Scalable and Resilient Routing for In-Band SDNs With a Distributed Hash Table-Based Approach

In-band mode of software-defined networking (SDN) offers cost-effective deployments by using same links for both control and data traffic. However, despite these advantages, it faces critical limitations such as (i) flooding during controller discovery, (ii) high latency due to asynchronous flow setup, (iii) excessive controller-switch communication overhead on the data plane, (iv) scalability issues with increasing network size, (v) inefficient route discovery, and (vi) poor fault tolerance. This paper aims to address the above issues by proposing a novel DHT-based improved routing scheme tailored for hybrid in-band SDNs, introducing a logically structured addressing and routing mechanism that eliminates flooding, minimizes controller involvement, and enhances routing scalability. The proposed scheme constructs a labeled directed acyclic graph (LDAG) during the network bootstrap phase, assigning logical identifiers (LIDs) to switches based on their relative position to the controller; mapping information is maintained at the controller; lookup and forwarding are decentralized through LID comparison, allowing nodes to independently determine the next hop. In the link/node failure scenarios, switches intelligently reroute via parent nodes using local information and default flows that significantly improve the network resilience. Performance evaluation demonstrates 45%–60% improvement in response time and packet loss compared to the existing state-of-the-art routing protocols, affirming the scheme's effectiveness for scalable, fault-tolerant hybrid in-band SDN deployments.