# Performance and Scalability Analysis of SDN-Based Large-Scale Wi-Fi Networks
## 5 Experiment, Results and Discussion
### Experiments and Results
#### 5.1.2 UDP Parameters Graph  
Figures 10-13 are based on the iperf log files and depict the UDP bandwidth graphs for access points 1, 2, 3, and 4. The \(Y\)-axis displays bandwidth in kbits/s, and the \(X\)-axis displays time in seconds. Figures 14-17 display the UDP jitter graphs; the \(X\)-axis displays time in seconds and the \(Y\)-axis displays jitter in milliseconds. The bandwidth for 10, 30, and 50 stations is comparable and spans from 282 to 694 kb/s, however for 100 stations, it drops to 172 to 682 kb/s. As the number of stations grows gradually, i.e., 53.675, 80.528, 92.052, and 136.52 ms, jitter somewhat increases. Figure 10: UDP bandwidth for 1 access point. Figure 11: UDP bandwidth for 2 access points. Figure 12: UDP bandwidth for 3 access points. Figure 14: UDP jitter for 1 access point. Figure 13: UDP bandwidth for 4 access points. Figure 16: UDP jitter for 3 access points. Figure 15: UDP jitter for 2 access points. RQ#2: The most important factor in determining the flow setup delay of SDN controllers is differences in network architecture. We concentrated our experiments on simple, linear, and tree topologies. Mininet-Wi-Fi topologies can be generated using scripts and commands presented in the previous section. As an example, we used a network with a single access point connected to the Ryu controller and ten stations attached to this access point as the simplest scenario. Stations trade ping flows to calculate the latency of the flow arrangement. The controller configures the uplink flow rule at the access point and passes the packet across the relevant output of the access point for the first ping request from station one to station two. We calculated the packet's round-trip time and noted it as flow setup latency. By sending ping requests from station one to station three, station ten, and so on, we repeated the process. We then calculated the mean of each flow setup delay. For a straightforward design, the typical flow startup latency is 0.75. Next, as indicated in the previous section, we took into account a linear topology made up of ten access points (AP1, AP2,..., AP10), with one station connected to each of them. To assess flow setup latency, we followed the same steps as we did for simple topology. Our estimated average flow setup time is 47.5 ms; the linear architecture has a substantially higher flow setup latency than the basic topology. Here, we present a report on the setup delay for a complex flow. We took into account a unique tree topology as defined in the preceding section. We took into account a hierarchy that consisted of a controller, a switch, three access points, and three stations connected to each AP. To assess flow setup latency, we followed the same steps as we did for simple topology. The average flow setup latency, we calculated, is 50.54 ms, which is much more than simple topology and hardly more than linear topology. We display the measurement results for various network topologies in Figure 18.  
RQ#3: We then took into account a more complicated situation. We took into account a unique tree topology, as defined in the preceding section. We took into account a hierarchy that consisted of a controller, a switch, three access points, and three stations connected to  
Figure 17: UDP jitter for 4 access points. each AP. We ran the RQ#3 script, increasing the number of switches with each run. Stations trade ping flows to calculate the latency of the flow arrangement. The controller receives a packet for the initial ping request from station one to station two. We calculated the packet's round-trip time and noted it as flow setup latency. By sending ping requests from station one to station three, station ten, and so on, we repeated the process. We then calculated the mean of each flow setup delay. The flow setup latencies for each execution are shown in Figure 19. As we raised the number of switches, we saw that the flow setup latencies drastically increased.