1 延迟容忍网络及其应用DTNandItsApplication 天津大学计算机科学与技术学院张钢教授gzhang 2009 7 西藏民族学院新技术讲座 2 RelatedConcept相关概念 互联网Internet无线局域网WLAN WirelessLAN 无线自组织网络MANET mobileadhocnetwork 延迟容忍网络DTN delaytolerantnetwork 机会网络Oppnets OpportunisticNetworks 3 SomeNetworks几种网络 Fundamentallydifferentwayoflookingatnetworks Internet WiredLAN WirelessLAN Celltower Infrastructure Celltower LAN Accesspoint 4 Internet互联网 5 Internet互联网 TheusabilityoftheInternetdependsonsomeimportantassumptions几个重要假设Continuous bidirectionalend to endpath连续 双向端到端通路Shortround trips往返时间短Symmetricdatarates对称数据传输率Lowerrorrates低错误率 6 SomeSpecialCases互联网中的特殊情况 Intermittentconnectivity间歇连接Longorvariabledelay长延迟 不定延迟Asymmetricdatarates非对称数据传输率Higherrorrates高出错率如果互联网出现这些特殊情况会怎样 7 8 WirelessLANorWLAN无线局域网 9 MANET无线自组织网络 MobileAdhocNetworking MANET 10 MANET无线自组织网络 MobileAdhocNetworking MANET Rapidlydeployable selfconfiguring快速部署 自配置Noneedforexistinginfrastructure不需要基础设施Wirelesslinks无线链路Nodesaremobile topologycanbeverydynamic结点移动 拓扑动态Nodesmustbeabletorelaytrafficsincecommunicatingnodesmightbeoutofrange结点必须能转发消息AMANETcanbeastandalonenetworkoritcanbeconnectedtoexternalnetworks Internet 可以是独立的网络 可以连接到外部网络 11 MANET无线自组织网络 MobileAdhocNetworking MANET Tosupportrobustandefficientoperationinmobilewirelessnetworksbyincorporatingroutingfunctionalityintomobilenodes路由功能合并到每个移动节点中Suchnetworksareenvisionedtohavedynamic sometimesrapidly changing random multihoptopologieswhicharelikelycomposedbyrelativelybandwidth constrainedwirelesslinks带宽受限的无线链路 12 MANET无线自组织网络 Goal目标toextendmobilityintotherealmofautonomous mobile wirelessdomains whereasetofnodes whichmaybecombinedroutersandhosts themselvesformthenetworkroutinginfrastructureinanadhocfashion把移动性扩展到自治 移动 无线领域 13 MANET无线自组织网络 Characteristics特点Dynamictopologies动态拓扑Bandwidth constrainedvariablecapacitylinks带宽受限Energy constrainedoperations能量受限Limitedphysicalsecurity物理安全有限Theneedforscalability可扩展 14 MANET无线自组织网络 MANET要求任一节点对之间存在至少一条完整的端到端通信路径可能导致网络不能连通问题节点移动节点稀疏射频关闭障碍物obstruction 15 DTN延迟容忍网络 Disruption Delay TolerantNetworking DTN 介绍最初是为星际网络IPN interplanetarynetwork 通信提出来的其主要目标是支持具有间歇性连通 延迟大 错误率高的不同网络的互联和互操作如互联Internet和传感器网络 移动自组织网络等 16 InterPlanetaryInternet星际网络 16 17 18 19 20 21 AnInterplanetaryInternetExample 22 WhatDoesIPDo End to Endprotocolsfailandclosetheconnectionduringextendeddisruptions在长时间的中断期间 端到端协议失败并关闭链接Theydonothandledisruptiongracefully 23 WhatIsDTN ConnectsHop by Hop NotEnd to End 点到点 ForwardsOverOutgoingLinks 流出链路 OpportunisticallyHoldsDatainPersistentStorage 持久存储器 WhenOutgoingLinksareDown NetworkProtocolsthatProvideReliableMessageDeliveryacrossintermittent disrupted dynamicnetworks提供跨越间歇 中断 动态网络的可靠消息传递的网络协议 24 DTN延迟容忍网络 DTN网络体系由多个底层运行独立通信协议的DTN域组成域间网关利用 存储 转发 的模式工作如果去往目标DTN域的链路存在 则转发消息否则 将消息存储在本地持久存储器中等待可用链路 25 TheBundleLayer BundledData ControlMinimizeNetworkTraversals捆绑的数据和控制使网络往返移动最小化 AvoidsProtocolChattiness MinimalDependenceonRemoteInformation最小依赖于远程信息 26 TheBundleLayer 27 TheBundleLayer 保管者 保管者 28 Step1 BundleCreationatSource 29 Step2 TransmissionbySource 30 Step3 First HopBundleProcessingandForwarding 31 Step4 Second HopBundleProcessingandForwarding 32 Step5 BundleReceptionbyDestination 33 OpportunisticNetworks机会网络 Inopportunisticnetworkingnoassumptionismadewithregardtotheexistenceofacompletepathbetweentwonodeswishingtocommunicate 在机会网络中并不假设在希望通信的两个结点之间存在完整的通路Nevertheless opportunisticnetworkingtechniquesallowsuchnodestoexchangemessagesbetweenthem 然而 机会网络技术允许这样的结点之间交换信息 34 OpportunisticNetworks机会网络 DifferentlyfromDTNs inopportunisticnetworkseachsinglenodeactsasagateway 与DTN网络不同的是 在机会网络中每个结点都是网关 35 OpportunisticNetworks机会网络 Anetworkconnectionbetweenthetwowomenneverexistsbut byopportunisticallyexploitingcontactsamongheterogeneousdevices themessageisdeliveredhop by hopclosertothedestination andeventuallytothedestinationitself 36 OpportunisticNetworks机会网络 Anoppnetgrowsfromitsseed theoriginalsetofnodesemployedtogetheratthetimeoftheinitialoppnetdeployment Theseedgrowsintoalargernetworkbyextendinginvitationstojointheoppnettoforeigndevices nodeclusters ornetworksthatitisabletocontact 37 OpportunisticNetworks机会网络 Themainfocusofresearchonopportunisticnetworkshasbeenonroutingandforwardingissues路由和向前推进问题Becausefindingroutestowardsthedesireddestinationinsuchdisconnectedenvironmentsisregardedasthemostcompellingissue 最引人注目的问题 38 OpportunisticNetworks机会网络 机会网络可以看成是具有一般DTN网络特征的无线自组网方法1 源节点必须缓存数据直到进入目标节点通信范围内才允许传输数据 39 OpportunisticNetworks机会网络 方法2 源节点将消息传输给邻居中继节点 该节点缓存消息再将消息转发给目标节点或遇到的其他中继节点 40 OpportunisticNetworks机会网络 41 OpportunisticNetworks机会网络 42 WhynotdeployInfrastructure 为什么不部署基础设施 InfrastructureexpensivetodeployProvidingInternetconnectivitytodevelopingregions KioskNetinWaterloo DigitalGangeticProjectinIndia 43 DTN OppnetApplicationsDTN 机会网络应用 Inter PlanetaryNetwork IPN 星际网络Terrestrialandinterplanetarylinks LONGdelaysandepisodicconnectivity陆地和星际链路 长延迟和断续连通性ZebraNet斑马网络Collectsinformationaboutdispersedzebrapopulations收集分散的斑马数量信息 43 44 DTN OppnetApplicationsDTN 机会网络应用 DataMules数据骡子Randomlymoveandcollectdatafromlow powersensors随意移动并