MPLS Traffic Engineering Soft Preemption

This document specifies Multiprotocol Label Switching (MPLS) TrafficEngineering Soft Preemption, a suite of protocol modificationsextending the concept of preemption with the goal of reducing/eliminating traffic disruption of preempted Traffic Engineering LabelSwitched Paths (TE LSPs). Initially MPLS RSVP-TE was definedsupporting only immediate TE LSP displacement upon preemption. Theutilization of a reroute request notification helps more gracefullymitigate the re-route process of preempted TE LSP. For the briefperiod soft preemption is activated, reservations (though notnecessarily traffic levels) are in effect under-provisioned until theTE LSP(s) can be re-routed. For this reason, the feature is primarilybut not exclusively interesting in MPLS enabled IP networks withDifferentiated Services and Traffic Engineering capabilities.