## 4 Proposed Routing Scheme
### Distributed Detour Routing Scheme
By contrast, DTDR floods all nodes within a predetermined \(n\) hop range, regardless of the position and direction of the failed links. The proposed scheme may vary depending on the geographical location of the satellite location. When considering situations with more traffic occurring in the Northern Hemisphere, the proposed scheme tends to utilize more intra-ISLs. In an LEO satellite network routing design, relying on inter-ISL for flooding may not always ensure the transmission of link-state information because of link failures. This can result in routing loops or increased delays if the nodes fail to receive link-state information and are, thus, unable to choose the optimal detour path. However, the proposed scheme can enhance reliability during selective flooding for end-to-end transmission by increasing intra-ISL utilization compared with DTDR. ## 6 Conclusions

In this paper, we introduced a distributed detour routing scheme designed to minimize the communication overhead in LEO satellite networks. The proposed scheme detours failed links through rapid detours by leveraging a selective flooding algorithm to set up detour paths. After link recovery, the node checks the recovered link information in the detour table and reverts to the original path. We implemented the LEO constellation based on the Iridium constellation and compared it to two benchmark routing algorithms. The results show that the proposed scheme reduces the end-to-end delay compared with the \(n\)-hop flooding detour path. Selective flooding restricts the communication overhead to the

Figure 11: Average intra-ISL usage rate for flooding according to link failure rate. MHR region. Finally, considering the realistic LEO satellite network, the proposed scheme uses more intra-ISL for information exchange. The proposed distributed detour scheme was designed for polar constellations. The optimal detour point is determined in advance in polar constellations, but it is not determined in other constellations. Therefore, scalability will be considered to be further investigated in Walker-delta and mixed constellations. Conceptualization, J.I., J.Y., S.K., and Y.K. ; methodology, J.I., J.Y., S.K., S.L., Y.K., J.P., and S.C.; software, J.I. and J.Y. ; validation, S.L., Y.K., and J.P.; formal analysis, J.I., J.Y., and S.K. ; investigation, J.I. and S.K. ; resources, J.I. ; data curation, J.I. ; writing--original draft preparation, J.I., J.Y., and S.C.; writing--review and editing, J.I., J.P., and S.C.; visualization, J.I. ; supervision, J.I. and S.K. ; project administration, S.C.; funding acquisition, S.C. All authors have read and agreed to the published version of this manuscript. This work was supported by the Electronics and Telecommunications Research Institute (ETRI) grant funded by the ICT R&D program of MSIT/IITP (No.2021-0-00847, Development of 3D Spatial Networking Technology/Development of 3D Spatial Satellite Communications Technology) and was supported by the Institute for Information & Communications Technology Planning & Evaluation (IITP) grant funded by the Korea Government (MSIT) (No. 2021-0-00368, Development of the 6G Service Targeted AI/ML-based Autonomous-Regulating Medium Access Control (6G STAR-MAC)). Not applicable. The data generated during this current study are available from the authors upon reasonable request. The authors declare no conflict of interest. The following abbreviations are used in this manuscript: \begin{tabular}{l l} LEO & Low Earth orbit \\ MEO & Medium Earth orbit \\ ISL & Inter-satellite link \\ RF & Radio frequency \\ PAT & Pointing, acquisition, and tracking \\ MHR & Minimum hop region \\ DTDR & Disruption tolerant distributed routing \\ OPSPF & Orbit prediction shortest path first \\ RT & Routing table \\ \end{tabular} 

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