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Versions: 00 01                                                         
L3VPN Working Group                                             K. Patel
Internet-Draft                                                 R. Raszuk
Intended status: Standards Track                           Cisco Systems
Expires: April 21, 2011                                      M. Djernaes
                                                        Juniper Networks
                                                                 J. Dong
                                                                 M. Chen
                                           Huawei Technologies Co., Ltd.
                                                        October 18, 2010


                 AFI Specific Route Target Distribution
            draft-keyur-bgp-af-specific-rt-constrain-00.txt

Abstract

   The current route target distribution specification described in
   RFC4684 defines Route Target NLRIs of maxiumum length of 12 bytes.
   Furthermore, the current specification mandates that Route Targets
   exchanged using the current specification are applied towards
   filtering for all VPN applications that uses the notion of Route
   Target BGP extended communities.

   In particular, the same Route Target distribution mechanism is used
   to exchange VPNv4, VPNv6 and L2VPN prefixes.  The IPv6 specific Route
   Target extended community is defined in RFC5701 as length of 20
   bytes.  Since the current specification only supports prefixes of
   maximum length of 12 bytes, the lack of an IPv6 specific Route Target
   reachability information may be a problem when an operator wants to
   use this application in a pure IPv6 environment.  This document
   defines an extension to the current constrained route distribution
   specification that allows BGP speakers to distribute Route Target
   prefixes using multiple different Address Families thereby limiting
   the application of Route Target prefix filters to the specific
   address family under which it is advertised.  Furtheremore, this
   document defines an extension that allows BGP to exchange longer
   length IPv6 Route Target prefixes.

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 http://datatracker.ietf.org/drafts/current/.




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Internet-Draft   AFI Specific Route Target Distribution     October 2010


   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
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   This Internet-Draft will expire on April 21, 2011.

Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   it for publication as an RFC or to translate it into languages other
   than English.


















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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 4
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . . . 4
   2.  BGP Constrained Route Target Capability . . . . . . . . . . . . 4
   3.  AFI specific Route Target NLRI Advertisements . . . . . . . . . 5
   4.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 6
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
   6.  Security Considerations . . . . . . . . . . . . . . . . . . . . 6
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 6
     7.1.  Normative References  . . . . . . . . . . . . . . . . . . . 6
     7.2.  Informative References  . . . . . . . . . . . . . . . . . . 7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 7






































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1.  Introduction

   The current constrained route distribution specification defined in
   [RFC4684] supports prefixes with a fixed maximum length of 12 bytes.
   Furthermore, the current specification mandates that the Route
   Targets exchanged using the current specification are applied towards
   filtering for all VPNv4, VPNv6, and L2VPN address families.

   This behavior needs to be modified for the following reasons:

   o  The IPv6 specific Route Target extended community defined in
      [RFC5701] is 20 bytes in length.  Since the current specification
      only supports prefixes of maximum length of 12 bytes, the lack of
      an IPv6 specific Route Target reachability information may be a
      problem when one wants to use this application in a pure IPv6
      environment.

   o  The behavior of applying filtering for all VPN address families
      (VPNv4, VPNv6 and L2VPN) is sub-optimal in cases where the
      operators want to assign common Route Targets and perform scoped
      filtering on an address family basis.

   This document defines an extension to the current constrained route
   distribution specification that allows BGP speakers to distribute
   Route Target prefixes using multiple different Adddress Families
   thereby limiting the application of Route Target filters to the
   specific address family under which it is advertised.  Address
   families that do not exchange Route Target information using their
   own AFI and SAFI = 132 MUST always use AFI=1 and SAFI=132 to exchange
   their Route Targets and filter prefixes accordingly.  Furthermore,
   Address families that do exchange the Route Target information using
   its own AFI and SAFI = 132 MUST override the Route Target information
   received in AFI=1 and SAFI=132.  In this way, the current extension
   would preserve the backward compatibility with [RFC4684].

1.1.  Requirements Language

   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 RFC 2119 [RFC2119].


2.  BGP Constrained Route Target Capability

   A BGP speaker that wishes to exchange Route Target membership
   information for any address family must use the Multiprotocol
   Extensions Capability Code, as defined in [RFC4760] section [5], to
   advertise the corresponding (AFI, SAFI) pair.



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   The BGP IPv6 Constrained Route Target capability is a new BGP
   Capability [RFC5492] defined with Multiprotocol Extension Capability
   code with AFI=2 and SAFI=132.

   The BGP L2VPN Constrained Route Target capability is a new BGP
   Capability [RFC5492] defined with Multiprotocol Extension Capability
   code with AFI=25 and SAFI=132.

   By advertising these capabilities to a peer, a BGP speaker conveys to
   the peer that the speaker supports and can interpret appropriate
   address family based Route Target reachability information and the
   related procedures described in this document along with the
   procedures described in [RFC4684].  When not present, the current
   Constrained Route Target AFI=1 and SAFI=132 MUST apply to all the VPN
   address families that did not exchanged the Constrained AFI specific
   capability.  Alternatively, the VPN address families that do
   successful negotiation of newly defined Constrained Route Target
   capabilities MUST override the Route Target information received in
   the Constrained Route Target Address family of AFI=1 and SAFI=132.
   In this way we make this specification fully backwards compatible
   with the existing deployments.


3.  AFI specific Route Target NLRI Advertisements

   Route Target membership NLRI is advertised in BGP UPDATE messages
   using the MP_REACH_NLRI and MP_UNREACH_NLRI attributes as defined in
   [RFC4760].  The [AFI, SAFI] value pair used to identify this NLRI is
   (AFI=X,SAFI=132) where X describes the address family to which
   Specific RT Constrained advertisement will apply.

   The NLRI field in the MP_REACH_NLRI and MP_UNREACH_NLRI is a prefix
   of 0 to 24 octets, encoded as defined in Section 4 of [5] for all the
   constrain route distribution AFI/SAFI other than AFI = 1 and SAFI =
   132.  The valid NLRI length value for AFI = 1 and SAFI = 132 is
   defined in [RFC4684].

   This prefix is structured as follows:













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           +-------------------------------+
           | origin as        (4 octets)   |
           +-------------------------------+
           | route target  (8 or 20 octets)|
           ~                               ~
           |                               |
           +-------------------------------+

   Except for the default route target, which is encoded as a zero-
   length prefix, the minimum prefix length is 32 bits.  As the origin-
   as field cannot be interpreted as a prefix.

   Route targets can then be expressed as prefixes, where, for instance,
   a prefix would encompass all route target extended communities
   assigned by a given Global Administrator [6].

   The default route target can be used to indicate to a peer the
   willingness to receive all VPN route advertisements such as, for
   instance, the case of a route reflector speaking to one of its PE
   router clients.


4.  Acknowledgements

   The authors would like to thank Pedro Marques, John Scudder and Alton
   Lo for discussions and review.


5.  IANA Considerations

   This draft does not require any new allocations by IANA.  In all
   address families constrained route target distribution will use the
   already allocated SAFI = 132.


6.  Security Considerations

   This extension to [RFC4684] does not change the underlying security
   issues inherent in the existing BGP and [RFC4684].


7.  References

7.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.




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   [RFC4271]  Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
              Protocol 4 (BGP-4)", RFC 4271, January 2006.

   [RFC4684]  Marques, P., Bonica, R., Fang, L., Martini, L., Raszuk,
              R., Patel, K., and J. Guichard, "Constrained Route
              Distribution for Border Gateway Protocol/MultiProtocol
              Label Switching (BGP/MPLS) Internet Protocol (IP) Virtual
              Private Networks (VPNs)", RFC 4684, November 2006.

   [RFC5492]  Scudder, J. and R. Chandra, "Capabilities Advertisement
              with BGP-4", RFC 5492, February 2009.

   [RFC5701]  Rekhter, Y., "IPv6 Address Specific BGP Extended Community
              Attribute", RFC 5701, November 2009.

7.2.  Informative References

   [RFC4760]  Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
              "Multiprotocol Extensions for BGP-4", RFC 4760,
              January 2007.


Authors' Addresses

   Keyur Patel
   Cisco Systems
   170 W. Tasman Drive
   San Jose, CA  95134
   USA

   Email: keyupate@cisco.com


   Robert Raszuk
   Cisco Systems
   170 W. Tasman Drive
   San Jose, CA  95134
   USA

   Email: raszuk@cisco.com











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Internet-Draft   AFI Specific Route Target Distribution     October 2010


   Martine Djernaes
   Juniper Networks
   1194 N. Mathilda Avenue
   Sunnyvale, CA  94089
   USA

   Email: mdjernaes@juniper.net


   Jie Dong
   Huawei Technologies Co., Ltd.
   KuiKe Building, No.9 Xinxi Rd.
   Hai-Dian District, Beijing  100085
   P.R. China

   Email: dongjie_dj@huawei.com


   Mach(Guoyi) Chen
   Huawei Technologies Co., Ltd.
   KuiKe Building, No.9 Xinxi Rd.
   Hai-Dian District, Beijing  100085
   P.R. China

   Email: mach@huawei.com


























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