Section: 4.3.2.2 Xn Control Plane
Content: The Xn control plane interface (Xn-C) is defined between two NG-RAN nodes. The control plane protocol stack of the Xn interface is shown on Figure 4.3.2.2-1. The transport network layer is built on SCTP on top of IP. The application layer signalling protocol is referred to as XnAP (Xn Application Protocol). The SCTP layer provides the guaranteed delivery of application layer messages. In the transport IP layer point-to-point transmission is used to deliver the signalling PDUs. Figure 4.3.2.2-1: Xn-C Protocol Stack The Xn-C interface supports the following functions: - Xn interface management; - UE mobility management, including context transfer and RAN paging; - Dual connectivity. Further details of Xn-C can be found in TS 38.420[ NG-RAN; Xn general aspects and principles ]  [17].