Micro-loop Prevention by Introducing a Local Convergence Delay
RFC 8333

Document Type RFC - Proposed Standard (March 2018; No errata)
Last updated 2018-03-28
Replaces draft-litkowski-rtgwg-uloop-delay
Stream IETF
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Stream WG state Submitted to IESG for Publication
Document shepherd Chris Bowers
Shepherd write-up Show (last changed 2017-08-08)
IESG IESG state RFC 8333 (Proposed Standard)
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Responsible AD Alia Atlas
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IANA IANA review state Version Changed - Review Needed
IANA action state No IC
Internet Engineering Task Force (IETF)                      S. Litkowski
Request for Comments: 8333                                   B. Decraene
Category: Standards Track                                         Orange
ISSN: 2070-1721                                              C. Filsfils
                                                           Cisco Systems
                                                             P. Francois
                                                  Individual Contributor
                                                              March 2018

     Micro-loop Prevention by Introducing a Local Convergence Delay

Abstract

   This document describes a mechanism for link-state routing protocols
   that prevents local transient forwarding loops in case of link
   failure.  This mechanism proposes a two-step convergence by
   introducing a delay between the convergence of the node adjacent to
   the topology change and the network-wide convergence.

   Because this mechanism delays the IGP convergence, it may only be
   used for planned maintenance or when Fast Reroute (FRR) protects the
   traffic during the time between the link failure and the IGP
   convergence.

   The mechanism is limited to the link-down event in order to keep the
   mechanism simple.

   Simulations using real network topologies have been performed and
   show that local loops are a significant portion (>50%) of the total
   forwarding loops.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc8333.

Litkowski, et al.            Standards Track                    [Page 1]
RFC 8333          Micro-loop Prevention by Local Delay        March 2018

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Litkowski, et al.            Standards Track                    [Page 2]
RFC 8333          Micro-loop Prevention by Local Delay        March 2018

Table of Contents

   1. Introduction ....................................................4
   2. Terminology .....................................................4
      2.1. Acronyms ...................................................4
      2.2. Requirements Language ......................................5
   3. Side Effects of Transient Forwarding Loops ......................5
      3.1. FRR Inefficiency ...........................................5
      3.2. Network Congestion .........................................8
   4. Overview of the Solution ........................................9
   5. Specification ...................................................9
      5.1. Definitions ................................................9
      5.2. Regular IGP Reaction ......................................10
      5.3. Local Events ..............................................10
      5.4. Local Delay for Link-Down Events ..........................11
   6. Applicability ..................................................11
      6.1. Applicable Case: Local Loops ..............................12
      6.2. Non-applicable Case: Remote Loops .........................12
   7. Simulations ....................................................13
   8. Deployment Considerations ......................................14
   9. Examples .......................................................15
      9.1. Local Link-Down Event .....................................15
      9.2. Local and Remote Event ....................................19
      9.3. Aborting Local Delay ......................................21
   10. Comparison with Other Solutions ...............................23
      10.1. PLSN .....................................................23
      10.2. oFIB .....................................................24
   11. IANA Considerations ...........................................24
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