5G SBA Architecture
An interactive map of the 5G Core Service-Based Architecture. Every NF sits on the common SBI (HTTP/2 + JSON over TLS) bus. Click any box to see its produced services, role and spec references — 3GPP TS 23.501 / 23.502.
AMF — Access and Mobility Management Function
Termination point of N1 (NAS) and N2 (NG-AP). Handles registration, connection, reachability and mobility management, NAS ciphering/integrity and relays SM messages to the SMF.
- Namf_Communication
- Namf_EventExposure
- Namf_MT
- Namf_Location
- 3GPP TS 23.501
- 3GPP TS 24.501
- 3GPP TS 29.518
Reference points
| Point | Description |
|---|---|
| N1 | NAS signalling between UE and AMF |
| N2 | NG-AP control plane between gNB and AMF |
| N3 | User-plane GTP-U tunnel between gNB and UPF |
| N4 | PFCP control between SMF and UPF |
| N6 | Interface from UPF to the Data Network (Internet / IMS / edge) |
| N9 | GTP-U between two UPFs (I-UPF ↔ A-UPF) |
| N11 | Service-based interface between AMF and SMF |
About the 5G Service-Based Architecture
Unlike the EPC, where every node-to-node interaction used a dedicated reference point (S11, S5, S6a…), 5G Core folds its control-plane NFs onto a common service bus. NFs expose RESTful APIs over HTTP/2 with JSON payloads, they register with the NRF on startup, and consumers discover producers dynamically. Reference points still exist where they matter — N1 (NAS), N2 (NG-AP to the gNB), N3 (GTP-U user plane), N4 (PFCP control of the UPF) and N6 (exit to the Data Network) — because those interfaces are stateful and performance-critical.
This diagram is a study aid. Click any NF to see its most common produced services and the TS that defines it. For a deeper dive into the stage-3 call flows, pair it with the 5G Auth Flow Visualizer and SUPI / SUCI Analyzer.
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