Loop-free convergence using oFIB
draft-ietf-rtgwg-ordered-fib-06

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Last updated 2012-06-10
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Network Working Group                                           M. Shand
Internet-Draft                                    Individual Contributor
Intended status: Informational                                 S. Bryant
Expires: December 12, 2012                                    S. Previdi
                                                             C. Filsfils
                                                           Cisco Systems
                                                             P. Francois
                                                Institute IMDEA Networks
                                                          O. Bonaventure
                                        Universite catholique de Louvain
                                                           June 10, 2012

                    Loop-free convergence using oFIB
                    draft-ietf-rtgwg-ordered-fib-06

Abstract

   This document describes a mechanism for use in conjunction with link
   state routing protocols which prevents the transient loops which
   would otherwise occur during topology changes.  It does this by
   correctly sequencing the FIB updates on the routers.

   This mechanism can be used in the case of non-urgent link or node
   shutdowns and restarts or link metric changes.  It can also be used
   in conjunction with a fast re-route mechanism which converts a sudden
   link or node failure into a non-urgent topology change.  This is
   possible where a complete repair path is provided for all affected
   destinations.

   After a non-urgent topology change, each router computes a rank that
   defines the time at which it can safely update its FIB.  A method for
   accelerating this loop-free convergence process by the use of
   completion messages is also described.

   The technology described in this document has been subject to
   extensive simulation using real network topologies and costs, and
   pathological convergence behaviour.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

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Internet-Draft      Loop-free convergence using oFIB           June 2012

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   This Internet-Draft will expire on December 12, 2012.

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   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   described in the Simplified BSD License.

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Table of Contents

   1.  Conventions used in the document . . . . . . . . . . . . . . .  4
   2.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  The required FIB update order  . . . . . . . . . . . . . . . .  5
     3.1.  Single Link Events . . . . . . . . . . . . . . . . . . . .  5
       3.1.1.  Link Down / Metric Increase  . . . . . . . . . . . . .  5
       3.1.2.  Link Up / Metric Decrease  . . . . . . . . . . . . . .  6
     3.2.  Multi-link events  . . . . . . . . . . . . . . . . . . . .  7
       3.2.1.  Router Down events . . . . . . . . . . . . . . . . . .  7
       3.2.2.  Router Up events . . . . . . . . . . . . . . . . . . .  7
       3.2.3.  Linecard Failure/Restoration Events  . . . . . . . . .  7
   4.  Applying ordered FIB updates . . . . . . . . . . . . . . . . .  8
     4.1.  Deducing the topology change . . . . . . . . . . . . . . .  8
     4.2.  Deciding if ordered FIB updates applies  . . . . . . . . .  8
   5.  Computation of the ordering  . . . . . . . . . . . . . . . . .  9
     5.1.  Link or Router Down or Metric Increase . . . . . . . . . .  9
     5.2.  Link or Router Up or Metric Decrease . . . . . . . . . . . 10
   6.  Acceleration of Ordered Convergence  . . . . . . . . . . . . . 10
     6.1.  Construction of the waiting list and notification list . . 11
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