دانلود رایگان مقاله انگلیسی مسائل مربوط به مقیاس پذیری کنترل پلن و رویکردهای شبکه های نرم افزار محور - الزویر 2017

Abstract

Software-Defined Networking (SDN) architecture has emerged in response to limitations of traditional networking architectures in satisfying today’s complex networking needs. In particular, SDN allows network administrators to manage network services through abstraction of lower-level functionality. However, SDN is a logically centralized technology. Therefore, scalability, and especially the control plane (i.e. controller) scalability in SDN is one of the problems that needs more attention. In this survey paper, we first discuss the scalability problems of controller(s) in an SDN architecture. We then comprehensively survey and summarize the characterizations and taxonomy of state-of-the-art studies in SDN control plane scalability. We organize the discussion on control plane scalability into two broad approaches: Topology-related approaches and Mechanisms-related approaches. In Topology-related approaches, we study the relation between topology of architectures and scalability issues. It has sub-categories of Centralized (Single) Controller Designs and Distributed approaches. Distributed approaches, in turn, have also sub-categories: Distributed (Flat) Controller Designs, Hierarchical Controller Designs, and Hybrid Designs. In Mechanisms-related approaches, we review the relation between various mechanisms used to optimize controllers and scalability issues. It has sub-categories of Parallelism-based Optimization and Control Plane Routing Scheme-based Optimization. Furthermore, we outline the potential challenges and open problems that need to be addressed further for more scalable SDN control planes.

Conclusions

Software Defined Networking is a promising emerging architecture for many networking environments such as data centers, enterprise networks, campus networks, cloud networks, and WAN. The major advantages of SDN are its programmability and agility. However, the scalability issues in the control plane is one major problem in SDN that needs more research attention. In the paper, we have firstly given an overview of the SDN architecture and OpenFlow protocol along with its support mechanisms for scalability. We have discussed the scalability as a concept in general and presented various metrics proposed for quantification of scalability. We have seen that there is no consensus on the definition of scalability. In other words, while the basic notion is intuitive, scalability does not evoke the same concept to everybody. In the context of SDN, scalability is characterized by the two prominent metrics, throughput and flow setup latency. Also, we have pointed out the main reasons that make the control plane a scalability bottleneck in SDN: Separation of Control Plane and Data Plane, Quantity of Events/Requests Handled by a Controller, and Controller-Switch Communication Delay. Furthermore, we have presented our organization for taxonomy of scalability-centric studies in two broad approaches: Topology-related approaches and Mechanisms-related approaches. While the former reviews the relation between topology of architectures and scalability issues, the latter discusses the relation between various mechanisms used to optimize controllers and scalability issues. Finally, we have outlined the potential challenges and open problems that need to be addressed further for more scalable SDN control planes: Controller(s) Failure, State/Policy Distribution/Consistency, Flow Rule Setup Latency, and Controller Placement.