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

The mobile core carries subscriber sessions, mobility and policy. 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.

To place N3 in the wider telecom-security picture, review NGAP, IAP, IPsec, IMS-AKA, GTP-U and N2 Handover: each entry cross-references back to this page so you can walk the topic in either direction.

Related terms

Related topic hubs

  • GTP Security GTP-C/GTP-U threats across S5/S8, N3/N9 and GRX/IPX borders under GSMA FS.20.
  • GTP Firewall GSMA FS.20 GTP-C/GTP-U screening on GRX/IPX borders.
  • Signaling Firewall Unified SS7/Diameter/GTP/SMS signaling firewall framework.
  • 5G Security 5G SBA, SEPP, SUCI, 5G-AKA, N32 and service-based interface security.

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