| In order to achieve richer and more powerful functions,and further improve the user experience and security performance,many multicast services have involved intermediary network function.However,the traditional network architecture bases on proprietary hardware devices to realize network functions.It is difficult to update network functions quickly and is impossible to provide elastic service capabilities.Fortunately,Network Function Virtualization(NFV)facilitate the deployment of new network function with increased agility.Based on that "agility ",finding the appropriate location to deploy network functions on the network becomes a key issue.It not only determines the efficiency of computing,storage,communication resources in network,but also affect the performance of multicast services that use these network functions.Therefore,this thesis studies the NFV based multicast technology,discussing NFV-enabled multicast topology construction problem(NFV-MTC Problem)which contains two subproblem:(1)Determining the location and the number of virtual network function(VNF)deployed on the network;(2)Building multicast topology using these VNFs.This thesis’ s main work is as follows:Firstly,the architecture and working principle of NFV,and NFV’s application in multicast scenarios are summarized by studying the relevant standards and literature.On this basis,this thesis build the model of multicast service which using intermediary network function.Then,based on the existing research work,this thesis studies the NFV-MTC problem in the case that the intermediary network service contains only one kind of network function.An improved algorithm(SC.VNF_MR Algorithm)is proposed by analyzing the existing NFV-MTC1 algorithm’s two shortcomings: Its theoretical sector is too large,and it is difficult to adapt to the case where the bandwidth consumption of the multicast stream is increased after processed by VNF.Through theoretical analysis and simulation,it is proved that C.VNF_MR Algorithm can improve the deficiency of NFV-MTC1 algorithm,and it can get the multicast scheme with less cost.Based on the previous research,this thesis explores the NFV-MTC problem in the case that the intermediary network service(chain)contains a variety of network functions.Considering that the network service chain needs more resources,the VNSC_MR algorithm designed in this thesis sets up the “VNF instance reuse strategy” for saving resources.By comparing the algorithm with the multicast algorithm without optimization strategy,proves that the VNSC_MR algorithm can effectively reduce the number of VNF instances running in the network and reduce the overall multicast cost of the network. |
