Link State protocols SPF trigger and delay algorithm impact on IGP micro-loops
draft-ietf-rtgwg-spf-uloop-pb-statement-03

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Last updated 2017-03-27
Replaces draft-litkowski-rtgwg-spf-uloop-pb-statement
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Routing Area Working Group                                  S. Litkowski
Internet-Draft                                   Orange Business Service
Intended status: Standards Track                             B. Decraene
Expires: September 28, 2017                                       Orange
                                                            M. Horneffer
                                                        Deutsche Telekom
                                                          March 27, 2017

   Link State protocols SPF trigger and delay algorithm impact on IGP
                              micro-loops
               draft-ietf-rtgwg-spf-uloop-pb-statement-03

Abstract

   A micro-loop is a packet forwarding loop that may occur transiently
   among two or more routers in a hop-by-hop packet forwarding paradigm.

   In this document, we are trying to analyze the impact of using
   different Link State IGP implementations in a single network in
   regards of micro-loops.  The analysis is focused on the SPF triggers
   and SPF delay algorithm.

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

   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
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   This Internet-Draft will expire on September 28, 2017.

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Internet-Draft                spf-microloop                   March 2017

Copyright Notice

   Copyright (c) 2017 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
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Problem statement . . . . . . . . . . . . . . . . . . . . . .   3
   3.  SPF trigger strategies  . . . . . . . . . . . . . . . . . . .   4
   4.  SPF delay strategies  . . . . . . . . . . . . . . . . . . . .   5
     4.1.  Two step SPF delay  . . . . . . . . . . . . . . . . . . .   5
     4.2.  Exponential backoff . . . . . . . . . . . . . . . . . . .   6
   5.  Mixing strategies . . . . . . . . . . . . . . . . . . . . . .   7
   6.  Proposed work items . . . . . . . . . . . . . . . . . . . . .  11
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  13
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  13
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  13
     10.2.  Informative References . . . . . . . . . . . . . . . . .  13
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  14

1.  Introduction

   Link State IGP protocols are based on a topology database on which a
   SPF (Shortest Path First) algorithm like Dijkstra is implemented to
   find the optimal routing paths.

   Specifications like IS-IS ([RFC1195]) propose some optimizations of
   the route computation (See Appendix C.1) but not all the
   implementations are following those not mandatory optimizations.

   We will call SPF trigger, the events that would lead to a new SPF
   computation based on the topology.

   Link State IGP protocols, like OSPF ([RFC2328]) and IS-IS
   ([RFC1195]), are using plenty of timers to control the router

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