# An Optimization Routing Algorithm Based on Segment Routing in Software-Defined Networks
## 4 Performance Evaluation
### Simulation Results
So the maximum link utilization of WSP is lower than SPF. The selection process of SWP is just the opposite of WSP and takes the remaining bandwidth of the path as the first consideration, so the maximum link utilization of SWP is lower than WSP. MIRA chooses the minimum interference path and reduces the blocking rate of the service, which helps improve the utilization rate of the network resource. As a result, its maximum link utilization rate is lower than SWP. Our proposed Algorithm 1 optimizes the link weight through a multi-objective optimization algorithm and achieves lower link utilization than the above four algorithms. However, the Lee algorithm considers  
Figure 4: The cost of all paths of the seven algorithms. the link congestion index when optimizing link weight and avoids link congestion. So, the maximum link utilization of the Lee algorithm is lower in our proposed Algorithm 1. However, the proposed Algorithm 2 makes some improvements in the selection of global optimal particles so that a more accurate solution is obtained. Thus, the proposed Algorithm 2 achieves the lowest maximum link utilization rate in seven comparison algorithms. Table 2 shows the average running time of different algorithms. The two routing algorithms we propoesd need longer running times than other traditional algorithms. The MOPSO algorithm needs multiple iterations to find the optimal solution. Moreover, our algorithm adds the path evaluation step after selecting the optimal k paths, which is not mentioned by other algorithms before. The improved MOPSO algorithm in the proposed Algorithm 2 improves the search performance in convergent speed when optimizing the link weights. The proposed Algorithm 2 takes less time than the proposed Algorithm 1. The two algorithms we proposed require more computation and increase the computational complexity of the control plane. However, with the improvement of computing power of hardware devices and the application of distributed multi-controllers in SDN, the computational complexity of control planes will be alleviated. Figure 5: Load balance of the seven algorithms. Figure 6: Maximum link utilization of the seven algorithms. In order to assess the overall performance of the seven algorithms, the seven paths calculated from the seven algorithms for each request are evaluated by the comprehensive evaluation model. The evaluation model not only can evaluate the overall performance of the target path but can also effectively evaluate the performance of a single network business based on user preferences, which is conducive to realizing a differentiated service network. We use a numerical value from 0 to 1 to express the value of path evaluation and indicates the overall transmission performance of the selected path. The larger the value, the better the overall performance of the path. The data in Table 3 represent the average value of comprehensive evaluation of each path in the corresponding number of requests when the three network applications have the same importance, namely \(W^{\prime}=[1/3,1/3,1/3]\). The data in Table 4 represent the average value of comprehensive evaluation of each path in the corresponding number of requests when the scheme weight \(W^{\prime}=[0.4,0.4,0.2]\). The data in Table 5 represent the average value of comprehensive evaluation of each path in the corresponding number of requests when the scheme weight \(W^{\prime}=[0.2,0.3,0.5]\). It can be seen from these three tables, as the importance of the three network applications specified by the user is different, the two algorithms we proposed have greater comprehensive evaluation values than other algorithms. The comprehensive evaluation values of the paths selected by the proposed Algorithm 1 and the proposed Algorithm 2 are better than those of the other five algorithms; our proposed algorithms select the path with the largest evaluation value by evaluating the model and the other five algorithms do not take it into account.