# Cloud-Enabled Deployment of 5G Core Network with Analytics Features
## 3 Background
### Network Slicing  
As the 5G network supports diversified services, it must meet a wide range of requirements for capacity, latency, isolation, and resilience. These requirements are often impossible to achieve simultaneously. Therefore, the mechanism responsible for network isolation, known as slicing, has been introduced.  
A slice is a logical network with components customized to meet the needs of a specific service. It uses a dedicated core network architecture and provides access to services located in external DNs. A DN can provide operator services, internet access, or third-party services [34].  
A network slice is uniquely identified by a Single Network Slice Selection Assistance Information (S-NSSAI). S-NSSAI consists of two values:  
* Slice/Service Type (SST), which describes the expected behavior of a slice in terms of services.
* The Slice Differentiator (SD), which is used to distinguish slices belonging to the SST.  
The optional SD is represented by a combination of 24 bits, while the mandatory SST is described using 8 bits. The differentiator allows Public Land Mobile Network (PLMN) operators to provide the same features to different groups of customers, such as groups of UE. Certain values for Service Types must be consistent within all deployed 5 GCNs.  
S-NSSAIs are not required to have a dedicated subset of resources, as they might be served by the same Network Slice Instance (NSI). Simultaneously, there may be numerous NSIs associated with an S-NSSAI. This is useful when a subset of resources in a 5 GCN becomes inaccessible, for instance, if a platform hosting NFs of an NSI fails. In such cases, another NSI serves as a fallback instance to provision the service [21].  
UEs may request access to a specific slice based on the S-NSSAI. Upon registration, UEs configured with different S-NSSAIs should access the corresponding network slice and establish PDU sessions accordingly. This enables slicing during the initial registration and service request, which are key operations that should be supported by the 5G network. Joint procedures can be used to determine whether a deployed 5G network operates correctly, making them a starting point for verifying the proposed testbed. Regarding these procedures, the 5 GCN should allow for:  
* Requesting a PDU session establishment by the common AMF to an adequate SMF instance based on the configured S-NSSAI.
* Creating a policy for the PDU session by the Policy Control Function (PCF).
* Establishing an N4 link between UPF and SMF for a given PDU session.
* Issuing Next-Generation Application Protocol (NGAP) (i.e., the message over the N2 link between AMF and gNodeB (gNB)) message to request establishing UP for the PDU session between 5G Access Network (5 GAN) (namely gNB) and UPF.
* Verifying that the UP creation has been successful, i.e., whether an N3 link has been established.
* Tunneling UE-generated traffic to the outbound DN (i.e., public internet) through UPF.  
Network slicing, when integrated with cloud-based deployments, offers new opportunities while also presenting new challenges [35; 36].