Study On Technologies Of Networks Virtualization On Optical Transport Networks

With the continuous popularization and development of the information network,the various emerging network businesses make the optical transport network to face two problems:the lack of network capacity and "network ossification".On the one hand,the speed of expanding the capacity of optical transmission network is much smaller than that of users’ demand for network bandwidth.On the other hand,the increasingly bloated and inefficient network architecture is unable to meet the demand of emerging network business,which causes "network ossification".Elastic optical network virtualization technology is an effective means to deal with the challenges faced by the optical transport network.It is due to two main reasons.Firstly,based on the elastic optical network,the network virtualization is able to logically abstract the network resource,share the resource and flexibly schedule the network resource to improve the network resource utilization.Hence,it helps to provide more network transmission capacity under the limited resources and alleviates the capacity pressure of optical transport network.Secondly,through providing users with logically isolated virtual networks on physical network,it is convenient for users to build customized network architecture for themselves to meet the demands of different specific network services so as to effectively solve "network ossification".The paper focuses on elastic optical network virtualization problem,researching in the spectrum allocation algorithm,network virtualization mapping algorithm,multi-layer network virtualization mapping algorithm and virtual network protection algorithm,and achieves some innovative results.The main innovative contributions are listed as follows.(1)Aiming at the problem of spectrum fragmentation and low resource utilization in spectrum allocation for elastic optical network in dynamic scenario,this paper considers the occupied holding time of spectrum and the capacity to meet request of available spectrum together,and proposes a algorithm based on holding-time-aware,MWHTD(Minimum weighted holding time difference),to improve the utilization of network resource.The algorithm utilizes the metric,WHTD(Weighted holding time difference),to measure the spectrum status and the degree of fragmentation of the candidate path.Based on the contiguous level of available spectrum and the release status of the occupied spectrum reflected by the WHTD metric,the algorithm further predicts the substrate path capacity to meet requests in the future.Through selecting the candidate method which keeps the spectrum in the network with minimum WHTD,the algorithm reduces the spectrum capacity loss of all substrate paths in the network,reduces the spectrum fragmentation and improves the network resource utilization.The simulation results show that,compared with other traditional algorithms,MWHTD algorithm decreases the blocking probability near by 18%.(2)Aiming at the problem of the cooperation and resource efficiency of node mapping and link mapping stages in network virtualization mapping for elastic optical network,according to the different scenarios,this paper cooperates the node mapping and link mapping stages and proposes DMTC(Degree-Prior minimum total cost)algorithm with constrain of geography and MARB(Maximum adjacency ratio of basis)algorithm without constrain of geography,respectively.The algorithms optimize the cooperative mechanism between the node mapping and link mapping stages to improve the network resource utilization in different scenarios.Based on the arrangement of virtual node according their weights,DMTC algorithm aims at minimizing the resource costs in mapping to jointly optimize the node mapping and link mapping so as to decrease the request blocking probability and utilization of network resource utilization.The algorithm directly selects the corresponding substrate path between the substrate mapping nodes which are mapped by two endpoints of a virtual link as the substrate mapping path for the corresponding virtual link,which cooperate the node mapping and link mapping jointly.The strategy of MARB algorithm for optimizing cooperation between the node mapping and link mapping stages aims at minimizing the hops of substrate mapping paths when link mapping.The strategies cooperate the hops of substrate mapping paths and the selecting strategy of substrate node in node mapping to propose minimum total cost node mapping algorithm and minimum adjacency ratio node mapping algorithm in the node mapping stages of the two algorithms,which select substrate mapping nodes for virtual nodes through predicting the hops of subsequent corresponding substrate mapping path to reduce the hops in substrate paths in order to reduce the spectrum utilization.The method will decrease the spectrum fragmentation in link mapping stage and help to easily find available spectrum resource for addressing spectrum allocation to meet more requests.The simulation results show that DMTC and MARB algorithms decrease the blocking probabilitiesand improve the network resource utilization.In particularly,compared with other traditional algorithms,DMTC algorithm and MARB algorithm decrease the blocking probabilities near by 16%and 40%,respectively.(3)Aiming at the problem of low efficiency in multi-layer networks virtualization mapping caused by the lack of information interconnection among different layers in the multi-layer network,this paper proposesMCRC(Minimum cross-layer resource cost)multi-layer network virtualization mapping algorithm to improve the resource utilization by cooperating the optical layer and IP layer and optimizing the resource selection strategy.The algorithm orderly selects substrate mapping nodes for each virtual node,according to the total resource of the substrate nodes and the degrees of virtual nodes,to improve the successful probability of node mapping.Then,Based on the improved AG(Auxiliary graph),aiming at improving the balance of resource allocation when link mapping,the algorithm adopts the method which measures the weight of substrate links according to their utilization status to calculate the weight for all substrate links.The algorithm selects appropriate IP links for the substrate mapping path for improving the utilization of IP links’ bandwidth through calculating the product of the difference between the bandwidth of request and the IP link,and the difference between the holding time of present request and all of the remained holding time of the remained requests in IP link.The strategy selecting the minimum product helps MCRC algorithm to address the multi-layer network virtualization mapping problem efficiently.The simulation results show that,compared with comparing algorithms,MCRC algorithm is able to decrease the request blocking probability.(4)Aiming at the problem of the resource redundancy and low resource utilization in virtual network protection,this paper utilizes the strategy of spectrum shared by protection path to propose DAMSC(Distance-adaptive minimum spectrum cost)virtual network protection algorithm for elastic optical network to improve the spectrum utilization and the successful probability for virtual network mapping.The algorithm firstly utilizes certain virtualization mapping algorithm to address the node mapping and work path mapping problem.For addressing the protection path mapping problem efficiently,this paper proposes the mathematical model of spectrum shared by protection path based on its own feathers.Furthermore,this paper defines the shared protection set for each FS(frequency slot)consisting of all of the substrate links which consist of the paths protected by the paths sharing the FS in present.Then,the paper utilizes the ratio between the number of the members in the set and the number of all substrate links as the shared probability of the present FS in the future.DAMSC algorithm takes the difference of the probability mentioned above before and after the utilization or sharing of the FS as the cost of utilizing this FS.Based on the method,with different modulation formats,DAMSC algorithm utilizes the distance-adaptive method to find the substrate protection path with minimum total FS cost for all virtual links in the layered graph of deleted network to reduce the resource redundancy and improve the spectrum utilization.The simulation results show that,compared with other traditional algorithms,DAMSC algorithm is able to decrease the request blocking probability,obviously.