OpenSN: An Open Source Library for Emulating LEO Satellite Networks

Building the Internet in Space: New Tools for Testing Satellite Networks

Low-Earth orbit satellite constellations like Starlink are transforming global communications, but testing the complex networking protocols that make them work requires specialized tools. A new open-source platform called OpenSN is making it easier for researchers to evaluate and improve satellite network technologies before they reach orbit.

The Challenge of Space-Based NetworksUnlike terrestrial networks where infrastructure remains static, LEO satellite constellations present unique networking challenges. The world is witnessing an unprecedented surge in satellite launches, with about 10 times more satellites now active compared to a decade ago, mostly in low Earth orbit (LEO). These mega-constellations, featuring hundreds to thousands of satellites orbiting at altitudes below 2,000 kilometers, must constantly adapt to changing topology as satellites move at speeds exceeding 27,000 kilometers per hour.The complexity of satellite network routing is immense. The complex architecture, changeable constellation topology, and frequent inter-satellite connection switching problems bring great challenges to the routing designs of satellite networks. Traditional internet routing protocols like OSPF struggle in space environments where each satellite can carry only a small number of ISL terminals because of size, weight, and power restrictions, and the range of ISLs is limited.

The OpenSN Solution

Researchers at Beihang University have developed OpenSN, an open-source container-based emulation platform specifically designed to address these challenges. Unlike previous tools that rely on discrete-event simulation or lightweight virtualization, OpenSN can run actual routing software on thousands of virtual satellites, providing unprecedented realism for testing satellite networking protocols.The key innovation in OpenSN lies in its container-based approach. Container-Based Emulation (CBE), where an environment of virtual hosts, switches, and links runs on a modern multicore server, using real application and kernel code with software-emulated network elements offers significant advantages over traditional simulation methods.

Performance Breakthroughs

OpenSN's performance improvements are substantial. The system can construct mega-constellations 5-10 times faster than existing tools like StarryNet and update link states 2-4 times faster than Mininet-based solutions. These improvements stem from several architectural innovations:

Streamlined Docker Operations: Traditional container-based emulators like StarryNet rely on Docker's command-line interface, creating unnecessary overhead. OpenSN uses Docker's official SDK directly and employs distributed architecture for better parallelism.

eBPF-Enhanced Networking: OpenSN incorporates extended Berkeley Packet Filter (eBPF) technology to accelerate link handovers - a critical requirement for satellite networks where connections change constantly as satellites move across the sky. This reduces handover time by up to 10 times compared to traditional virtual link management.

Multi-Machine Scalability: Unlike previous tools limited to single machines, OpenSN distributes workloads across multiple servers using VXLAN tunneling, enabling emulation of constellations with thousands of satellites.## Real-World Scale Testing

The researchers demonstrated OpenSN's capabilities by successfully emulating a five-shell Starlink constellation with 4,408 satellites - a scale that approaches current real-world deployments. As of May 2025, the constellation consists of over 7,600 mass-produced small satellites in low Earth orbit (LEO) that communicate with designated ground transceivers, and Starlink comprises 65% of all active satellites.

This achievement is significant because it enables researchers to test routing protocols and network architectures under realistic conditions before deploying them in space. The system can emulate not only the satellites themselves but also the complex interactions between inter-satellite links (ISLs), ground station handovers, and dynamic topology changes that occur as satellites orbit Earth.

Open Science for Space NetworksOpenSN represents a crucial step toward democratizing satellite network research. The platform is available through the project website (https://opensn-library.github.io), enabling researchers worldwide to access sophisticated satellite network emulation capabilities without the prohibitive costs of space-based testing.

This open approach is particularly important as the complex architecture, changeable constellation topology, and frequent inter-satellite connection switching problems bring great challenges to the routing designs of satellite networks, making the study of the routing methods in satellite networks a research hotspot. By providing a common platform for experimentation, OpenSN could accelerate innovation in satellite networking protocols and help establish industry standards.

Future Directions and Applications

The development of OpenSN arrives at a critical time for satellite communications. If all current commercial satellite plans were to be realized within the next decade, we would have more, possibly substantially more, than 65 thousand satellites circling Earth. This unprecedented scale demands new approaches to network management, routing, and security.

OpenSN's extensible architecture supports multiple research directions. The platform can emulate different routing protocols, test novel network architectures beyond traditional IP networking, and evaluate the integration of satellite networks with terrestrial 5G and future 6G systems. Researchers have already used OpenSN to investigate advanced routing schemes, evaluate congestion control mechanisms, and test content delivery networks optimized for space environments.

The tool also supports research into security protocols for satellite networks - an increasingly important concern as these systems become critical infrastructure. The ability to test security mechanisms in controlled, reproducible environments before deployment in space could help prevent vulnerabilities in operational systems.

Challenges and Limitations

Despite its achievements, OpenSN faces several challenges. The computational requirements for emulating mega-constellations remain substantial, requiring high-performance computing clusters for the largest simulations. The platform currently focuses on Layer 3 networking protocols, though plans exist to extend support to physical and data link layer simulations.

The rapid evolution of real satellite technologies also presents an ongoing challenge. As companies like SpaceX continue deploying new satellite generations with enhanced capabilities, emulation platforms must constantly evolve to match the capabilities of operational systems.

Conclusion

OpenSN represents a significant advancement in satellite network research capabilities. By providing an open-source, scalable platform for testing satellite networking protocols at unprecedented scales, it promises to accelerate innovation in this rapidly growing field. As satellite constellations become integral to global communications infrastructure, tools like OpenSN will prove essential for ensuring these networks operate efficiently, securely, and reliably.

The platform's success in emulating complex scenarios like the five-shell Starlink constellation demonstrates the potential for virtual testing to complement and eventually replace some aspects of expensive space-based trials. For the research community, OpenSN offers an unprecedented opportunity to explore the networking challenges of space at a scale previously impossible, potentially leading to breakthroughs that will benefit the next generation of satellite internet services.

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OpenSN: An Open Source Library for Emulating LEO Satellite Networks