Signaling RSVP-TE Tunnels on a Shared MPLS Forwarding Plane

Abstract

As the scale of MPLS RSVP-TE networks has grown, so the number of\nLabel Switched Paths (LSPs) supported by individual network elements\nhas increased. Various implementation recommendations have been\nproposed to manage the resulting increase in control plane state.\nHowever, those changes have had no effect on the number of labels that\na transit Label Switching Router (LSR) has to support in the\nforwarding plane. That number is governed by the number of LSPs\ntransiting or terminated at the LSR and is directly related to the\ntotal LSP state in the control plane. This document defines a\nmechanism to prevent the maximum size of the label space limit on an\nLSR from being a constraint to control plane scaling on that node. It\nintroduces the notion of pre-installed per Traffic Engineering\n(TE) link labels that can be shared by MPLS RSVP-TE LSPs that\ntraverse these TE links. This approach significantly reduces the\nforwarding plane state required to support a large number of LSPs.\nThis couples the feature benefits of the RSVP-TE control plane with\nthe simplicity of the Segment Routing MPLS forwarding plane.