# Fast Reroute Mechanism for Satellite Networks Based on Segment Routing and Dual Timers Switching
## 4 Performance Evaluation
### Simulation Setup  
The experiments in this study are conducted using a constellation of 100 satellites of the same specifications in a 1000 km orbit, consisting of 10 orbital planes, each containing 10 satellites. The inter-satellite link delay varies dynamically between 10 ms and 20 ms.  
To evaluate the effectiveness of the proposed scheme, comparisons are made with several baseline FRR methods [7]:  
1. SS-FRR Scheme: This scheme integrates segment routing, enabling satellites with greater computational resources to autonomously generate backup paths without relying on ground controllers. This reduces the interaction delay associated with centralized routing.
2. Backup Path-based Link-State Routing Fault Detection Mechanism (BP-LSRFD): This mechanism detects faults within 3 s of occurrence and swiftly switches to backup paths.  
Backup Path-based BFD Detection (BP-BFD): This mechanism detects faults within 90 ms and promptly switches to backup paths.
* Link-State Routing Fault Detection Mechanism(LSRFD): This mechanism detects faults within 3 s, recalculates routes, and floods fault information across the network.  
Previous studies have evaluated FRR-based routing schemes in satellite networks using metrics such as routing interruption time, storage overhead for backup path forwarding tables, and computational resource utilization [22; 23; 24]. To demonstrate the superiority of the proposed SRDT-FRR scheme, this study focuses on the routing interruption time and primary-backup path switching overhead as key performance metrics.  
It should be noted that a single performance metric is insufficient to comprehensively and accurately evaluate the advantages and disadvantages of various schemes. Therefore, this study applies min-max normalization to the two selected performance metrics and subsequently calculates weighted impact scores. These scores serve as a critical basis for comprehensively assessing the relative performance of different schemes, ensuring the scientific validity and reliability of the evaluation results. This approach more accurately underscores the advantages and significance of the SRDT-FRR scheme in satellite network routing. A shorter routing interruption time indicates better network stability and continuity. Therefore, this study places greater emphasis on the metric of routing interruption time. Based on this consideration, a relatively higher weight is assigned to routing interruption time when calculating the weighted impact scores. Correspondingly, a smaller weighted score reflects the superior overall performance of the respective scheme, indicating a higher capability to meet the requirements for efficient and stable operation in satellite networks.  
The simulation duration is set to 6000 s. To comprehensively evaluate the fault recovery capabilities of the SRDT-FRR scheme, three fault scenarios are designed, with one packet transmitted every 1 ms to calculate the routing interruption time:  
* Fault scenario a: Three random stable faults (5 s each). This scenario tests the fault recovery capability of the SRDT-FRR scheme under stable faults;
* Fault scenario b: Three random transient faults (500 ms each). This scenario evaluates the low switching overhead of the SRDT-FRR scheme during transient faults;
* Fault scenario c: Mixed faults (three 5 s stable faults and three 500 ms transient faults). This scenario assesses the scheme's sensitivity to transient faults, demonstrating its ability to promptly detect and recover from such faults, reducing the routing interruption time.