## 6 Results  
The present section analyzes the results obtained from the transparent architectures and provides a technical discussion. The objective is to compare the architectures in terms of RTT and jitter in order to understand their feasibility for diverse use cases. As a baseline to evaluate the impact of the NTN transparent architectures, we firstly collect metrics from a 5G TN (i.e., without satellite links) deployed in our controlled laboratory LAN. The RTT and jitter metrics obtained from tests in each architecture are, respectively, shown in Tables 4 and 5. These tables present the minimum, first quartile (Q1), median, third quartile (Q3), maximum, mean, and standard deviation values, providing a numerical summary equivalent to a boxplot. Likewise, Figure 11 illustrates the key elements within the deployment that influence the test outcomes (explained below). The following section opens a discussion about these outcomes. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Architecture** & _Machine (A)_ & _VM_ & _Machine (B)_ & **WireGuard** & **ZSTD** \\ \hline Backhaul & UE and gNB & - & 5 GC & Yes & No \\ \hline Midhaul & UE, DU and RU & CU & 5 GC & Yes & No \\ \hline NR & UE & gNB & 5 GC & No & Yes \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Allocation of the 5G components across the testbed nodes to deploy the proposed transparent architecture. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Arch.**} & \multicolumn{6}{c}{**RTT (ms)**} \\ \cline{2-9}  & **Min** & **Q1** & **Q2** & **Q3** & **Max** & **Mean** & **StDev** \\ \hline TN & 14.94 & 15.45 & 15.63 & 15.81 & 16.14 & 15.64 & 0.79 \\ \hline Backhaul & 47.12 & 50.96 & 51.67 & 53.90 & 56.06 & 52.00 & 1.94 \\ \hline Midhaul & 50.97 & 57.13 & 60.27 & 64.08 & 68.62 & 60.23 & 4.95 \\ \hline NR & 1072.45 & 1079.95 & 1093.40 & 1106.62 & 1134.17 & 1097.60 & 254.2 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Statistics (without outliers) of RTT between the UE and the UPF achieved by each architecture. Figure 11: Illustrative description of the potential vulnerabilities that may influence the results obtained from each transparent architecture. (**a**) Backhaul. (**b**) Midhaul. (**c**) NR. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Arch.**} & \multicolumn{6}{c}{**Jitter (ms)**} \\ \cline{2-9}  & **Min** & **Q1** & **Q2** & **Q3** & **Max** & **Mean** & **StDev** \\ \hline TN & 1.41 & 1.85 & 2.06 & 2.40 & 2.96 & 2.07 & 0.49 \\ \hline Backhaul & 4.91 & 5.98 & 6.53 & 7.57 & 9.73 & 6.89 & 1.27 \\ \hline Midhaul & 5.18 & 8.50 & 10.59 & 14.16 & 16.11 & 11.13 & 3.35 \\ \hline NR & 280.13 & 345.02 & 366.96 & 389.94 & 439.55 & 366.23 & 37.94 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Statistics (without outliers) of jitter between the UE and the UPF achieved by each architecture. The TN architecture exhibits stable values, with a mean RTT of approximately 15 ms and a mean jitter of 2 ms. It demonstrates that OAI is capable of executing a robust 5G network without major performance constraints. The backhaul architecture increases both the mean RTT and the mean jitter up to 52 ms and 7 ms, respectively, approximating the maximum values shown in Figure 5 for the 1-stream TCP connection. The midhaul architecture presents a slightly larger degradation than backhaul, with a mean RTT above 60 ms and a mean jitter of nearly 11 ms. In contrast to backhaul, midhaul reveals susceptibility to delays, as the satellite link affects time-sensitive procedures during the initial steps of the UE attachment. The procedure specifically impacted is the Random Access (RA), through which the UE allocates radio resources to communicate with the gNB. Briefly, the RA procedure encompasses a sequence of messages between UE and gNB, designated Msg1/2/3/4. While Msg1 and Msg2 are handled by Media Access Control (MAC), Msg3 and Msg4 are handled by Radio Resource Control (RRC). In the midhaul architecture, the satellite link is placed between the DU and the CU, which host MAC and RRC, respectively.