# Mitigating DDoS Attacks in LEO Satellite Networks Through Bottleneck Minimize Routing
## 2 Background and Related Work
### Satellite Security  
The routing paradigms of terrestrial networks and LSNs exhibits fundamental differences. Terrestrial infrastructures benefit from stable node distributions and quasi-static topologies, whereas LSN routing must address dynamic orbital reconfigurations and stringent resource constraints. This volatility renders conventional security mechanisms inapplicable, necessitating domain-specific secure routing frameworks for space environments. In this context, several researchers have proposed innovative solutions to address these unique challenges. Some studies enhance the unpredictability of path selection by incorporating random or predefined weighting mechanisms into routing. Ref. [40] developed Secure Enhanced Multipath Routing (SEMR), leveraging randomized breadth-first search (BFS) to generate unpredictable paths. Ref. [41] introduced Load-Balanced Multipath Routing (LBMR), employing Least Common Multiple (LCM)-based weight allocation for temporal-aware traffic splitting. Ref. [42] proposed an enhanced ant-colony pheromone model combined with an optional forwarding mechanism. When a node becomes inundated by traffic, both its heuristic value and pheromone concentration are dynamically reduced, promptly steering traffic toward healthy links to defend against DDoS attacks. In a ground-relay-assisted Starlink topology, [PERSON]. [43] introduced a hop-count-prioritized shortest-path scheme that splits a session's traffic across two path segments and instantaneously activates a backup route as soon as a failure is detected on the primary link. Ref. [44] proposed advanced k-RAND, a random routing algorithm. This algorithm integrates Bayesian optimization to dynamically blend classic routing strategies. The experimental results demonstrate a 2.05% increase in attacker costs compared to static algorithms, validating its adaptive defense capabilities. To ensure the trusted identities of satellite nodes and the security of their messages, blockchain technology has recently been incorporated into routing and multicast design. In [45], blockchain was integrated aboard satellites by designating each satellite node as a network participant; smart contracts and a distributed ledger were then employed to execute encrypted in-orbit data transmissions. Ref. [46] proposed a blockchain-based trustworthy multicast routing framework that leverages decentralized node authentication and combines an ant-colony algorithm with a scenario-aware hybrid switching strategy to isolate malicious nodes, construct a trusted multicast tree, and implement DDoS defense. Some researchers have also explored machine learning- or deep learning-assisted DDoS defense. [PERSON] et al. [47] introduced a Graph Neural Network-based MultiPath Traffic Engineering (GNN-MPTE), which centrally computes multiple disjoint paths at the ground controller to circumvent attacked links and automatically distribute traffic onto healthy paths. Ref. [48] proposed a deep learning-based trust-routing framework that combines Dempster-Shafer (D-S) evidence theory with variational autoencoder (VAE) based anomaly detection, integrating the generated security factors into an ant-colony algorithm to dynamically avoid malicious nodes. There are several other security enhancement schemes that also offer valuable strategies for mitigating DDoS attacks. Ref. [49] proposed a distributed node-trust evaluation and secure-routing framework that collects inter-node interaction data to compute both direct and indirect trust, then fuses these via a D-S framework to derive an overall trust score--significantly improving the packet-delivery ratio and reducing packet-loss rate. Ref. [50] introduced an ICN network architecture that integrates a centralized software-defined networking (SDN) control plane with an information-centric networking (ICN) data plane.