Performance of MPTCP over emulated LEO satellite networks with ECMP routing

Low Earth Orbit (LEO) satellite networks are gaining prominence in 6G and large-scale IoT infrastructures, where traffic patterns range from low-rate telemetry to bandwidth-intensive applications such as high-resolution sensing, edge-assisted computation, and real-time vehicular services. Next-generation LEO constellations are designed to support high-capacity connectivity and heterogeneous IoT/6G services, some of which demand sustained high throughput and strict reliability guarantees. Multipath TCP (MPTCP) offers a transport-layer solution by enabling simultaneous use of multiple paths through concurrent subflows. This paper evaluates MPTCP version 1 in a LEO environment using bLEO , a new emulation tool for LEO networks specifically developed by the authors for this work. bLEO is an eBPF-based emulator capable of handling heavily loaded, large-scale constellations while providing efficient real-time control of link delay and state dynamics. We demonstrate MPTCP integration in Linux, including default scheduler behavior and subflow configuration. Additionally, we leverage Equal-Cost Multi-Path (ECMP) routing via OSPF using FRRouting to distribute MPTCP subflows across multiple network paths. The experimental results reveal a fundamental trade-off between robustness and scalability in the Linux MPTCP scheduler: although it maintains session continuity under handovers and failures, it underutilizes available paths unless load conditions force progressive subflow activation, reflecting a conservative design that prioritizes reordering avoidance and performance stability over full multipath utilization. The proposed platform serves as a flexible foundation for evaluating transport-layer protocols in dynamic satellite scenarios. • Evaluates the performance of Multipath TCP (MPTCP) in emulated LEO satellite networks with ECMP routing. • Integrates MPTCP with OSPF-based ECMP routing using FRRouting in a Linux environment. • Investigates subflow allocation and default scheduler behavior under dynamic LEO topologies. • Demonstrates how ECMP forwarding influences MPTCP path diversity and throughput in satellite networks.