5G • Core Network
N9 Interface
N9 Reference Point (Inter-UPF)
User plane tunnel between Intermediate UPF (I-UPF) and PDU Session Anchor UPF (PSA).
Technical Explanation
In distributed edge deployments or during mobility, multiple UPFs are chained. The N9 interface connects an Intermediate UPF located near the radio edge to the anchor UPF (PSA) via a GTP-U tunnel, enabling localized traffic breakout while maintaining anchor IP continuity.
Key Functions
- Tunnels user plane traffic between chained UPF nodes
- Connects Edge Intermediate UPFs to Central Anchor UPFs (PSA)
- Preserves IP address continuity during edge mobility relocations
Specifications
3GPP TS 23.501, TS 29.281
Interfaces
N9
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