XnAP
Xn Application Protocol

XnAP is the control protocol used between gNBs to support a variety of RAN related procedures, such as establishing Dual Connectivity, coordination of Xn based handovers, data forwarding and RAN Paging. During the handover process, the source gNB will provide the target gNB with all the necessary information it needs to handle the subscriber, including security and User Plane connectivity information. For Dual Connectivity, the Master gNB will use XnAP to set up a Secondary gNB, with each gNB serving the user simultaneously.