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