int representation of 5G system architectures [3]. service-based and reference-point representations are two different representations of the 5GC which make it distinguished from LTE EPC. Service-based interfaces and reference points are two different ways to model interactions between architectural entities. A reference point is a conceptual point at the conjunction of two non-overlapping functional groups. A reference point can be replaced by one or more service-based interfaces that provide equiva- lent functionality. A unique reference point exists between two NFs, which means even if the functionality of two reference points is the same with different NFs, different reference point names must be assigned. However, when service-based interface representation is used, the same service-based interface is assigned if the functionality is equal on each interface. The functional description of the network functions is as follows [3]: Authentication server function (AUSF) is responsible for performing authentication pro- cess with the user terminals. AMF is responsible for termination of RAN control-plane interface (N2) and NAS (N1); ciphering and integrity protection of NAS messages; registration management; connection management; mobility management; lawful interception; transport of session management messages between UE and SMF; transparent proxy for routing session management messages; access authentication and authorization; and security anchor function (SEAF) and security context management (SCM). In addition to the functional- ities described earlier, the AMF may support functions associated with non-3GPP ANs. Data network (DN) comprises operator's services, Internet access, or other services. 144 Chapter 1 Unstructured data storage network function (UDSF) is an optional function that supports storage and retrieval of information as unstructured data by any NF and the deploy- ments can choose to collocate UDSF with other NFs such as UDR. Network exposure function (NEF) to securely expose the services and ca