BGP Multiple Nexthops
draft-bhagat-bgp-multiple-nexthops-00

Document Type Active Internet-Draft (individual)
Author Amit Bhagat 
Last updated 2021-03-23
Stream (None)
Intended RFC status (None)
Formats plain text xml pdf htmlized (tools) htmlized bibtex
Stream Stream state (No stream defined)
Consensus Boilerplate Unknown
RFC Editor Note (None)
IESG IESG state I-D Exists
Telechat date
Responsible AD (None)
Send notices to (None)
IDR Working Group                                              A. Bhagat
Internet-Draft                                                    Amazon
Intended status: Informational                            March 23, 2021
Expires: September 24, 2021

                         BGP Multiple Nexthops
                 draft-bhagat-bgp-multiple-nexthops-00

Abstract

   This document presents a new feature in BGP that allows grouping of
   multiple BGP sessions between a pair of speakers and sending multiple
   nexthops for a single prefix.  This helps avoid sending and receiving
   duplicate routes across all sessions.

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
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on September 24, 2021.

Copyright Notice

   Copyright (c) 2021 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
   (https://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.

Bhagat                 Expires September 24, 2021               [Page 1]
Internet-Draft     draft-bhagat-bgp-multiple-nexthops         March 2021

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Capability Support  . . . . . . . . . . . . . . . . . . . . .   2
   3.  Operation . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Multiprotocol Extensions  . . . . . . . . . . . . . . . . . .   4
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   4
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .   4
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   In Data Center networks where CLOS fabrics are built solely using BGP
   [RFC4271], it is very common to have topology where a pair of routers
   have multiple BGP sessions between them - a single BGP session over
   every link.  Each BGP session is independent of the others and BGP
   messages are sent and received over every BGP session.  There are
   various reasons for following this design pattern but the main reason
   is that when links within the LAG interfaces go down, that results in
   inconsistent bandwidth availability which is not reflected at the
   routing level.  This causes the capacity models to not work correctly
   and can also result in network congestion.

   While the maintenance of these independent BGP sessions is trivial,
   routers sending and receiving duplicate BGP UPDATE messages for
   hundreds or thousands of routes, leads to unnecessarily generating,
   processing and storing of routes.  These duplicate messages provide
   no extra information except capability to select and install multiple
   paths for routes.  Every route in the BGP UPDATE messages has same
   BGP path attributes except the NEXT_HOP attribute.

   This document provides a way to advertise the route only one time
   with multiple NEXT_HOP attributes to achieve the same benefits as
   having the same route advertised multiple times over multiple BGP
   sessions with different NEXT_HOP attributes.

2.  Capability Support

   A new Capability Optional parameter will be communicated in BGP Open
   message.  A BGP speaker SHOULD use Capability Advertisement procedure
   in [RFC3392] to announce the support.  The Capability Code is to be
   assigned by IANA.

Bhagat                 Expires September 24, 2021               [Page 2]
Internet-Draft     draft-bhagat-bgp-multiple-nexthops         March 2021

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |     Type      |    Length     |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |      AFI                      |  Reserved     |  SAFI         |
Show full document text