Study Of Request-routing In Content Distribution Network Based On Software-defined Networking

Content distribution network(CDN)provides users efficient access to services by placing node servers close to the users.After years of development,CDN has been widely used,but a reverse proxy-assisted acceleration causes the network traffic opaque,lack of network openness and other issues.As one of the important directions of future network,the appearance of software defined networking(SDN)provides a new solution for the development of traditional CDN.This issue discusses improving the traditional CDN control mechanism using the software-defined ideology,unified managing network traffic and obtaining the network topology information through the control plane.This paper firstly studies the scalability of controller placement,on the basic of the study discusses CDN architecture based on SDN,finally designs the video streaming transmission strategy in SDN-based CDN request routing.Specifically,this paper includes the following three parts:(1)Controller placement based on hierarchical multi-center SDN.Software defined networking is a style of computer networking that separates the control plane from the data plane,shifting the control plane to a centralized controller in order to achieve network flexibility and openness.The controller placement is a key prerequisite to successful SDN.The current study examines the hierarchically distributed control plane controller placement problem,utilizing a multi-level k-way switch partition algorithm to divide large scale network topology.This paper also fixes the traditional SDN controller placement problem,changing zoning and intra-domain controller placement by reducing the edge-cut in order to lower the number of inter-domain flows.Simulation results show that the multi-level k-way switch partition algorithm can effectively reduce control flow overhead and flow set-up time,compared with other traditional algorithms.(2)Introduction of CDN architecture based on SDN.Meet the requirements of the CDN service system through reforming the SDN controller.Firstly,add DNS interface,redirect components and load balancing components to SDN controller.Then,connect a cache server for each switch in order to cache content and rewrite the OpenFlow protocol to provide service for CDN system.Finally,introduce simulation experiment based on Floodlight and Mininet,modify Floodlight and Mininet corresponding modules to rewrite OpenFlow protocol.(3)OpenFlow oriented content distribution network video stream transmission strategy.CDN can provide stable services for content delivery through proxy nodes,while there are some problems in CDN,for example lacking of openness increased the difficulty of CDN control.SDN separates the control plane from the data forwarding plane for network equipment,and it realizes the flexible control of the network,and provides a possible solution to solve the lacking of openness problem in CDN.Firstly,this paper introduces the CDN architecture based on SDN,and controller interface improved based on OpenFlow,secondly introduces that routing the base layer of SVC encoded video as a lossless-QoS way,while the enhancement layers routed as a best effort way.For sequential stream,using the idea of service composition to process video stream,using LIAC(Least Inverse Available Capacity)algorithm to select the best route met service composition and least-hop.