In this paper, we propose to tackle the joint dynamic routing and admission control (JRAC) problem for the IP traffic flows in MPLS networks without rerouting the already admitted flows. Two mathematical programming models are proposed for this problem.The numerical results have demonstrated that the proposed approach can offer less flow blocking rate and reduce significantly the mean end-to-end delay (or the mean end-to-end packet loss rate). The proposed approach is able to make the decision to admit or not a new flow rapidly (a few milliseconds).