Why did 5G replace Diameter with HTTP/2 in the core network?
5G's SBA core functions (AMF, SMF, PCF, UDM) communicate over REST APIs built on HTTP/2 — chosen for multiplexing, low latency, efficient header compression, and many parallel connections, which suit a cloud-native service-oriented core. LTE used Diameter (for authentication, policy, charging); 5G largely replaced it with HTTP/2 for more flexible, web-based, scalable services.
HTTP/2 in 5G:
- The core network functions (AMF, SMF, PCF, UDM) communicate via REST-based APIs built on HTTP/2
- Advantages of HTTP/2: multiplexing, low latency, efficient header compression, support for many parallel connections
- These make it ideal for the cloud-native, service-oriented architecture of the 5G core
The change from LTE:
- In LTE, core communication often used the Diameter protocol — especially for authentication, policy control, and charging
- In 5G, Diameter was largely replaced by HTTP/2-based interfaces to enable more flexible, web-based, easily scalable network services
Why this matters: the move from Diameter (a telecom-specific signalling protocol) to HTTP/2 (the protocol of the modern web) is emblematic of 5G's whole philosophy — the core network becomes a web-scale software system. It lets telecom vendors use the same tooling, libraries, and cloud platforms as any web company, accelerating innovation.
Tip: "LTE = Diameter; 5G = HTTP/2 REST APIs." This single swap captures the cloud-native shift: the 5G core is built like a web service, not like legacy telecom.
Go deeper:
Diameter (protocol) (Wikipedia) — what LTE used: the AAA protocol with its 3GPP interfaces that HTTP/2 SBA displaced.- HTTP/2 (Wikipedia) — the multiplexing and header-compression properties this card credits for the cloud-native swap.