# Design of Optical Tunnel Switching Networks for Big Data Applications
## 3 Torus Optical Tunnel Switch Network with 25 Nodes  
Figure 4 shows a two-plane Torus topology optical switching network with 25 nodes. Each module is composed of 16 servers, 2 MUXs, 2 CDMUXs, an SDN switch and 2 nodes, with a node in each plane, as shown in Figure 5, where each node is a \(5\times 5\) WSS.  
Figure 4: Two-plane Torus topology optical tunnel switching network with 25 nodes.  
Figure 5: A module of two-plane Torus topology optical tunnel switching network.  
Figure 3: A module of multi-plane Torus topology optical tunnel switching network.  
The X-axis and Y-axis wavelength assignments of each node are shown in Table 1. A total of 40 wavelengths are shared and reused with different planes. Figure 6 shows the first plane tunnel creation of a two-plane Torus topology optical tunnel switching network with 25 nodes. Suppose node N \((1,5)\) wants to build a tunnel to node N \((4,5)\), because the two nodes are in the same X-axis loop, and therefore \(\lambda_{3}\) (refer to the blue word in Table 1) can establish a direct tunnel. But node N \((1,5)\) needs to build a tunnel to node N \((5,3)\), because they are not in the same X-axis loop, therefore it is necessary to establish a relay tunnel; that is, first establish a direct tunnel to node N \((5,5)\) with \(\lambda_{4}\) (refer to the red word in Table 1), and transfer to the SDN switch and then transfer to node N \((5,3)\) with \(\lambda_{38}\) (refer to the red word in Table 1). N \((1,5)\) also needs to build a direct tunnel to node N \((5,5)\), and therefore, the tunnel from the node N \((1,5)\) to the node N \((5,5)\) is shared with the previous relay tunnel. That is to say, the traffic volume of the two tunnels will be integrated, so the average traffic volume cannot exceed 50%. Of course, the SDN switch at node N \((5,5)\) must separate the two nodes' traffic according to different IP addresses into the correct servers of the two nodes. That is, the traffic to the node N \((5,5)\) is left, and the traffic to the node N \((5,3)\) is transferred out via the SDN switch.  
However, if each direct tunnel is responsible for transferring a relay tunnel node, there are still 8 nodes that cannot receive traffic from node N \((1,5)\), so if each direct tunnel is responsible for transferring two relay tunnel nodes, then node N \((1,5)\) can transmit traffic to any other 24 nodes. However, sharing a direct tunnel between the three nodes reduces the average throughput of traffic to 33% approximately. Therefore, it is necessary to add a plane Torus topology optical tunnel switching network to increase the throughput of traffic. If two planes of the Torus topology optical switching network are used, each plane is responsible for one relay tunnel node, which is equal to two direct tunnels to three nodes, so the throughput of traffic can reach an average of about 66%. Moreover, one module shares two nodes, and one module has only 16 servers. If these servers are evenly distributed  
\begin{table}
\begin{tabular}{c c c c c|c c c} \hline \hline
**Node** & \multicolumn{3}{c}{**X-Axis Wavelength**} & \multicolumn{3}{c}{**Y-Axis Wavelength**} \\ \hline N \((1,5)\) & \(\lambda_{1}\) & \(\lambda_{2}\) & \(\lambda_{3}\) & \(\lambda_{4}\) & \(\lambda_{5}\) & \(\lambda_{6}\) & \(\lambda_{7}\) & \(\lambda_{8}\) \\ N \((2,5)\) & \(\lambda_{9}\) & \(\lambda_{10}\) & \(\lambda_{11}\) & \(\lambda_{12}\) & \(\lambda_{13}\) & \(\lambda_{1 to 24 modules, the average throughput of traffic is only about 66%. Therefore, the two-plane Torus topology optical switching network is sufficient to provide 100% of the server's average throughput of traffic. Of course, if the traffic is not evenly distributed, the distribution of the tunnels must be adjusted.