信息通信专业Data-drivenOverlayNetwork.ppt

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1、 Data-driven Overlay Network 目录nApplication layer multicastnData driven DesignnPeer-to-peer Receiver-driven OverlaysnComparisonn一些想法Application Level Multicast Application Level Multicast VS.IP Multicastn效率：IP组播比应用层组播效率高，q部署：应用层组播比IP组播容易部署。nIP组播需要改变路由器和end-system的上的IP层协议。部署困难n应用层组播只需要对end-system添加应用

2、层的软件就可以实现。部署容易n由于应用层组播只是在end-system添加应用层的软件，所以应用层组播又叫end-system multicast应用层组播的研究现状n应用层的研究由两部分构成：qOverlay constructqData deliveryn今天讲的是Overlay constructnApproachesqMesh-first approachn首先构建mesh结构，在mesh基础上构建最佳树qTree-first approachn直接构建treeqOther approachesnEg:混合模型,NICE;CAN,ScribeData driven Design（Rec

3、eiver-driven）nAvailability of data guides the flow directions,not a specific overlay structurenSuitable for overlay with high dynamic nodes:multiple parentsnExamples:Coolstreaming,PRO,PALSPeer-to-peer Receiver-driven OverlaysnThe main design philosophyqIndependently and selfishly choose the best way

4、 to connect to the OverlaynTwo key Componentsqpeer discover(PD)qpeer selection(PS)Peer DiscovernInitial parents selection new peer connect to the original servernTarget selection determine a target peer for gossipnContent selection select sgm records that are most useful for target peer.(Bidirection

5、al gossip)nImage maintenance integrate new records and discard excess records Interactions between PD and PS Peer-to-peer Receiver-driven OverlaysnPs mechanism is essentially a progressive search within the local image for a subset of parent peersnWhen should a new parent be selectqinitial phaseqrep

6、lacing a poorly-performing peerqImprovement in performancenConservative approachqa demand-driven fashion!Comparison of ALM and Data-drivennFairness(Defined by bandwidth ratio)qData-driven approach is better!nReliance to failuresqData-driven approach is better!nLocalityqData-driven approach can not c

7、oncern locality!一些想法nPRO中许多参数如根据带宽和延时对节点进行排序，每个节点拥有的父节点数等，都没有明确，需要进一步的细化工作。nCross-ISP的traffic尽量少n符合locality特性n与分层编码的结合分层编码n分层编码的主要思想：q把源视频流编码成几个不同的层，一个基础层，多个增强层。q比如共有5个层，1，2，3，4，5。由于受到接收端带宽的限制，只能接收3层，则接收端要求发送端只发送1，2，3。这样就能适应不同接收节点带宽的不同。q当然收到1，2，3层的视频质量不如收到1，2，3，4，5层的视频质量高，但是所需的带宽也小了。Layer 1Layer 2+Layer 3Thank you for attention！