## 5 Simulation Results and Discussion
### Discussion of ns-3 Simulation Results
Consequently, the \(PDR\) drops to 0 for the simulation from 50 s up to 110 s. This can also be corroborated by Table 3.  
When the network is simulated for 210 s, then network \(\mathcal{N}_{1}\) fails again (first failure in case study-I) at 150 s and remains in the failed state up to 210 s. Therefore, no data can be communicated by the PMU over this network from the PMU at interface 191.168.1.1 to the PDC at interface 170.1.3.2 from 150 s to 210 s. This can be verified, as the last packet transmitted corresponding to this flow is at 149.96 s. Moreover, network \(\mathcal{N}_{1}\) is operational for up to 150 s. Thus, the PDC receives all 2224 packets transmitted by the PMU. Thus, all packets are received at the PDC, which results in a \(PDR\) value equal to 1 for this flow. For simulation beyond 150 s and up to 210 s, as network \(\mathcal{N}_{1}\) remains failed, no further data can be communicated using this network. In response to the failure of network \(\mathcal{N}_{1}\), the PMU reroutes data through an alternative route at interface 170.1.2.1, which is through network \(\mathcal{N}_{3}\) over the Internet \(\mathcal{N}_{2}\). Nevertheless, network \(\mathcal{N}_{4}\) is now available, but configured with 75% background traffic (with a data rate of 10 Kbps). This ensures the existence of a backup path between the PMU and PDC. Therefore, the PDC receives 1995 packets out of 3000 transmitted packets by the PMU at interface 170.1.2.1, resulting in a packet loss ratio of 30.7051%. Consequently, the performance of the network in terms of the \(PDR\) is better as compared with case study-I. Specifically, the average \(PDR\) corresponding to both flows is equal, corroborated by Table 3. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & \multicolumn{2}{c}{**Observation**} & \multicolumn{2}{c}{**Number of**} & \multicolumn{2}{c}{**Number of Packets**} & \multicolumn{2}{c}{**Total**} & \multicolumn{2}{c}{**Total**} \\  & \multicolumn{2}{c}{**Packets Sent**} & \multicolumn{2}{c}{**Received at 170.1.3.2**} & \multicolumn{2}{c}{**Number**} & \multicolumn{2}{c}{**Number**} \\  & \multicolumn{2}{c}{**Start**} & \multicolumn{2}{c}{**Stop**} & \multicolumn{2}{c}{**From Source Interface**} & \multicolumn{2}{c}{**From Source Interface**} & \multicolumn{2}{c}{**of**} & \multicolumn{2}{c}{**of**} \\  & \multicolumn{2}{c}{**Time (s)**} & \multicolumn{2}{c}{**Time (s)**} & \multicolumn{2}{c}{**Time (s)**} & \multicolumn{2}{c}{**Packets**} & \multicolumn{2}{c}{**Packets**} \\  & \multicolumn{2}{c}{**Time (s)**} & \multicolumn{2}{c}{**191.168.1.1**} & \multicolumn{2}{c}{**170.1.2.1**} & \multicolumn{2}{c}{**191.168.1.1**} & \multicolumn{2}{c}{**170.1.2.1**} & \multicolumn{2}{c}{**Sent**} & \multicolumn{2}{c}{**Received**} \\ \hline  & 210 & 220 & 250 & 0 & 250 & 0 & 250 & 250 & 1 \\ \cline{2-8}  & 220 & 230 & 250 & 0 & 250 & 0 & 250 & 250 & 1 \\ \cline{2-8}  & 230 & 240 & 250 & 0 & 250 & 0 & 250 & 250 & 1 \\ \cline{2-8}  & 240 & 250 & 0 & 250 & 0 & 250 & 250 & 250 & 1 \\ \cline{2-8}  & 250 & 260 & 0 & 250 & 0 & 250 & 250 & 250 & 1 \\ \cline{2-8}  & 260 & 270 & 0 & 250 & 0 & 250 & 250 & 250 & 1 \\ \cline{2-8}  & 270 & 280 & 0 & 250 & 0 & 250 & 250 & 250 & 1 \\ \cline{2-8}  & 280 & 290 & 250 & 0 & 250 & 0 & 250 & 250 & 1 \\ \cline{2-8}  & 290 & 300 & 225 & 0 & 225 & 0 & 225 & 225 & 1 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: \(Cont.\)When the network is simulated for 280 s, network \(\mathcal{N}_{1}\) is configured to fail again (first failure in case study-I and second failure in case study-II) at 240 s and remains failed up to 280 s. Therefore, no data can be communicated by the PMU over this network from the PMU at interface 191.168.1.1 to the PDC at interface 170.1.3.2 from 240 s to 280 s. This can be verified as the last packet transmitted at 239.96 s corresponds to this flow.