A packet switched (PS) core network (CN) supporting several quality of services levels, comprising at least a serving node (SGSN), a gateway node (GGSN), a home location register (HLR), a short message service gateway and interworking unit (SMS-GMSC, SMS-IWMSC), charging gateway functionality (CGF), and a public data network (PDN) comprising an application server (AS). The core network is adapted for carrying out a packet data protocol (PDP) context activation in which a PDP address is assigned to a mobile station and in which a given quality of service is assigned through the network in a communication session between the mobile station and the application processor in question, whereby the application server (AS) initiates a context activation in which the QoS is seeked altered for the mobile station.