In order to improve the communication efficiency without using multi-antennae terminals, cooperative communications implement one or several single antenna relays to assist the transmission between a source and a destination. The design of such a cooperative network, involves several layers of the OSI model. Transmission and multiplexing techniques are addressed at the physical layer whereas the management of the cooperative network (activation of a cooperative mode, selection of relays) is done at the Medium Access Control (MAC) layer and the layers above. After an overview of protocols that have been designed in this domain, we propose an original framework of a cooperative network, at the system level. Inspired from models of the ITU normative organization, our cooperative network model is based on two planes: a data plane and a control plane. A validation of the framework is given by modeling an existing cooperative MAC protocol.