## 5 Simulation Results
Figure 8: Simulation results: (**a**) protection path construction success rate varies with link key resources in the case of different protection thresholds in NSFNET; (**b**) protection path construction success rate varies with link key resources in the case of different protection thresholds in USNET. Figure 7: Simulation results: (**a**) blocking rate of key service requests varies with key resource in the case of different untrusted node numbers in NSFNET; (**b**) blocking rate of key service requests varies with key resource in the case of different untrusted node numbers in USNET. It can be seen from Figure 8 that the rise of protection threshold can also increase the probability of successful construction of protection path. With the increase in key protection threshold, the protection path construction success rate rises gradually. Comparing the curves in Figure 8a,b vertically, on the one hand, the success rate of protection path construction rises with the increase in protection threshold. On the other hand, as the protection threshold increases, the difference in the different curves of protection path construction success rate decreases with the same key resource. As shown in Figure 9a,b, the key recourse is set to 80 unit/s. In this condition, the impact of the change of key protection threshold on the protection path construction success rate of different numbers of untrusted nodes was tested. The trend of curve change is roughly similar in the two diagrams. With the increase in protection threshold, the protection path success rate goes up. When the protection threshold is the largest, the protection path construction success rate is also the maximum value. However, too many protection paths can have a negative impact on the smoothness of working paths to other services. Therefore, different protection thresholds are needed to adjust the conflict. When the number of untrusted nodes is different, the larger number of untrusted nodes can cause lower protection path construction rate in the case of the same \(\eta\). The reason is that the requirements of untrusted nodes are more stringent than trusted nodes. In this case, the percentage of key protection threshold \(\eta\) is set to 0.8. As shown in Figure 10a,b, the change of protection path construction success rate with different numbers of untrusted nodes is tested in the two different topologies. With the increase in key resources, the success rate of protection path construction rises. When the key resource reaches the maximum of the data shown in Figure 10a,b, the success rate of protection path construction can reach 100% in the case of the smallest untrusted node number. Figure 9: Simulation results: (**a**) protection path construction success rate varies with \(\eta\) in the case of different untrusted node numbers in NSFNET; (**b**) protection path construction success rate varies with \(\eta\) in the case of different untrusted node numbers in USNET. Comparing the curves in Figure 10a,b vertically, the success of protection path construction decreases with the increase in the number of untrusted nodes. In Figure 10b, when the key resource is set to 112 unit/s, assuming that the number of untrusted nodes is reduced from 6 to 5, the appreciation of protection path construction successful rate can rise about 4%. The number of untrusted nodes and key resource both have a significant impact on the success rate of protection path construction.