SPF Back-off algorithm for link state IGPs
draft-ietf-rtgwg-backoff-algo-01

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Network Working Group                                        B. Decraene
Internet-Draft                                                    Orange
Intended status: Standards Track                            S. Litkowski
Expires: December 21, 2015                       Orange Business Service
                                                              H. Gredler
                                                  Juniper Networks, Inc.
                                                               A. Lindem
                                                           Cisco Systems
                                                             P. Francois
                                                IMDEA Networks Institute
                                                           June 19, 2015

               SPF Back-off algorithm for link state IGPs
                    draft-ietf-rtgwg-backoff-algo-01

Abstract

   This document defines a standard algorithm to back-off link-state IGP
   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 proximate IGP
   events.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

Status of This Memo

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   This Internet-Draft will expire on December 21, 2015.

Decraene, et al.        Expires December 21, 2015               [Page 1]
Internet-Draft           SPF back-off algorithm                June 2015

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   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  High level goals  . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Definitions and parameters  . . . . . . . . . . . . . . . . .   3
   4.  Principles of SPF delay algorithm . . . . . . . . . . . . . .   4
   5.  Specification of the SPF delay algorithm  . . . . . . . . . .   5
   6.  Parameters  . . . . . . . . . . . . . . . . . . . . . . . . .   6
   7.  Impact on micro-loops . . . . . . . . . . . . . . . . . . . .   6
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   9.  Security considerations . . . . . . . . . . . . . . . . . . .   7
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     11.1.  Normative References . . . . . . . . . . . . . . . . . .   7
     11.2.  Informative References . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   Link state IGPs, such as IS-IS [ISO10589-Second-Edition] and OSPF
   [RFC2328], perform distributed route computation on all routers of
   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 at the same time.

   In general, when the network is stable, there is a desire to compute
   the new SPF as soon as the failure is detected in order to quickly
   route around the failure.  However, when the network is experiencing
   multiple proximate failures over a short period of time, there is a
   conflicting desire to limit the frequency of SPF computations.
   Indeed, this allows a reduction in control plane resources used by
   IGPs and all protocols/subsystem reacting on the attendant route
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