The single, linear, tree, torus, and custom topologies were created in Mininet and connected separately to Ryu, Floodlight, OpenDayLight, and ONOS controllers. To evaluate throughput, jitter, and packet loss considering the most distant hosts, the Iperf [24] test was performed when a topology was associated with a specific controller. One was considered as an Iperf server and the other as an Iperf client between the two furthest hosts. The Iperf server was started in TCP mode to evaluate throughput. A throughput observation was performed after 50 TCP packets were transmitted from the client to the server. The server was running in UDP mode when jitter and data loss were calculated. At this time, 50 UDP packets have been sent from clients. To determine the delay, the server received 50 packets from the client and the average response time (RTT) was used to determine the network latency.
The experiments are carried out and the results are shown in Figs. 7, 8, 9, and 10.
A. Throughput
Ryu outperforms all controllers in all topologies, with the linear topology having the best throughput (56.5 Mbps) and the torus topology having the lowest throughput (38.9 Mbps). ONOS achieves the second-highest throughput in linear topology (54.2 Mbps) and tree topology (51.2 Mbps). OpenDayLight achieves the third-highest throughput in linear topology (52.8 Mbps) and custom topology (42.1 Mbps). Floodlight achieves the lowest throughput in all topologies; It is highest in the linear topology (50.2 Mbps) and lowest in the torus topology (35.6 Mbps).
Fig. 7. Throughput comparison of RYU, Floolight, OpenDayLight, ONOS.
B. Latency
Ryu has the lowest latency across all topologies; The highest latency is observed in the torus topology (0.8 ms) and the lowest in the linear topology (0.4 ms). ONOS has the second lowest latency in linear topology (0.4 ms) and tree topology (0.6 ms). OpenDayLight has the third lowest latency in linear topology (0.4 ms) and custom topology (0.6 ms). Floodlight has the highest latency of all topologies, the highest in the torus topology (1.0 ms) and the lowest in the linear topology (0.5 ms).
Fig. 8. Latency comparison of RYU, Floolight, OpenDayLight, ONOS.
C. Jitter
Ryu has the lowest jitter across all topologies, with the lowest in the linear topology (0.4 ms) and the highest in the torus topology (1.0 ms). ONOS has the second lowest jitter in linear topology (0.4 ms) and tree topology (0.6 ms). OpenDayLight has the third lowest jitter in linear topology (0.5 ms) and custom topology (0.7 ms). Floodlight has the highest jitter in all topologies, the highest in the pipe topology (1.2 ms) and the lowest in the line topology (0.6 ms).
Fig. 9. Jitter comparison of RYU, Floolight, OpenDayLight, ONOS.
D. Packet Loss
Ryu records the lowest packet loss across all topologies, with the lowest in the linear topology (0.3%) and the highest in the torus topology (0.8%). ONOS records the second-lowest packet loss in both linear topology (0.3%) and tree topology (0.5%). OpenDayLight records the third lowest packet loss in the linear topology (0.4%) and the custom topology (0.6%). Floodlight has the highest packet loss across all topologies, with the highest in the torus topology (1.0%) and the lowest in the linear topology (0.5%).
Fig. 10. Packet Loss comparison of RYU, Floolight, OpenDayLight, ONOS.
In summary, Ryu outperforms Floodlight, OpenDayLight, and ONOS in terms of throughput, jitter, latency, and packet loss across multiple network topologies. In summary, Ryu is the best controller for high-performance networks, followed by ONOS. OpenDayLight and Floodlight are suitable for research and development and large networks, respectively. The best topology for high-performance networks is tree topology, followed by linear topology. Single topologies work well for small networks, although custom and torus topologies are suitable for specific use cases. The results also highlight the importance of topology selection and controller placement in SDN networks. The combination of Ryu and linear topology produces the best results. The results provide valuable insights for practitioners, scholars, and network administrators that aim to optimize the SDN network's performance and achieve its full potential.