Advertisement of Multiple Paths in BGP
RFC 7911

Document Type RFC - Proposed Standard (July 2016; No errata)
Last updated 2016-07-11
Replaces draft-walton-bgp-add-paths
Stream IETF
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Stream WG state Submitted to IESG for Publication Jun 2015
Document shepherd Russ White
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IESG IESG state RFC 7911 (Proposed Standard)
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Responsible AD Alia Atlas
Send notices to "Russ White" <russ@riw.us>
IANA IANA review state Version Changed - Review Needed
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Internet Engineering Task Force (IETF)                         D. Walton
Request for Comments: 7911                              Cumulus Networks
Category: Standards Track                                      A. Retana
ISSN: 2070-1721                                                  E. Chen
                                                     Cisco Systems, Inc.
                                                              J. Scudder
                                                        Juniper Networks
                                                               July 2016

                 Advertisement of Multiple Paths in BGP

Abstract

   This document defines a BGP extension that allows the advertisement
   of multiple paths for the same address prefix without the new paths
   implicitly replacing any previous ones.  The essence of the extension
   is that each path is identified by a Path Identifier in addition to
   the address prefix.

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/rfc7911.

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 7911                        ADD-PATH                       July 2016

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Specification of Requirements . . . . . . . . . . . . . .   2
   2.  How to Identify a Path  . . . . . . . . . . . . . . . . . . .   3
   3.  Extended NLRI Encodings . . . . . . . . . . . . . . . . . . .   3
   4.  ADD-PATH Capability . . . . . . . . . . . . . . . . . . . . .   4
   5.  Operation . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   6.  Deployment Considerations . . . . . . . . . . . . . . . . . .   5
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   The BGP specification [RFC4271] defines an Update-Send Process to
   advertise the routes chosen by the Decision Process to other BGP
   speakers.  No provisions are made to allow the advertisement of
   multiple paths for the same address prefix or Network Layer
   Reachability Information (NLRI).  In fact, a route with the same NLRI
   as a previously advertised route implicitly replaces the previous
   advertisement.

   This document defines a BGP extension that allows the advertisement
   of multiple paths for the same address prefix without the new paths
   implicitly replacing any previous ones.  The essence of the extension
   is that each path is identified by a Path Identifier in addition to
   the address prefix.

   The availability of the additional paths can help reduce or eliminate
   persistent route oscillations [RFC3345].  It can also help with
   optimal routing and routing convergence in a network by providing
   potential alternate or backup paths, respectively.

1.1.  Specification of Requirements

   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].
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