Third generation mobile networks offers services diversified to users, while guaranteeing acceptable QoS (quality of service). This results in the setting up of strategies of increasingly complex management. UMTS (Universal Mobile Telecommunication System)/IP (Internet protocol) is a typical example of these new networks. This paper is thus centred on this technology, particularly on its multimedia domain and its strategies of control of session and resources pre-reservation. In order to offer the various services, by respecting the acceptable level of QoS required by the users, it is necessary to guarantee minimum QoS by service. This directs the RM (resources managers) towards the utilisation of pre-reservation protocol containing rule of policy such as the consensus protocol. This orientation is already under consideration by 3GPP which adopted protocols COPS and SIP for the procedures of authorization of session and domain resources IM of UMTS network. In such context, the subject of this study is focused consequently on setting up consensus protocol within the management and check procedures for multimedia services in UMTS/IP network. The study of the practicability and the consensus evaluation, constitute the principal contribution of this work.