Service Function Chain Orchestration Mechanism For Network Virtualization Environment

Network virtualization technology enables multiple virtual networks running on the same physical networks in a logically isolated manner,and the users can deploy network services in the virtual networks.Network function virtualization enables the dedicated hardware-based network functions in a virtualized manner running on general purpose hardware,such as servers,switches and storage devices.The virtual network functions can be deployed or migrated flexibly,hence the operating cost of network services can be greatly reduced.It has important theoretical significance and application value to investigate service function chain orchestration in network virtualization environment.Orchestrating service function chains in network virtualization environment can be divided into two phases:virtual network embedding and service function chain orchestration.Virtual network embedding partitions the network resources for a virtual network request with node and link resource constraints.Service fiunction chain orchestration deploy network services with specific requirements in a partitioned virtual network.At present,existing investigations of service function chain orchestration in network virtualization environment still has the following limitations:(1)the traffic steering of service function chain is implemented by SDN technology,however the SDN network has limited flow entry space,existing investigations of virtual network embedding seldom consider this characteristic;(2)existing SFC orchestration methods also need to be improved in terms of resource utilization and service reliability;(3)existing orchestration methods do not delve into the impact of the topology of abstract physical nodes on the deployment of virtual network functions.To solve the above problems,the research content and significance of this paper are as follow:(1)Aiming at the problem of low acceptance rate of virtual network embedding caused by the limitation of flow table resources in SDN network,we propose a virtual network embedding mechanism to satisfy the resource limit of flow table.Firstly,the mechanism maps the virtual link with high bandwidth resource demand and its corresponding virtual nodes,this will help to decrease the bandwidth and flow entry overhead.Secondly,when all the virtual links and their corresponding virtual nodes are mapped,the substrate node with minimum controller-to-switch delay is chosen to be the controller of the virtual network.Simulation results show that our proposed mechanism can effectively reduce the resource overhead of virtual network embedding and improve the acceptance ratio.(2)Aiming at the problem of high operation cost of network services and low resource utilization of network functions,we propose a cost-aware service function chain orchestration mechanism.Firstly,we consider both the virtual network function cost and the bandwidth resource cost.Moreover,when the virtual network function has sufficient computing resource,it can be used by multiple service function chains in order to increase the resource utilization.Secondly,in order to guarantee the quality of network services,we should make sure that the computational resource load of the physical node does not exceed its threshold value.Simulation results show that our proposed mechanism uses less computing and bandwidth resources to orchestrate the service function chains while ensuring the quality of the network services.(3)Aiming at the problem that the virtual network functions have high failure probability and it is difficult to satisfy the reliability request of network services,we propose a cost-aware and reliability-guaranteed orchestration mechanism.The mechanism has two phases:service function chain orchestration and virtual network function backup.Firstly,the problem of service function chain orchestration is formulated into a Hidden Markov Model,and we use the Viterbi algorithm to calculate the orchestration results with higher reliability and lower operation cost.Secondly,based on the backup cost and reliability increment,we calculate the importance of the virtual network function.We backup the virtual network function with the highest importance value to decrease the backup resource cost.Simulation results show that our proposed mechanism guarantees the service reliability with less computing,bandwidth and backup cost.(4)Aiming at the problem that data-intensive network service will generate large amount of bandwidth resource consumption within the data center,we propose topology-aware virtual network function deployment strategy.Firstly,the service function graph composed by the virtual network functions interconnected with each other within the data center is constructed a Gomory-Hu tree and we design a tree-deploy algorithm.Secondly,we analyzes the cost matrixes of three different data center topologies(common tree,VL2 and fat-tree).The virtual network function deployment strategy is based on divide and conquer,we recursively invoke the tree-deploy algorithm from the top to the bottom,until all the virtual network functions are deployed into the servers.Simulation results show that our proposed strategy can reduce the bandwidth consumption and the economic cost of network service operation.