## 5 Evaluation
### Network Evaluation
#### 5.3.1 Virtual Network Evaluation  
In this section we evaluate the metrics of reachable nodes that have joined the physical bearer network and unreachable nodes joining the overlay network plane and the success rate of lookups. We use the previous address generation algorithm to generate 7000 addresses, which are randomly assigned to each node via the control node, without distinguishing between reachable and unreachable nodes, and record the addresses with the node's IP address and port number for backup. First, we evaluate the joining of nodes to the overlay virtual plane. To avoid single point failure and single point bottleneck of the bootstrap nodes, we randomly selected five nodes as bootstrap nodes, hard-coded the bootstrap nodes into the control center, and the nodes randomly selected a bootstrap node when joining the overlay network. We used a total of 7000 nodes for our experiments and randomly selected 30% of them, 2100 nodes, as unreachable nodes \(u_{i}\) and the remaining 4900 nodes as reachable nodes, with the bootstrap nodes included in the reachable nodes \(r_{i}\). The reachable and unreachable  
Figure 15: ECS experimental architecture. nodes are randomly distributed among all nodes. The parameter N for the unreachable nodes to access the network is taken as 1. Two sets of experiments were conducted. In the first set of experiments, when the bootstrap node is created and the rest of the nodes join the overlay network through the bootstrap node in turn, we obtain the average value of packets sent and received by the nodes in the network when 1000, 2000, 3000,..., 7000 nodes join the network. In the second set of experiments, the rest of the nodes join the overlay network through the bootstrap nodes in turn. We pause the joining of the rest of the nodes when 1000, 2000, 3000,..., 7000 nodes join the network, then wait for 100 s and obtain the average value of the packets sent and received by the nodes in the network. The experimental results are shown in the four curves in Figure 16.  
The lower two curves show the number of packets sent and received by nodes joining without waiting time, while the upper two curves show the number of packets sent and received after 100 s of waiting time, both of which show an increasing trend. The difference between the top two curves is larger than the bottom two curves and tends to increase as the number of nodes increases, while the difference between the bottom two curves remains more or less the same. Overall, the slope of the two curves decreases slowly as the number of nodes increases and does not exceed 1 at the maximum slope, indicating that the average consumption of network resources by nodes becomes smaller as the network size increases. As the size of the network increases, the tendency to increase the average time complexity of building the network and the interactive refresh work after building decreases, which is a beneficial effect for us to build larger networks. Next, we verified the success rate of finding reachable and unreachable nodes. As in the previous experiment, we used 30% of unreachable nodes and set N to 1. We constructed overlay networks of 1000, 2000, 3000,..., 7000 nodes and brought the nodes to a stable state of the DHT. Then, we select no less than 10 reachable nodes, and no less than five reachable nodes and no less than five unreachable nodes for each reachable node for different network size cases, and count the number of successes in each group as a proportion of the total number of successes, as shown in Figure 17.  
In the figure we can see that the success rate is high when the network is small, with both unreachable and reachable nodes reaching around 96%. As the size of the network increases the success rate of reachable nodes decreases slightly, and the unreachable nodes start to decrease more at 4000 nodes, but then levels off at larger network sizes.