# Slicing on the Road: Enabling the Automotive Vertical through 5G Network Softwarization
## 3 5G-V2X Network Slicing Architecture
### Architecture Components
The Management and Orchestration (MANO) realm includes a Slice Manager, a Slice Orchestrator, an SDN Controller, and an Infrastructure Manager. * Slice Manager. It operates at a _per-slice_ level and is responsible for: (_i_) slice description through well-defined templates; (_ii_) slice instantiation, which encompasses the identification of CP/UP architecture, interfaces, slice-specific and common VNFs/PNFs, and RAN/CN/device parameter settings; and (_iii_) slice life-cycle management, which entails slice configuration, adaptation and monitoring to fulfill isolation constraints and agreed SLAs. * Slicing Orchestrator. It enables the brokering of resources (hosted in the device, at the edge, on the network and on the cloud) among multiple slices of the same operator. It interacts with the NRF to build the service/network chains by leveraging off-the-shelf NFs and additional AFs, if required. V2X services, especially safety ones, should be supported over unfettered geographical coverage with available resources irrelevant of the specific operator. Thus, it is vital that the slicing orchestrator also exchanges information with peer entities of other Mobile Network Operators (MNOs) to enable seamless platform sharing among operators at a global scale for continuous and guaranteed user experience, according to the _federated network slicing_ concept, under discussion within different standardization bodies (e.g., 3 GPP [34] and GSMA [35]) and particularly challenging for V2X due to frequent roaming events. * SDN Controller. Network resources are managed by logically centralized and physically distributed SDN controllers (Figure 3, left) dealing with traffic engineering functions, network statistics monitoring and implementing southbound interface protocols, e.g., OpenFlow (OF) [36], to install flow-level rules in SDN-capable nodes. Vehicle mobility poses serious issues to the run-time configuration of a slice. Quick path resource allocation algorithms in the backhaul/fronthaul segments are needed to allocate network resources and migrate NFs in another area, while reducing disruption periods. With MEC servers, live migration and service redirection are necessary actions, which further increase the mobility management and handover complexity [37]. To this purpose, a SDN _mobility management_ application becomes crucial to collect radio-related data (e.g., received signal strength), the load status of each RAN node,and information about the position/trajectory of each vehicle, as provided by ME services. To ensure low-latency operation and facilitate the interaction with the ME services, the SDN mobility management network application can be transferred to the MEC server, as also suggested in [37]. Such a design choice, illustrated in Figure 3 (right), emphasizes the potential of the synergy between MEC and SDN in coping with the V2X challenges. Through the collected information and the up-to-date network state, the mobility management application can trigger: _(i)_ seamless UP/CP functions migration (also their pre-fetching, whenever possible); _(ii)_ network resources reconfiguration in the active slice(s); and _(iii)_ handover procedures, e.g., according to the actual load status of each cell, instead of only considering Received Signal Strength Indicator (RSSI). * Infrastructure Manager. It is in charge of orchestrating the infrastructure layer, by monitoring the processing and storage status of edge and cloud servers. To this purpose, it can build upon the ETSI NFV framework [38].