Abstract: A traffic trunk can be characterized by administrator in optical traffic engineering, and an attribute of a traffic trunk is a parameter assigned to it which influences its behav-ioral characteristics. The priority attribute defines the relative importance of traffic trunks. If a constraint-based routing framework is used, then priorities become very important in im-plementations permitting preemption. Preemption is used to assure that high priority traffic trunks can always be routed through relatively favorable paths at connection establishment within a differentiated services environment. The main objective of this paper is to discuss how to preempt at Label Switch Path(LSP) establishment according to the attribute of traffic trunk, and two new schemes, Minimum Connection Bandwidth Interrupt Method(MCBIM) and Minimum Connection Number Interrupt Method (MCNIM), arc presented. They make full use of established LSP information to determine how to route an arriving request. Simulation results show that these two schemes can improve the performance of the network significantly.