# An Efficient Network Resource Management in SDN for Cloud Services
## 5 Performance Evaluation
Therefore, the maximum amount of data that can be sent through the optimal paths over the past 5 min is the sum of the amount of data in the top 120 flows based on the amount of data that enters during the corresponding amount of time. If the sum of the network utilizations of the optimal paths is 1, it indicates that all of the top 120 flows are assigned to the optimal paths. In the graph, the empty-blue-square line represents the results of paths 3 and 4 with long hop counts. The solid-black-square line represents the network utilization of the data transmitted through paths 1 and 2, which are optimal paths owing to the small number of hops. The solid-red-triangle line represents the sum of the amount of data transmitted through paths 1 and 2, and shows how much data flows through the optimal paths. If this value is 1, it indicates that the maximum amount of data that could be sent through the optimal paths was actually sent through those paths. The results confirm that the network utilization of paths 1 and 2 gradually decreases over time for the OSPF algorithm. Meanwhile, the utilization of paths 1 and 2 increases over time for the proposed algorithm. In the experiments, a total of 200 services were requested. At the first 0-5 min, the numbers of flows for multimedia services and web services were 20 and 180, respectively. Thus, many flows for the web services were allocated to optimal paths (paths 1 and 2) in the beginning. In this situation, the OSPF does not change the flows allocated to the optimal paths even though the number of flows for the multimedia services, which have a large amount of data transmitted, increases over time. In contrast, the proposed algorithm dynamically reallocates the paths based on the continuously checked priority of the flows. It lowers the priority of the web flows when new multimedia flows enters. Therefore, it changes the flows allocated to the optimal paths from  
Figure 5: Network topology for the experiments. the web services to the multimedia services when new multimedia services come in, thus leading to an increase in the efficiency in terms of network usage as shown in Figure 7b. Figure 6: Workloads for the experiments: (**a**) Workload-A; (**b**) Workload-B; (**c**) Workload-C; (**d**) Workload-D; (**e**) Workload-E; (**f**) Workload-F. The same results are observed in the other workloads as shown in Figures 8-12. However, the performance evaluation results of Workload-C in Figure 9 show an insignificant difference between the two algorithms. This is because the OSPF also uses the network efficiently as more multimedia services are initially requested than the number of web services and the number of multimedia services remains the same, thus resulting in the transmission of multimedia services through paths 1 and 2 from beginning to end. Figure 8: Experimental results for Workload-B: (**a**) OSPF algorithm; (**b**) proposed algorithm. Figure 7: Experimental results for Workload-A: (**a**) Open Shortest Path First (OSPF) algorithm; (**b**) proposed algorithm. Figure 9: Experimental results for Workload-C: (**a**) OSPF algorithm; (**b**) proposed algorithm. Figure 13 shows a graph of the total network utilization during the entire experiment time. The total network utilization refers to the amount of data transmitted through paths 1 and 2 divided by the maximum amount of data that can be transmitted for each workload. The results show that the total network utilization of the proposed algorithm is 29.4% higher than that of OSPF on average. The proposed algorithm shows 69.2% higher utilization than OSPF on Workload-A and 1% higher on Workload-C. Workload-A starts with 180 web services sending a relatively small amount of data and 20 multimedia services sending a relatively large amount of data. The number of flows of web services decreases and the number of flows of multimedia services increases gradually over time. In this situation, OSPF mostly assigns the web flows to the optimal paths in the beginning and does not replace them with the incoming multimedia flows.