Devices, methods, communication nodes, base stations, storage media, and other embodiments are provided for managing associations in a communication network. In one example embodiment, a New Radio (NR) node is configured for NR user-plane protocol communications between a master node (MN) and a secondary node (SN). The NR node is configured to generate a downlink (DL) user data message with downlink user data, initiate transmission of the DL user data message to a second node, and process a DL data delivery status message from the second node in response to the DL user data message. In various embodiments, polling and SCG split-bearer configurations are supported by such messaging. In some embodiments, packet data convergence protocol (PDCP) serial numbers are communicated for transmission and retransmission management. In some embodiments, DL configurations initiated by and SN are enabled, as well as UL configurations initiated by either an MN or an SN.