Interconnection of Segment Routing Domains - Problem Statement and Solution Landscape
draft-farrel-spring-sr-domain-interconnect-04

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SPRING Working Group                                           A. Farrel
Internet-Draft                                                  J. Drake
Intended status: Informational                          Juniper Networks
Expires: December 15, 2018                                 June 13, 2018

   Interconnection of Segment Routing Domains - Problem Statement and
                           Solution Landscape
             draft-farrel-spring-sr-domain-interconnect-04

Abstract

   Segment Routing (SR) is a forwarding paradigm for use in MPLS and
   IPv6 networks.  It is intended to be deployed in discrete domains
   that may be data centers, access networks, or other networks that are
   under the control of a single operator and that can easily be
   upgraded to support this new technology.

   Traffic originating in one SR domain often terminates in another SR
   domain, but must transit a backbone network that provides
   interconnection between those domains.

   This document describes a mechanism for providing connectivity
   between SR domains to enable end-to-end or domain-to-domain traffic
   engineering.

   The approach described allows connectivity between SR domains,
   utilizes traffic engineering mechanisms (RSVP-TE or Segment Routing)
   across the backbone network, makes heavy use of pre-existing
   technologies, and requires the specification of very few additional
   mechanisms.

   This document provides some background and a problem statement,
   explains the solution mechanism, gives references to other documents
   that define protocol mechanisms, and provides examples.  It does not
   define any new protocol mechanisms.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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Farrel & Drake          Expires December 15, 2018               [Page 1]
Internet-Draft           SR Domain Interconnect                June 2018

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
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   This Internet-Draft will expire on December 15, 2018.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Problem Statement . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Solution Technologies . . . . . . . . . . . . . . . . . . . .   7
     3.1.  Characteristics of Solution Technologies  . . . . . . . .   7
   4.  Decomposing the Problem . . . . . . . . . . . . . . . . . . .   9
   5.  Solution Space  . . . . . . . . . . . . . . . . . . . . . . .  11
     5.1.  Global Optimization of the Paths  . . . . . . . . . . . .  11
     5.2.  Figuring Out the GWs at a Destination Domain for a Given
           Prefix  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     5.3.  Figuring Out the Backbone Egress ASBRs  . . . . . . . . .  12
     5.4.  Making use of RSVP-TE LSPs Across the Backbone  . . . . .  12
     5.5.  Data Plane  . . . . . . . . . . . . . . . . . . . . . . .  13
     5.6.  Centralized and Distributed Controllers . . . . . . . . .  15
   6.  BGP-LS Considerations . . . . . . . . . . . . . . . . . . . .  18
   7.  Worked Examples . . . . . . . . . . . . . . . . . . . . . . .  21
   8.  Label Stack Depth Considerations  . . . . . . . . . . . . . .  26
     8.1.  Worked Example  . . . . . . . . . . . . . . . . . . . . .  27
   9.  Gateway Considerations  . . . . . . . . . . . . . . . . . . .  28
     9.1.  Domain Gateway Auto-Discovery . . . . . . . . . . . . . .  28
     9.2.  Relationship to BGP Link State and Egress Peer
           Engineering . . . . . . . . . . . . . . . . . . . . . . .  29
     9.3.  Advertising a Domain Route Externally . . . . . . . . . .  29
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