Control entity and method for setting up a session in a communications network, subscriber database and communications network The invention relates to a control entity for setting up a session in a communications network, comprising an input device for receiving a request to set up a session in the communications network, a processor unit for processing the request, and an output device for sending messages. The control entity further comprising or having access to a memory for storing information. The processor unit is arranged to determine if the request comprises a valid Communication Service Identifier, CSI, the Communication Service Identifier identifying the type of communication service of the session that is to be established over the communications network. And if the request does not comprise a valid Communication Service Identifier to execute a default CSI procedure using default CSI information stored in the memory.