A method for operating a network entity is provided in a wireless communications network. The method includes receiving a message comprising a temporary identifier of a mobile entity. The temporary identifier is used to temporarily identify the mobile entity. The temporary identifier includes an identifier of variable length which is used to identify a core network control entity which controls the mobile entity when connected to the network. The method determines a length indicator present in the temporary identifier, where the length indicator indicates a length of the identifier in the temporary identifier. The method determines the identifier in the temporary identifier based on the length indicator and the core network control entity based on the identifier, and transmits the received message to the determined core network control entity.