XnAP (Xn Application Protocol)

Also known as: Xn Application Protocol

XnAP is the 3GPP signalling protocol between neighbouring 5G gNBs over the Xn interface (TS 38.423). It supports inter-gNB handover, dual connectivity, UE context transfer and load management, allowing the RAN to make mobility decisions without always involving the AMF. It is the 5G equivalent of LTE's X2AP.

Categories: Radio Access NetworkSignalingProtocols and Standards

XnAP 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 XnAP in the wider telecom-security picture, review MTSI, 1G, 5G SA, 5GNR, 6G and ADSL — each entry cross-references back to this page so you can walk the topic in either direction.

Related terms

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