# Rethinking LEO Mega-Constellation Routing to Provide Fast Internet Access Services
## 4 Evaluation
### Results and Analysis  
(1) Average Internet Access Latency:We conducted simulations to evaluate the delay performance of the IFAR algorithm on a large-scale LEO constellation of 500 satellites, and compared it with the OSPF algorithm. To quantify the network's performance, we defined the network relative load as the ratio of all user requests received by the satellite network to the total bandwidth of the feeder link.  
We conducted experiments under varying network relative loads, as illustrated in Figure 6. The average internet access delay is defined as the average delay between the packet sent from the user terminal to the satellite network and successfully downloaded from the satellite network to the terrestrial server. Our findings revealed that when the network load is light, the OSPF algorithm outperforms the IFAR algorithm, in terms of delay performance. This can be attributed to the fact that the IFAR algorithm rapidly transmits data to the ground station and subsequently accesses the server through ground optical fiber, while the OSPF protocol first forwards data packets to the ground station closest to the server through the ISLs, before accessing the server. As a result, data forwarded by the OSPF algorithm travels a longer distance in space. Because the speed of light in space is 40% faster than the speed of light in optical fiber, packets can travel faster on satellite networks than on the ground, when there is no congestion.  
As the network load increases, the experiment using the OSPF algorithm results in a considerable number of data packets being forwarded on the satellite network. This causes the bandwidth resources of the ISLs to gradually deplete, resulting in packets being unable to be forwarded promptly in the cache. Network congestion ensues, which in turn increases the queuing delay of packets, consequently impacting the internet access delay of users. In contrast, in the simulation utilizing the IFAR algorithm, data will be quickly downloaded from the matching landing satellites to the ground network, and then the abundant and robust optical fiber will be used for data transmission. Consequently, a large number of packets are prevented from traveling long distances through the ISLs, thereby effectively mitigating congestion in the satellite network.  
(2) Average Packet Loss Rate: As the ISL is not stable enough, it will often fail and cause packet loss. Therefore, a large number of packets forwarded by ISLs may not only cause congestion, but also increase the packet loss rate, as shown in Figure 7. The average packet loss rate is defined as, the ratio of packet loss caused by unstable inter-satellite links to the total number of packets received by the satellite network.  
When the network load is low, the OSPF algorithm resorts to forwarding packets on the ISL through multiple hops, thereby compounding the packet loss rate and resulting in a high average network packet loss rate. In contrast, the IFAR algorithm relies on the stable and resource-rich ground network to forward more packets, effectively circumventing packet loss caused by the instability of ISLs. As the network load increases, the satellite  
Figure 6: The average internet access latency of users under different network loads.  
network becomes increasingly congested, and the packet loss rate of both algorithms starts to rise. This is because the OSPF algorithm discards a substantial amount of packets, that either exceed their lifetime limits or the cache capacity is insufficient. The IAFR algorithm can only transmit data between matching satellites, avoiding long-distance transmission by ISLs, and meeting the needs of users for fast access to the internet.