1. A method for use by an apparatus of a communication network, the method comprising: receiving a session establishment request for a user or user equipment attaching to the communication network; detecting that the user or user equipment belongs to a usage group, based on group identity information that is allocated to the user or user equipment and identifies the usage group, wherein the detecting comprises requesting the group identity information from a database based on an identifier of the user or user equipment received with the session establishment request for the user or user equipment; detecting, based on the group identity information, whether or not a first rules function out of several rules functions has been allocated to another user or user equipment of the usage group; in case it is detected that the first rules function has been allocated to another user or user equipment of the usage group, selecting, for the user or user equipment, the first rules function and sending a request message to request the session establishment from the first rules function or sending a redirect message to redirect the user or user equipment to the first rules function, for requesting the session establishment from the first rules function.