## 7 Performance Analysis  
### Simulation Design  
We derived the orbital parameters of the satellite through STK, built a LEO satellite network simulation platform in OPNET and compared and analyzed the actual performance of different algorithms in sun outage scenarios. The Walker parameters \(N/P/F\) of the polar-orbit satellite constellation used in this article are 324/9/4.05, the orbital altitude is \(h=1160\) km, and the orbital inclination is \(\theta=89^{\circ}\). There are two seams between the first orbit and the last orbit, and no link is built between the seams. According to the traffic model described in Section 3.2, the time interval between data packet arrivals between any two satellite nodes \(v_{i}\) and \(v_{j}\) follows an exponential distribution with parameter \(\frac{1}{\lambda_{i,j,t}}\):  
\[T_{i,j,t}\,\sim\,\,Exp\left(\frac{1}{\lambda_{i,j,t}}\right). \tag{21}\]  
The parameters in the local pre-rerouting algorithm (LPRA) in this article are set as follows. The high-load link threshold in the limited area is \(\alpha=2\), and the initial value of the maximum link load is \(\beta=0.8\). The time period for collecting routing information before sun outage is \(t_{c}=20\) s, and the reserved time period for collecting routing information and calculating paths is \(t_{s}=5\) s. The calculation formula of virtual topology cycle is  
\[T=\frac{2\pi\sqrt{\left(R+h\right)^{3}/GM}}{N/P} \tag{22}\]  
Here, \(G\) is the gravitational constant, \(M\) is the mass of the earth, \(R\) is the radius of the earth and \(N/P\) is the number of satellites in each orbit. According to the constellation scale in this article, \(T=180.9225\) s.  
In the simulation, the scope of the limited area can be set based on the traffic density of the satellite location. For the constellation size used in the simulation within this article, if the satellite where the sun outage occurs is located over North America or Eurasia, the limited area hop number can be \(n=4\) or \(5\); if the sun outage occurs over other continents, \(n=3\) can be used; if the sun outage occurs over the ocean far away from the mainland, we use \(n=2\). The main simulation parameter settings are shown in Table 2.  
We compared the algorithm in this article with the SPF (shortest path first) algorithm and the IADR algorithm. SPF allows all nodes to forward packets through the shortest path \begin{table}
\begin{tabular}{c c c} \hline
**Parameter** & **Definition** & **Value** \\ \hline \(N/P/F\) & Walker parameters & 324/9/4.05 \\ \hline \(h\) & Orbital altitude & 1160 km \\ \hline \(\theta\) & Orbital inclination & 89\({}^{\circ}\) \\ \hline \(T_{i,j,t}\) & Time interval between data packet arrivals & \(T_{i,j,t}\,\sim\,\,Exp\left(\frac{1}{\lambda_{i,j,t}}\right)\) \\ \hline \(\alpha\) & High-load link threshold & 2 \\ \hline \(\beta\) & The initial value of the maximum link load & 0.8 \\ \hline \(t_{c}\) & The time period for collecting routing information & 20 s \\ \hline \(t_{s}\) & The reserved time period for collecting routing information and calculating paths & 5 s \\ \hline \(T\) & Virtual topology cycle & 180.9225 s \\ \hline \(n\) & Limited area hop number & Determined by the location of the satellite \\ \hline \end{tabular}
\end{table} 
Table 2: Simulation parameter settings. after link failure, while the IADR algorithm first evaluates link utilization within a limited area. Based on the links the path passes through, the path with the lowest utilization is selected from the set of alternative paths as the forwarding path after sun outage failure. All algorithm paths or routing tables are calculated, generated and stored in the corresponding space router in advance. When sun outage occurs, the space router immediately changes the forwarding method. We analyzed the services that originally passed through the failed link and calculate their average end-to-end delay and packet loss rate during the sun outage to evaluate the performance of different algorithms.