Section: 4.2 Architecture reference model 4.2.1 General
Content: This specification describes the architecture for the 5G System. The 5G architecture is defined as service-based and the interaction between network functions is represented in two ways. - A service-based representation, where network functions (e.g. AMF) within the Control Plane enables other authorized network functions to access their services. This representation also includes point-to-point reference points where necessary. - A reference point representation, shows the interaction exist between the NF services in the network functions described by point-to-point reference point (e.g. N11) between any two network functions (e.g. AMF and SMF). Service-based interfaces are listed in clause 4.2.6. Reference points are listed in clause 4.2.7. Network functions within the 5GC Control Plane shall only use service-based interfaces for their interactions. NOTE 1: The interactions between NF services within one NF are not specified in this Release of the specification. NFs and NF services can communicate directly, referred to as Direct Communication, or indirectly via the SCP, referred to as Indirect Communication. For more information on communication options, see Annex E and clauses under 6.3.1 and 7.1.2. In addition to the architecture descriptions in clause 4, the following areas are further described in other specifications: - NG-RAN architecture is described in TS 38.300[ NR; NR and NG-RAN Overall description; Stage-2 ]  [27] and TS 38.401[ NG-RAN; Architecture description ]  [42]. - Security architecture is described in TS 33.501[ Security architecture and procedures for 5G System ]  [29] and TS 33.535[ Authentication and Key Management for Applications (AKMA) based on 3GPP credentials in the 5G System (5GS) ]  [124]. - Charging architecture is described in TS 32.240[ Telecommunication management; Charging management; Charging architecture and principles ]  [41]. - 5G Media streaming architecture is described in TS 26.501[ 5G Media Streaming (5GMS); General description and architecture ]  [135]. NOTE 3: The NFs listed in clause 4.2.2 are described in the following clauses or in the specifications above.