In the next-generation communication systems, the mobile terminals will be considerably more diverse than nowadays, andthe users will have a greater choice of access technologies, offering different QoS, security, cost, and so on. However, the “best” decision to select an interface and an access network from many other possible combinations has to be taken. This decision will dependon information such as: the user preferences, the requirements from applications, the device capabilities, the performances and capabilities of the available networks, the network operators constraints, etc. Thispaper describes an add-on middleware which deals with interface automatic configuration and selection. Our goal is twofold: to provideusers with “seamless” roaming between heterogeneous access networks, and to allow them to always stay connected through the “best” acces snetwork.