# A Performance Evaluation for Software Defined Networks with P4
## 7 Discussion  
In the context of this research, we explored the performance of SDN with _Ov5_ (_SDN+Ov5_) and SDN with _P4_ (_SDN+P4_). We have seen that _SDN+P4_ outperforms _SDN+Ov5_ for each of our case studies using different types of traffic and topologies. We investigated the overhead created due to the slow path utilisation of OvS and the performance variation in comparison to a P4 target switch. With the evolution of the Internet and the increased number of connected devices, networks will face congestion. With more and more packets requiring processing using a controller, a network model that utilises a slow path approach such as OvS will potentially lead to an exponential growth in traffic congestion. During this research, we have saturated the links in our elected network (Sections 5.1 and 5.2) to test how the network will cope with an increased load in traffic. Our results suggest that the network can maintain a gain in performance whilst links are saturated with traffic for the _SDN+P4_ environment in comparison to that experienced with _SDN+Ov5_. The evolution of 5G and beyond has led to the need to evaluate methods for reducing the delay at the core. Initialising programmability in the network has been shown to increase performance at the core. To the best of our knowledge, current literature does not evaluate the performance of the network when the control plane and data plane programmability (_SDN+P4_) is employed in comparison to the control plane (SDN+Ov5) programmability. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multicolumn{4}{c}{**b. Performance of TCP Traffic in Case Study 6**} \\ \hline  & \multicolumn{2}{c}{**Internet Topology-Mixed Traffic (TCP)**} \\ \cline{2-4}  & _SDN+Ov5_ & _SDN+P4_ & **Improvement** \\ \hline Throughput & \(0.99\times 10^{7}\) bps & \(1.18\times 10^{7}\) bps & \(19\%\) \\ \hline Packet Loss & \(0.4\%\) & \(0.1\%\) & \((-75\%)\) \\ \hline Delay & \(3.2\) s & \(1.1\) s & \((-65\%)\) \\ \hline Syn Delay & \(3.84\) ms & \(2.1\) ms & \((-45\%)\) \\ \hline Data transmitted & \(0.82\) GB & \(1.01\) GB & \(23\%\) \\ \hline \hline \multicolumn{4}{c}{**c. Performance of UDP Traffic in Case Study 6**} \\ \hline  & \multicolumn{2}{c}{**Internet Topology-Mixed Traffic (UDP)**} \\ \cline{2-4}  & _SDN+Ov5_ & _SDN+P4_ & **Improvement** \\ \hline Throughput & \(9\times 10^{6}\) bps & \(1.2\times 10^{7}\) bps & \(33\%\) \\ \hline Packet Loss & \(36\%\) & \(11\%\) & \((-69\%)\) \\ \hline Delay & \(2.516\) s & \(1.034\) s & \((-58\%)\) \\ \hline Jitter & \(0.292\) ms & \(0.201\) ms & \((-31\%)\) \\ \hline Data transmitted & \(1.456\) GB & \(1.602\) GB & \(10\%\) \\ \hline \hline \multicolumn{4}{c}{**d. Performance of SDN Traffic in Case Study 6**} \\ \hline  & \multicolumn{2}{c}{**Internet Topology-Mixed Traffic (CDN)**} \\ \cline{2-4}  & _SDN+Ov5_ & _SDN+P4_ & **Improvement** \\ \hline Throughput & \(0.97\times 10^{6}\) bps & \(1.4\times 10^{6}\) bps & \(44\%\) \\ \hline Data transmitted & \(1183.4\) MB & \(1451.3\) MB & \(23\%\) \\ \hline Buffering delay & \(20\) s & \(7.8\) s & \((-61\%)\) \\ \hline Jitter & \(0.422\) ms & \(0.331\) ms & \((-21\%)\) \\ \hline \hline \end{tabular}
\end{table} 
Table 6: _Cont._We evaluated the performance of applications in Sections 4 and 5, where _SDN+P4_ has been employed in contrast to _SDN+OvS_. For a time-sensitive application with minimal latency requirements, reducing the delay at the core can be essential. For example, for Vehicle-to-Vehicle (V2V) and Ultra Reliable Low Latency Communication (URLLC) applications. A solution, that processes packets in parallel as opposed to sequential processing in OvS, has been considered in this research and its effect on performance in applications. Our research has established that with the initialisation of _SDN+P4_ with parallel processing of packets, various applications have achieved an improvement in performance in comparison to applications run over _SDN+OvS_. We also evaluated the quality of applications that occurred due to faster processing achieved with _SDN+P4_ in comparison to _SDN+OvS_.