# A Study of 5G Edge-Central Core Network Split Options
## 5 Testbed Implementation and Evaluation Results
### Locally Administered Edge Network  
For the locally administrated edge networks deployment model, two virtual machines were deployed at the edge, one including the AMF and SMF functionality and one with a UPF for local offloading. Another two virtual machines were deployed at the central location completing the core network, one with the AUSF and UDM functions and one with a second UPF for the centrally bound data traffic. Similarly, to the local offload split options, the measurements were first executed for the satellite backhaul followed by the local measurements with Ethernet backhaul. Each of the measurements were executed 25 times. The median delays of the procedures are presented in Table 2.  
For the locally administrated edge networks, the 5G registration has a similar delay as in the local offload model. This is due to the large number of procedure steps which are executed between the AMF and the AUSF for the authentication and authorization of the UE and due to the lack of the other optional update procedures towards previous components which were not implemented in the Open5 GCore. The 5G registration procedure had a slightly larger delay for Ethernet than in the case of the local offload as presented in Table 1. This is due to the split of the core network functions on top of two virtual machines instead  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Procedure** & \begin{tabular}{c} **5G** \\ **Registration** \\ \end{tabular} & \begin{tabular}{c} **PDU Session** \\ **Establishment** \\ \end{tabular} & \begin{tabular}{c} **PFCP** \\ **Messages** \\ \end{tabular} & \
\begin{tabular}{c} **5G** \\ **Deregister** \\ \end{tabular} &
\begin{tabular}{c} **Control: Backhaul** \\ **RTT** \\ \end{tabular} \\ \hline With satellite backhaul (ms) & 1369 & 1415 & 630 & 1320 & 582 \\ \hline With Ethernet backhaul/ locally measured (ms) & 16.7 & 42.8 & 2.6 & 14 & 2 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Median delay of local offload 5G core network functionality split control plane procedures.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Procedure** & \begin{tabular}{c} **5G** \\ **Registration** \\ \end{tabular} & \begin{tabular}{c} **PDU Session** \\ **Establishment** \\ \end{tabular} & \begin{tabular}{c} **PFCP** \\ **Messages** \\ \end{tabular} & \
\begin{tabular}{c} **5G** \\ **Deregister** \\ \end{tabular} &
\begin{tabular}{c} **Control: Backhaul** \\ **RTT** \\ \end{tabular} \\ \hline With satellite backhaul (ms) & 1380 & 40 & 2 & 1342 & 581 \\ \hline With Ethernet backhaul/ locally measured (ms) & 20.7 & 38.8 & 2 & 14.2 & 2 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Median delay of locally administrated edge network deployment option control plane procedures.  
of one. We will study this area further if such ultra-low delay of the control procedures would be required by the use cases.  
As the AMF and the SMF were both located at the edge, the PFCP messages were exchanged only locally, with the local UPF having a 2 ms median. As such, the PDU session establishment was very fast regardless of the backhaul capabilities. It is assumed that a similar result would also be obtained for the other PDU session procedures including the modification, termination or establishment of other bearers. These measurements relate only to the local procedures. For the end-to-end ones where the central UPF is used, the delays should be like the local offload case, this time having the PFCP messages exchange on the other direction.