Constrained Route Distribution for Border Gateway Protocol/MultiProtocol Label Switching (BGP/MPLS) Internet Protocol (IP) Virtual Private Networks (VPNs)
RFC 4684

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Network Working Group                                         P. Marques
Request for Comments: 4684                                     R. Bonica
Updates: 4364                                           Juniper Networks
Category: Standards Track                                        L. Fang
                                                              L. Martini
                                                               R. Raszuk
                                                                K. Patel
                                                             J. Guichard
                                                     Cisco Systems, Inc.
                                                           November 2006

                  Constrained Route Distribution for
    Border Gateway Protocol/MultiProtocol Label Switching (BGP/MPLS)
         Internet Protocol (IP) Virtual Private Networks (VPNs)

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The IETF Trust (2006).

Abstract

   This document defines Multi-Protocol BGP (MP-BGP) procedures that
   allow BGP speakers to exchange Route Target reachability information.
   This information can be used to build a route distribution graph in
   order to limit the propagation of Virtual Private Network (VPN)
   Network Layer Reachability Information (NLRI) between different
   autonomous systems or distinct clusters of the same autonomous
   system.  This document updates RFC 4364.

Marques, et al.             Standards Track                     [Page 1]
RFC 4684              Route Target (RT) Constrain          November 2006

Table of Contents

   1. Introduction ....................................................2
      1.1. Terminology ................................................3
   2. Specification of Requirements ...................................4
   3. NLRI Distribution ...............................................4
      3.1. Inter-AS VPN Route Distribution ............................4
      3.2. Intra-AS VPN Route Distribution ............................6
   4. Route Target Membership NLRI Advertisements .....................8
   5. Capability Advertisement ........................................9
   6. Operation .......................................................9
   7. Deployment Considerations ......................................10
   8. Security Considerations ........................................11
   9. Acknowledgements ...............................................11
   10. References ....................................................11
      10.1. Normative References .....................................11
      10.2. Informative References ...................................12

1.  Introduction

   In BGP/MPLS IP VPNs, PE routers use Route Target (RT) extended
   communities to control the distribution of routes into VRFs.  Within
   a given iBGP mesh, PE routers need only hold routes marked with Route
   Targets pertaining to VRFs that have local CE attachments.

   It is common, however, for an autonomous system to use route
   reflection [2] in order to simplify the process of bringing up a new
   PE router in the network and to limit the size of the iBGP peering
   mesh.

   In such a scenario, as well as when VPNs may have members in more
   than one autonomous system, the number of routes carried by the
   inter-cluster or inter-as distribution routers is an important
   consideration.

   In order to limit the VPN routing information that is maintained at a
   given route reflector, RFC 4364 [3] suggests, in Section 4.3.3, the
   use of "Cooperative Route Filtering" [7] between route reflectors.
   This document extends the RFC 4364 [3] Outbound Route Filtering (ORF)
   work to include support for multiple autonomous systems and
   asymmetric VPN topologies such as hub-and-spoke.

   Although it would be possible to extend the encoding currently
   defined for the extended-community ORF in order to achieve this
   purpose, BGP itself already has all the necessary machinery for
   dissemination of arbitrary information in a loop-free fashion, both
   within a single autonomous system, as well as across multiple
   autonomous systems.

Marques, et al.             Standards Track                     [Page 2]
RFC 4684              Route Target (RT) Constrain          November 2006

   This document builds on the model described in RFC 4364 [3] and on
   the concept of cooperative route filtering by adding the ability to
   propagate Route Target membership information between iBGP meshes.
   It is designed to supersede "cooperative route filtering" for VPN