A method of operating a terminal in a wireless communication system is provided. The method includes obtaining, from a radio link control (RLC) entity associated with a cell group of the terminal, information about a number of retransmissions of a packet, identifying whether packet duplication is activated, based on information indicating that the number of retransmissions of the packet reaches a maximum number of retransmissions of the packet, and transmitting, to a base station, a message indicating a failure of retransmission of the packet, based on a result of the identifying.