## 4 Multipath Service Node Selection Algorithm
### Node Selection Algorithm  
Researchers have proposed many solutions to the problem of intermediate node selection for multipath relay transmission [35; 38; 39]. [PERSON] et al. proposed the Random-K method to solve the problem of how to select the intermediate one-hop nodes [35]. Random-K randomly selects K nodes from the set of candidate nodes, and selects the node that responds first as the intermediate node. Random selection algorithm is relatively simple, but it is difficult to guarantee the quality of the path. [PERSON] et al. included node centrality and path difference in the consideration of node selection, and proposed an incremental heuristic algorithm to obtain the relay node set [38]. This method requires global topology information and calculation of node betweenness centrality, which has large overhead and scalability problems. [PERSON] et al. used some geometric mechanisms to select intermediate nodes in the view based on spatial coordinates, and used the link offset angle to characterize the correlation between relay links [39]. This method only considers the impact of path overlap on multipath transmission performance without considering the link state factor. In the multipath transmission scenario, high link overlap between sub-paths or poor link state of sub-paths will lead to low data transmission performance. It is not enough to select nodes only by path link overlap or path state, especially in application scenarios with high throughput requirements. Therefore, we consider the independence between sub-paths and the link state of the path as the criteria for node selection. Many existing network service providers have deployed different bearer networks in the same geographical area to provide data communication services for users, making the bearer network rich in link resources. Autonomous systems (AS) arethe basic unit of the bearer network, different AS will cover the same geographical area. In these geographical regions, different ASes are relatively independent, and data can only be exchanged at the network exchange exit, so that different AS internal paths have a lower degree of intersection. Therefore, when multipath transmission is required between two geographical regions, if there are multiple ASs covering these two regions, the low link overlap between sub-paths can be guaranteed by selecting multipath service nodes within different ASs. Since there may be multiple multipath service nodes in the same AS, the sub-paths constructed by these nodes often have high link overlap. Therefore, for multipath service nodes belonging to the same AS, we calculate the path link state between the edge node and each multipath service node through Equation (3), and select the optimal node. As mentioned above, we propose a cluster-based multipath service node selection method, CMSUS. Edge nodes that support multipath services obtain multipath service node sets through NMS when they are online. In order to ensure a low path link overlap, each multipath service node registers its device information to NMS according to TAG, and the TAG value is AS number. In order to make full use of low-load links and ensure a lower path link overlap, edge nodes perform a path state-aware node selection algorithm aggregated according to TAG. The edge nodes first classify the multipath service node set according to the TAG value, then detect the path state information of the multipath service nodes in each classification, and select the optimal node to join the candidate node set. The node selection algorithm executed by edge nodes takes the set of multipath service nodes returned by NMRS as input and the set of optimal candidate nodes as output.