Distributed management of exclusive resources in collaborative multimedia systems

Collaborative multimedia systems encompass many Internet applications such as desktop conferencing and interactive distance learning. These applications often contain resources, such as audio, video and shared applications, that must be accessed exclusively by one participant at a time. We present a distributed algorithm that manages the access to these exclusive resources. The algorithm is based on the assumption that the transport layer provides reliable multicasting. Resources are classified into two main classes: primitive and composite. Composite resources consist of a set of two or more primitive resources. A token is associated with each resource unit, and a participant must obtain the resource´s token before using the resource. To use a resource, certain permissions may be needed from certain entities such as the session coordinator, the current resource holder and, in some cases, the resource itself. The algorithm guarantees that at any given time, the resource is held by exactly one participant and the token of any resource will never be lost under all possible failure conditions