# Application-Aware SDN-Based Iterative Reconfigurable Routing Protocol for Internet of Things (IoT)
## 4 Heterogeneous Network Model of Proposed Model
### Distributed SDN-Enabled Iteratively Reconfigurable Internet of Things (DSDN-IRIoT)  
The proposed network model of DSDN-IRIoT is equipped with a distributed layer of multiple SDN controllers at the control layers which actively collect network key information from OpenFlow enabled IoT devices at the forwarding layer. The multiple SDN controllers at the control layer provide distributed clustering coordination, and network scalability is available due to additional network resources of the control layer as control layer is coupled within Base Station (BS), so it drastically reduces the computational and energy resources burdon of forwarding layer devices. The network scalability offers additional network applications for dense network resources. The abstract of the network architecture of DSDN-IRIoT is shown in Figure 2.  
Mainly, the SDN enabled network architecture consists of the following layers; infrastructure layer, control layer, and application layer. Meanwhile, every unique layers set of communication protocols and collectively formulate the effective open standard protocol stack. Precisely, the application layer consists of SADFIR-Visor that supervises the information collected from the control and infrastructure layer and coordinates with different application layer APIs. The programmability of application layers APIs generates the expected network response from northbound layers, and SADFIR-Visor handovers the response to designated network controllers. Similarly, at the protocol stack level of the application layer, Inter-Networking Processing (INP) protocol utilizes a path selection algorithm that instructs the controller to dictate specific routing schemes at the infrastructure layer. In this paper, we propose a SADFIR routing algorithm to establish a path selection mechanism. The SADFIR formulates the periodic route reconfiguration mechanisms on behalf of the periodically retrieved information from the control and infrastructure layer. Link Layer Discovery Protocol (LLDP) is a crucial protocol to collect network topology and network heterogeneity. At the control layer, multiple controller agents like; flow manager agent, topology server agent and routing agent actively communicate with northbound and southbound APIs. Similarly, the infrastructure layer consists of smart IoT devices. These intelligent IoT devices are equipped according to the application of the network, but some of the components are essential for all the accessories such as; Sensing Unit (SU) and Power Unit (PU) which accumulatively makes a Micro Controller Unit (MCU) that maintains the basic operations of IoT device with limited computational capacity. As SDN-enabled IoT devices are equipped with OpenFlow, so these devices are designed to have insufficient memory to maintain the forwarding tables generated by SDN controllers.  
\begin{table}
\begin{tabular}{p{85.4 pt} p{42.7 pt} p{42.7 pt} p{42.7 pt} p{42.7 pt} p{42.7 pt} p{42.7 pt}} \hline \hline
**Management Architecture** & **Network Scalability** & **Application Awareness** & **Heterogeneity Awareness** & **Topology Discovery** & **Computational Cost** & **Periodic Reconfiguration** \\ \hline SDWN [31] & ✓ & ✓ & & & & ✓ \\ \hline ACEEC [32] & ✓ & & & & ✓ & \\ \hline MCEEC [33] & & ✓ & & & ✓ & \\ \hline EESRA [34] & ✓ & & ✓ & ✓ & & \\ \hline EBRP [35] & & & ✓ & & ✓ & \\ \hline SADFIR & ✓ & ✓ & ✓ & ✓ & ✓ & ✓ \\ \hline \hline \end{tabular}
\end{table}
Table 1: _Cont._