Segment-Routing over Forwarding Adjacency Links
draft-saad-sr-fa-link-00

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SPRING Working Group                                             T. Saad
Internet-Draft                                                 V. Beeram
Intended status: Informational                                  C. Barth
Expires: May 5, 2020                              Juniper Networks, Inc.
                                                       November 02, 2019

            Segment-Routing over Forwarding Adjacency Links
                        draft-saad-sr-fa-link-00

Abstract

   Label Switched Paths (LSPs) set up in Multiprotocol Label Switching
   (MPLS) networks can be used to form Forwarding Adjacency (FA) links
   that carry traffic in those networks.  An FA link can be assigned
   Traffic Engineering (TE) parameters that allow other LSR(s) to
   include it in their constrained path computation.  FA link(s) can be
   also assigned Segment-Routing (SR) segments that enable the steering
   of traffic on to the associated FA link(s).  The TE and SR attributes
   of an FA link can be advertised using known link state protocols.
   This document elaborates on the usage of FA link(s) and their
   attributes in SR enabled networks.

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   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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   (https://trustee.ietf.org/license-info) in effect on the date of

Saad, et al.               Expires May 5, 2020                  [Page 1]
Internet-Draft              SR over FA Links               November 2019

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Forwarding Adjacency Links  . . . . . . . . . . . . . . . . .   3
     3.1.  Creation and Management . . . . . . . . . . . . . . . . .   3
     3.2.  Link Flooding . . . . . . . . . . . . . . . . . . . . . .   4
     3.3.  Underlay LSP(s) . . . . . . . . . . . . . . . . . . . . .   4
     3.4.  State Changes . . . . . . . . . . . . . . . . . . . . . .   4
     3.5.  TE Parameters . . . . . . . . . . . . . . . . . . . . . .   5
     3.6.  Link Local and Remote Identifiers . . . . . . . . . . . .   5
   4.  Segment-Routing over FA Links . . . . . . . . . . . . . . . .   6
     4.1.  SR IGP Segments for FA  . . . . . . . . . . . . . . . . .   6
       4.1.1.  Parallel Adjacencies  . . . . . . . . . . . . . . . .   7
     4.2.  SR BGP Segments for FA  . . . . . . . . . . . . . . . . .   7
     4.3.  Applicability to Interdomain  . . . . . . . . . . . . . .   8
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   7.  Acknowledgement . . . . . . . . . . . . . . . . . . . . . . .   8
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   To improve scalability in Multi-Protocol Label Switching (MPLS)
   networks, it may be useful to create a hierarchy of LSPs as
   Forwarding Adjacencies (FA).  The concept of FA link(s) and FA-LSP(s)
   was introduced in [RFC4206].

   In Segment-Routing (SR), this is particularly useful for two main
   reasons.

   First, it allows the stitching of sub-path(s) so as to realize an
   end-to-end SR path.  Each sub-path can be represented by a FA link
   that is supported by one or more underlying LSP(s).  The underlying
   LSP(s) that support an FA link can be setup using different
   technologies- including RSVP-TE, LDP, and SR.  The sub-path(s), or FA
   link(s) in this case, can possibly interconnect multiple
   administrative domains, allowing each FA link within a domain to use
   a different technology to setup the underlying LSP(s).
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