageflow,usuallypacketsarefullsize,andsometimestherewillbeahugedataframes;Whilevoicetrafficisusuallyinasmallpackettransmission.Inaddition,therearedifferenttwokindsoftraffictransportdemand:

voicetrafficissensitivetodelay,thisistoensurethequalityofvoicecommunication,theiSCSIissensitivetolowlatency,butneedmorebandwidth.Almostwithoutanytoolsinthetraditionalnetworkscandifferentiatebetweenthetwokindsofflowpathandchoosedifferentdependingonthetypeoftrafficdatatomeetthespecificneedsoftwokindsoftraffic.IsSDNhopetosolvealltheseproblems.

1.SDNarchitecture

AccordingtothedefinitionofONF,SDNisdividedintoinfrastructurelayer,controllayerandapplicationlayer,asshowninfigure1.Virtualizationininfrastructureandcontrollayerontwolevels,theequipmentlevelofvirtualization,suchasaphysicalsupportmultiplelogicalswitch;Whichrealizesthenetworklevelvirtualization,firstisSDNcontrollerwilloftheentirenetworkasalogicalsuperswitchesonmanagementcontrol,thesecondwillbethephysicalresourcesfurtheraccordingtotheport,themediaaccesscontrol（MAC）address,IPaddressandotherinformationisdividedintomultiplevirtualnetworkinaccordancewithtraditionalpracticeinthefieldofcommunication,inthearchitecturediagrambelowforsouth,aboveforthenorth,sotheinterfacebetweeninfrastructureandforwardlayercalledsouthinterface.ONFstandardizedisOpenFlowprotocol,theInternetengineeringtaskforce（IETF）routingsysteminterface（rs）protocolisbeingworkedout.Controllayerandapplicationlayercallednorthtointerfaces,theinterfacesbetweentheindustrymainstreamimplementationisbasedonthehypertexttransferprotocol（HTTP）RESTfulinterface,theconcreteprogramminginterfacedifferaccordingtothedifferentapplicationscenarios.

Figure1SDNlayeredarchitectureenlargeimages

InamoregeneralizedSDNarchitecture,controllayerandbusinesschoreographylayer,themainresourcesofSDNdomainbetweentheunityoftheunifiedmanagement,SDNnetworkandotherresourcesscheduling,suchas0penstack+SDNdatacentersolutions.

Unifieddispatchingcalculation,networkandstorageresources,itisequivalenttothebusinesschoreographylayerofSDN.StandinginthepointofviewofSDN,howcontrollayerisdividedintotheconcretebehaviorofvendorapplicationsolutions,implementation,asthetransmissioncontrolprotocol,networkprotocol（TCP/IP）don'tcareabouttheapplicationlayerfurtherlayereddesign,referredtoastheapplicationlayer.StandinginthewholenetworkarchitecturelevelSDN,industryexistdifferentopinions:

（1）SDNonlyregionalnetworkrenovation,toSDNcontroldomainasasuperequipment.SDNtransverseinterfacedoesnotchangetheoriginalnetwork,bordergatewayprotocol（BGP）/multi-protocollabelswitching（MPLS）isstillvalid.

（2）SDNcontrolfielddefinitionspecifically/enhancedSDNeast-westbetweeninterfaces,SDNastheentirenetworkcontrolplane.

Theauthorbelievesthatthefirstschemeismorerealistic,conducivetothesmoothevolutionofthenetwork.Thesecondsolutionofeast-westinterfacecaneitherthroughtheexpansionofexistingBGP,MPLSprotocolimplementation,orcanberealizedthroughthenorthtotheinterfaceintheaspectofbusinesschoreography,ifyouwanttodefinemorespecializedSDNeast-westinterface,althoughitispossibletoenhancetheabilityofthewholenetwork,butalsoincreasethedifficultyfordeployment,theindustryisunderexploration.

2.TheZENICarchitectureandkeytechnologytorealizecontrolsurfaces

ImplementationisbasedontheexistingopensourcefromacademiaSDNcontrollerOpenFlowagreement,theforwardmodelisalsoboundtoaspecificOpenFlowprotocolversion".Forthecommercialsystem,mustconsidertheentireproductlifecycleagreementthecompatibilityoftheinterface,considerthedifferenceofdifferentapplicationscenariosandmoremanufacturers,thedifferenceofmulti-protocolinterface,thereforeSDNcontrolsurfacesmustbesetacompatibleversionOpenFlow,avarietyofforwardcontrolprotocolandthedifferentabilityofabstraction,wecallforwardingabstractionlayer（FAL）,ontopofthisforthenetworkoperatingsystem（NOS）coreandtheapplicationlayerprovidestheinterfaceisindependentofthespecificagreementandtheabilityofhardware.InOpenDaylight,thisleveliscalledabusinessabstractionlayer（SAL）".

ThispaperimplementedaSDNcontroller-ZENIC,itsarchitectureisshowninfigure2.Figure2top-downmainlyincludesprotocolstack,drivingandforwardabstractionlayer,NOSkernelandapplicationlayer.

Figure2ZENICarchitectureenlargeimages

2.1forwardabstractionlayeranddrivelayer

Forwardforwardabstractionlayerdefinesaunifiedcontrolinterface,includingtheabstractforwardingstatebelow,turningability,hardwareresources,published,read/operationsuchasstatistics,equivalenttodrivethebaseclass.Forwardabstractionlayeralsoforwardmanagementfacedriverinstance,accordingtotheforwardingplanewhenaccesstothebasicabilitytonegotiatethedifferentinstancesofdrive,willforwardthecontrolconnectionisboundtothecorrespondingdriverinstance.

Eachspecificdevicedriverimplementationforwardabstractionlayerinterface,completedifferentinterfaceprotocolsandhardwareabilitytoforwardtheunificationoftheabstractionlayeradaptation.Fromthepointofviewofcontrolsurfaceandtheupperapplications,FALtransmitmanipulationinterfaceprovidesaunified,butduetotheforwardingthecapacitydifferenceisbigger,theapplicationforforwardingtheoperationthereisthepossibilityoffailure,thereforeFALneedtoprovideapplicationforwardinterfacesurfaceabilityget/negotiation.ZENICisimplementedforOpenFlow1.1adaptivenegotiation/1.2/1.3.

2.2thenetworkoperatingsystemkernellayer

NOSkernellayeristhemanagementofthenetwork,thesystemresources,includingtopologymanagement,host,interfaces,resourcemanagement,publicationmanagement,andmanagethephysicaltopology,virtualtopology,turninanetworkofinformationdatabase,etc.Ingeneral,thekernellayer,thereisnodefaultforwardnetworklogictohandle,buttopreservetheaccuratenetworktopology,theresourcesstatusandstorage,synthesisofthepublished,accepttheapplicationforsubscriptionandapplicationsofnetwork,resourcestatefornetworkresources,forwardlogicaloperation.

Topologymanagement,theimplementationofthecurrentcanbeimplementedbasedonstandardizationofOpenFlowcycledistributedacrossthelinkdetectionisbasedoncontrollermessage,Ethernetisgenerallybasedonlinklayerdiscoveryprotocol（LLDP）implementation.Forwardthisimplementationhastheadvantageofsurfacecompletelywithoutperception,thedisadvantageisthatmorelinkandshortertesttimer,controllerofhighoverhead.Anotherwayistohavetheforwardingplanemaintenancelinktesttimer,todet