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This book reviews the concept of Software-Defined Networking (SDN) by studying the SDN architecture. It provides a detailed analysis of state-of-the-art distributed SDN controller platforms by assessing their advantages and drawbacks and classifying them in novel ways according to various criteria.
Additionally, a thorough examination of the major challenges of existing distributed SDN controllers is provided along with insights into emerging and future trends in that area. Decentralization challenges in large-scale networks are tackled using three novel approaches, applied to the SDN control plane presented in the book. The first approach addresses the SDN controller placement optimization problem in large-scale IoT-like networks by proposing novel scalability and reliability aware controller placement strategies. The second and third approaches tackle the knowledge sharing problem between the distributed controllers by suggesting adaptive multilevel consistency models following the concept of continuous Quorum-based consistency. These approaches have been validated using different SDN applications, developed from real-world SDN controllers.
Due to the emergence of new kinds of communication and networking technologies (e.g. the Internet of Things (IoT), mobile trends, network virtualization) and the rise of many advanced services (e.g. real-time services, e-health, multimedia, smart cities, gaming) supported by these technologies, today’s networks – considered relatively static, “ossified” and “challenging to manage”– are no longer suitable to handle the complexity and diversity of network information being disseminated in today’s modern and dynamic networking environments.
There is a strong need to shift the current network architecture to a new model that adapts to such changes and leverages new control strategies to ease network management and automation, leading to better network performance and lower operating costs. In this context, software-defined networking (SDN) has emerged as a new networking paradigm that decouples network control and forwarding functions, enabling the network control to become directly programmable and the underlying infrastructure to be abstracted for applications and services.
SDN attempts to centralize the network control, thus offering improved visibility and flexibility to manage the network, optimize its performance and reduce its operating costs. However, centralized SDN designs, in which the control plane logic is physically centralized in a single software component called the SDN controller, present numerous challenges including the issues of control plane reliability, scalability and performance. To meet these challenges, it is necessary for the SDN control architecture to evolve toward a physically decentralized system. However, such physically distributed but logically centralized SDN platforms bring additional challenges.
In this book, we aim to provide a thorough exploration of the SDN technology and, more importantly, we deal with the SDN decentralization problem in the context of large-scale networks. We propose novel approaches to decentralize the SDN control plane without forgoing the centralization benefits of SDN. Part of this book was initially based on the work conducted within the framework of Fetia Bannour’s PhD thesis. This work was subsequently developed into a book to facilitate understanding of the decentralized SDN control plane. The latter may indeed be implemented using the existing distributed SDN controllers. However, their significant number, along with their particular pros and cons, made the choice extremely difficult for those who attempted to adopt a distributed SDN architecture in large-scale deployments.
Introduction
Toward a Decentralized SDN Control Architecture: Overview and Taxonomy
Decentralized SDN Control: Major Open Challenges
Scalability and Reliability Aware SDN Controller Placement Strategies
Adaptive and Continuous Consistency for Distributed SDN Controllers: Anti-Entropy Reconciliation Mechanism
Adaptive and Continuous Consistency for Distributed SDN Controllers: Quorum-Based Replication
Conclusions and Perspectives