MPLS Traffic Engineering Soft Preemption

This document specifies Multiprotocol Label Switching (MPLS) Traffic Engineering Soft Preemption, a suite of protocol modifications extending the concept of preemption with the goal of reducing/ eliminating traffic disruption of preempted Traffic Engineering Label Switched Paths (TE LSPs). Initially MPLS RSVP-TE was defined supporting only immediate TE LSP displacement upon preemption. The utilization of a reroute request notification helps more gracefully mitigate the re-route process of preempted TE LSP. For the brief period soft preemption is activated, reservations (though not necessarily traffic levels) are in effect under-provisioned until the TE LSP(s) can be re-routed. For this reason, the feature is primarily but not exclusively interesting in MPLS enabled IP networks with Differentiated Services and Traffic Engineering capabilities.