Segment Routing MPLS Interworking with LDP
RFC 8661
| Document | Type | RFC - Proposed Standard (December 2019; No errata) | |
|---|---|---|---|
| Authors | Ahmed Bashandy , Clarence Filsfils , Stefano Previdi , Bruno Decraene , Stephane Litkowski | ||
| Last updated | 2019-12-06 | ||
| Replaces | draft-filsfils-spring-segment-routing-ldp-interop | ||
| Stream | Internet Engineering Task Force (IETF) | ||
| Formats | plain text html xml pdf htmlized (tools) htmlized bibtex | ||
| Reviews | |||
| Stream | WG state | Submitted to IESG for Publication | |
| Document shepherd | Rob Shakir | ||
| Shepherd write-up | Show (last changed 2017-07-12) | ||
| IESG | IESG state | RFC 8661 (Proposed Standard) | |
| Action Holders |
(None)
|
||
| Consensus Boilerplate | Yes | ||
| Telechat date | |||
| Responsible AD | Alvaro Retana | ||
| Send notices to | aretana.ietf@gmail.com, Rob Shakir <robjs@google.com> | ||
| IANA | IANA review state | Version Changed - Review Needed | |
| IANA action state | No IANA Actions | ||
Internet Engineering Task Force (IETF) A. Bashandy, Ed.
Request for Comments: 8661 Individual
Category: Standards Track C. Filsfils, Ed.
ISSN: 2070-1721 Cisco Systems, Inc.
S. Previdi
Huawei Technologies
B. Decraene
S. Litkowski
Orange
December 2019
Segment Routing MPLS Interworking with LDP
Abstract
A Segment Routing (SR) node steers a packet through a controlled set
of instructions, called segments, by prepending the packet with an SR
header. A segment can represent any instruction, topological or
service based. SR allows enforcing a flow through any topological
path while maintaining per-flow state only at the ingress node to the
SR domain.
The Segment Routing architecture can be directly applied to the MPLS
data plane with no change in the forwarding plane. This document
describes how Segment Routing MPLS operates in a network where LDP is
deployed and in the case where SR-capable and non-SR-capable nodes
coexist.
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/rfc8661.
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
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction
1.1. Requirements Language
2. SR-LDP Ships-in-the-Night Coexistence
2.1. MPLS2MPLS, MPLS2IP, and IP2MPLS Coexistence
3. SR and LDP Interworking
3.1. LDP to SR
3.1.1. LDP to SR Behavior
3.2. SR to LDP
3.2.1. Segment Routing Mapping Server (SRMS)
3.2.2. SR to LDP Behavior
3.2.3. Interoperability of Multiple SRMSes and Prefix-SID
Advertisements
4. SR-LDP Interworking Use Cases
4.1. SR Protection of LDP-Based Traffic
4.2. Eliminating Targeted LDP Sessions
4.3. Guaranteed FRR Coverage
4.4. Inter-AS Option C, Carrier's Carrier
5. IANA Considerations
6. Manageability Considerations
6.1. SR and LDP Coexistence
6.2. Data-Plane Verification
7. Security Considerations
8. References
8.1. Normative References
8.2. Informative References
Appendix A. Migration from LDP to SR
Acknowledgements
Contributors
Authors' Addresses
1. Introduction
Segment Routing, as described in [RFC8402], can be used on top of the
MPLS data plane without any modification as described in [RFC8660].
Segment Routing control plane can coexist with current label
distribution protocols such as LDP [RFC5036].
This document outlines the mechanisms through which SR interworks
with LDP in cases where a mix of SR-capable and non-SR-capable
routers coexist within the same network and more precisely in the
same routing domain.
Section 2 describes the coexistence of SR with other MPLS control-
plane protocols. Section 3 documents the interworking between SR and
LDP in the case of nonhomogeneous deployment. Section 4 describes
how a partial SR deployment can be used to provide SR benefits to
LDP-based traffic including a possible application of SR in the
context of interdomain MPLS use cases. Appendix A documents a method
to migrate from LDP to SR-based MPLS tunneling.
Typically, an implementation will allow an operator to select
(through configuration) which of the described modes of SR and LDP
coexistence to use.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
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