# Design of Optical Tunnel Switching Networks for Big Data Applications
## 5 Network Performance and Its Applications  
### Performance Evaluation  
For a detailed description of the switch performance, Figure 10 shows the tunnel assignment of a two-plane optical tunnel switching network with 25 nodes. Each node of the \(5\times 5\) Torus network has 8 direct tunnels and 16 relay tunnels to transfer data to other nodes. According to the uniform distribution of traffic, on average, a direct tunnel allows two relay tunnels (16/8) to share bandwidth,  
Figure 8: A module of Three-plane Torus topology optical tunnel switching network. Figure 9: Tunnel creation of first plane. such as node N (5, 5), node N (5, 4) and node N (5, 3) share a direct tunnel from node N (1, 5) to node N (5, 5), as well as node N (1, 4), node N (2, 4) and node N (4, 4) share another direct tunnel from node N (1, 5) to node N (1, 4). If a plane uses only a relay tunnel to share the bandwidth of the direct tunnel, the network needs dual planes. Therefore, we can connect from node N (1, 5) to all nodes on the network at the same time. These three nodes will share the bandwidth of the direct tunnel, and each node will use an average of two-thirds of the bandwidth of the two planes. One SDN switch per node can use 16 wavelength bandwidths for 16 servers (\(2\times 8\)). If the 16 wavelength bandwidths of the 16 servers are transmitted to the other 24 node modules on average, the average traffic is also 2/3 of the wavelength bandwidth (16/24). Figure 11 shows the tunnel assignment of a three-plane optical tunnel switching network with 49 nodes. Each node of the \(7\times 7\) Torus network has 12 direct tunnels and 36 relay tunnels to transfer data to other nodes. According to the uniform distribution of traffic, on average, a direct tunnel allows three relay tunnels (36/12) to share bandwidth, such that node N (7, 7), node N (7, 6), node N (7, 5) and node N (7, 4) share a direct tunnel, and the tunnel runs from node N (1, 7) to node N (7, 7). If one plane uses only a relay tunnel to share the bandwidth of the direct tunnel, the network requires three planes. Therefore, we can connect from node N (1, 7) to all nodes on the network at the same time. The four nodes will share the bandwidth of the direct tunnel, and each node uses an average of 3/4 wavelength bandwidth across the three planes. One SDN switch per node can use 36 wavelength bandwidth for 36 servers (\(3\times 12\)). If these 36 wavelength bandwidths for 36 servers are transmitted to the other 48 node modules on average, the average traffic is also 3/4 of the wavelength bandwidth (36/48). To investigate the performance of optical tunnel switching networks, we capture traffic from the Internet core network of Chunghwa Telecom Co., Ltd. in Taiwan (a major provider of telecommunications services). According to the data captured from the core network of a traditional  
Figure 11: Tunnel assignment of a three-plane optical tunnel switching network with 49 nodes. Figure 10: Tunnel assignment of a two-plane optical tunnel switching network with 25 nodes. Ethernet switch, the traffic of Ethernet packets is shown in Figure 12, where the X-axis represents various packet sizes. The number of packets of various packet sizes is shown at the bottom of Figure 12, the total number of bytes (TN) of various packet sizes is shown in the middle of Figure 12, and the cumulative total number of bytes (CTN) of various packet sizes is shown at the top of Figure 12. In other words, if the number of packets is equal to N\(i\) for various packet sizes, where \(i\) is denoted the packet size. For various packet sizes, the characteristics of TN and CTN are as follows:  
\[\text{TN}=N_{i}\times i\text{ and GTN}_{j}=\sum_{i=1}^{j}(N_{i}\times i) \tag{4}\]  
where \(j\) is the maximum packet size, and the maximum \(j\) for Ethernet packets is 1538 bytes. Figure 13 shows the traffic analysis of Ethernet packets. The top of Figure 13 shows the cumulative percentage of packets of various packet sizes, while the bottom shows the cumulative percentage of bytes of various packet sizes.