Disclosed are a communication scheme and a system thereof for converging an IoT technology and a 5G communication system for supporting a high data transmission rate beyond that of a 4G system. The disclosure can be applied to intelligent services (for example, services related to a smart home, smart building, smart city, smart car, connected car, health care digital education, retail business, security, and safety) based on the 5G communication technology and the IoT-related technology. Disclosed are a method and an apparatus for supporting a multimedia telephony (MMTEL) system, a method and an apparatus for efficiently operating a new QoS layer (service data access protocol (SDAP)), and a method and an apparatus for efficiently supporting a bandwidth part in the SCell in carrier aggregation or in dual connectivity.