A method and system controls services in a packet data based communication network comprising terminal devices and service entities. In response to a change detected in the state of a connection between a terminal device and a gateway node, a service policy request for the terminal device is sent from the gateway node to a session control means. Service policies including service information indicating which service entities and in which order are to be utilized for providing services to the terminal device, are generated. Service policies are sent to the gateway node. At the service entities, services are provided.