# A Multipath Data-Scheduling Strategy Based on Path Correlation for Information-Centric Networking
## 2 Related Works
### Multipath Transmission Technology  
ECMP [10] has been widely used in DCNs due to its simplicity and low deployment cost. It distributes traffic to equivalent multiple paths, achieving multipath load balancing. However, this equal distribution of traffic makes its performance poor in asymmetric network topologies. Weighted Cost Multi-Path (WCMP) [20] can distribute traffic proportionally among multiple links, but its scalability is poor and can only be deployed in medium or small networks. In addition, segment routing [11] encodes the transmission path in the data packet header, making the transmission path definable. Especially after the introduction of SDN technology, the performance of segment routing has been effectively improved. In contrast to the above methods, some researchers have proposed the concept of overlay routing. The overlay network builds virtual paths on the underlying physical network and defines virtual topology and routing patterns based on application requirements. Overlay routing focuses on how to establish routing rules among the virtual nodes in an overlay network to customize the extension of Internet services. Detour [15] deploys overlay nodes in the network called smart gateways, which probe the delay, packet loss rate, and other metrics on the underlying physical network in real time and then forward the data through tunnels to bypass the faulty path. In [16], the authors propose the Resilient Overlay Network (RON), which enables the quick detection and recovery of fault paths. RON employs a full network connection and periodically probes the status of virtual links between overlay nodes. The network topology and path information are distributed to each neighboring node through a link-state routing protocol similar to Open Shortest Path First (OSPF) [21]. Once the current path is congested or fails, it can quickly switch to the optimal alternative relay path. Through experiments, RON found that using only single-hop indirect routing through a single intermediate node can yield most of the benefits in terms of latency and packet loss. Therefore, selecting appropriate relay nodes between the source and destination to exploit path diversity to bypass faults or congestion has drawn the attention of researchers. [PERSON] et al. [22] presented a clustering-based method which clusters the overlay nodes for which the overlap rate of relay paths between the source and destination exceeds a threshold. Randomly selecting only one overlay node in the same cluster increases the difference between relay paths, thereby enhancing the ability to avoid failures. Similarly, the authors in [23] proposed an earliest-diversity heuristic algorithm which selects the relay node that is separated from the current path earliest as the next hop. It is based on the assumption that the earlier a path separates from the original path, the less likely it is to intersect with the original path again. In addition, [PERSON] et al. [24] used a heuristic algorithm to increase the overlay nodes incrementally so that the link overlap rate between relay paths was minimal. In [25], the author proposed to preferentially select overlay nodes with less failure probability to build relay paths. This method assumesthat the failure probabilities of all links in the network are known conditions, which is obviously unrealistic.