# Slicing on the Road: Enabling the Automotive Vertical through 5G Network Softwarization
## 6 Proof-of-Concept Experimental Evaluation
### Implementation Choices and Details  
All source code to reproduce the experiments and a figure of the software prototype architecture are available in our project repository [43]. The following implementation choices were considered to emulate the V2X environment:  
* Vehicles were emulated as multi-interface wireless hosts capable of connecting to both eNodeBs and APs/RSUs.
* Heterogeneous RATs were modeled by configuring range and data rates of (R)AN nodes so to resemble either eNodeBs or Wi-Fi APs/RSUs, deployed by different MNOs as OF-capable switches, connected to the backbone and to nearby MEC servers.
* V2X ASs can be hosted either at a MEC server or in remote cloud facilities. In both cases, they were modeled as wired hosts.
* A Remote Authentication Dial-In User Service (RADIUS) server protocol (FreeRadius provides a multi-protocol policy server, supporting RADIUS, DHCPv4 and VMPS, and is available online: [[https://freeradius.org/](https://freeradius.org/)]([https://freeradius.org/](https://freeradius.org/))) was used for Authentication, Authorization, and Accounting (AAA) purposes, resembling the behavior of the NSSF when interacting with the AUSF and UDM to check subscription information during the slice attachment procedures.  
Figure 4: Main required interactions for the roaming procedure.  
* As for the SDN Controller, Ryu (It was chosen due to Python programming friendliness and OpenFlow 1.3 support, including metering functionality to measure and control the rate of packets allowing to enforce rate limiting for roaming users; the code is available at: [[https://github.com/ramonfontes/ryu](https://github.com/ramonfontes/ryu)]([https://github.com/ramonfontes/ryu](https://github.com/ramonfontes/ryu))) was properly extended to run the network slicing and mobility management applications conceived to support V2X. More specifically, it processes radio control information by vehicular devices and tracks their connectivity and position. Based on collected information, the V2X slicing SDN application triggers the service migration (Please, note the simplification compared to the theoretical framework, where this functionality is implemented by the Infrastructure Manager) and configures the interfaces/links to be used for endpoints communication.  
In the first reference scenario, we evaluated the capacity aggregation with a single SDN controller implementation tracking resources spanning the domains of different MNOs, i.e., converging the functions of the Slice Managers and Slicing Orchestrators along the roaming procedures of the proposed framework. By receiving RADIUS messages, the SDN controller tracks the user subscription information and enforces slice policy rules accordingly.  
In the second reference scenario, in turn, we evaluated the load-aware handover decision with and without slicing federation, where different SDN controllers handling network resources (in particular RAN nodes) belonging to different operators share information such as RSSI and load status. With this information, controllers trigger handover actions to improve the slice performance stability and provide low latency.