Routing Spectrum Allocation Research For Service Function Chaining In Optical Network Data Center

Network Function Virtualization(NFV)was proposed to use Virtualised Network Functions(VNFs)to replace middle-boxes to give the network functiuon services.In the NFV architecture,the process that the traffic is steered by VNFs in a certain order is named Service Function Chaining(SFC).Currently,most researches about SFC are dealing with the problem of VNFs deployment or routing problem in the traditional electricity switch Data Centers.However,with the wider bandwidth,the optical network Data Centers is more suitable to tackle the converage flow which needs wider bandwidth.In optical network Data Centers,the routing and spectrum allocation must meet the constraint of spectrum consistency and continuity.Thus,the research findings in electricity switch Data Centers can not be applied in optical network Data Centers directly.However,researches in optical network Data Centers were insufficient.In order to decrease the spectrum expenditure during the routing process of SFC in optical network Data Centers,we proposed a spectrum-aware routing allocation algorithm called TBBA(Traveling Salesman Problem-Branch and Bound-Allocation).The TBBA designs a sepectrum-aware HC-VNFs allocation scheme firstly,which is different from the one that only takes the O/E/O into consideration.It tries to decrease the sepectrum requirements after the allocation by deploying the HC-VNFs of a SFC request on less Pods.Next we analysize the character of flow in SFC,on the basis of which we decided to use the Branch-and-Bound algorithm to search the minimum spectrum cost route and to build TBBA.Then we built a typical Fat-Tree Optical-Electrical-hybrid Data Center network simulation environment,where we test the blocking probability and the spectrum utility of TBBA and R-base(Random based)algorithm,which is a basic algorithm for SFC routing and spectrum problem.According to the simulation result,TBBA is able to receive a lower blocking probability and a higher spectrum utility in the same traffic load compared with R-base.For improving the service ability of network,balancing the usage of spectrum on every link as well as avoiding the spectrum fragmentation,we built a link functionU.The function is able to measure the usage of spectrum on links from both the spectrum occupancy rate and the fragmentation of spectrum.Basing on link functionU,we designed function U2.The design of function U2 takes both the sum of U and the standard deviation of these Uinto consideration,which reflects the difference of U among links.Using the TBBA as routing algorithm,we proposed an RSA of SFC called TBBA-U(TSP-Branch and Bound-Allocation with U),which uses function U2 to finish spectrum allocation.In the Fat-Tree Optical-Electrical-hybrid Data Center simulation environment,we test the block probability of TBBA-U and other algorithms,in a dynamic environment.The simulation results show that the TBBA-U algorithm achieves a lower block probability.Furthermore,it reflects that using the function U2 as the measure of spectrum allocation is able to enhance the ability of network service and get a good performance.