Framework for Loop-free convergence using oFIB
draft-ietf-rtgwg-ordered-fib-09

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Document Type Active Internet-Draft (rtgwg WG)
Last updated 2013-05-03 (latest revision 2013-01-31)
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Send notices to rtgwg-chairs@tools.ietf.org, draft-ietf-rtgwg-ordered-fib@tools.ietf.org
Network Working Group                                           M. Shand
Internet-Draft                                    Individual Contributor
Intended status: Informational                                 S. Bryant
Expires: August 4, 2013                                       S. Previdi
                                                             C. Filsfils
                                                           Cisco Systems
                                                             P. Francois
                                                Institute IMDEA Networks
                                                          O. Bonaventure
                                        Universite catholique de Louvain
                                                        January 31, 2013

             Framework for Loop-free convergence using oFIB
                    draft-ietf-rtgwg-ordered-fib-09

Abstract

   This document describes the framework of 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 forwarding information base
   (FIB) updates on the routers.

   This mechanism can be used in the case of non-urgent (management
   action) 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.  However the mechanism described
   in this document are purely illustrative of the general approach and
   do not constitute a protocol specification.  The document represents
   a snapshot of the work of the Routing Area Working Group at the time
   of publication and is published as a document of record.  Further
   work is needed before implementation or deployment.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the

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   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on August 4, 2013.

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Table of Contents

   1.  The Purpose of this Document . . . . . . . . . . . . . . . . .  4
   2.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  The required FIB update order  . . . . . . . . . . . . . . . .  6
     3.1.  Single Link Events . . . . . . . . . . . . . . . . . . . .  6
       3.1.1.  Link Down / Metric Increase  . . . . . . . . . . . . .  6
       3.1.2.  Link Up / Metric Decrease  . . . . . . . . . . . . . .  7
     3.2.  Multi-link events  . . . . . . . . . . . . . . . . . . . .  7
       3.2.1.  Router Down events . . . . . . . . . . . . . . . . . .  8
       3.2.2.  Router Up events . . . . . . . . . . . . . . . . . . .  8
       3.2.3.  Linecard Failure/Restoration Events  . . . . . . . . .  8
   4.  Applying ordered FIB updates . . . . . . . . . . . . . . . . .  8
     4.1.  Deducing the topology change . . . . . . . . . . . . . . .  8
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