## 4 Semi-Physical Platform Setup and Evaluation for SDN-Based ISTNs
### Test of Data Communication Network in the Semi-Physical Platform  
In Section 3.2, managing and controlling messages (e.g., control plane protocols and network management system messages) are transmitted in UDP frames for the simplicity of validation. As mentioned earlier, managing and controlling messages can be communicated between nodes in ISTNs using the **data communication network** field, the **extended control field**, in the AOS frame, as shown in Figure 5. In Figure 16a,b, there is a data communication network test for the configuration of static forwarding information base in node vx_simulator_02 from the network management system, which uses node vx_simulator_01 as the gateway. After receiving a managing and controlling message from the management plane, e.g., the configuration of static forwarding information base, through the northbound interface, node vx_simulator_01 will verify the destination SCID No. first. That is, if destination SCID No. is not 1, this managing and controlling message will be divided into segments and inserted into the **data communication network** field of ten continuous AOS frames before being transmitted to the destination node along the routing path for managing and controlling messages based on the shortest path algorithm (i.e., Dijkstra algorithm), as shown in Table 4. Figure 17 depicts the ten continuous AOS frames captured by ILA in FPGA board #1's port 4. FPGA board #2, on the other hand, reunites the segments of managing and controlling message by extracting the **data communication network** field from those ten continuous AOS frames. If the destination SCID No. is 2, node vx_simulator_02 then configures a static forwarding information base. Otherwise, node vx_simulator_02 forwards the managing and controlling message to the next node.  
\begin{table}
\begin{tabular}{c c c c} \hline  & **vx_simulator\_01** & **vx_simulator\_02** & **vx_simulator\_03** \\ \hline Routing path & Out-port: 4 & In-port: 4, Out-port: 1 & In-port: 1 \\ \hline \end{tabular}
\end{table}
Table 4: The routing path for managing and controlling messages from node vx_simulator_01 to node vx_simulator_02 and node vx_simulator_03, respectively, in the semi-physical platform.  
Figure 15: The SNMP MIB of the semi-physical platform.  
The satellite constellation constitutes a constantly altering networking architecture owing to the link connection variation caused by satellites' orbital movements. Types of management and controlling flooding messages, i.e., satellite link plan of connections (SLPC) described in Section 3.2, are proposed for a better adaptation to the shifting satellite constellation. These messages make use of the predictability and periodicity of satellite network topology, which repeats itself over time, and also include periodic routing phases with changes in the route computation process for both managing and controlling messages and data. These kinds of managing and controlling messages are flooded to each node in the network for the update of previous OSPF LSDB with new ones according to the current network topology, and the destination SCID No. is **0 xFFFF**, as shown in Figure 18.  
Figure 16: The configuration from the network management system to the remote node uses the data communication network overhead in the AOS frame. (**a**) The configuration of static forwarding information base from the network management system (SNMP manager). (**b**) The managing and controlling message of static FIB transmitted by node vx_simulator_01 through southbound interface.  
Figure 17: A data communication network sequence diagram for a managing and controlling message, i.e., static FIB, from node vx_simulator_01 (SCID 1) to node vx_simulator_02 (SCID 2).