## 4 Semi-Physical Platform Setup and Evaluation for SDN-Based ISTNs
### Test of Label-Based AOS Frame Switching in the Semi-Physical Platform
Figure 15 shows the detail configurations to set up the bi-directional label switching path from node vx_simulator_01 (SCID 1) to vx_simulator_03 (SCID 3), i.e., lspSrcSCID equals 1 for the source node SCID, lspDstSCID equals 3 for the destination node SCID, lspForwardPathIPv6 AddrHigh64 High, lspForwardPathIPv6 AddrHigh, and lspForwardPathIPv6 AddrLow64 Low equal FE80::0:0:30: (4269801472 and 48 in decimal format) as forwarding equivalence class of forward label switching path, lspBackwardPathIPv6 AddrHigh64 High, lspBackwardPathIPv6 AddrHigh64 Low, lspBackwardPathIPv6 AddrHigh, and lspBackwardPathIPv6 AddrLow64 Low equal FE80::0:0:10:: (4269801472 and 16 in decimal format) as forwarding equivalence class of backward label switching path, lspAliveTime equals 100 s for the link duration time, lspForwardPathBandwidth equals 100 Mbps for the forward bandwidth, lspBackwardPathBandwidth equals 200 Mbps for the backward bandwidth, lspForwardPathDelay equals 1000 ms for the forward latency, and lspBackwardPathDelay equals 1000 ms for the backward latency. The explicit constraint label distribution process is shown in Figure 21 for node vx_simulator_01 (Figure 21a), node vx_simulator_02 (Figure 21b), and node vx_simulator_03 (Figure 21c), respectively, and Table 5 summarizes the forward and backward in/out-labels and in/out-ports of the label switching path. To demonstrate the label-based AOS frame switching, the IP capture tool Wireshark and integrated logic analyzer (ILA) of XILINX VIVADO (version 18.3) are used to probe the IP data, in/out-labels, and in/out-ports of AOS frames, as shown in Figure 22. The IPv6 data transmitted from node vx_simulator_01 to node vx_simulator_03 are captured with Wireshark, as shown in Figure 22a. Figure 22b shows the encapsulation of IPv6 data in the **transfer frame data field** of the AOS frame, which is pushed with the out-label (i.e., 0x00D2) and the forwarding equivalence class (i.e., the destination IPv6 address FE80::0:0:30::) and sent out of node vx_simulator_01's port 3 (ingress LER) according to the forwarding information base. Once the AOS frame with in-label (i.e., 0x00D2) is received, node vx_simulator_02 will immediately swap in-label (i.e., 0x00D2) to out-label (i.e., 0 xFFFF, because node vx_simulator_02 is the last but one in the forward label switching path) and send the swapped AOS frame to port 1 according to the label forwarding information base, as shown in Figure 22c. In the end, when node vx_simulator_03 (LER) receives an AOS frame with in-label (i.e., 0 xFFFF), it will pop the in-label, de-capsulate the IPv6 data from the **transfer frame data field**, and send the IPv6 data to the corresponding terminal, as shown in Figure 22d, and vice versa for the backward label switching path as shown in Figure 23a-d. Table 5 summarizes the in/out-labels and in/out-ports for the bi-directional label switching path AOS frame switching process. Figure 22: The label-based AOS frame switching in forward label switching path under the circumstances of bi-directional link between node vx_simulator_01 (ingress LER, SCID 1), node vx_simulator_02 (LSR, SCID 2) and node vx_simulator_03 (egress LER, SCID 3) in the semi-physical platform. (a) The IPv6 data transmitted from node vx_simulator_01 (SCID 1) to node vx_simulator_03 (SCID 3). (b) The forward-FIB-based label pushing of AOS frame in node vx_simulator_01 (SCID 1). (c) The forward-LFIB-based label swapping of AOS frame in node vx_simulator_02 (SCID 2). (d) The forward-FIB-based label popping of AOS frame in node vx_simulator_03 (SCID 3). The third step is to test bi-directional label switching path setup under the circumstances of uni-directional link between simulated nodes in the semi-physical platform as tested in the software platform in Section 3.2.