In at least one embodiment, Xn interface may include an Xn user plane (Xn-U) interface and an Xn control plane (Xn-C) interface. In at least one embodiment, Xn-U may provide non-guaranteed delivery of user plane PDUs and support/provide data forwarding and flow control functionality. In at least one embodiment, Xn-C may provide management and error handling functionality, functionality to manage a Xn-C interface; mobility support for UE 2102 in a connected mode (e.g., CM-CONNECTED) including functionality to manage UE mobility for connected mode between one or more (R)AN node 2108. In at least one embodiment, mobility support may include context transfer from an old (source) serving (R)AN node 2108 to new (target) serving (R)AN node 2108; and control of user plane tunnels between old (source) serving (R)AN node 2108 to new (target) serving (R)AN node 2108.
In at least one embodiment, a protocol stack of a Xn-U may include a transport network layer built on Internet Protocol (IP) transport layer, and a GTP-U layer on top of a UDP and/or IP layer(s) to carry user plane PDUs. In at least one embodiment, Xn-C protocol stack may include an application layer signaling protocol (referred to as Xn Application Protocol (Xn-AP)) and a transport network layer that is built on an SCTP layer. In at least one embodiment, SCTP layer may be on top of an IP layer. In at least one embodiment, SCTP layer provides a guaranteed delivery of application layer messages. In at least one embodiment, in a transport IP layer point-to-point transmission is used to deliver signaling PDUs. In at least one embodiment, Xn-U protocol stack and/or a Xn-C protocol stack may be same or similar to an user plane and/or control plane protocol stack(s) shown and described herein.