Software-Defined Networking (SDN) has emerged as a revolutionary architecture in computer networks, offering comprehensive network control and monitoring capabilities. However, securing the east–west interface, which is crucial for communication between distributed SDN controllers, remains a significant challenge. This study proposes a novel blockchain-based security framework that integrates Ethereum technology with customized blockchain algorithms for authentication, encryption, and access control. The framework introduces decentralized mechanisms to protect against diverse attacks, including false data injection, man-in-the-middle (MitM), and unauthorized access. Experimental results demonstrate the effectiveness of this framework in securing distributed controllers while maintaining high network performance and low latency, paving the way for more resilient and trustworthy SDN infrastructures.

The east-west interface in Software Defined Networking (SDN) plays a crucial role in enabling inter-controller communication, which is vital for scalability, load balancing, and fault tolerance in distributed SDN environments. Despite its importance, this interface remains vulnerable to serious security threats, such as Man-in-the-Middle (MitM), unauthorized access, False Data Injection (FDI), and Distributed Denial-of-Service (DDoS) attacks. Unlike previous studies and reviews that focus broadly on SDN security, this paper presents a comprehensive review of the current security challenges and proposed solutions that are specific to the east-west interface. The literature is organized into five categories: cryptographic techniques, authentication and access control, blockchain-based mechanisms, Machine Learning (ML) approaches, and hybrid models. In addition, an analytical contribution is provided by introducing a threat-solution coverage matrix that maps each reviewed solution to the specific types of attacks it mitigates. This analysis highlights under-addressed vulnerabilities and uncovers critical research gaps. Future research directions are provided, including the adoption of zero-trust architectures and the need for standardized benchmarking protocols.

Software defined networking (SDN) increasingly integrates multiple controllers from diverse vendors to enhance network scalability, flexibility, and reliability. However, such heterogeneous deployments pose significant security threats, especially at the east-west interface which is connecting these controllers. Existing solutions are inadequate for ensuring robust protection across multi-vendor SDN environments as most of them are meant to a specific type of attacks, use centralized solution, or designed for homogeneous SDN environments. This study proposes a blockchain-based security framework to address existing security gaps within heterogeneous SDN environments. The framework establishes a decentralized, robust, and interoperable security layer for distributed SDN controllers. By utilizing the Ethereum blockchain with customized smart contract-based checks, the proposed approach enables mutual authentication among controllers, secures data exchange, and controls network access. The framework effectively mitigates common SDN threats such as distributed denial-of-service (DDoS), man-in-the-middle (MitM), false data injection, and unauthorized access. Experimental results highlight the practicality of the solution, achieving a stable throughput of approximately 20 transactions per second with an average authentication latency of 28–40 ms. These results demonstrate that the proposed framework not only enhances inter-controller communication security but also maintains the network performance, making it a reliable and scalable solution for real-world SDN deployments.