# Performance and Scalability Analysis of SDN-Based Large-Scale Wi-Fi Networks
## 2 Related Work
The proposed model estimates path costs based on five criteria: adaptive network packet size, accurate packet numbers, the overall required time interval, QoS link capacity (bandwidth), and the number of hops (shortest path), enabling the SDN controller to minimize decision time for selecting flows. The proposed algorithm is evaluated with a dataset containing information about routing delay. The model incorporates three criteria, namely packet size, number, and time, to determine the optimal packet delay and subsequently calculate the cost of each path. Results from a benchmark comparison between the proposed algorithm and state-of-the-art alternatives show a significant reduction in delay time, estimated to be a few milliseconds, for selecting an optimal recovery path. Consequently, the proposed algorithm can reduce bottleneck routes and resource utilization, leading to increased QoE (Quality of Experience) for both objective and subjective video streaming. Specifically, the proposed model reduces delay time for route selection up to 96.3%, resulting in greater end-user satisfaction. A software component of SDN known as the SDN controller has the responsibility for managing the flow control of a network. In SDN, the controller is the primary entity that stands among the applications and the networking devices. Each and every communication that takes place between apps and network devices goes through the SDN controller. There are number of SDN controllers; some well-known SDN controllers [11; 17; 19] are shown in Table 1.  
The vast majority of the SDN studies that have been proposed in published papers are small-scale Wi-Fi networks that use SDN. However, due to the growing adoption of Wi-Fi networks and the significance of these networks for the Internet of Things, SDN must be integrated with Wi-Fi networks. Integration of Wi-Fi networks with SDN controllers is thought to be able to overcome a significant number of performance difficulties that are associated with Wi-Fi networks. For this reason, a performance analysis of an actual large-scale SDN Wi-Fi network is necessary for upcoming Internet of things networks [10]. SDN was initially created for wired networks; however, wireless networks can also benefit from its principles. In order to manage and control the access points and switches that make up a WiFi network, many SDN controllers, including Ryu, support Wi-Fi networks. There are several well-known SDN controllers with varying degrees of Wi-Fi network support, including Ryu, Floodlight, Beacon, POX, and ONOS. Ryu has a solid track record of supporting Wi-Fi networks and offering a wide range of protocol support, including OpenFlow and Netconf, which are frequently used in Wi-Fi networks. Floodlight is suitable for managing Wi-Fi networks because it, like Ryu, supports OpenFlow and Netconf. However, Floodlight's focus is more on large-scale data center networks, which may not be the primary use case for Wi-Fi networks. On the other hand, Beacon is a research-focused SDN controller that is not frequently used in real-world environments. Although it manages Wi-Fi networks and supports OpenFlow, it might not offer Ryu's level of performance, scalability, and reliability. Similar to this, POX is a compact SDN controller that is frequently employed in academic and research settings. While it can be used to manage Wi-Fi networks, Ryu's more powerful controllers have more functionality and scalability [23; 24; 25]. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**1** & Floodlight & Linux & Java & Fair & Centralized & Big Switch Network & No & Yes & Good \\ \hline
**2** & Ryu & Linux, Windows & & & & & & & & \\
[11; 17; 19] & & & & & & & & & & \\ \hline
**3** & Beacon & Linux, Windows & & & & & & & & \\
[11; 17; 19] & & & & & & & & & & \\ \hline
**4** & POX & Linux, Windows & & & & & & & & \\
[11; 17; 19] & & & & & & & & & \\ \hline
**5** & ONOS & Linux & Java & High & Distributed & Cisco & No & Yes & Good \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison of SDN controllers.