## 2 Related Work  
### Multipath Transmission in IP Networks  
The multi-homing scenario is one of the most commonly used methods to achieve multipath transmission. Stream Control Transmission Protocol (SCTP) and Transmission Control Protocol (TCP) are basic protocols widely used in multi-homing scenarios. At present, MPTCP and Concurrent Multipath Transfer for SCTP (CMT-SCTP) are the focus of the Internet Engineering Task Force (IETF) and academia [4]. MPTCP is an extension of TCP that does not affect the underlying TCP components. The basic design idea of MPTCP is to divide the transmitted traffic into more sub-flows. Each sub-flow establishes a separate end-to-end session and then aggregates into a single flow at the receiving end. This mechanism is transparent to the upper application. The upper application can add or delete the interface address to the address pool via Application Programming Interface (API), but it cannot directly manage MPTCP. SCTP is designed by Signaling Transport (SIGTRAN) organization to transmit signaling messages over IP networks. It is an end-to-end transmission protocol for data streams, and multi-homing represents one of the important characteristics of SCTP. [PERSON] et al. proposed CMT-SCTP to realize multipath transfer between multi-homed hosts by using the multi-homed characteristic of SCTP. CMT-SCTP can carry out the concurrent multipath transmission on the established multiple paths or select other paths for data transmission in time when one path fails. However, multi-homing multipath requires at least one terminal device to have multiple network interfaces, which is difficult to meet in practical applications. Moreover, the multi-homed implementation cannot accurately understand the status of the underlying network and is susceptible to path differences, resulting in a decline in transmission performance.  
On the Internet, researchers have proposed many multipath routing protocols for multipath transmission. ECMP [5] is a simple multipath routing protocol and has been integrated into many traditional routing environments. ECMP has typically deployed on routers and routes packets over multiple paths with the same weight, using a simple polling strategy to allocate traffic. However, in the actual network, the link state information such as bandwidth, delay and packet loss rate of each path is not the same, so equating the path weight cannot make good use of bandwidth, especially when there is a large path difference. To solve the problem of ECMP, Google proposed WCMP [6], which can be very flexible in accordance with the path weight in proportion to the transfer of traffic on the link, reducing the flow bandwidth changes to 1/25. However, the calculation method of multi-path routing is more complex than single-path routing. For example, in Open Shortest Path First (OSPF), the time complexity of a single shortest path with N network nodes is O(NlogN), while the time complexity of a k-shortest multipath calculation is O(KN + NlogN) [12]. Compared with single-path routing, multipath routing increases computational complexity and requires additional storage. More importantly, the increase in routing complexity leads to a decrease in scalability.