Shortest Path First (SPF) Back-Off Delay Algorithm for Link-State IGPs
RFC 8405

Document Type RFC - Proposed Standard (June 2018; No errata)
Last updated 2018-06-25
Replaces draft-decraene-rtgwg-backoff-algo
Stream IETF
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Stream WG state Submitted to IESG for Publication
Document shepherd Uma Chunduri
Shepherd write-up Show (last changed 2018-01-22)
IESG IESG state RFC 8405 (Proposed Standard)
Consensus Boilerplate Yes
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Responsible AD Alia Atlas
Send notices to Uma Chunduri <uma.chunduri@huawei.com>
IANA IANA review state Version Changed - Review Needed
IANA action state No IC
Internet Engineering Task Force (IETF)                       B. Decraene
Request for Comments: 8405                                        Orange
Category: Standards Track                                   S. Litkowski
ISSN: 2070-1721                                  Orange Business Service
                                                              H. Gredler
                                                            RtBrick Inc.
                                                               A. Lindem
                                                           Cisco Systems
                                                             P. Francois

                                                               C. Bowers
                                                  Juniper Networks, Inc.
                                                               June 2018

 Shortest Path First (SPF) Back-Off Delay Algorithm for Link-State IGPs

Abstract

   This document defines a standard algorithm to temporarily postpone or
   "back off" link-state IGP Shortest Path First (SPF) computations.
   This reduces the computational load and churn on IGP nodes when
   multiple temporally close network events trigger multiple SPF
   computations.

   Having one standard algorithm improves interoperability by reducing
   the probability and/or duration of transient forwarding loops during
   the IGP convergence when the IGP reacts to multiple temporally close
   IGP events.

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/rfc8405.

Decraene, et al.             Standards Track                    [Page 1]
RFC 8405              SPF Back-Off Delay Algorithm             June 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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  High-Level Goals  . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Definitions and Parameters  . . . . . . . . . . . . . . . . .   4
   4.  Principles of the SPF Delay Algorithm . . . . . . . . . . . .   5
   5.  Specification of the SPF Delay State Machine  . . . . . . . .   6
     5.1.  State Machine . . . . . . . . . . . . . . . . . . . . . .   6
     5.2.  States  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     5.3.  Timers  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     5.4.  FSM Events  . . . . . . . . . . . . . . . . . . . . . . .   7
   6.  Parameters  . . . . . . . . . . . . . . . . . . . . . . . . .   9
   7.  Partial Deployment  . . . . . . . . . . . . . . . . . . . . .  10
   8.  Impact on Micro-loops . . . . . . . . . . . . . . . . . . . .  11
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  11
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  11
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  11
     11.2.  Informative References . . . . . . . . . . . . . . . . .  11
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  13
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  13

Decraene, et al.             Standards Track                    [Page 2]
RFC 8405              SPF Back-Off Delay Algorithm             June 2018

1.  Introduction

   Link-state IGPs, such as IS-IS [ISO10589], OSPF [RFC2328], and OSPFv3
   [RFC5340], perform distributed route computation on all routers in
   the area/level.  In order to have consistent routing tables across
   the network, such distributed computation requires that all routers
   have the same version of the network topology (Link-State Database
   (LSDB)) and perform their computation essentially at the same time.
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