A method performed by a base station in a communication system, the method comprising: transmitting , to a network node via an Sx interface, which is an interface between the base station and the network node, a first SxAP message including a radio resource control, RRC, message received from a terminal and an Sx interface based identifier allocated by the base station to identify the terminal over the Sx interface, wherein the RRC message is transmitted to the network node without being interpreted by the base station; receiving , from the network node via the Sx interface, a second SxAP message including an identifier to be transmitted to the terminal and associated with a random access procedure, an Sx interface based identifier allocated by the network node to identify the terminal over the Sx interface, an identifier of a data radio bearer, and uplink tunnel information for data reception associated with the data radio bearer on the Sx interface, wherein the uplink tunnel information comprises an internet protocol, IP, address and information for identifying an uplink tunnel; and transmitting , to the network node via the Sx interface, a third SxAP message as a response to the second SxAP message, the third SxAP message including an identifier of a successfully established data radio bearer and downlink tunnel information for data reception associated with the data radio bearer on the Sx interface, wherein the downlink tunnel information comprises an IP address and information for identifying a downlink tunnel, wherein the base station includes a radio link control, RLC, layer, a medium access control, MAC, layer and a physical, PHY, layer, and wherein the network node includes an RRC layer and a packet data convergence protocol, PDCP, layer. transmitting , to a network node via an Sx interface, which is an interface between the base station and the network node, a first SxAP message including a radio resource control, RRC, message received from a terminal and an Sx interface based identifier allocated by the base station to identify the terminal over the Sx interface, wherein the RRC message is transmitted to the network node without being interpreted by the base station; receiving , from the network node via the Sx interface, a second SxAP message including an identifier to be transmitted to the terminal and associated with a random access procedure, an Sx interface based identifier allocated by the network node to identify the terminal over the Sx interface, an identifier of a data radio bearer, and uplink tunnel information for data reception associated with the data radio bearer on the Sx interface, wherein the uplink tunnel information comprises an internet protocol, IP, address and information for identifying an uplink tunnel; and transmitting , to the network node via the Sx interface, a third SxAP message as a response to the second SxAP message, the third SxAP message including an identifier of a successfully established data radio bearer and downlink tunnel information for data reception associated with the data radio bearer on the Sx interface, wherein the downlink tunnel information comprises an IP address and information for identifying a downlink tunnel, wherein the base station includes a radio link control, RLC, layer, a medium access control, MAC, layer and a physical, PHY, layer, and wherein the network node includes an RRC layer and a packet data convergence protocol, PDCP, layer. <EOS>