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 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.

Signaling protocols carry the control-plane messages that set up calls, register subscribers 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 as 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: each entry cross-references back to this page so you can walk the topic in either direction.

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Browse the full TelcoSec Glossary, the Ultimate Guide to Mobile Network Security, or the P1 Arsenal of telecom-security tools.