翻译以原文和在同一文件中前

RajJain，Subharthi网络虚拟化是云计算现在以及今后取得成功的关键。在本文中，解释虚拟化用交付上的研究对SDN的适用性进行讨论。逛虚拟商场，网上获得虚拟教育，进行虚拟，当然，我们的很多计算也是虚拟的。而每个虚拟机可以提供给不同的用户，高速的链路和高性能的也可以这样为多用户：共享同一资源的多个用户可能彼此之间并不信任，所以为用户提供是的。聚合：如果某些资源太小，我们可以试着让其组成一个较大的虚拟资源。以存今天的计算机已有非常复杂以及多层次的缓存机制。虚拟化很自然就成为了下一络架构要提供的许多功能的关键。网络的虚拟化也不是一个新概念了，在基于X.25的电信网络和其所有后续网络的虚拟通道就允许多个用户共个大的物理信道。虚拟局域网(VLANs)可以使一个公司中的不同部门在同一个物理的区域网络中实现。而虚拟网络( s)则能使部门和员工在公共网络中享受与私有网络相同级别的性。近所研究出来的标准与SDN便是本文的。是笔者对基于SDN的多云环境应用交付的研究，最后将是我们的总结与结论。组件已有许多彼此相互竞争的虚拟化标准，许多研究人员还在研究的标准。复杂了。我们都知道IP地址不仅是定位码，它还是系统识别码，所以当一个系统移动IEEE802地址都只是系统识别码（而非定位码）所以在系统移动时它并不改变。因此，当使用三层路由器形成多个二层网络的网络连接时，常常需要创建整个网络的虚拟二层网络。以松散的角度来看，多个IP网络一起组成了一个以太网。2.1所示，一种解决办法是使用提供虚拟化处理器的管理程序根据虚拟机的数量来创建相应数量的虚拟网卡（vNIC。这些虚拟网卡通过虚拟交换机我们使用p前缀代表physicalv前缀代表virtual来形容虚拟对象。2.12.1中展示了三种不同的方法。第(VEB)方法的优点是透明而直接。但是它的竞争对手，这样会显著提高软件开销，返回给同一机器上的其他虚拟机。IEEE802.1Qbg标准制定使用VEBVEPA。2.22.2IEEE802.1BRvLANs会像图2.3那样会通过三层网络多个不同的数据中心。2.3同一物理机内属于不同VLAN这次也有多种解决这个问题的方法。VMware及其合作公司提倡使用虚拟可扩展局中心的虚拟接口上。之前所提到的基于IP的介质控制(MAC)在此处可以适用。也换机、三层路由器、应用交付控制器等都低费高效地组合在一起。欧洲电信标准软件定义网络是的网络技术革新。整个网络产业，包括网络设备提供商、网络标准化应用程序接口当然集中式的控制存在扩展问题，但分布式下也同样存在。对于这两种情况，我们显的一个优势在于它状态改变与策略改变速度要比完全分布式的控制系统快很多。另式的，数据平面仍完全是分布式的。在一个完全分布式的控制平面上实现规则的动态变化就要复杂许多。序层和一个控制系统层。目前已经出现了多种控制器，例如Floodlight、OpenDaylight3.1软件定义网络提供最主要的南向API是由开放式网络提出了OpenFlow协议。还有许多专有的（I2RS单网络管理协议（SNMP网络配置（Net-Conf转发与控制分离元素（ S，（PCE（CDNI，有一般用途的南向控制API。南向API目前还未被标准化。每个控制器都可能拥有不同的编程接口。直到这些西向的API为相邻域或在同一域中的不同控制器提供沟通。来进行传输。流一般包含一个交换过程很长的数据包流。在这种情况下，控制器对收端口进行定义。图3.2中显示一个典型的流表条目。控制流表条目对匹配的数据网络企业们对SDN表现出了极大的。SDN有望使网络变得可编程、可轻松分今后的业务流程中。必须的是，NFV和SDN是高度互补的技术。它们不依赖于彼L3以及它上层的应用流量。应用流量管理会根据应用程序的类别，应用程序部署环境（应用程序分区和、中介服务的安全与性能等，用户和服务 求和请求都发送到不同的服务器组。用户上下文的一个例子是移动智能使用者与个人电脑用户。网络上下文的一个载以及其开关状态。此外，大多数服务都需要多个TCP段，该服务实际上需要经性能增强（SSL装载机，WAN优化器）等部分来实现服务部署。这些分部都可以通过多个目的地（基于，分区）送达。因此，应用服务提供商(ASP)需要在它们的私有现在大多数应用程序（包括智能上的游戏）需要为全球的用户服务并需要分布得计算和设施。但是，在一个非常动态的多云环境下使用ASP路由策略是不可能务提供商可以适用OpenADN感知数据平面实体为提供应用交付服务。6项创新合并在一起以实现这个目标：OPENFlow,SDN,会话拼接，跨层通信，间接寻址，MPLSlike应用程序流（APLS，应用程序交换。4.1在OpenADN中，ASP控制器将其策略分发至控制平面的ISP4.1所示，OpenADNASPISP的控制器进行通信，并给ISPISP控制器可以进行相应的控制平面编程。除了需要一个北向的API，OpenADN还需要扩展一些南向API—OpenFlow。可以在全球互联网的任何位置。当然，为了达到最能，它们应位于靠近没有必要改变网络，因为只有一些边缘设备需要互联网服务提供商采用这种方式的经济因素是在部署了少数应用OpenADN的交IEEE和因特在这一方向上的发展是软件定义网络(SDN)，SDN的关键创新包括有数据与 /members/downloads/specifications/iov/sr-iov1_1_20Jan10.pdf,availableonlytomembers.IEEEStd.802.1Qbg-2012,“IEEEStandardforLocalandMetropolitanAreaNetworks—MediaAccessControl(MAC)BridgesandVirtualBridgedLocalAreaNetworks—Amendment21:EdgeVirtualBridging,”July5,2012,,p.R.Perlmanetal.,“RoutingBridges(RBridges):BaseProtocolSpecification,”IEEERFC6325,July2011,99pages,.M.Sridharanetal.,“NVGRE:NetworkVirtualizationUsingGenericRoutingEncapsulation,”IETFDraftdraftsridharan-virtualization-nvgre-03.txt,Aug.,pp.M.Mahalingametal.,“VXLAN:AFrameworkforOverlayingVirtualizedLayer2NetworksoverLayer3Networks,”IETFDraftdraft-mahalingam-dutt-dcops-vxlan-04.txt,May8,2013,22pages,.B.Davie,Ed.,J.Gross,“AStaessTransportTunnelingProtocolforNetworkVirtualization(STT),”IETFDraftdraft-davie-stt-03.txt,Mar.12,2013,19.IEEEStd802.1BR-2012,“IEEEStandardforLocalandMetropolitanAreaNetworks—VirtualBridgedLocalAreaNetworks—BridgePortExtension,”July16,2012,135pages,.T.Nartenetal.,“ProblemStatement:OverlaysforNetworkVirtualization,”IETFDraftdraft-ietf-nvo3-overlayproblem-statement-04,July31,2013,24pages,.ETSI,“NFVWhitepaper,”Oct22,2012,FloodlightOpenFlowController, OpenNetworkingFoundation,“OpenFlowSwitchSpecification,V1.3.2,”Apr.25,2013,131pages,.Cisco’sOnetformKit S.PaulandR.Jain,“OpenADN:AppsonGlobalCloudsUsingOpenFlowandSoftwareDefinedNetworking,”1stInt’l.Wksp.ManagementandSecurityforCloudComputing,Dec.7,2012.CloudCloudNetworkingandNetworkVirtualizationandCloudComputing:ASurveyRajJainandSubharthiPaul,WashingtonThisworkwassupportedinpartbyagrantfromProgramandNSFCISEGrant#

rentandfuturesuccessofcloudcomputing.Inthisarticle,weexinkeyreasonsforvirtualiza-tionandbrieflyexinseveralofthenetworkingthathavebeendevelopedrecentlyies.Inparticular,weexinsoftwaredefinednetworking,whichisthekeytonetworkpro-bilitywithourownresearchonOpenADN—applicationdeliveryinamulti-cloudenviron-aspectsofourlife.Today,ourworkcesareallvirtualizationsistheInternetandvariousized.SeveralnewstandardsandThisarticleisasurveyofthese.Therearemanyreasonswhyweneedtovirtualizeresources.Thefivemostcommonreasonsare:Sharing:Whenaresourceistoobigforamulti-coreprocessors.Eachprocessorcanrunmultiplevirtualmachines(VMs),andeachmachinecanbeusedbyadifferentandlarge-capacitydisks.toprovideisolationamongusers.Usersabletomonitortheactivitiesorinterfereapplyevenifdifferentusersbelongtothesameorganizationsincedifferentdepart-

engineering)mayhavedatathatisconfi-dentialtothedepartment.Aggregation:Iftheresourceistoosmall,itispossibletoconstructalargevirtualbeusedtomakeuplargereliablestorage.Dynamics:Oftenresourcerequirementstoreallocatetheresourcequicklyisrequired.Thisiseasierwithvirtualresourcesthanwithphysicalresources.theeaseofmanagement.Virtualdevicesthroughstandard Virtualizationinanexpensivepartoftheoriginalcomputers,sovirtualmemoryconceptsweredevelopedinthe1970s.Studyandcomparisonofvariouspagewithvirtualdisks,virtualcompactdisk(CD)drives,leadingtocloudstoragetoday.Virtual-virtualizationofserversandcloudcomputing.Computernetworkingistheplumbingofcomputing,andlikeplumbinginallbeautifulbuildings,networkingisthekeytomanyoftheVirtualizationinnetworkingisalsonotanewconcept.VirtualchannelsinX.25-based municationnetworksandallsubsequentnet-worksallowmultipleuserstosharealargephysicalchannel.Virtuallocalareanetworks(VLANs)allowmultipledepartmentsofacom-panytoshareaphysicalLANwithisolation. 0163-6804/13/$25.00©2013 IEEECommunicationsMagazine•Novembercompaniesandemployeestousepublicnet-intheirprivatenetworks.lybycloudcomputing.Severalnewstandardshavebeendevelopedandarebeingdeveloped.Softwaredefinednetworking(SDN)alsohelpsinnetworkvirtualization.TheserecentstandardsandSDNarethetopicsofthisarticle.tion.SoftwaredefinednetworkingapplicationdeliveryusingSDNisdescribed.Finally,asummaryfollows.Networkfacecard(NIC)inthehost,whichisconnectedtoalayer2(L2)network(Ethernet,WiFi,etc.)interconnectedviaswitches(a.k.a.bridges)toformanL2network,whichisonesubnetinaes.Eachofthesenetworkcomponents—NIC,tualized.Therearemultiple,oftencompeting,standardsforvirtualizationofseveralofthesecomponents.Severalnewonesarebeingdevel-er,itsIPaddressmustchange,whichcompli-asystemmoves,itsL3identifierchanges.InspiteofallthedevelopmentsofIP,itissubnet(withinoneL2)thanbetweenusedinL2networks(bothEthernetandWiFi)aresystemidentifiers(notlocators)anddonot

AlthoughAlthoughdiscussionsofprovidingcomputingasautilityhavebeenaroundforquitesometime,therealphysicalimplementationofcloudcomputingcamewhenAmazonannouncedElasticComputing2(EC2)onAugust25,2006.The(unverified)folkloreisthatwhenAmazon’sCEOvisitedthecompa-nydatacenter,hewasamazedbythenumberofcomputers.Sincedatacen-ters,likemostothercomputingfacilities,aredesignedtoavoidcrasheswhenoverloaded,thenormalutilizationofsystemsislow.TheAmazonCEOthere-foreaskedtofigureoutawaytomanagethehardwareinaprogr mannerwhereallthemanagementcouldbedoneeasilyremoyusingappli-cationprogramminginterfaces(APIs).Thisallowedthemtorentouttheunusedcapacity;sobeganthecomputerrentalbusinesswenowcallcloudcomputing.Theconceptwasimmediaysuccessfulsinceitrelievedcus-tomersofalltheheadachesofmanagingequipmentthathastobecontinu-ouslyupdatedtokeepupwiththelatest .Sharinganunderutilizedresourceisgoodforcloudservicecustomersaswellasforthecloudserviceproviders.Sidebar1.GenesisofcloudviaL3routers,itisoftendesirabletocreateavirtualL2networkthatspanstheentirenetwork.Inaloosesense,severalIPnetworkstogetherappearasoneEthernetnetwork.VirtualizationofEachcomputersystemneedsatleastoneL2calNIC.However,ifwerunmultipleVMsonAsshowninFig.1,onewaytosolvethisprob-lemisforthe“hypervisor”softwarethatpro-manyvirtualNICs(vNICs)asthereareVMs.ThesevNICsareinterconnectedviaavirtualcalNIC(pNIC).MultiplepNICsareconnectedtionofusingp-prefixforphysicalandv-prefixareshownbysolidlines.IEEECommunicationsMagazine•November Thesecondrecentdevelopmentthatispartlyresponsibleforthegrowthofcloudcomputingandisfuelinganeedfornetworkinginnovationsissmartphoneapps.OnJune29,2007,Appleannouncedthe withtheassoci-atedappstore.Althoughtherewereseveralgenerationsofsmartphonesbeforethen,theappstorewasamarketinginnovationthatchangedthelandscapeforapplicationdevelopers.Today,allbusinessesincludingbanks,retailstores,andserviceprovidershavetheirownapps,andeachoftheseappsneedstoserveaglobalaudience.CloudcomputingprovidesaneasyThesecondrecentdevelopmentthatispartlyresponsibleforthegrowthofcloudcomputingandisfuelinganeedfornetworkinginnovationsissmartphoneapps.OnJune29,2007,Appleannouncedthe withtheassoci-atedappstore.Althoughtherewereseveralgenerationsofsmartphonesbeforethen,theappstorewasamarketinginnovationthatchangedthelandscapeforapplicationdevelopers.Today,allbusinessesincludingbanks,retailstores,andserviceprovidershavetheirownapps,andeachoftheseappsneedstoserveaglobalaudience.Cloudcomputingprovidesaneasywayfortheseapplicationserviceproviderstoobtaincomputingservicesworldwide.However,networkingfeaturesrequiredforapplicationpartition-ingovermultiplecloudsownedbymultiplecloudserviceprovidersarestilllacking.Hence,thereisaneedforvirtualizationoftheInternet,asdiscussedfurtherinthisarticle.Thefirstapproach,providingasoftwarevNICviahypervisor,istheoneproposedbyVMsoft-warevendors.ThisvirtualEthernetbridge(VEB)approachhasthevirtueofbeingtrans-outthatthereissignificantsoftwareoverhead,andvNICsmaynotbeeasilymanageablebyexternalnetworkmanagementsoftware.Also,vNICsmaynotprovideallthefeaturestoday’spNICsprovide.SopNICvendors(orpNICchipization(SR-IOV)onthe interconnect(PCI)bus[1].Theswitchvendors(orpSwitchchipvendors)haveyetanothersetofsolutionsthatprovidevirtualchannelsfornetportaggregator(VEPA),whichpassesthementsinter-VMcommunicationpoliciesandreflectssometrafficbacktootherVMsintheVEBandVEPA.VirtualizationofnumberofphysicalmachinesthatneedtobeconnectedonanL2networkistypicallymuchlargerthanthis.Therefore,severallayersof[3],showninFig.2,allowsformingavirtual

bridgewithalargenumberofportsusingportextendersthataresimplerelaysandmaybephysicalorvirtual(likeavSwitch).VirtualLANsinOneadditionalprobleminthecloudenviron-mentisthatmultipleVMsinasinglephysicalmachinemaybelongtodifferentsandthusneedtobeindifferentvirtualLANs(VLANs).Asdiscussedearlier,eachoftheseVLANsmaynetworks,asshowninFig.3.alpartnercompanieshaveproposedvirtualextensibleLANs(VXLANs)[4].Networkvirtu-alizationusinggenericroutingencapsulation(NVGRE)[5]andtheStaessTransportTun-neling(STT)protocol[6]aretwootherpropos-alsbeingconsideredintheNetworkVirtualizationoverL3(NVO3)workinggroupoftheInternetEngineeringTask VirtualizationMulti-SiteDataIfa hasmultipledatacenterslocatedquicklyandeasily.Thatis,itmaywantallitsspanningallthesedatacenters.Again,amedi-umaccesscontrol(MAC)overIPapproachliketheonesproposedearliermaybeused.Trans-tospanalargecampusnetwork,canalsobeusedforthis.NetworkFunctionStandardmulti-coreprocessorsarenowsofastthatitispossibletodesignnetworkingdevicesusingsoftwaremodulesthatrunonstandardprocessors.Bycombiningmanydifferentfunc-tionalmodules,anynetworkingdevice—L2andsoon—canbecomposedcosteffectivelyFunctionVirtualization(NFV)groupofthe tute(ETSI)isworkingondevelostandardstoenablethis[9].PortPortPortPortPort IEEECommunicationsMagazine•NovemberVLAN22VLAN34VLAN34VLAN74VLAN74VLAN98VLAN98VLAN22L3Softwaredefinednetworkingisthetions.Allcompo-industry,includingSoftwaredefinednetworkingisthetions.Allcompo-industry,includingserviceproviders,ingonorlookingforwardtovariousaspectsofSDN.SoftwareDefinedofthenetworkingindustry,includingnetworkThissectionprovidesanoverviewofSDN. Standardizationofapplicationprogramminginterfaces(APIs)EachoftheseinnovationsisexinedbrieflyNetworkingprotocolsareoftenarrangedinthreenes:data,control,andmanagement.Thedataneconsistsofallthemessagesthataregeneratedbytheusers.TotransporttheseusingL3routingprotocolssuchasOpenShort-estPathFirst(OSPF)orL2forwardingproto-ingequipment.Thisisdonevianetworkman-OneofthekeyinnovationsofSDNisthatthecontrolshouldbeseparatedfromthedatane.Thedataneconsistsofforwardingtheandimplementedinacontrollerthatpreparestheforwardingtable.Theswitchesimplementplified.ThisreducesthecomplexityandcostCentralizationoftheControlTheU.S.DepartmentofDefensefundedAdvancedResearchProjectAgency

(ARPAnet)researchintheearly1960stocounterthethreatthattheentirenationwidemunicationcenters,whichwerehighlycentralizedandownedbyasingleatthattime,weretobeattacked.ARPAnettributedarchitectureinwhichthecommunica-tioncontinuesandpacketsfindthepath(ifoneexists)evenifmanyoftherouters enon-operational.Boththedataandcontrolnesweretotallydistributed.Forexample,eachmationwiththeirneighborsandneighbors’neighbors,andsoon.ThisdistributedcontrolparadigmwasoneofthepillarsofInternetCentralization,whichwasconsideredabadthinguntilafewyearsago,isnowconsideredgood,andforgoodreason.Mostorganizationsandteamsarerunusingcentralizedcontrol.Ifanemployeefallssick,he/shesimplycallstheboss,andthebossmakesarrangementsfortheworktocontinueinhis/herabsence.Nowcon-istotallydistributed.Thesickemployee,sayJohn,willhavetocallallhisco-employeesandlthemthathe/sheissick.TheywilllotherabitoftimebeforeeveryonewillknowaboutJohn’ssickness,andtheneveryonewilldecideishowcurrentInternetcontrolprotocolswork.Ofcourse,centralizationhasscalingissuesbutsododistributedmethods.Forbothcases,weneedtodividethenetworkintosubsetsorareasthataresmallenoughtohaveacommoncontrolstrategy.Aclearadvantageofcentral-izedcontrolisthatthestatechangesorbeusedtotakeoverincaseoffailuresofthefullydistributed.IEEECommunicationsMagazine•November NorthboundSouthboundNorthboundSouthboundNetworkcontrollerOpeninacentralcon-trolchangesbyeffect,withasuit-ableAPI,onecanofpoliciesandchangethemdynamicallyasthesystemstatesorneedschange. Nowthatthecontrolneiscentralizedinaagertoimplementcontrolchangesbysimplychangingthecontrolprogram.Ineffect,withasuitableAPI,onecanimplementavarietyoftemstatesorneedschange.importantaspectoftheSDN.Aprogrblecontrolneineffectallowsthenetworktobetotallydistributedcontrolne.StandardizedAsshowninFig.4,SDNconsistsofacentral-izedcontrolnewithasouthboundAPIforandanorthboundAPIforcommunicationwithacontrolsystemlayer.Anumberofcontrollersarealreadyavailable.Floodlight[10]isoneexample.OpenDaylight[11]isa efforttodevelopanopensourcecontroller.AwhichisbeingstandardizedbytheOpenNet-workingFoundation.Anumberofproprietaryableforlegacyequipmentfromrespectiveven-dors.Somearguethatanumberofpreviously(XMPP),InterfacetotheRoutingSystem(I2RS),SoftwareDrivenNetworkingProtocol(SDNP),ActiveVirtualNetworkManagement

tion(S),PathComputationElementnection(CDNI),arealsopotentialsouthboundAPIs.However,giventhateachofthesewassouthboundcontrolAPI.NorthboundAPIshavenotbeenstandard-izedyet.Eachcontrollermayhaveadifferentprogramminginterface.UntilthisAPIisstan-dardized,developmentofnetworkapplicationsforSDNwillbelimited.Thereisalsoaneedforaneast-westAPIthatwillallowdifferentcon-trollersfromneighboringsorinthesametocommunicatewitheachother.Flow-BasedsizeshavegrownexponentiallyusingMoore’slaw,andsohavethefilesizes.Thepacketsize,thetraffictodayconsistsofasequenceofpack-etsratherthanasinglepacket.Forexample,aodoftime.Insuchcases,ifacontroldecisionismadeforthefirstpacketoftheflow,itcanbereusedforallsubsequentpackets.Thus,flow-basedcontrolsignificantlyreducesthetrafficbetweenthecontrollerandtheforwardingele-ment.Thecontrolinformationisrequestedbyaflowisreceivedandisusedforallsubsequentpacketsoftheflow.AflowcanbedefinedbyanymaskonthepacketheadersandtheinputcalflowtableentryisshowninFig.5.Thecon-troltableentryspecifieshowtohandlethe IEEECommunicationsMagazine•NovemberMatchMatchPacket+byteForwardtoportEncapsulateandforwardtocontrollerSendtonormalprocessingpipelineModifyfields and packetswiththematchingheader.Italsocon-aboutthematchingflows.estinSDN.SDNisexpectedtomakethenet-worksprogrbleandeasilypartitionablecloudcomputingwherethenetworkinfra-structureissharedbyanumberofcompetingentities.Also,givensimplifieddatane,theforwardingelementsareexpectedtobeverytionalexpenditureforserviceproviders,cloudserviceproviders,andenterprisedatacentersthatuselotsofswitchesandrouters.SDNislikeatsunamithatistakingoverotherpartsofthecomputingindustryaswell.Moreandmoredevicesarefollowingthesoft-waredefinedpathwithmostofthelogicimple-mentedinsoftwareoverstandardprocessors.definedrouters,andsoon.RegardlessofwhathappenstocurrentapproachestoSDN,itiscertainthatthenet-worksoftomorrowwillbemoreprogrblethantoday.Progrbilitywill eacom-alargenumberofdevicescanbeprogrammed(akaorchestrated)simultaneously.TheexactAPIsthatwill ecommonwillbedecidedbytransitionstrategiessincebillionsoflegacynetworkingdeviceswillneedtobeincludedinanyorchestration.ItmustbepointedoutthatNFVandSDNnotdependentoneachother.DeliveryUsingWhilecurrentSDN-basedeffortsaremostlyrestrictedtoL3andbelow(networktraffic),it

titioningandreplication,intermediaryserviceservercontexts(load,mobility,failures,etc.),andapplicationQoSrequirements.Thisisapplicationshas eincreasinglycomplexeveninsideasingleprivatedatacenter.multiplehosts.Also,theservicemaybeparti-titionhostedonadifferentgroupofservers.Aservicemaybepartitionedbasedon:Content:Forexample,evenforthesameservice(e.g. )accounting mendationrequestsandergroups.Context:Usercontext,networkcontext,ormessagestoberouteddifferently.Anexampleofusercontextisasmartphoneuservs.adesktopuser.Anexampleofnetworkcontextisthegeographicallocationoftheuserandthestateofthenetworklinks.Anmore,mostservicesrequiremultipleTCPseg-ments,whereaccessingtheserviceactuallyrequiresgoingthroughasequenceofmiddleIEEECommunicationsMagazine•November OpenADN(OpenADNFigure6.InOpenADN,ASPs’controllersconveytheirpoliciestoancontrollerinthecontroltransformation/translation(e.g.,transcoders,datacompression)andperformanceenhance-ment(e.g.,SSLoffloaders,WANoptimizers)mentscanbeservedbymultipledestinationstionserviceproviders(ASPs)thereforeimple-mentcomplexapplicationrouting(APR)mechanismsinsidetheirprivatedatacenters.ProblemMostapplicationsnow(includinggamesonsmartphones)needtoserveglobalaudiencesandneedserverslocatedallaroundtheworld.tiesusingcloudservicesfrommultiplecloudprovidersdistributedthroughouttheworld.However,theproblemofroutingusingASPs’policiesinaverydynamicmulti-cloudenviron-mentisnotpossiblesinceInternetservicepro-viders(ISPs)offernoservicetodynamicallyroutemessagestoadifferentserverusinganASP’spolicies.SolutionOurvisionistodesignanewsession-layerioncalledOpenApplicationDeliveryNetwork(OpenADN)[15]thatallowsASPstomentpoliciesandapplicationdeliverycon-straintsatthegranularityofapplicationmessagesandpackets.Itallowsthemtoachievealltheapplicationdeliveryservicestheyusetodayinprivatedatacentersintheglobalmulti-cloudenvironment.OpenADNisbasedonthestan-dardizeddatane,diversifiedcontrolnedesignframeworkproposedbySDN.UsingOpenADN-awaredataneentities,ISPs

innovations:OpenFlow,SDN,sessionsplicing,applicationlabelswitching).AsshowninFig.6,OpenADNallowsASPs’controllerstocommunicatewiththeISP’scon-trollerandprovidetheISPwiththeirserverpoliciesandserverstatessothattheISP’scon-ly.InadditiontorequiringanorthboundAPI,OpenADNalsorequiressomeextensionstothesouthboundAPI—OpenFlow.OpenADNtakesnetworkvirtualizationtotheextremeofmakingtheglobalInternetProxiescanbelocatedanywhereontheglobalInternet.Ofcourse,theyshouldbeoptimalperformance.trafficcanpassthroughOpenADNboxes,andOpenADNtrafficcanpassthroughlegacyboxes.NochangestothecoreInternetareneces-sarysinceonlysomeedgedevicesneedtobeOpenADN/SDN/OpenFlow-aware.TheIncrementaldeploymentcanstartwithjustaEconomicincentivesforfirstadoptersaretobefoundbyISPsthatdeployafewoftheseswitches,andthoseASPsthatuseOpenADNwillbenefitimmediayfromthetechnology.ISPskeepcompletecontrolovertheirnet-controlovertheirapplicationdata,whichmaybeandencrypted.ThekeymessagesofthisarticleCloudcomputingisaresultofadvancesinvirtualizationincomputing,storage,andNetworkingvirtualizationisstillinitsinfan-(IETF),andseveralarestillbeing3Oneofthekeyrecentdevelopmentsinthisdirectionissoftwaredefinednetworking.ofthecontrolanddatanes,centraliza-tionofcontrol,progrbility,andstan-dardsouthbound,northbound,andberofdevicestoeasilybeorchestrated5WeareworkingonOpenADN,whichisanetworkapplicationbasedonSDNthateryinamulti-cloudenvironment. IEEECommunicationsMagazine•NovemberPCI-SIG,“SingleRootI/OVirtualizationandSharing1.1Specification,”htt loads/specifications/iov/sr-iov1_1_20Jan10.pdf,availableonlytomembers.IEEEStd.802.1Qbg-2012,“IEEEStandardforLocalandMetropolitanAreaNetworks—MediaAccessControl(MAC)BridgesandVirtualBridgedLocalAreaNetworks—Amendment21:EdgeVirtualBridging,”July5,2012,load/802.1Qbg-2012.pdf,p.R.Perlmanetal.,“RoutingBridges(RBridges):BasePro-tocolSpecification,”IEE