The invention relates to a method, an interface device and system of computational devices for enabling starting of sessions from a first to a second network and to a computer program product performing the method. A name and service query is received (68) in an interface from a first computational device communicating via the first network concerning a second device in the second network. The query includes a first address of the second network in a first addressing realm. A second address and a service port number of the second device in a second addressing realm is looked up (70), the first address and a session port number are bound to the second address and the service port number (76), and the query is answered with a message comprising the first address and session port number (78).