# Dynamic Control Architecture Based on Software Defined Networking for the Internet of Things
## 2 Related Works  
The IoT context provides the use of hundreds and thousands of interconnected nodes for sensing and monitoring services. Usually, these devices have limited resources to carry out proactive routing protocols which require to store routing table entries, or cannot afford the complexity and overhead of the network topology discovery, due to the elevate number of neighbours, as is required in reactive routing protocols. Recently, the advantages of SDN architecture have been applied even in IoT domain, allowing a dynamic separation of the CP from DP. SDN is envisioned to make dynamic, robust and scalable both the design and operation of IoT services. In particular, the utility and the challenges of SDN-based technologies when applied to IoT can be found in the targeted surveys [9; 17; 18; 19]. According to a basic SDN architecture, a Controller allows real-time network configurations of sensors and actuators to optimise data flows according to the available resources, without depending from specific underlying network features. In addition, distributed SDN CParchitectures, involving multiple SDN Controllers, have been proposed for achieving a global view of wide area network. Hybrid SDN-based architectures are also considered with some SDN Controllers dedicated to nodes afar and a centralised Controller to detect failures on low level local SDN Controllers. In any case, advanced efficient routing strategies need to be identified to support SDN-IoT efficient management, matching QoS requirements or reconfiguring devices through the selection of the best nodes and links, which is effectively performed by adopting the OpenFlow-enabled Wireless Sensor Networks (WSN) [20; 21], a popular SouthBound SDN protocol. In the following, we consider mainly papers which detail energy-aware routing proposals. The authors of [22] presented a software-defined clustered sensor networks (SD-CSN) arranged into clusters managed by one SDN Controller. About 1000 nodes divided in five clusters exchange messages and forward packets among themselves according to the policies of the SDN Controller. This solution provides a scalable architecture for IoT, since it can route data packets flows among the devices. The same model, i.e., a centralised control and hierarchical cluster structure, is proposed in [23]. The Lion Optimization (LO) algorithm creates both the clusters of sensor nodes and the routes to forward data. A hierarchical structure allows a global control of the WSN, making easier the deployment of network-wide management protocols and on demand applications. Software defined energy aware routing (SD-EAR) proposed in [24] divides the sensor network into clusters with a SDN Controller associated to each cluster, where Controllers know the topologies of the associated cluster as well as of the border nodes. Each Controller evaluates the best path from the source to destination if the destination falls in its area or, alternatively, it can send a request to discover the route to destination, taking into account the residual energy of nodes. Moreover, SD-EAR adopts sleeping strategy to reduce energy consumption in the network. The contribution in [25] analyses the application of the SDN architecture to improve security and energy efficiency in the WSN domain. In particular, the SDN Controller executes the Sensor Protocol for Information via Negotiation (SPIN) protocol to generate neighbours table and, then, to select the best next hop, according to its energy level and link quality. Then, the selected node is used by sensor node to forward the information. [PERSON] et al. [26] considered a reconfigurable distributed protocol, called Application-aware Distributed adaptive Flow Iterative Reconfiguring (SADFIR). It uses multiple distributed SDN Controllers selected among IoT nodes as cluster heads (CH) and computes the residual resources of the IoT devices. Then, SADFIR distributes the selected CHs to the IoT infrastructure allowing distributed cluster formation of heterogeneous network.