Abstract : The work presented in this thesis fits into the overall theme of adaptability of communication systems for QoS. The proposed contribution focuses on the dynamic adaptation of configurable transport protocols to meet the QoS requirements of distributed multimedia applications in the context of cooperative activities such as emergency operations. The first part was conducted in the framework of the NetQoS European project and concerns the proposal of a conceptual architecture for implementing adaptation at the Transport layer. Within a policy-based approach, our contribution has addressed the development of the architecture of the main component. This component is in charge of designing, adapting and enforcing operational policies to the entities responsible for direct QoS management, typically at Transport level. The second part focuses on the decision problem and proposes a novel approach for collaborative management of transport protocols for supporting adaptive QoS in cooperative group activities. The approach explored is to focus on transport connections with the highest priority to the detriment of lower priority connections, within the allowed sending rate. We consider the problem of allocating bandwidth between these connections. After defining the problem and the data required for its resolution, we formulate it as a linear programming problem solved by the simplex method. Two minimization criteria are considered and discussed. Finally, measures of performance achieved in simulation highlight the benefits and limitations of proposed solutions.