F1 Interface

In telecom networks, F1 is the 3GPP-defined interface between the gNB-CU and gNB-DU in a split RAN architecture. It is split into F1-C for control plane and F1-U for user plane, both typically secured with IPsec or DTLS.

Categories: Radio Access NetworkSignalingSecurity Controls

F1 Interface 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.

Signaling protocols carry the control-plane instructions that set up calls, register subscribers, hand over sessions and route SMS. SS7, Diameter, GTP-C and SIP are the four dominant families, and interconnect exposure of any of them is treated by GSMA FS.11 / FS.19 / FS.20 as a top-tier telecom risk.

To place F1 Interface in the wider telecom-security picture, review Xn Interface, SIP, 5G Reference Points, Sigma Rules, Inter-PLMN Security and Lawful Interception.

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