Most answers stop at:
SMF assigns the IP
But the real story is more interesting 
In 5G, IP allocation is tightly coupled with PDU Session establishment.
Here’s how it actually works:
UE requests a PDU Session
AMF forwards the request to SMF
SMF selects the appropriate UPF
Now comes the key part
The IP address can be allocated in multiple ways:
Directly by UPF (most common in deployments)
Via an external DHCP server
From a predefined IP pool managed by the operator
But here’s what makes 5G different:
IP allocation is not just “assignment”
It’s a policy-driven decision
Based on:
- Slice (S-NSSAI)
- DNN (Data Network Name)
- QoS requirements
Which means
Two users in the same network can get completely different IP handling behavior.
In simple words:
5G doesn’t just assign IPs —
it assigns them intelligently based on service context.
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