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 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 XnAP in the wider telecom-security picture, review NGAP, S1AP, Diameter, Xn Interface, RANAP and AMF.

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