Loop avoidance using Segment Routing
draft-bashandy-rtgwg-segment-routing-uloop-04

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Last updated 2018-09-24
Replaces draft-francois-rtgwg-segment-routing-uloop
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Network Working Group                                    Ahmed Bashandy
Internet Draft                                        Clarence Filsfils
Intended status: Standards Track                    Cisco Systems, Inc.
Expires: March 2019                                  Stephane Litkowski
                                                                 Orange
                                                        Pierre Francois
                                                 Individual Contributor
                                                     September 24, 2018

                  Loop avoidance using Segment Routing
              draft-bashandy-rtgwg-segment-routing-uloop-04

Abstract

This document presents a mechanism aimed at providing loop avoidance
in the case of IGP network convergence event.  The solution relies on
the temporary use of SR policies ensuring loop-freeness over the
post-convergence paths from the converging node to the destination.

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Bashandy                Expires March 24, 2019                 [Page 1]
Internet-Draft            SR Loop Avoidance              September 2018

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Table of Contents

   1. Introduction...................................................2
      1.1. Conventions used in this document.........................3
   2. Loop-free two-stage convergence process........................4
   3. Computing loop-avoiding SR policies............................5
   4. Analysis.......................................................5
      4.1. Incremental Deployment....................................5
      4.2. No impact on capacity planning............................5
   5. Security Considerations........................................6
   6. IANA Considerations............................................6
   7. Contributors...................................................6
   8. References.....................................................6
      8.1. Normative References......................................6
      8.2. Informative References....................................6
   9. Acknowledgments................................................6

1. Introduction

   Forwarding loops happen during the convergence of the IGP, as a
   result of transient inconsistency among forwarding states of the
   nodes of the network.

   This document provides a mechanism leveraging Segment Routing to
   ensure loop-freeness during the IGP reconvergence process following
   a link-state change event.

Bashandy                Expires March 24, 2019                 [Page 2]
Internet-Draft            SR Loop Avoidance              September 2018

   We use Figure 1 to illustrate the mechanism.  In this scenario, all
   the IGP link metrics are 1, excepted R3-R4 whose metric is 100, and
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