# A Game Model and Fault Recovery Algorithm for SDN Multi-Domain
## 1 Introduction  
With the rapid development of the Internet of Things (IoT), the Wireless Sensor Network (WSN) [1] is becoming increasingly important. As WSN scales up, optimizing the flexibility, reliability, and energy consumption of the overall network becomes critical [2]. SDN [3], as an emerging approach for WSN, is increasingly favored by researchers in data centers and network architecture due to its ability to address complex issues more quickly and flexibly through the separation of control and forwarding mechanisms, as well as its philosophy of programming network functions. The abstract and centralized control plane can effectively enhance the efficiency of network resource allocation, while the programmable forwarding plane achieves software-hardware separation, making the entire WSN architecture more flexible and scalable. However, with the diversification of the network deployment environment, the influence of a complex environment and the expansion of network scale pose numerous challenges to the control plane composed of a single controller. To ensure high network availability, how to guarantee the high reliability of SDN controllers has become one of the research focuses. The software-defined approach divides WSNs into a centralized control plane and a programmable one, which offers more flexible network management. Controllers, as the fundamental components of the control plane that manage the data plane, have a significant impact on the overall dependability of the network due to their inherent reliability. Therefore, sensor network reliability issues within the SDN architecture can be categorized into two types: those pertaining to the control plane, influenced by controllers, and those associated with the data plane, encompassing forwarding devices and links. The control layer is logically centralized, and when controllers lose control over the data plane, it can result in localized network failures at best and potentially cause the entire network to collapse in severe cases. One research approach for the reliability of the control plane is to establish a controller cluster. Distributed controllers provide redundant backups of state information, and the utilization of distributed data storage technology can mitigate network malfunctions caused by individual controller failures, thereby enhancing control plane reliability. For instance, ONOS [4] employs a distributed control plane where state information distributed across multiple controllers is managed and maintained for consistency by Zookeeper [5]. Another approach involves setting up a dedicated set of servers to store the state information of the controller, and the controller only needs to read the state information from these servers to carry out fault analysis [6]. Although the network based on SDN architecture has resolved the problems of overcrowding and closure of WSN, the hierarchical network itself has encountered challenges in automatic management and reliable operation. A clustered control plane enhances the network's fault tolerance against single points of failure in controllers, making the network more stable and reliable when facing controller failures, but there are still some unresolved issues. Challenges remain in aspects such as collaboration and synchronization between controllers, as well as rapid fault detection and autonomous recovery. These problems become even more prominent in large-scale and complex WSN environments. Therefore, it is necessary to research an effective fault monitoring and autonomous recovery mechanism for multi-domain controllers in SDN to improve the reliability of the WSN system.