We are undergoing a revolution in the world of telecommunications. On one hand, the data access and distribution nets have increased their capacity thanks to high frequency optic fiber and radio links. On the other hand, the final user is no longer limited in mobility and capacity to the possibilities offered by a modem connected to a telephone line, as access to the net and to multimedia contents can be obtained from a mobile terminal. This means communications are no longer restricted to a specific physical space (the office at work or at home), but haven transformed into personal communications, wherever the person is.