Controller placement in software defined emerging networks: a review and future directions

Software-defined networking (SDN) is envisioned to be a main pillar in the management of emerging networks such as satellite networks (SatNets), vehicular ad hoc networks (VANET), and the Internet of Things (IoT). The concept of SDN decouples data and control planes. This allows for flexible management and configuration of network resources, enabling more efficient and dynamic network operations. The location of the controller(s) is a significant design concern for the SDN control plane, impacting several network performance parameters including latency, resiliency, energy efficiency, load balancing, etc. Several solutions have been proposed to address the controller placement problem (CPP). In this paper, we explain the CPP in SDN and discuss its importance before presenting a complete review of the CPP in software-defined emerging networks (SDEN). The problem was addressed in different ways in different emerging networks. This is due to the differences in characteristics and environment among the various types of emerging networks. However, there are some similar characteristics among VANETs, SatNet, and IoT. This allows some CPP solutions to be adopted from other emerging networks. For instance, both VANETs and SatNets are dynamic networks, thus some CPP solutions in VANETs can be adopted and adapted to work in SatNets. Throughout this review, we discuss the influencing factors and environmental requirements which should be considered while placing controllers in SatNets, VANETs, and IoT. Also, we discussed the limitations of existing solutions. Finally, the review concludes with a discussion on critical issues in CPP and potential future research directions.