# A Distributed Multicast QoS Routing Construction Approach in Information-Centric Networking
## 2 Related Work  
The IP Multicast technology was initially introduced by [PERSON] in 1988 [31] and has since garnered significant recognition in both academic and industrial domains [32]. Many research institutes and organizations worldwide have conducted extensive studies on multicast routing, considering it a crucial and indispensable technology. Multicast QoS routing can be categorized into centralized and distributed approaches. In centralized schemes, network nodes have comprehensive information of the entire network topology and state [9], and a central control node computes the full routing tree. Unfortunately, there are several limitations to this strategy, such as scalability concerns and potential single points of failure. Protocol Independent Multicast-Sparse Mode (PIM-SM) [33] is a multicast routing architecture capable of establishing distribution trees efficiently across the wide-area Internet. It constructs multicast trees based on unicast routing from multicast members to the root of the multicast tree. The [PERSON], Markowsky, and Berman's algorithm (KMB) [34] uses the Prim algorithm [35] to generate a minimal spanning tree in a centralized manner. This tree is then pruned to produce a multicast tree by removing unnecessary branches. The Bounded Shortest Multicast Algorithm (BSMA) [36] starts by determining the least delay tree using the well-known Dijkstra method. The overall cost of the tree is then decreased by replacing expensive edges with cheaper pathways, subject to satisfying latency constraints. Nevertheless, the computation process necessitates many iterations, each involving calculating k shortest paths. Due to the high time complexity, this method is unsuitable for resolving large-scale networks. Ref. [37] is a source-driven tree search algorithm proposed by [PERSON] ([PERSON]'s Algo). The source node keeps track of routing data from tree nodes to receivers in a state information table. Whenever a member sends a join request, information about the multicast status is transferred from the source to leaf nodes and updated along the way. The source node collects responses from leaf nodes and selects the best leaf node to construct a path to the receiver. Nevertheless, this method relies on the unrealistic assumption that the shortest delay path between any two nodes is invariably the most cost-efficient, which is inconsistent with actual circumstances. Furthermore, it has been demonstrated that [PERSON]'s Algo can result in loops under some conditions [38]. [PERSON] et al. proposed a distributed algorithm [39] rooted in Minimum Spanning Tree (MST) with a similar concept to [PERSON]'s Algo. Initially, FIND messages are propagated downwards from the root throughout the tree. Each tree node receiving a FIND message computes the optimal path independently and responds to the source with a message. Ultimately, the source selects an optimal path from all received responses to construct branches of the multicast tree. However, [PERSON] et al. 's algorithm shares similar issues with [PERSON]'s Algo, exhibiting significant time and message processing complexity. In Spanning-Joins [40], the receiver broadcasts a join request message within the neighborhood to locate tree nodes. Tree nodes receiving the request send response messages to the receiver, collecting QoS information along the path. Receivers select a path based on the information in the response messages. When a satisfactory path is not found, the search scope is expanded, significantly increasing the search cost. In [41], the authors propose the QoS-sensitive Multicast Internet Protocol (QoSMIC). Initially, receivers conduct a local search; in the event of failure, they dispatch messages to designated management nodes to initiate a tree search. During the tree search phase, request messages are multicast throughout the tree, and a path selection mechanism similar to Spanning-Joins is executed.