This paper describes a real-time testbed emulating an all-IP B3G (Beyond 3rd Generation) network that includes UTRAN, GERAN, and WLAN emulation and the corresponding common core network based on DiffServ (Differentiated Services) technology and MPLS (Multiprotocol Label Switching). In such a complex scenario, considering real user applications and end-to-end (e2e) QoS, it is convenient to develop emulation platforms, where algorithms and applications can be tested in realistic conditions, not achievable by means of non-real-time simulations. Presented testbed will be used to evaluate three main objectives: to test the e2e QoS experienced by a user in a heterogeneous mobile environment with IP connectivity, to test and validate specific algorithms and mechanisms, and to evaluate real implementations of some subsystems.