LSP Preemption Policies for MPLS Traffic Engineering
When the establishment of a higher priority (Traffic Engineering Label Switched Path) TE LSP requires the preemption of a set of lower priority TE LSPs, a node has to make a local decision to select which TE LSPs will be preempted. The preempted LSPs are then rerouted by their respective Head-end Label Switch Router (LSR). This document presents a flexible policy that can be used to achieve different objectives: preempt the lowest priority LSPs; preempt the minimum number of LSPs; preempt the set of TE LSPs that provide the closest amount of bandwidth to the required bandwidth for the preempting TE LSPs (to minimize bandwidth wastage); preempt the LSPs that will have the maximum chance to get rerouted. Simulation results are given and a comparison among several different policies, with respect to preemption cascading, number of preempted LSPs, priority, wasted bandwidth and blocking probability is also included.