# TOAR: Toward Resisting AS-Level Adversary Correlation Attacks Optimal Anonymous Routing
## 6 Evaluation
### Network Performance Measurement  
In the second part of the experiment, the anonymous routing method described in STAR [23] is used to measure the performance of TOAR for route forwarding under different path lengths. All experiments are conducted using the SDN network simulator Mininet, and the Mininet version is 2.3.0d6. Meanwhile, the hardware consists of one server running Ubuntu 16.04 LTS operating system (Canonical Ltd., London, UK) with Intel(r)Core(tm)7-9700@ 3.00 GHz CPU (Intel Corporation, Santa Clara, CA, USA). Ryu and Open vSwitch are installed, acting as the SDN controller and virtual switch and, the network topology is the Internode topology from the Zoo dataset, which includes 66 nodes, with each node functioning as an SDN switch. An SID is assigned to each node, representing its unique identifier. As shown in Figure 10, Algorithms 1 and 2 are integrated into the Ryu controller. STAR uses SDN topology discovery as the input for shortest path computation to generate the segment list for segment routing and sends OpenFlow rules to the OVS switches, which perform matching and forwarding based on SIDs. Based on SDN topology discovery, an AS relationship table with exit policies is generated and used as input for the TOAR routing search algorithm, which then generates the segment routing list according to the computed optimal route.  
Throughout evaluation for TOAR:  
Iperf is used to assess the throughput of both TOAR-disabled (normal route forwarding) and TOAR-enabled (anonymous route forwarding) systems by varying data sizes (with the path length set to a default of 3). As illustrated in Figure 11, the throughput for both systems rises as the data size increases. However, rather than directly forwarding packets, TOAR requires additional processing time for route sampling, which results in reduced throughput, but enhances security and privacy protection.  
Figure 10: SDN experiment environment.  
Figure 9: Percentage of search effectiveness.  
* Anonymous route effectiveness:  
We further evaluate the throughput of route forwarding in order to illustrate the effectiveness of anonymous route with TOAR. IP forwarding is used as our performance baseline. For comparison, three reference systems are introduced: STAR [23], TOAR (high anonymity), and lightweight TOAR (low anonymity).  
Figure 12 demonstrates the trade-off between anonymity and latency in different schemes. IP performs the best with the lowest latency, but it does not provide anonymity. Tor has the highest latency, and its latency increases the fastest as path length increases. TOAR has moderate latency, but the test results are slightly lower than STAR because STAR does not consider exit policies and calculates routes based on the shortest path.  
Figure 13 demonstrates the effectiveness of all schemes when varying the packet size from 128 bytes to 1500 bytes. According to the experimental results, the throughput performance of the TOAR and STAR schemes is close, indicating that the performance of our scheme is comparable to that of STAR. In the case that only three routing nodes are selected for anonymous forwarding and other routing nodes are forwarded normally, the lightweight TOAR scheme can achieve nearly 70% of the throughput of the IP scheme, as shown in Figure 13.  
Figure 11: Impact of data size changed on throughput.  
Figure 12: Communication latency.  
From above, TOAR enhances the anonymity of the communication system while maintaining the throughput within an acceptable range, ensuring the effectiveness of the proposed scheme.