The Use of Path Segment in SR-MPLS and MPLS Interworking
draft-xiong-mpls-path-segment-sr-mpls-interworking-01

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MPLS                                                          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-MPLS and MPLS Interworking
         draft-xiong-mpls-path-segment-sr-mpls-interworking-01

Abstract

   This document discusses the SR-MPLS and MPLS interworking scenarios
   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-MPLS and MPLS In 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.  SR-MPLS Interworking with MPLS  . . . . . . . . . . . . . . .   4
     3.1.  Stitching Model with Path Segment . . . . . . . . . . . .   5
     3.2.  Nesting Model with Path Segment . . . . . . . . . . . . .   6
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .   7
   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".  SR supports a 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.

   In some scenarios, for example, a mobile backhaul transport network,
   it is required to provide end-to-end bidirectional tunnel across
   multiple domains.  IP/MPLS technology can be deployed in these
   domains, which may serve as an access, aggregation, or core network.
   Further, using SR architecture, the IP/MPLS network may be upgraded
   to support the SR-MPLS technology.  As such transformation is
   performed incrementally, by one domain at the time, operators are
   faced with a requirement to support the interworking between MPLS and
   SR-MPLS networks at the boundaries to provide the end-to-end
   bidirectional service.  [I-D.ietf-spring-mpls-path-segment] defined a
   path segment identifier to support SR path PM, end-to-end 1+1 SR path
   protection and bidirectional SR paths correlation.

   As defined in [RFC8402], the headend of an SR Policy binds a Bingding
   Segment ID (BSID) to a 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 into an end-to-end SR path in the
   nesting model.  The BSID and path segment can be combined to achieve
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