SBA Interface
The 5G architecture is based on a Service-Based Architecture (SBA). This architecture provides a modular framework from which you can deploy common applications using components of multiple sources and suppliers. The 3GPP defines the SBA for a 5G core network as delivered by a set of interconnected Network Functions (NFs), such as SMF. A network function can access services of other network functions.
The NFs communicate with each other through Service Based Interfaces (SBI). The SBI is the Application Programming Interface (API)-based communication (REST interface) that uses the HTTP/2 protocol.