7.1. Service-Based Representation
The figure above follows TS 23.501 figure 4.2.3-1 and attaches every control-plane NF to the common service-based interconnect through the SBI that the NF exposes, for example Namf for the AMF (TS 23.501 clause 4.2.6). Any NF can consume the services of any other NF over this interconnect, so the figure shows which NFs are part of the 5GC rather than which pairs of NFs interact. The NF services use version 2 of the Hypertext Transfer Protocol (HTTP), HTTP/2, over the Transmission Control Protocol (TCP), as TS 29.500 specifies for the technical realization of the service-based architecture. The UE, the NG-RAN, and the DN do not expose an SBI and therefore connect to the 5GC through the reference points N1, N2, N3, and N6. The SMF controls the UPF over the N4 reference point; the Nupf SBI of the UPF only serves specific exposure features (TS 23.501 clause 4.2.16) and is not shown.
Compared with TS 23.501 figure 4.2.3-1, the figure adds the UDR and the NWDAF, which NOTE 4 and NOTE 5 of TS 23.501 clause 4.2.3 leave out of the TS 23.501 figures for clarity, and the UDSF, the CHF, and the 5G-EIR, which TS 23.501 figure 4.2.3-1 does not show either. The figure leaves out the Edge Application Server Discovery Function (EASDF), which TS 23.501 figure 4.2.3-1 shows, together with the NFs of other specific features, for example the UE radio Capability Management Function (UCMF), the Time Sensitive Communication and Time Synchronization Function (TSCTSF), the Data Collection Coordination Function (DCCF), the Messaging Framework Adaptor Function (MFAF), and the Analytics Data Repository Function (ADRF) (TS 23.501 clause 4.2.2).