A method for access traffic steering, switching, and splitting (ATSSS) in a network and a network entity for performing the method are disclosed. When the execution of the ATSSS from the first access network to the second access network is determined, a first message requesting the SMF to confirm the connection state of the terminals for the first access network and the second access network may be transmitted to AMF. The SMF may receive information on the connection state of the terminal from the AMF.