This paper deals with the problem of providing Quality of Service (QoS) in heterogeneous networks. It proposes an approach that is able to build a generic signalling control protocol to offer a guaranteed QoS in a set of heterogeneous Internet domains. The given protocol manages during the admission control phase the end-to-end requests of the QoS connections with respect to their QoS requirements. The idea is to show that a minimum amount of information is needed to implement the resulting controlled end-to-end paths. In the meantime, paths within each domain have no constraints, our signalling being independent of the intra domain routing protocol. The purpose of this approach is to be able to give to all users and to all domain providers the maximum degree of freedom to implement the most efficient solutions for their domains.