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Distribution of Diverse BGP Paths
RFC 6774

Internet Engineering Task Force (IETF)                    R. Raszuk, Ed.
Request for Comments: 6774                                       NTT MCL
Category: Informational                                      R. Fernando
ISSN: 2070-1721                                                 K. Patel
                                                           Cisco Systems
                                                            D. McPherson
                                                                Verisign
                                                               K. Kumaki
                                                        KDDI Corporation
                                                           November 2012

                   Distribution of Diverse BGP Paths

Abstract

   The BGP4 protocol specifies the selection and propagation of a single
   best path for each prefix.  As defined and widely deployed today, BGP
   has no mechanisms to distribute alternate paths that are not
   considered best path between its speakers.  This behavior results in
   a number of disadvantages for new applications and services.

   The main objective of this document is to observe that by simply
   adding a new session between a route reflector and its client, the
   Nth best path can be distributed.  This document also compares
   existing solutions and proposed ideas that enable distribution of
   more paths than just the best path.

   This proposal does not specify any changes to the BGP protocol
   definition.  It does not require a software upgrade of provider edge
   (PE) routers acting as route reflector clients.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   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).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

   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/rfc6774.

Raszuk, et al.                Informational                     [Page 1]
RFC 6774              Diverse-BGP-Path Distribution        November 2012

Copyright Notice

   Copyright (c) 2012 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.

Table of Contents

   1. Introduction ....................................................2
   2. History .........................................................3
      2.1. BGP Add-Paths Proposal .....................................3
   3. Goals ...........................................................5
   4. Multi-Plane Route Reflection ....................................6
      4.1. Co-located Best- and Backup-Path RRs .......................8
      4.2. Randomly Located Best- and Backup-Path RRs ................10
      4.3. Multi-Plane Route Servers for Internet Exchanges ..........12
   5. Discussion on Current Models of IBGP Route Distribution ........13
      5.1. Full Mesh .................................................13
      5.2. Confederations ............................................14
      5.3. Route Reflectors ..........................................15
   6. Deployment Considerations ......................................15
   7. Summary of Benefits ............................................17
   8. Applications ...................................................18
   9. Security Considerations ........................................19
   10. Contributors ..................................................19
   11. Acknowledgments ...............................................20
   12. References ....................................................20
       12.1. Normative References ....................................20
       12.2. Informative References ..................................20

1.  Introduction

   The current BGP4 protocol specification [RFC4271] allows for the
   selection and propagation of only one best path for each prefix.  As

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