Measures for use in processing data in a telecommunications network. A request message is received in relation to establishment of a communication session involving a given subscriber. Subscriber configuration data is received in relation to the establishment. The subscriber configuration data includes a set of one or more trigger points at which one or more application services should be invoked in relation to communication sessions for the given subscriber. At least one trigger point from the set of trigger points is encoded into an identifier for the communication session within the request message. The request message including the identifier for the communication session in which the at least one trigger point has been encoded is transmitted.