# On the Rollout of Network Slicing in Carrier Networks: A Technology Radar
## 5 CN Domain
### Add-on Features  
The 5 GC arena provides a lot of value-added capabilities that have a direct impact on the use of slicing, and that operators can progressively incorporate into their commercial networks. In the short term (i.e., deploy ring in the radar), operators are focused on the introduction of edge computing. Edge computing is an evolution of cloud computing that allows moving workloads from centralized data centers (e.g., central PoPs) down to the telco edge nodes (e.g., regional PoPs), closer to consumers. In network slicing, edge computing is a must; in fact, bringing application hosting closer to the UE's access point of attachment allows achieving an efficient service delivery through the reduced end-to-end latency and load on the TN. The capabilities enabled by edge computing technology can be clustered into two solution sets:  
* **Baseline edge computing**: provides support for application hosting and user-to-application connectivity. To that end, two network capabilities are needed. On the one hand, application placement capability, which allows for the optimized deployment of service applications at the target edge node, based on criteria such as resource availability, geographical areas, cost and latency requirements. On the other hand, edge node discovery capability, which represents the ability to identify an edge node capable of serving application clients (running on devices). In fact, when an application client wants to connect to an application, there is a need to discover the optimal edge node, which is the one that runs instances of the application, has the necessary resources (CPU, GPU, etc.) and provides the lowest network latency. For this discovery, there exists two solutions: DNS based (network layer solution, specified by 3 GPP SA2) and device based (application layer solution, specified by 3 GPP SA6). For further information on the pros and cons of these solutions, see [49]. * **Advanced edge computing**: provides mobility support in edge computing scenarios. As the user moves, it might happen that the current edge node is no longer valid, either because of SLA violation (e.g., the latency between the UE and serving node exceeds the maximum delay budget) or maintenance reasons (e.g., a node failure). This situation results in the user moving to a new edge node, a process that needs to be completed with the premise of keeping a seamless user service experience. This requires the availability of three main network capabilities: (i) service continuity capability; (ii) application re-location capability, i.e., to move the VM/container hosting the application instance from the source to the target edge node; (iii) context migration capability, i.e., to transfer the context from the stateful application towards the target edge node. In the medium term (i.e., test ring in the radar), as long as standards and commercial products mature, operators are expected to enrich slicing functionality with the following solutions:  
* **NWDAF**: the Network Data Analytics Function (NWDAF) [50] is a 3 GPP Rel-16 function that provides network analysis information (upon request) about 5 GC network entities. It provides S-NSSAI level analytics, and hence it may become the entry point to realize Artificial Intelligence (AI) in 5 GC slices. NWDAF consumers can query for slice load levels and slice QoE measurements, or subscribe to slice-specific notifications that provide periodic updates or anomaly alerts. As shown in Figure 4, examples of NWDAF consumers include: the Network Slice Selection Function (NSSF), which uses the S-NSSAI level analytics to add real-time intelligence to its slice selection algorithms; the PCF, which makes use of NWDAF info to optimize policy decisions on individual 5 GC slices; and the NSSMF. 3 GPP TS 23.288 [51] reports use cases on the use of NWDAF to extract network analytics on a per network slice level.