The Use of Path Segment in SR-MPLS and MPLS Interworking
draft-xiong-mpls-path-segment-sr-mpls-interworking-02

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MPLS                                                            Q. Xiong
Internet-Draft                                                 G. Mirsky
Intended status: Informational                           ZTE Corporation
Expires: January 14, 2021                                       W. Cheng
                                                            China Mobile
                                                           July 13, 2020

        The Use of Path Segment in SR-MPLS and MPLS Interworking
         draft-xiong-mpls-path-segment-sr-mpls-interworking-02

Abstract

   This document illustrates the SR-MPLS and MPLS interworking scenarios
   to support end-to-end bidirectional tunnel across multiple domains
   with the use of Path Segments.

Status of This Memo

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   This Internet-Draft will expire on January 14, 2021.

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Internet-DraThe Use of Path Segment in SR-MPLS and MPLS Inter  July 2020

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 of Path Segments  . . . . . . . . . . . . . . .   5
     3.2.  Nesting of Path Segments  . . . . . . . . . . . . . . . .   6
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   7.  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".  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 [RFC8660].  SR-MPLS leverages
   the MPLS label stack to construct the SR path.

   IP/MPLS technology can be deployed in 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.  As
   defined in [RFC8402], the headend of an SR Policy binds a Binding
   Segment ID(B-SID) to its policy.  The B-SID could be bound to a SID
   List or selected path and used to stitch the SR list and the SR Label
   Switched Paths (LSP) across multiple domains.  The use of the B-SID
   is recommended to reduce the size of the label stack and stitch the
   SR LSPs.

   In some scenarios, for example, a mobile backhaul transport network,
   it is required to provide end-to-end bidirectional path across SR and
   MPLS networks.  The Path Segment as defined in
   [I-D.ietf-spring-mpls-path-segment] can be used to support
   bidirectional tunnel scenarios such as SR path Performance
   Measurement (PM), end-to-end 1+1 SR path protection and bidirectional
   SR paths correlation.

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