Back in LTE, the user data journey was simple - SGW received the data from eNodeB, passed it to PGW, and PGW decided where to send it next.
A clear relay race - but rigid and centralized.
But in 5G, speed alone isn’t enough.
You need flexibility, scalability, and edge awareness.
That’s where the UPF (User Plane Function) enters.
What used to be SGW + PGW is now refactored into a distributed fabric of UPFs - some near the edge for ultra-low latency,
others deeper in the core for heavy data processing.
And the real hero behind this coordination?
SMF – Session Management Function.
SMF is the one who:
Sets up the N3 tunnel between gNB and UPF,
Controls multiple UPFs (edge + core) via N4,
Orchestrates traffic steering based on session type, QoS, and latency needs,
Dynamically adapts sessions when UE moves or services change.
In short:
SMF builds the path. UPF delivers the data.
And together, they unlock what SGW + PGW never could:
A user plane that moves with the user.
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