# Multi-Constraint and Multi-Policy Path Hopping Active Defense Method Based on SDN
## 2 Related Works
Furthermore, in the process of executing path hopping, the IP address port number and path of the routing interface hop in coordination, which expands the hopping space to a certain extent and increases the complexity of hopping. However, this method only calculates the shortest path between two points and uses a pure random path selection method, does not consider factors such as key nodes, narrows the path hopping space, and reduces the unpredictability of hopping. In terms of path hopping selection, existing research mostly has randomness and insufficient constraints, making it difficult to obtain larger benefits. For this reason, [PERSON] et al. [12] proposed a network moving target defense technique based on optimal forwarding path migration (OFPM), which aims to maximize the defense benefits and solve transient problems that occur when paths are hopping. This technique combines SMT to constrain the capacity, delay, and accessibility of the transmission path; establishes a safety capacity matrix based on the maximum flow-minimum cut idea; and selects the hopping cycle and hopping path based on this. This method not only improves defense benefits but also ensures the effectiveness of path selection. [PERSON] et al. [13] proposed a spatio-temporal random optimization method for network routing mutation based on multi-objective decision (SSO-RM). This method combines the maximum ability of the network to resist attacks and the ability of the attacker to learn, constructs the problem constraints into a random model, and analyzes the effectiveness of the attack from time and space. [PERSON] et al. [14] divided a large complex network into local networks, then used the Floyd-Warshall algorithm to calculate the path hopping space within each region, and finally combined them into the overall hopping space, effectively improving the defense benefits of route hopping. All of these have not fully considered key nodes in the path and the similarity of the path. [PERSON] [15] constrained path delay, similarity, usage timing, and key nodes, calculated path weights based on key nodes, and used this as the basis for hopping path selection, enhancing the diversity and computational difficulty of path hopping to achieve adaptive adjustment of path hopping. However, this method is for eavesdropping attacks and does not consider the situation where the network is subjected to flooding attacks. [PERSON] et al. [16] proposed an adaptive routing hopping technology based on deep learning. This technology generates a hopping space through SMT constraint solving according to the traffic of the intrusion detection system, the remaining credit of the node, and the quality of service, and iteratively selects the optimal hopping path by self-learning attack characteristics. [PERSON] et al. [17] proposed a method to select the optimal hopping path by Q-learning attack strategy. This method calculates the optimal hopping strategy through the Kolmogorov model, achieving adaptive adjustment of the hopping cycle and learning rate. [PERSON] [2] proposed an adaptive routing hopping technology of a path state matrix. This method constrains link bandwidth, transmission delay, and node overlap, calculates all non-repetitive paths between communication terminals through backtracking, and then builds a state matrix according to the remaining bandwidth and forwarding quantity of the link and calculates the path weight as the basis for path selection; however, this method limits the path hopping space. [PERSON] [18] proposed a random routing hopping method that calculates path weights based on node degree centrality, betweenness centrality, and closeness centrality, and adaptively adjusts path selection probability according to network congestion. This method can effectively avoid the repeated use of key nodes and can adaptively select hopping paths according to the bandwidth of the path, which has a certain effect in resisting flooding attacks.