Research On Network Service Orchestration Mechanisms Based On SDN And NFV

It makes people's lives more and more convenient by the massive-scale deployment of the Internet in this world.However,the operations of configuration,policy enforcement,modification,and test become more and more difficult for operators especially in the largescale network due to the vertically integrated structure of Internet(network control and data forwarding are tightly coupled).This status quo slows down network innovation and development.Besides,tremendous incompatible,closed and heterogeneous dedicated equipments are deployed in the network in order to satisfy customers' diversified demands and high Quality of Service(QoS).These dedicated equipments are also called middle-boxes.It becomes very hard to move or update these middle-boxes,once they are deployed in the network.Therefore,the network becomes more and more ossification,due to the continuously increased number of middle-boxes.Such situation not only leads to high Capital Expenditures(CAPEX)and Operation Expenses(OPEX),but also reduces the flexibility of service composition and provisioning greatly.With the fast evolution of standard Commercial-Off-The-Shelf(COTS)appliance in recent years,both academia and industry begin to search for new network paradigms for solving the above-mentioned problems in legacy networks.Among the new network paradigms,there are two representatives and they are:1)Software-Defined Networking(SDN),which was born from the lab of Stanford University;2)Network Function Virtualization(NFV),which was jointly proposed by over twenty of the world's largest telecom companies such as America Telephone and Telegraph(AT&T),British Telecom(BT)and Deutsche Telekom(DT).In particular,SDN enables the centralized management,control and programming by decoupling network control from data forwarding.NFV implements network functions in the form of software by decoupling network functionalities from the underlying hardware.The appearances of SDN and NFV not only reduce network cost,but also improve service orchestration and provisioning flexibility.In addition,SDN and NFV are highly complementary.On one hand,the centralized control of SDN accelerates the deployment of NFV.On the other hand,the fast service creation and scale abilities of NFV improve the agility of SDN.Currently,SDN and NFV have attracted a lot of attention from both academia and industry.The related researches are primarily focused on the service orchestration including configuration,deployment and provisioning mechanisms.Despite this,most of them are suitable for small-scale or relatively static network environment,and are weak when it comes to the(super)large-scale and dynamic network environment.Therefore,SDN and NFV bring both opportunities and challenges for exploring novel,flexible and low-cost service orchestration solutions.Our work aims at studying and solving the service orchestration and provisioning challenges in current Internet via introducing the two new paradigms SDN and NFV.The innovation and contribution of our work are summarized as follows:(1)We propose a basic network service orchestration and provisioning framework by intergrating SDN and NFV,in which the flexible,low-cost,reliable and scalable service provisioning is achieved.This framework is mainly composed of network service management module,virtual service function catalog module,service orchestration algorithm module and performance optimization module.In particular,the service management module accepts various requests and transforms them into the suitable formats which can be handled by the service orchestration module.The virtual function catalog module can provide various virtual functions for service orchestration module.The service orchestration module is in charge of service configuration,composition,deployment and provisioning according to users' requirements.The performance optimization module is responsible for further optimizing the performance of the already deployed services.As a result,the service orchestration and performance optimization modules are key elements of this framework.Targeting different scenarios,we study and propose many orchestration algorithms.The results indicate that this framework can satisfy users' requirements effectively by using different orchestration algorithms.(2)In order to solve the network ossification problem,SDN decouples network control and data forwarding to achieve high flexibility and innovation,while NFV decouples network functionalities and the underlying dedicated hardware to ahiceve low-cost.In this way,the concept of Virtual Network Function(VNF)is introduced,which implements various kinds of network functions in the form of software.Different sequences of VNFs represent different types of Service Function Chains(SFC).Therefore,we can constitute various kinds of services by changing the composition of VNFs,which improves the flexibility greatly.Despite this,these VNFs have to be deployed in physical networks before they can actually provide services,and different VNF deployment and traffic steering solutions will affect the QoS directly.In addition,different solutions are proposed to handle different types of service chain requests(including unicast and multicast).In this work,we propose unicast-based SFC provisioning and multicast-based SFC provisioning algorithms respectively.For the former,it jointly leverages the global control and local optimization to fulfill the dynamic VNF deployment.After that,the unicast-based SFC provisioning is fulfilled toward the objectives of network load balance and cost minimization.For the latter,it first decouples the service function deployment and multicast traffic forwarding.Then,it implements the multicast SFC provisioning based on the minimum spanning tree.Apart from providing fast SFC provisioning,it also supports service scalability,so as to serve the customers in large-scale networks.(3)The traditional services composed of middle-boxes cannot actually satisfy all users'requirements now,because once the middle-boxes are deployed,they are hard to be modified,while the users' demands are diverse.On the contrary,the SFCs composed of VNFs can provide high flexibility.When the SFCs are deployed in the network,there may exist requests demanding to add new or remove existing VNFs according to business needs.This behavior is called the SFC recomposition.Although we can still use the SFC provisioning algorithms to solve the scenario of SFC recomposition directly,it will lead to unnecessary cost due to the fact that the SFC provisioning algorithms have to change the overall SFC deployment solution,while the SFC recomposition only requires changing part of it.Considering this,we propose different algorithms for the scenarios of unicast-based SFC recomposition and multicast-based SFC recomposition.For the former,it uses proactive and reactive mechanisms to add or remove VNFs respectively.The proactive mechanism intends to optimize the currently in-use service function path based on different criteria,while the reactive mechanism handles the SFC recomposition by using the already built service path.For the latter,it separates the function deployment and multicast traffic forwarding.Then,it constructs the multicast forwarding tree using the minimum spanning tree.In this way,the operations of VNF adding and removing can be mapped to the operations of building and pruning branches of the multicast forwarding tree.The results indicate that the SFC recomposition algorithms can achieve better performance when dealing with the already deployed SFCs,compared with the SFC provisioning algorithms.(4)In order to further optimize the performance of network service,we propose a network calculus based performance estimation model,in which the performance of deployed services can be estimated according to current network status.By comparing the estimated results with the users' original minimum allowed service quality,we can judge whether the users' requirements are satisfied.For the customers whose requirements are not satisfied,this work proposes two kinds of optimization algorithms with respect to the VNF scheduling and the VNF migration respectively.For the former,most researchers assume that each VNF instance only belongs to only one SFC,that is,one VNF instance cannot be shared by other SFCs.In this way,a lot of resource fragments are generated,which in turn leads to low resource utilization.Targeting on this scenario,we propose a fair VNF scheduling mechanism based on the size of SFCs,which addresses the resource conflict problem when multiple SFCs share the same VNF instance.For the latter,we propose a VNF migration algorithm to handle the cases of resource shortage and link overload that cannot be effectively solved by the VNF scheduling algorithm.Considering the fact that one VNF instance may be shared by multiple SFCs,we not only leverage the global network view offered by SDN to calculate the migration solution,but also base on the Technique for Order Preference by Similarity to an Ideal Solution(TOPSIS)to minimize the affection caused by VNF migration.The results show that the two optimization mechanisms can improve the SFC quality further on the basis of SFC provisioning and recomposition.In summary,the appearances of SDN and NFV not only bring opportunities for network innovation,but also introduce challenges for service orchestration.Based on the opportunities brought by SDN and NFV,we design and propose four different service orchestration and optimization mechanisms for solving different challenges.Besides,these mechanisms are evaluated over some real-world topologies in terms of service provisioning cost,time overhead,routing delay,throughput and scalability,etc.Our research achievements have strong theoretical value and practical significance,and can be used to guide the service orchestration and provisioning in the next generation Internet with a new perspective.