With the migration of real-time applications such as voice onto IP-based platforms, the existing IP network capabilities become inadequate to provide the quality-of- service (QoS) levels that the end-users are accustomed to. While new protocols such as DiffServ and MPLS allow some amount of traffic prioritization, guaranteed QoS requires admission control and dynamic resource management. Over-reservation has the advantage of infrequent variations but leads to wastage of resources. Under- reservation, on the other hand, does not meet the QoS expectations of the user flows. In this paper, we consider the architecture based on SIP (Session Initiation Protocol) over MPLS to provide control admission. In this architecture, we propose a new method to reserve optimally the bandwidth of an LSP (Label Switched Path), avoiding an excess of bandwidth renegotiations on the basis of prediction of future traffic.