It is evident that there exists a diverse range of network requirements for the support of both current and new distributed multimedia applications. Such requirements may include strictly defined bounds on the timely delivery of multimedia data, and a simple best-effort messaging service. Whatever the network requirements an application has, it is essential that network services can be offered to an application in a clear and consistent manner. Much research has already been carried out which examines and proposes approaches to network control, and in particular the employment of open signalling techniques. The work presented in this paper goes beyond the use of open interfacing for network control and management. We additionally propose the use of these techniques in both the control plane, through request/reply control interfaces and the data plane, through continuous interaction based stream interfaces. The interface abstractions proposed are principally aimed at the support of distributed multimedia applications and their strict Quality of Service (QoS) requirements over heterogeneous networks.