The transition from 4G to 5G is not a simple one-to-one node renaming. The MME, which handled both mobility management and session management in a single monolith, is deliberately split into the AMF for access and mobility tasks and the SMF for session establishment and IP address allocation. Similarly the SGW and PGW, which served as separate user-plane gateways chained in series, are consolidated into a single User Plane Function. This decomposition follows a key 5G design principle — separate concerns cleanly so each function can be scaled, upgraded, and deployed independently without affecting its neighbors.