The Use of Path Segment in SR Inter-domain Scenarios
draft-xiong-spring-path-segment-sr-inter-domain-01

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SPRING                                                        Quan Xiong
Internet-Draft                                               Greg Mirsky
Intended status: Standards Track                         ZTE Corporation
Expires: April 19, 2020                                   Weiqiang Cheng
                                                            China Mobile
                                                        October 17, 2019

          The Use of Path Segment in SR Inter-domain Scenarios
           draft-xiong-spring-path-segment-sr-inter-domain-01

Abstract

   This document discusses the inter-domain scenarios for SR-MPLS
   networks and proposes the solution with the use of path segments.

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   This Internet-Draft will expire on April 19, 2020.

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Quan Xiong, et al.       Expires April 19, 2020                 [Page 1]
Internet-DrafThe Use of Path Segment in SR Inter-domain Sce October 2019

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions used in this document . . . . . . . . . . . . . .   3
     2.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Requirements Language . . . . . . . . . . . . . . . . . .   4
   3.  Path Segment for SR-MPLS Inter-domain . . . . . . . . . . . .   4
     3.1.  Inter-domain Path Segment . . . . . . . . . . . . . . . .   4
     3.2.  End-to-end Path Segment . . . . . . . . . . . . . . . . .   4
   4.  SR-MPLS Inter-domain Scenarios  . . . . . . . . . . . . . . .   5
     4.1.  Stitching Inter-domain with i-Path  . . . . . . . . . . .   5
     4.2.  Nesting Inter-domain with e-Path  . . . . . . . . . . . .   6
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   Segment Routing (SR) leverages the source routing paradigm.  A node
   steers a packet through an SR Policy instantiated as an ordered list
   of instructions called "segments".  A segment can represent any
   instruction, topological or service based.  A segment can have a
   semantic local to an SR node or global within an SR domain.  SR
   supports per-flow explicit routing while maintaining per-flow state
   only at the ingress nodes of the SR domain.  Segment Routing can be
   instantiated on MPLS data plane which is referred to as SR-MPLS
   [I-D.ietf-spring-segment-routing-mpls].  SR-MPLS leverages the MPLS
   label stack to construct the SR path.

   [I-D.ietf-spring-mpls-path-segment] defines a path segment identifier
   to support bidirectional path correlation for transport network.  In
   the multi-domain scenarios, the SR bidirectional end-to-end tunnel
   MAY be established with the use of path segments.  The SR-MPLS inter-
   domain models include the stitching and nesting inter-domain models.
   Path segment MAY be used to indicate the inter-domain path or the
   end-to-end path and correlate the inter-domain paths or end-to-end
   unidirectional paths to achieve the path monitoring.

   As defined in [RFC8402], the headend of an SR Policy binds a Binding
   Segment ID(BSID) to its policy.  The BSID could be bound to a SID
   List or selected path and used to stitch the service across multiple
   domains.  For example, as discussed in Section 3
   [I-D.ietf-spring-mpls-path-segment], the BSID can be used to identify
   a sub-path and stitched them to an end-to-end SR path in the nesting