## 5 Performance Evaluation
### Basic Performance Evaluation
#### 5.1.1 Dynamic Threshold Control Parameter  
The control parameter \(\alpha\) plays a critical role in the DT buffer management scheme, as it directly affects the proportional relationship between the threshold and the remaining buffer size. However, there is no systematic method for determining \(\alpha\), and it must be adaptively configured according to different network environments. In [41], it is noted that extremely large or small values of \(\alpha\) can lead to significant performance degradation, and it is recommended to set \(\alpha\) within a range of 0.5 to 2.0. Currently, various manufacturers adjust this parameter for specific service scenarios. For example, Cisco's Nexus 9300-H series switches [49] use a default \(\alpha\) of 14, while Huawei [50] allows \(\alpha\) to be configured as an integer between 0 and 10 to provide priority-based traffic control services. We evaluate throughput with \(\alpha\) ranging from 1 to 10 across four experimental scenarios. Each scenario is simulated over 10 rounds, and the average throughput is calculated, as illustrated in Figure 6. In all scenarios, throughput initially increases before declining as \(\alpha\) changes. When \(\alpha\) is small, the larger reserved buffer threshold leads to a more aggressive congestion assessment, causing premature packet forwarding and underutilization of buffer resources. As \(\alpha\) increases, the reserved buffer size decreases, allowing more packets to benefit from reordering services, thus improving system throughput. However, further increases in \(\alpha\) reduce the reserved buffer space, which makes it insufficient to handle burst traffic, leading to buffer overflow and packet retransmission, ultimately reducing throughput. The experimental results indicate that the peak throughput in all scenarios occurs when the value of \(\alpha\) is either 5 or 6. In Scenario 1, where there is a significant difference in delay, the throughput values are very close when \(\alpha\) is set to 5 or 6. However, in Scenarios 3 and 4, which have significant bandwidth differences, there is a slight probability of data overflow during the experiment when \(\alpha\) is set to 6. Based on a comprehensive analysis of the experimental results, we set \(\alpha\) to 5 in subsequent experiments to maintain high throughput while ensuring some resilience against burst traffic. \begin{table}
\begin{tabular}{l c} \hline \hline
**Parameter** & **Value** \\ \hline Pareto-\(\alpha\) & [0.606, 0.726] \\ Pareto-\(\beta\) & 92 \\ Packet Size & [64, 1024] bytes \\ Flow Size & [8K, 2M] bytes \\ Buffer Size (B) & FlowSize\({}_{\text{max}}+\sum_{i=1}^{k}\text{BDP}_{i}\) \\ Update Interval (\(\Delta t\)) & 10 ms \\ EWMA Parameter (\(\gamma\)) & 0.8 \\ PHRD Flow Marking Time (\(T\)) & \(\frac{\gamma}{2}\sum_{i=1}^{k}\text{Delay}_{i}\) \\ Data Source Link Bandwidth/Delay & 100 Mbps/1 ms \\ Receiver Link Bandwidth/Delay & 100 Mbps/1 ms \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Experimental parameter setup. To provide a more intuitive demonstration of the DT scheme's impact on regulating reserved buffer size, we design the following periodic traffic transmission experiment: In four scenarios, the value of \(\alpha\) is set to 1, 5, and 10, and 30 traffic flows are transmitted at 0.25 s intervals over a 10 s simulation. Due to the random distribution of flow sizes, buffer occupancy fluctuates over time. As shown in Figure 7, across all experimental scenarios, the buffer management mechanism is triggered when available buffer space reaches the reserved buffer threshold (indicated by the gray-marked intervals). When \(\alpha=1\), the reserved buffer ratio is too large, causing the buffer to enter a restrictive state when occupancy reaches about 70%, resulting in underutilization of buffer resources. Conversely, when \(\alpha=10\), the threshold is too small, preventing the reserved buffer from effectively adjusting during burst traffic, which leads to data overflow (indicated by the red markers).