NF interaction model — SBI, HTTP/2, JSON, OpenAPI

The Service-Based Interface in Plain Terms

The Service-Based Interface (SBI) is 3GPP's way of saying "modern REST-like API." When an SMF needs to ask the AMF for context information, it makes an HTTP/2 GET request. When the AMF needs to instruct the AUSF to authenticate a UE, it POSTs a JSON payload. Each NF service is defined by an OpenAPI 3.0 specification, published by 3GPP, listing every endpoint, request schema, response schema, and error code. The same tooling that backend engineers already use — Swagger UI, openapi-generator, Postman — works directly on 5GC SBI specs. This is a deliberate choice: 3GPP wanted the API style to…