In an advisable network scenario the peripheral non-DiffServ access networks, mainly IntServ networks with the RSVP signalling protocol but the approach could be generalized (H.323, SIP, MPEG-4, etc.), are connected to a DiffServ core network (as for the access network, the approach could be generalised to an MPLS core network). In such a scenario the key elements are the Edge and Border Routers, which manage the interoperability between diverse domains. In our solution the functionality of both devices are unified within a single element called X-DiffServ Border Router (X-DS BR, where X is for a generic access network architecture, e.g. IntServ). Our solution focuses on the possibility of integrating diverse protocols used in the Access Network. In a general scenario, applications speaking different "languages" may coexist, and the access point of the Core Network, that is the X-DS Border Router, must understand all these languages. For this purpose, an extension (a new unified client-type) to COPS protocol was defined. This innovative mechanism is used to transport admission control messages despite of the signalling protocol (e.g. RSVP, SIP, H.323) and from the QoS protocol (e.g. DiffServ/MPLS). Therefore a single client could be supported by the Bandwidth Broker while the complexity is shifted on the border router where a appropriate Inter Working Unit (IWU) is used to map protocol specific messages into generalised client messages.