Signaling RSVP-TE Tunnels on a Shared MPLS Forwarding Plane
RFC 8577
Internet Engineering Task Force (IETF) H. Sitaraman
Request for Comments: 8577 V. Beeram
Category: Standards Track Juniper Networks
ISSN: 2070-1721 T. Parikh
Verizon
T. Saad
Cisco Systems
April 2019
Signaling RSVP-TE Tunnels on a Shared MPLS Forwarding Plane
Abstract
As the scale of MPLS RSVP-TE networks has grown, the number of Label
Switched Paths (LSPs) supported by individual network elements has
increased. Various implementation recommendations have been proposed
to manage the resulting increase in the amount of control-plane state
information.
However, those changes have had no effect on the number of labels
that a transit Label Switching Router (LSR) has to support in the
forwarding plane. That number is governed by the number of LSPs
transiting or terminated at the LSR and is directly related to the
total LSP state in the control plane.
This document defines a mechanism to prevent the maximum size of the
label space limit on an LSR from being a constraint to control-plane
scaling on that node. It introduces the notion of preinstalled
'per-TE link labels' that can be shared by MPLS RSVP-TE LSPs that
traverse these TE links. This approach significantly reduces the
forwarding-plane state required to support a large number of LSPs.
This couples the feature benefits of the RSVP-TE control plane with
the simplicity of the Segment Routing (SR) MPLS forwarding plane.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8577.
Sitaraman, et al. Standards Track [Page 1]
RFC 8577 RSVP-TE Shared Labels April 2019
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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described in the Simplified BSD License.
Sitaraman, et al. Standards Track [Page 2]
RFC 8577 RSVP-TE Shared Labels April 2019
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1. Requirements Language . . . . . . . . . . . . . . . . . . 6
3. Allocation of TE Link Labels . . . . . . . . . . . . . . . . 6
4. Segment Routed RSVP-TE Tunnel Setup . . . . . . . . . . . . . 6
5. Delegating Label Stack Imposition . . . . . . . . . . . . . . 8
5.1. Stacking at the Ingress . . . . . . . . . . . . . . . . . 8
5.1.1. Stack to Reach Delegation Hop . . . . . . . . . . . . 9
5.1.2. Stack to Reach Egress . . . . . . . . . . . . . . . . 10
5.2. Explicit Delegation . . . . . . . . . . . . . . . . . . . 11
5.3. Automatic Delegation . . . . . . . . . . . . . . . . . . 11
5.3.1. Effective Transport Label-Stack Depth (ETLD) . . . . 11
6. Mixing TE Link Labels and Regular Labels in an RSVP-TE Tunnel 13
7. Construction of Label Stacks . . . . . . . . . . . . . . . . 14
8. Facility Backup Protection . . . . . . . . . . . . . . . . . 14
8.1. Link Protection . . . . . . . . . . . . . . . . . . . . . 14
9. Protocol Extensions . . . . . . . . . . . . . . . . . . . . . 15
9.1. Requirements . . . . . . . . . . . . . . . . . . . . . . 15
9.2. Attribute Flags TLV: TE Link Label . . . . . . . . . . . 16
9.3. RRO Label Sub-object Flag: TE Link Label . . . . . . . . 16
9.4. Attribute Flags TLV: LSI-D . . . . . . . . . . . . . . . 16
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