N3 Reference Point (gNB to UPF)

Also known as: N3 reference point, N3 interface

N3 is the 3GPP reference point between the gNB (or ng-eNB) and the UPF that carries user-plane traffic over GTP-U inside the 5G core. Because N3 typically traverses the operator's transport network, it is a high-value target for lawful intercept, DDoS and topology-mapping attacks; IPsec is mandatory to protect N3 unless it runs over an equivalently trusted transport (3GPP TS 33.501).

Categories: Radio Access NetworkCore NetworkSignaling

N3 in context

The radio access network is the layer where mobile devices attach to the operator's infrastructure. Attacks in this layer include IMSI catching, rogue base stations, downgrade attacks and jamming, and defenses hinge on mutual authentication, integrity-protected signaling and Open RAN supply-chain hygiene.

The mobile core is where subscriber sessions, mobility and policy live. In 4G it is the EPC (MME, HSS, S/PGW); in 5G it is the Service-Based Architecture with AMF, SMF, UPF, AUSF, UDM and the NRF. Core exposure is the difference between a single-subscriber leak and a fleet-wide breach.

To place N3 in the wider telecom-security picture, review NGAP, IAP, IPsec, IMS-AKA, GTP-U and N2 Handover.