Earlier Networks (e.g. 2G, 3G/4G, Wireline / Fixed, etc..) required a dedicated signalling layer to help with efficient rout(e)ing of information and to enable resources to be used for Telephony / Data sessions.
2G / GSM required a STP – Signalling Transfer Point – to handle non-circuit related signalling, e.g. MAP, CAP V2, etc..
4G / LTE required a Diameter Router for HSS, MME, OCS, PCRF, IMS, etc.. Diameter is a AAA – Authentication, Authorisation and Accounting – protocol. The Diameter Router is known as a DSC – Diameter Signalling Controller.
5G requires a “layer” for HTTP/2. 5G introduces a Service Based Architecture that will use HTTP/2 API method() calls with different Network Functions. This has to be considered as a part of the production 5G deployment.