The invention is concerned with a method in a communication network for invoking services, the communication network including at least one or more terminals and at least two service entities. In the method the terminal deduces necessary support and service components for providing an end-user service. A set of configuration requests is constructed at the terminal, each associated with one or more specific service entities for invoking individual service components composing a service. Each configuration request is forwarded from the terminal to the service entity/entities indirectly, by using a special network support function for configuring service entities--the assembler unit of the invention--or directly in a way, which is chosen in accordance with pre-defined criteria. The invention is also concerned with a communication network, a terminal and an assembler unit to perform the method.