# Multi-Constraint and Multi-Policy Path Hopping Active Defense Method Based on SDN
## 5 Experiment and Result Analysis
### Performance Analysis of SDADM
#### 5.2.2 Data Transmission Delay  
When enhancing the path hopping space and security, it will inevitably cause some performance consumption. Among them, the transmission delay of data, as a major evaluation indicator, largely shows the user's experience. This section mainly analyzes the transmission delay of the SDADM hopping strategy by comparing the three path hopping strategies of no path hopping, PSM-ARM, and SDADM under different data transmission rates. In the parameter settings, the path bandwidth is uniformly set to 100 Mb/s, and data are transmitted between H1 and H2 at rates of 20 Mb/s, 40 Mb/s, 60 Mb/s, and 80 Mb/s, respectively, to record and analyze the transmission delay of each path hopping strategy at different transmission rates. The comparative experimental results are shown in Figure 7, where the horizontal axis is the transmission rate, and the vertical axis is the transmission delay. From Figure 7, it can be seen that in the absence of path switching, traditional data transmission follows the shortest path, resulting in lower transmission delays. As the transmission rate increases, the transmission delay also increases, albeit with a small variation, ranging between 0.09 ms and 0.21 ms. On the other hand, the data  
Figure 6: Comparison of path transition space generation time.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Topology** & **Abilene** & **Ans** & **Agis** & **BICS** & **SANET** & **DFN** \\ \hline
**Nodes** & 11 & 18 & 25 & 33 & 43 & 58 \\
**Links** & 14 & 25 & 30 & 48 & 45 & 87 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Experimental topology data.  
transmission paths of PSM-ARM and SDADM are constantly changing, deviating from the traditional shortest path approach, leading to increased transmission delays compared to no path switching. PSM-ARM utilizes backtracking to select path nodes, generating completely unique transmission paths without repetitions, and incorporates dynamic periodic switching. This approach slightly improves transmission delays compared to traditional networks, with delays ranging between 0.09 ms and 0.21 ms as the transmission rate increases.  
The path switching strategy of SDADM, designed in this study, shows further improvements in transmission delays compared to PSM-ARM for several reasons: (1) The utilization of backtracking by PSM-ARM to generate non-repeating paths significantly constrains the path switching space, leading to repetitive path usage over time. In contrast, SDADM expands the path switching space to enhance the diversity and unpredictability of path switching, improving defensive capabilities by selecting all communication paths between hosts that meet the constraints. This may lead to longer paths during switching, causing increased transmission delays. (2) To prevent packet loss due to mishandling during path switching, the strategy in this study involves adding flow table entries in reverse order, affecting data transmission when flow table entries are issued for nodes shared between the switching path and the previous cycle's path, leading to increased delays. (3) SDADM imposes constraints on link remaining bandwidth and critical nodes to better counter eavesdropping and link-flooding attacks, employing two adaptive switching strategies. Switching strategies impact the issuance of flow tables, resulting in increased transmission delays. Despite the increased transmission delays of SDADM compared to PSM-ARM, they remain below 0.3 ms, within an acceptable range throughout data transmission. Experimental results demonstrate that SDADM offers a significantly larger path switching space than PSM-ARM, greatly enhancing the diversity and unpredictability of path switching, confusing attackers effectively, and defending against eavesdropping  
Figure 7: Comparison of delay at different data transmission rates.  
and link-flooding attacks. Therefore, the sacrifices made in terms of delays are deemed worthwhile overall.