# SatScope: A Data-Driven Simulator for Low-Earth-Orbit Satellite Internet
## 3 SatScope Model Framework
### Ground Segment Modeling
#### 3.2.2 Traceroute Classify  
The Starlink network offloads traffic to ground-based networks rather than relying solely on its LEO satellite constellation. Consequently, the original Traceroute records cannot be used directly and require classification to isolate data segments that depend on LEO satellite communications. Unlike traditional IP-managed satellite systems, Starlink does not utilize IP addresses for satellite management, making it impossible to classify Traceroute records based on satellite IP addresses. According to public information from Starlink [18; 45] and prior research [38], the network employs specific IP address ranges, such as 206.224.64.0/24, for Point of Presence (POP) nodes preceding ground stations. Leveraging this characteristic, we can identify Traceroute records that involve communication through the LEO satellite constellation, as illustrated in Figure 6.  
Based on the complexity of Traceroute paths in the Starlink network, we classify the Traceroute path data using the following methods: (1) Traceroute paths where the destination address is reachable and that pass through specific POP segments; (2) Traceroute paths where the destination address is unreachable but which pass through specific POP segments; (3) Traceroute paths where the backbone network information is not recorded  
Figure 6: The correlation between the distribution of physical devices and IP addresses. The figure above illustrates the relationship between physical devices and IP addresses in the most common connection mode of Starlink. Starlink employs CGNAT [38] (Carrier\(-\)Grade Network Address Translation) technology, which allows multiple users to share a single public IP address, thereby conserving IPv4 address resources. The internal Starlink network uses the dedicated subnet 100.16.0.0/10, which is specifically allocated for CGNAT, enhancing network security and management flexibility. due to rate limitations in the edge network; (4) Traceroute paths that do not use LEO satellite constellation routing and have unreachable destination addresses. Here, we need to focus on the first two types of Traceroute path data. After performing rDNS resolution on the reachable destination addresses of the first type of Traceroute paths (using a script to access [[http://ip-api.com/json/](http://ip-api.com/json/)]([http://ip-api.com/json/](http://ip-api.com/json/)), accessed on 20 May 2025, to obtain city-level IP geolocation; using a script to access 8.8.8.8.53 to obtain rDNS resolution of IP addresses), we found that these IP addresses are all POP points, supporting Starlink's ground access. The LEO satellite internet Starlink currently has over 5900 POP points, with their distribution shown in Figure 7.  
In the USA, Atlanta, leads with 978 POP points (16.81% of the total), serving as a core node for Starlink's internet access. Los Angeles follows closely with 744 POP points (12.79%), and Seattle contributes 639 POP points (10.99%). Additionally, Madrid in Spain and Sao Paulo in Brazil are significant nodes, contributing 476 (8.18%) and 341 (5.86%) POP points, respectively. Notably, beyond these major cities, another 30 cities collectively contribute 739 POP points (12.71%), highlighting the global support for Starlink's ground access infrastructure beyond its primary nodes. From a continental perspective, over 70% of the POP points are concentrated in North America to facilitate Starlink's interaction with ground networks. South America and Europe each have more than 300 POP points. The distribution of Starlink's IP addresses indicates that network performance in specific regions is closely tied to the number of POP points. Increased interaction points with ground networks result in lower latency and higher throughput for users. The second category of Traceroute records a number of approximately 130,249, accounting for 61.76% of all Traceroute records. According to previous research [38] and  
Figure 7: The affiliation of POP points to cities and countries.