Topology Independent Fast Reroute using Segment Routing
draft-francois-rtgwg-segment-routing-ti-lfa-01

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Network Working Group                                    Pierre Francois
Internet-Draft                                         Clarence Filsfils
Intended status: Standards Track                          Ahmed Bashandy
Expires: November 18, 2016                           Cisco Systems, Inc.
                                                          Bruno Decraene
                                                      Stephane Litkowski
                                                                  Orange
                                                            May 17, 2016

        Topology Independent Fast Reroute using Segment Routing
             draft-francois-rtgwg-segment-routing-ti-lfa-01

Abstract

   This document presents Topology Independent Loop-free Alternate Fast
   Re-route (TI-LFA), aimed at providing protection of node and
   adjacency segments within the Segment Routing (SR) framework.  This
   Fast Re-route (FRR) behavior builds on proven IP-FRR concepts being
   LFAs, remote LFAs (RLFA), and remote LFAs with directed forwarding
   (DLFA).  It extends these concepts to provide guaranteed coverage in
   any IGP network.  A key aspect of TI-LFA is the FRR path selection
   approach establising protection over post-convergence paths from the
   point of local repair, dramatically reducing the operational need to
   control the tie-breaks among various FRR options.

Status of this Memo

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   This Internet-Draft will expire on November 18, 2016.

Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

Pierre Francois, et al.  Expires November 18, 2016              [Page 1]
Internet-Draft                  SR TI-LFA                       May 2016

   This document is subject to BCP 78 and the IETF Trust's Legal
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   (http://trustee.ietf.org/license-info) in effect on the date of
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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Intersecting P-Space and Q-Space with post-convergence
       paths  . . . . . . . . . . . . . . . . . . . . . . . . . . . .  5
     3.1.  P-Space property computation for a resource X  . . . . . .  5
     3.2.  Q-Space property computation for a link S-F, over
           post-convergence paths . . . . . . . . . . . . . . . . . .  6
     3.3.  Q-Space property computation for a set of links
           adjacent to S, over post-convergence paths . . . . . . . .  6
     3.4.  Q-Space property computation for a node F, over
           post-convergence paths . . . . . . . . . . . . . . . . . .  6
   4.  TI-LFA Repair Tunnel . . . . . . . . . . . . . . . . . . . . .  6
     4.1.  The repair node is a direct neighbor . . . . . . . . . . .  7
     4.2.  The repair node is a PQ node . . . . . . . . . . . . . . .  7
     4.3.  The repair is a Q node, neighbor of the last P node  . . .  7
     4.4.  Connecting distant P and Q nodes along
           post-convergence paths . . . . . . . . . . . . . . . . . .  7
   5.  Protecting segments  . . . . . . . . . . . . . . . . . . . . .  7
     5.1.  The active segment is a node segment . . . . . . . . . . .  7
     5.2.  The active segment is an adjacency segment . . . . . . . .  8
       5.2.1.  Protecting [Adjacency, Adjacency] segment lists  . . .  8
       5.2.2.  Protecting [Adjacency, Node] segment lists . . . . . .  8
     5.3.  Protecting SR policy midpoints against node failure  . . .  9
       5.3.1.  Protecting {F, T, D} or {S->F, T, D} . . . . . . . . .  9
       5.3.2.  Protecting {F, F->T, D} or {S->F, F->T, D} . . . . . .  9
   6.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10

Pierre Francois, et al.  Expires November 18, 2016              [Page 2]
Internet-Draft                  SR TI-LFA                       May 2016