Solutions for BGP Persistent Route Oscillation
RFC 7964

Document Type RFC - Proposed Standard (September 2016; No errata)
Last updated 2016-09-29
Replaces draft-idr-bgp-route-oscillation-stop, draft-walton-bgp-route-oscillation-stop
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Stream WG state Submitted to IESG for Publication (wg milestone: Jun 2015 - Submit Advertisement... )
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Internet Engineering Task Force (IETF)                         D. Walton
Request for Comments: 7964                              Cumulus Networks
Category: Standards Track                                      A. Retana
ISSN: 2070-1721                                                  E. Chen
                                                     Cisco Systems, Inc.
                                                              J. Scudder
                                                        Juniper Networks
                                                          September 2016

             Solutions for BGP Persistent Route Oscillation

Abstract

   Routing information reduction by BGP Route Reflection or
   Confederation can result in persistent internal BGP route
   oscillations with certain routing setups and network topologies.
   This document specifies two sets of additional paths that can be used
   to eliminate these route oscillations in a network.

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
   http://www.rfc-editor.org/info/rfc7964.

Copyright Notice

   Copyright (c) 2016 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
   (http://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.

Walton, et al.               Standards Track                    [Page 1]
RFC 7964                BGP Oscillation Solutions         September 2016

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements Language . . . . . . . . . . . . . . . . . . . .   3
   3.  Advertise All the Available Paths . . . . . . . . . . . . . .   3
   4.  Advertise the Group Best Paths  . . . . . . . . . . . . . . .   3
   5.  Route Reflection and Confederation  . . . . . . . . . . . . .   4
     5.1.  Route Reflection  . . . . . . . . . . . . . . . . . . . .   5
     5.2.  Confederation . . . . . . . . . . . . . . . . . . . . . .   5
   6.  Deployment Considerations . . . . . . . . . . . . . . . . . .   6
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Appendix A.  Why the Group Best Paths Are Adequate  . . . . . . .   8
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   As documented in [RFC3345], routing information reduction by BGP
   Route Reflection [RFC4456] or BGP Confederation [RFC5065] can result
   in persistent Internal BGP (IBGP) route oscillations with certain
   routing setups and network topologies.  Except for a couple of
   artificially engineered network topologies, the MULTI_EXIT_DISC (MED)
   attribute [RFC4271] has played a pivotal role in virtually all known
   persistent IBGP route oscillations.  For the sake of brevity, we use
   the term "MED-induced route oscillation" hereafter to refer to a
   persistent IBGP route oscillation in which the MED plays a role.

   In order to eliminate MED-induced route oscillations and to achieve
   consistent routing in a network, a route reflector or a confederation
   Autonomous System Border Router (ASBR) needs to advertise more than
   just the best path for an address prefix.  Our goal is to identify
   the necessary set of paths for an address prefix that needs to be
   advertised by a route reflector or a confederation ASBR to prevent
   the condition.

   In this document, we describe two sets of paths for an address prefix
   that can be advertised by a BGP route reflector or confederation ASBR
   to eliminate MED-induced route oscillations in a network.  The first
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