A method by a user plane function (UPF) is provided. The method includes receiving, from a session management function (SMF), a first message to request at least one quality of service (QoS) monitoring for a data flow, the first message including information on a packet transmission delay and information on a first QoS value related to a threshold for the packet transmission delay, sending, to a base station, a monitoring packet, determining a second QoS value corresponding to a delay between the UPF and the base station, identifying whether a QoS event is triggered based on the first QoS value and the second QoS value, and sending, to the SMF, a second message in case that the QoS event is triggered.