There are provided measures for enabling/realizing external steering of access traffic multipath communication in a mobile communication system, e.g. an external access traffic multipath communication steering function. Some such measures include that a session management function element or instance in a mobile communication system initiates control of establishment of at least one user plane session for access traffic multipath communication, obtains communication information of an external steering function element or instance to be used for steering access traffic multipath communication in the at least one user plane session, creates access traffic multipath communication rules, forwarding action rules and multi access rules for access traffic multipath communication in the at least one user plane session, and provides the access traffic multipath communication rules and the communication information of the external steering function element or instance to the communication function element or instance.