## 4 Testbed Results
### GOOSE Results  
The results we obtained from conducting all initial latency tests, as described in Section 3.3, are shown in Table 1. For each of these tests, 1000 cycles were executed following the defined transportation topology and method. We expected these tests to yield similar values for the \"Difference to L2-Eth\" row between the two devices, as this row demonstrates the added latency compared to a standard GOOSE network's latency. This would indicate a relative independence of device implementation regarding the observed behavior. We also expected the latency difference for each test to fall within both devices' calculated 95% confidence intervals, indicating a high confidence that the mean latency is within the given range of values. We hypothesized that our tests would demonstrate a small increase in latency for each routing step added across the different test scenarios, with a comparatively larger increase in latency resulting from the introduction of the 5G network. While our tests conclusively confirmed this hypothesis, we also observed a notable difference in the average response time between the different devices. From these results, we can observe that the discrepancy in the difference rows can be explained by the 95% confidence intervals of each individual device. Device 1 exhibited 1.164 ms added latency for the TCP test, whereas Device 2 exhibited 0.618 ms. These results may come across as inconsistent latency across devices. However, the confidence intervals show Device 1's \(\pm\) 0.391 ms and Device 2's \(\pm\) 0.302 ms, giving a full range of 0.693 ms. This implies that our dataset contained a large amount of noise or outliers, which was investigated through network optimization. The main point of interest in this table is the noticeable increase in latency from utilizing TCP routing and also from adding 5G communication. These results are shown graphically in Figure 8. Although there was added latency resulting from TCP, as shown in the TCP and TCP 2-Hop scenarios, there was a far greater impact on the latency resulting from 5G. When comparing the scenarios with and without 5G, we observed a 3.898 ms latency increase for Device 1 and a 3.852 ms latency increase for Device 2. The relatively large confidence interval spread is likely a result of the IED-specific behavior for message processing and contact closing. As shown in Figure 8, the 5G and 5G-TLS scenarios exhibited similar latency increases for both devices when compared to the configurations not utilizing 5G. In these results, an interesting point to note is the lower latency exhibited by Device 1 in the 5G-TLS scenario compared to the 5G-TCP scenario. We attribute this to the wider range of response times for Device 1 compared to Device 2 and the existence of outliers in our data. Given the confidence interval spread for both devices' 5G communication, we conclude that the latency difference between 5G TCP and 5G TLS is smaller than our confidence interval's resolution. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & & **L2-Eth** & **TCP** & **TCP 2-Hop** & **5G** & **5G-TLS** \\ \hline \multirow{3}{*}{Dev 1} & Latency & 14.152 & 15.316 & 15.797 & 19.214 & 19.056 \\ \cline{2-7}  & CI 95 \% Spread \(\pm\) & 0.171 & 0.391 & 1.476 & 0.205 & 0.226 \\ \cline{2-7}  & Difference from L2-Eth & - & 1.164 & 1.645 & 5.062 & 4.904 \\ \hline \multirow{3}{*}{Dev 2} & Latency & 5.797 & 6.415 & 6.478 & 10.267 & 10.325 \\ \cline{2-7}  & CI 95 Spread \% \(\pm\) & 0.082 & 0.302 & 0.299 & 0.105 & 0.110 \\ \cline{1-1} \cline{2-7}  & Difference from L2-Eth & - & 0.618 & 0.681 & 4.470 & 4.528 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Mean latency measurements (ms). This is further illustrated in Figure 9, where a comparison of the results for each configuration is shown separately for both IEDs. In this figure, it can be seen that each device maintained a relatively stable distribution of the measured response times across all tested configurations.