# Artificial Intelligence Enabled Routing in Software Defined Networking
## 4 Performance Evaluation
### Results and Discussions  
The performance of the proposed AIER mechanism is compared with that of static and dynamic routing schemes by varying the data rate of each source-to-destination pair. Performance measures include the average throughput, packet loss ratio, and packet delay for different monitoring periods (3, 5, or 10 s). The effectiveness and superiority of the AIER mechanism are demonstrated by the simulation results.  
Figure 11 shows the average throughput of each flow versus data rate for different monitoring periods. The average throughput with static routing is the smallest among the three schemes and descends to the increasing data rate regardless of the monitoring period. This phenomenon is because all data flows send their data through the same path due to the shortest path selection. Unlike static routing, dynamic routing can change transmission paths periodically if a predefined congestion condition occurs. In contrast to the AIER mechanism, no increasing amount is observed in the average throughput with dynamic routing when data rate is increased, as packet loss occurs before path reconfiguration is complete. In other words, the AIER mechanism is not influenced much by the monitoring period duration. Besides, the AIER mechanism has a smaller path reconfiguration frequency than dynamic routing, as the former scheme can perform more suitable path configuration as soon as possible. Thus, the AIER mechanism performs better in terms of average throughput than either static or dynamic routing. Figure 12 shows packet delay versus data rate for different monitoring periods. Similar to the aforementioned elaboration, the AIER mechanism exhibits better performance in packet delay compared with the other two routing schemes, particularly when the network load is heavy. This is because the AIER mechanism is capable of predicting better paths for each flow from past experiences.  
Figure 11: _Cont._Regarding packet loss performance, Figure 13 presents packet loss ratio versus data rate for different monitoring periods. Packet loss ratio increases as the data rate grows. Each link bandwidth is 250 Mbps; thus, the data rate of each flow reaching approximately 70 Mbps begins to cause excessive single-link burden and packet loss owing to the shortest path selection. However, dynamic routing can adjust path allocation periodically to alleviate congestion in the shortest path. Hence, it has a smaller packet loss ratio compared with static routing. It is noteworthy Figure 13 illustrates that nearly no packet loss is observed with the AIER mechanism until the data rate of each flow increases to 120 Mbps. Thus, the AIER mechanism demonstrates a significant improvement in packet loss owing to its intelligent path selection design with congestion avoidance.  
Figure 11: Average flow throughput vs. data rate for different monitoring periods. (**a**) Monitoring period = 3 s; (**b**) Monitoring period = 5 s; (**c**) Monitoring period = 10 s.  
Figure 12: _Cont._  
Figure 12: Packet delay vs. data rate for different monitoring periods. **(a)** Monitoring period = 3 s; **(b)** Monitoring period = 5 s; **(c)** Monitoring period = 10 s.  
Figure 13: _Cont._