A method for controlling traffic transmission in a control server of a communication system includes receiving information of an application corresponding to a network session; receiving, from a network node, information related to a network congestion condition with respect to the network session; and controlling a traffic flow of the network session on the basis of a traffic quality policy which is determined on the basis of the received application information and/or the information related to the network congestion condition. The control server can receive, from an electronic device, the application information of an application corresponding to the network session. The control server can determine the quality policy on the basis of the application information. The control sever can control the traffic flow of the network session according to the quality policy.