## 6 Network Topology Creation Using Mininet-WiFi
### Network Topology S2(5/6)1--Different Access Network and Shared Core, Railway Track Parallel to Road
To emulate the railway tracks being perpendicular to the road, the y-coordinate of the moving node Car1 is kept constant (y = 70) while moving in the defined virtual space, and the x-coordinate of node Train1 is kept constant (x = 130) while moving in the defined virtual space, as shown in Figure 6.

A pictorial representation of this scenario is shown in Figure 7, where we can see that access points ap1 and ap2 are shared by both the domains, and the railway track is perpendicular to the road. This particular scenario for railway and road coexistence represents the \"Level Crossing\" at cross points. Figure 6: 54(5/6)4 hosts and access points: Mininet-WFi graph. Figure 7: 54(5/6)4: Shared Access Network and Shared Core, Track Perpendicular to Road. Figure 8 shows the network topology for scenario S4(5/6)4 created with Mininet-Wifi. Car1, Car2, Train1, and Train2 are connected to access point ap1, whereas Car3 and Train3 are connected to access point ap2. Hosts CarServer and RailServer are connected to switch S22. Similar to topology S2(5/6)1, in this topology, Car1 and Train1 are defined with moving functionality. Comparing Figures 5 and 8, we can see that in Figure 5 both domains have dedicated access networks, but in Figure 8, both domains, i.e., railways and roads, share the same access network. ## 7 Selected Tools to Generate Data Traffic to Validate the Scenarios

To map the data traffic generation that can define the scenarios mentioned in Table 2, different tools are analyzed and selected. These mentioned scenarios are taken from the documentation of 5 GRail project Deliverable D6.1 [7]. This section provides information about the selected tools that are used to generate the data traffic. Along with this, it also explains the procedure to install these tools and which parameters should be selected to generate the desired data streams. \begin{table}
\begin{tabular}{c c c} \hline \hline Scenario & \multicolumn{2}{c}{Considered Tool to Demonstrate the Scenario} & \multicolumn{1}{c}{**Tool Information**} \\ \hline Voice Communication for Operational & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} \\ Purposes & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} \\ Standard Data Communication & & \\ \hline Critical Data Communication & & \\ Very Critical Data Communication & \multicolumn{1}{c}{} & \\ \hline Message & & \\ Critical Video Communication for Observation & & To demonstrate video transmission from train \\ Purpose & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} \\ Very Critical Video Communication & & \\ Associated with Train Safety & & \\ \hline Measure Network Quality of Services (DoS) & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} \\ \end{tabular}
\end{table} 
Table 2: Selected tools to generate different kinds of data traffic for compliance with real-case scenario [7]. Figure 8: S4(5/6)4: Shared Access Network and Shared Core, Track Perpendicular to Road Topology: ONOS screenshot. The following tools are used and tested to generate different kinds of data traf c compliant with real-case scenarios:

1. iperf3: lperf3 is a network performance measurement tool. It is able to execute on Linux, Unix, Android, macOS, and Windows platforms. It works in client and server mode functionality. It has the ability to generate user datagram protocol (UDP) and transmission control protocol (TCP) packets from one host/client and send them to another host/server. It generates a packet data stream to measure the throughput, bandwidth, and packet loss between two hosts [28, 29]. The installation le and documentation to use iperf3 are given in the link [29]. The iperf3 tool is used to send and receive UDP and TCP data packet streams to demonstrate voice communication and standard data communication for operational purposes between car-to-car and assigned car service servers or train-to-train and assigned rail service servers. Table 3 shows the commands used to generate the UDP/TCP data traf c from the client host to the server host. 2.