# A Performance Evaluation for Software Defined Networks with P4
## 5 Results and Analysis of Tier 1--Single Type of Traffic Run
### Case Study 4- Content Delivery Network  
In this case study, we used a VLC-player for our experiments due to its ability to program video streaming via a Python script and to collect data for video traffic and its lightweight deployment. Figure 8 presents the captured data of a video stream for all three topologies. Figure 8a-c show that for each of the three topologies, the video for _SDN+P4_ had a higher throughput than with _SDN+OvS_. Table 4 shows further that, throughput has improved by 60% in the multi-path topology, 77% in the grid topology and 60% in the Internet topology for _SDN+P4_ in comparison to _SDN+OvS_. The high throughput achieved \begin{table}
\begin{tabular}{c c c c} \hline \hline \multicolumn{5}{c}{**a. Network Performance of UDP Transfer in Simple Multi-Path Topology**} \\ \hline \hline \multicolumn{5}{c}{**Multi-Path Topology-Single Type of Traffic (UDP)**} \\ \cline{2-4}  & _SDN+OvS_ & _SDN+P4_ & **Improvement** \\ \hline Throughput & \(1.06\times 10^{7}\) bps & \(1.2\times 10^{7}\) bps & \(13\%\) \\ \hline Packet Loss & 22\% & 9\% & (\(-59\%\)) \\ \hline Delay & 1.9519 s & 0.3221 s & (\(-83\%\)) \\ \hline Jitter & 0.298 ms & 0.231 ms & (\(-22\%\)) \\ \hline Data transmitted & 1 GB & 1 GB & N/A \\ \hline Total transmission time & 640 s & 514 s & (\(-14\%\)) \\ \hline \multicolumn{5}{c}{**b. Network Performance of UDP Transfer in Simple-Grid Topology**} \\ \hline \hline \multicolumn{5}{c}{**Grid Topology-Single Type of Traffic (UDP)**} \\ \cline{2-4}  & _SDN+OvS_ & _SDN+P4_ & **Improvement** \\ \hline Throughput & \(1.04\times 10^{7}\) bps & \(1.2\times 10^{7}\) bps & \(15\%\) \\ \hline Packet Loss & 37\% & 7\% & (\(-81\%\)) \\ \hline Delay & 1.9344 s & 0.3744 s & (\(-80\%\)) \\ \hline Jitter & 0.371 ms & 0.204 ms & (\(-45\%\)) \\ \hline Data transmitted & 1 GB & 1 GB & N/A \\ \hline Total transmission time & 670 s & 524 s & (\(-17\%\)) \\ \hline \hline \multicolumn{5}{c}{**c. Network Performance of UDP Transfer in the Internet Topology**} \\ \hline \hline \multicolumn{5}{c}{**Internet Topology-Single Type of Traffic (UDP)**} \\ \cline{2-4}  & _SDN+OvS_ & _SDN+P4_ & **Improvement** \\ \hline Throughput & \(0.98\times 10^{7}\) bps & \(1.2\times 10^{7}\) bps & \(22\%\) \\ \hline Packet Loss & 39\% & 8\% & (\(-79\%\)) \\ \hline Delay & 1.9905 s & 1.0432 s & (\(-60\%\)) \\ \hline Jitter & 0.301 ms & 0.2007 ms & (\(-33.3\%\)) \\ \hline Data transmitted & 1.4723 GB & 1.6178 GB & \(10\%\) \\ \hline Total transmission time & 1200 s & 1200 s & N/A \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Network performance for case study 3—UDP traffic. with _SDN+P4_, resulted in an increased amount of data being transferred between hosts. As shown in Table 4, the amount of data transmitted improved by 46% in the multi-path topology, 50% in the grid topology and 43% in the Internet topology for _SDN+P4_ in comparison to _SDN+OvS_. A notable delay in initiating the video stream can be observed in Figure 8a-c for _SDN+OvS_ (blue line). This again is due to the delay caused in route discovery, resulting in a delayed start for the video with later termination for _SDN+OvS_. This can be seen by observing the averaged buffering delay illustrated in Table 4. Buffering delay in _SDN+P4_ has been reduced by 69%, 84% and 83% for topologies I, II and III respectively in comparison to _SDN+OvS_. Figure 9a-c present the observed jitter during the CDN transmission. Equation (1) was used once again to calculate the averaged values for the jitter. As shown in Table 4, jitter in _SDN+P4_ has been reduced by 35%, 41% and 23% respectively in comparison to _SDN+OvS_ for all three topologies. In our experiments, multi-path and grid topologies streamed a video for 600s, whilst the Internet topology streamed a video for 1200 s. Although the streaming times are different, the performance gain remained constant across all three topologies. Figure 8: Throughput of video content transfer in case study 4.