Software-Defined Networking (SDN) and fog computing are pivotal in supporting computationally intensive tasks within Internet of Things (IoT) applications, enhancing efficiency and reliability. However, many IoT applications are constrained by communication paths prone to link failures, necessitating robust fault tolerance techniques to ensure reliable traffic flow. In particular, real-time IoT applications demand stringent reliability and bandwidth requirements (constraints), which are challenging to meet simultaneously. Although previous research has investigated SDN-based routing to improve reliability, developing a routing algorithm that satisfies both reliability and bandwidth constraints remains an NP-hard problem. In this paper, we propose two novel routing algorithms: Reliability Aware Bandwidth constrained Routing (RABR) and Reliability and Bandwidth Constrained Routing (RBCR), specifically designed for SDN-enabled environments. Our approach prioritizes service reliability while meeting strict reliability and bandwidth criteria. The proposed solution integrates several phases, including reliability aware and bandwidth constrained path routing and flow duplication through parallel/hybrid and sequential routing methods. Furthermore, we introduce a greedy heuristic algorithm, implemented by the SDN controller with an efficient time complexity. Simulation results demonstrate that our algorithm surpasses state-of-the-art approaches in critical metrics such as reliability, reliability-bandwidth success rate, and Runtime. As such, our solution emerges as a robust choice for SDN-enabled IoT environments.

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