RFC 3345 (rfc3345) - Page 1 of 19

Border Gateway Protocol (BGP) Persistent Route Oscillation Condition

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Network Working Group                                       D. McPherson
Request for Comments: 3345                                           TCB
Category: Informational                                          V. Gill
                                                   AOL Time Warner, Inc.
                                                               D. Walton
                                                               A. Retana
                                                     Cisco Systems, Inc.
                                                             August 2002


  Border Gateway Protocol (BGP) Persistent Route Oscillation Condition

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2002).  All Rights Reserved.

Abstract

   In particular configurations, the BGP scaling mechanisms defined in
   "BGP Route Reflection - An Alternative to Full Mesh IBGP" and
   "Autonomous System Confederations for BGP" will introduce persistent
   BGP route oscillation.  This document discusses the two types of
   persistent route oscillation that have been identified, describes
   when these conditions will occur, and provides some network design
   guidelines to avoid introducing such occurrences.

1. Introduction

   The Border Gateway Protocol (BGP) is an inter-Autonomous System
   routing protocol.  The primary function of a BGP speaking system is
   to exchange network reachability information with other BGP systems.

   In particular configurations, the BGP [1] scaling mechanisms defined
   in "BGP Route Reflection - An Alternative to Full Mesh IBGP" [2] and
   "Autonomous System Confederations for BGP" [3] will introduce
   persistent BGP route oscillation.

   The problem is inherent in the way BGP works: locally defined routing
   policies may conflict globally, and certain types of conflicts can
   cause persistent oscillation of the protocol.  Given current
   practices, we happen to see the problem manifest itself in the
   context of MED + route reflectors or confederations.



McPherson, et al.            Informational
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