# Dynamic Control Architecture Based on Software Defined Networking for the Internet of Things
## 1 Introduction  
The Internet of Things (IoT) represents a unifying paradigm that aims at automating business processes, since smart things are connected at any place/time via a _network of networks_ and empowered with data analytics features [1, 2, 3]. This concept could be actualised to several areas, including smart homes/buildings, smart cities, intelligent healthcare, smart traffic and smart environments to name a few [4]. To this end, many enterprises leverage on IoT devices to collect relevant and heterogeneous data and better manage their processes, however two major challenges need to be faced for the expansion of the IoT. First, security issues become more complex in the IoT use case, because: (i) usually unattended and constrained devices are extremely vulnerable; (ii) access networks can be violated to enter the system; and (iii) an attack to the Cloud services can alter the end-to-end (e2e) application logic. The second main challenge is represented by the network connectivity, since it is required for each of the devices to be able to connect in an efficient way. The above interrelated challenges can be answered by applying the software-defined networking (SDN) approach [5, 6]. The core idea of SDN is the separation of data payloads from the controlling data that, in turns, determines the messages path. This is usually achieved by separating Data Plane (DP) and Control Plane (CP) in order to simplify traditional networks operation management. Specifically, the SDN Controller(s) within CP generates the rules for data forwarding, while devices only forward traffic executing the aforementioned rules. The advantages achievable by the SDN paradigm rely on the fact that the Controller maintains a _global viewof the underlying network, so it can dynamically optimise e2e data flows according to the state of the network, integrating both Cloud and Fog computing domains [7; 8]. The SDN principle could be perfectly paired with the IoT as an effective way to solve its actual limitations [9; 10]. In particular, IoT devices could be secured when they are operated on a separate network. This is because it makes more sense to secure the devices at the network level, rather than at the individual device level. Specifically, the application of the SDN principle allows to dynamically partition a _physical_ network into different _virtual_ networks, as it has been previously achieved through Virtual Local Area Network (VLAN) protocols to manage broadcast domains in an efficient and flexible way. Moreover, SDN represents a more general model for separating at a more higher level, i.e., to translate service requirements into an actual network configuration [11]. In addition to this, many IoT applications are time-sensitive, and, consequently, the optimisation of connectivity with the storing/processing resources is a priority performed while achieving the goal of load balancing. This is effective especially when it is expected to have the computing nodes _near_ where the data are being used, due to severe jitter or latency requirements [12; 13]. In this perspective, the combined use of IoT with SDN is one of the main catalysts for pushing resources to the _edge_ of the network and simplifying the interaction with a distributed and dynamic Application Plane (AP). However, the main constraint of a typical IoT domain is concerned with energy limitation, as smart devices are requested to perform battery intensive sensing/communications tasks, likely to greatly increase, due to the wide and pervasive adoption of this paradigm [14]. It compels the adoption of efficient energy management policies, which is commonly addressed as _green_ IoT, where this means a reduction of devices energy consumption of IoT in order to fulfil a smart world with sustainability [15; 16]. To this purpose, the proposed approach effectively introduces the SDN concept into a typical IoT ecosystem in order to optimise the e2e flows delivery by means of a centralised and agile multifaceted forwarding strategy.