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Versions: (draft-rosen-l3vpn-mvpn-infra-addrs) 00 01 02 03 04 05 RFC 6515

L3VPN Working Group                                       Rahul Aggarwal
Internet Draft                                    Juniper Networks, Inc.
Intended Status: Proposed Standard
Updates: draft-ietf-l3vpn-2547bis-mcast-bgp-08.txt         Eric C. Rosen
Expires: August 16, 2011                             Cisco Systems, Inc.

                                                       February 16, 2011


IPv4 and IPv6 Infrastructure Addresses in BGP Updates for Multicast VPN


                draft-ietf-l3vpn-mvpn-infra-addrs-03.txt

Abstract

   To provide Multicast VPN (MVPN) service, Provider Edge routers
   originate BGP Update messages that carry Multicast-VPN ("MCAST-VPN")
   BGP routes; they also originate unicast VPN routes that carry MVPN-
   specific attributes.  These routes encode addresses from the
   customer's address space, as well as addresses from the provider's
   address space.  These two address spaces are independent, and the
   address family (IPv4 or IPv6) of the two spaces may or may not be the
   same.  These routes always contain an "address family" field that
   specifies whether the customer addresses are IPv4 addresses or
   whether they are IPv6 addresses.  However, there is no field that
   explicitly specifies the address family of the provider addresses.
   To ensure interoperability, this document specifies that provider
   IPv4 addresses are always encoded in these update messages as four-
   octet addresses, and that the distinction between IPv4 and IPv6 is
   signaled solely by the length of the address field.  Specific cases
   are explained in detail.


Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   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."



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Table of Contents

 1          Introduction  ..........................................   3
 1.1        Specification of requirements  .........................   3
 1.2        Acronyms Used in this Document  ........................   3
 1.3        IPv4 and IPv6 Addresses in MCAST-VPN Routes  ...........   4
 2          PE Addresses in MCAST-VPN Routes  ......................   5
 3          VRF Route Import Extended Community  ...................   6
 4          PMSI Tunnel Attributes in I-PMSI A-D Routes  ...........   6
 4.1        Relationship to AFI Value  .............................   7
 4.2        Relationship to Next Hop Address Family  ...............   7
 5          IANA Considerations  ...................................   7
 6          Security Considerations  ...............................   8
 7          Acknowledgments  .......................................   8
 8          Authors' Addresses  ....................................   8
 9          Normative References  ..................................   8
10          Informational References  ..............................   9







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1. Introduction

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].


1.2. Acronyms Used in this Document

   This document uses a number of acronyms, mostly taken directly from
   the BGP and VPN specifications.

     - A-D Route: Auto-Discovery Route [MVPN]

     - AFI: Address Family Identifier [BGP-MP]

     - AS: Autonomous System [BGP]

     - I-PMSI: Inclusive PMSI [RFC4364]

     - MCAST-VPN: Multicast Virtual Private Network [MVPN-BGP]

     - MP_REACH_NLRI: Multiprotocol Reachable NLRI [BGP-MP]

     - MP_UNREACH_NLRI; Multiprotocol Unreachable NLRI [BGP-MP]

     - PMSI: Provider Multicast Service Interface [MVPN]

     - NLRI: Network Layer Reachability Information [BGP]

     - PE: Provider Edge [RFC4364]

     - S-PMSI: Selective PMSI [RFC4364]

     - SAFI: Subsequent Address Field Identifier [BGP-MP]

     - SP: Service Provider












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1.3. IPv4 and IPv6 Addresses in MCAST-VPN Routes

   [MVPN-BGP] defines a new set of BGP route types that are used by SPs
   to provide Multicast Virtual Private Network service to their
   customers.  These routes have a newly defined BGP NLRI, the "MCAST-
   VPN" NLRI.  MCAST-VPN NLRI is carried in the NLRI field of the
   MP_REACH_NLRI/MP_UNREACH_NLRI attributes defined in [BGP-MP].  The
   SAFI field of the MP_REACH_NLRI/MP_UNREACH_NLRI attribute is used to
   identify the NLRI as being an MCAST-VPN NLRI.

   When the SAFI field of an MP_REACH_NLRI/MP_UNREACH_NLRI attribute has
   the "MCAST-VPN" value, the AFI field has two defined values: 1 and 2.
   AFI 1 indicates that any customer multicast addresses occurring in
   the MP_REACH_NLRI/MP_UNREACH_NLRI attribute are IPv4 addresses; AFI 2
   indicates that any such addresses are IPv6 addresses.

   However, some of the MCAST-VPN routes also contain addresses of PE
   routers in the SP network.  An SP with an IPv4 network may provide
   MVPN service for customers that use IPv6, and an SP with an IPv6
   network may provide MVPN service for customers that use IPv4.
   Therefore the address family of the PE addresses MUST NOT be inferred
   from the AFI field of the associated MP_REACH_NLRI/MP_UNREACH_NLRI
   attribute.

   The purpose of this document is to make it clear that whenever a PE
   address occurs in an MCAST-VPN route (whether in the NLRI or in an
   attribute), the IP address family of that address is determined by
   the length of the address (a length of 4 octets for IPv4 addresses, a
   length of 16 octets for IPv6 addresses), NOT by the AFI field of the
   route.

   In particular, if a SP with an IPv4 core network is providing
   MVPN/IPv6 service to a customer, the PE addresses in the MCAST-VPN
   routes will be four-octet IPv4 routes, even though the AFI of those
   routes will have the value 2.

   Some previous specifications (e.g., [RFC4659] and [RFC4798]) have
   taken a different approach, requiring that in any routes containing
   IPv6 or VPN-IPv6 customer addresses, the IPv4 PE addresses be
   represented as IPv6-mapped IPv4 addresses [RFC4291].  This document
   does not use that approach.  Rather, this specification uses the
   approach adopted in [RFC4684] and [RFC5549].  The MCAST-VPN routes
   contain enough information to enable the IP address family of the PE
   addresses to be inferred from the address lengths.

   [MVPN-BGP] also defines an attribute, the "VRF Route Import Extended
   Community", that is attached to unicast VPN-IPv4 or VPN-IPv6 routes.
   This extended community contains a PE address, and this document



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   specifies how to encode an IPv6 address in this attribute,
   independent of whether the attribute is attached to a VPN-IPv4 route
   or a VPN-IPv6 route.

   Some previous specifications (e.g., [RFC4659] and [RFC4798]) have
   taken a different approach, requiring that in any routes containing
   IPv6 or VPN-IPv6 customer addresses, the IPv4 PE addresses be
   represented as IPv6-mapped IPv4 addresses [RFC4291].  This document
   does not use that approach.  Rather, this specification uses the
   approach adopted in [RFC4684] and [RFC5549].  The MCAST-VPN routes
   contain enough information to enable the IP address family of the PE
   addresses to be inferred from the address lengths.

   This document also clarifies an issue with respect to the
   significance of the Address Family field of an Intra-AS I-PMSI A-D
   route that carries a PMSI Tunnel Attribute.


2. PE Addresses in MCAST-VPN Routes

   PE addresses occur in MCAST-VPN routes in the following places:

      1. "Network Address of Next Hop" field in the MP_REACH_NLRI
         attribute, as defined in section 3 of [BGP-MP].  This field is
         preceded by a "length of next hop address" field.  Hence it is
         always clear whether the address is an IPv4 address (length is
         4) or an IPv6 address (length is 16).  If the length of next
         hop address is neither 4 nor 16, the MP_REACH_NLRI attribute
         MUST be considered to be "incorrect", and MUST be handled as
         specified in section 7 of [BGP-MP].

      2. "Intra-AS I-PMSI A-D route". All MCAST-VPN routes begin with a
         one-octet route type field, followed by a one-octet "NLRI
         length" field.  In the Intra-AS I-PMSI A-D route, the length is
         followed by an 8-octet RD, which is then followed by the
         "Originating Router's IP Address" field.  The length of this
         field (4 octets for IPv4 or 16 octets for IPv6 can thus be
         inferred from the NLRI length field (which will be either 12 or
         24, respectively).  If the inferred length of the "Originating
         Router's IP Address" field is neither 4 nor 16, the
         MP_REACH_NLRI attribute MUST be considered to be "incorrect",
         and MUST be handled as specified in section 7 of [BGP-MP].

      3. "S-PMSI A-D Route".  In this route, the "NLRI length" field is
         followed by an 8-octet RD, a variable length "multicast source"
         field, a variable length "multicast group" field, and an
         "Originating Router's IP Address" field.  The two variable
         length fields have their own length fields.  From these two



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         length fields and the NLRI length field, one can compute the
         length of the "Originating Router's IP Address" field, which
         again is either 4 for IPv4 or 16 for IPv6.  If the computed
         length of the "Originating Router's IP Address" field is
         neither 4 nor 16, the MP_REACH_NLRI attribute MUST be
         considered to be "incorrect", and MUST be handled as specified
         in section 7 of [BGP-MP].

      4. "Leaf A-D Route".  In this route, the "NLRI length" field is
         following by a variable length "route key", which is followed
         by the "Originating Router's IP Address" field.  The Route Key
         has its own length field.  From the NLRI length and the route
         key length, one can compute the length of the "Originating
         Router's IP Address" field.  If the computed length of the
         "Originating Router's IP Address" field is neither 4 nor 16,
         the MP_REACH_NLRI attribute MUST be considered to be
         "incorrect", and MUST be handled as specified in section 7 of
         [BGP-MP].




3. VRF Route Import Extended Community

   The "VRF Route Import Extended Community", specified in [MVPN-BGP],
   is an attribute carried by unicast VPN-IPv4 or VPN-IPv6 routes.  It
   is an "IPv4 Address Specific Extended Community" of type "VRF Route
   Import"; hence it can only carry an IPv4 address.  To carry an IPv6
   address, an "IPv6 Address Specific Extended Community" [RFC5701], of
   type "VRF Route Import", must be used.  A codepoint for this type of
   extended community will be allocated by IANA.


4. PMSI Tunnel Attributes in I-PMSI A-D Routes

   When a PMSI Tunnel Attribute occurs in an I-PMSI A-D route originated
   by a particular PE or ASBR, it identifies a tunnel that the PE/ASBR
   uses by default for carrying the multicast traffic of a particular
   customer MVPN.  The proper encoding and interpretation of the PMSI
   Tunnel attribute is affected by both the AFI and "Network Address of
   Next Hop" fields.










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4.1. Relationship to AFI Value

   When the PMSI Tunnel Attribute occurs in a BGP Update message with a
   MP_REACH_NLRI attribute whose AFI is 1, the meaning is that the
   identified tunnel is used by default to carry IPv4 MVPN traffic for a
   particular customer MVPN. When the PMSI Tunnel Attribute occurs in a
   BGP Update message with a MP_REACH_NLRI attribute whose AFI is 2, the
   meaning is that the identified tunnel is used by default to carry
   IPv6 MVPN traffic for a particular customer MVPN.  To assign both
   IPv4 and IPv6 MVPN traffic to an I-PMSI tunnel, two I-PMSI A-D routes
   MUST be used, one whose MP_REACH_NLRI has an AFI of 1, and one whose
   MP_REACH_NLRI has an AFI of 2.  To use the same tunnel for both IPv4
   and IPv6 traffic, the same value of the PMSI Tunnel attribute can be
   used in each route.


4.2. Relationship to Next Hop Address Family

   If the "Network Address of Next Hop" field in the MP_REACH_NLRI
   attribute contains an IPv4 address, then any IP addresses appearing
   in the "Tunnel Identifier" field of the PMSI Tunnel Attribute MUST be
   IPv4 addresses.

   If the "Network Address of Next Hop" field in the MP_REACH_NLRI
   attribute contains an IPv6 address, then any IP addresses appearing
   in the "Tunnel Identifier" field of the PMSI Tunnel Attribute MUST be
   IPv6 addresses.

   If these conditions are not met, the PMSI Tunnel Attribute MUST be
   handled as a "malformed" PMSI Tunnel Attribute, as specified in
   section 5 [MVPN-BGP].



5. IANA Considerations

   IANA is requested to assign a codepoint for "VRF Route Import" in the
   "IPv6 Address Specific Extended Community" registry.  The codepoint
   should be assigned from the "transitive communities" portion of the
   namespace.  We suggest assignment of the value 0x000b (to correspond
   to the value that is already assigned for "VRF Route Import" in the
   "IPv4 Address Specific Extended Community" registry).  The references
   should be to this document and to [MVPN-BGP].








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6. Security Considerations

   This document does not raise any security considerations beyond those
   raised by [MVPN-BGP].


7. Acknowledgments

   The authors wish to thank Dongling Duan, Keyur Patel, Yakov Rekhter,
   and Karthik Subramanian.


8. Authors' Addresses

   Rahul Aggarwal
   Juniper Networks
   1194 North Mathilda Ave.
   Sunnyvale, CA 94089
   Email: rahul@juniper.net



   Eric C. Rosen
   Cisco Systems, Inc.
   1414 Massachusetts Avenue
   Boxborough, MA, 01719
   E-mail: erosen@cisco.com



9. Normative References

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

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

   [MVPN] E. Rosen, R. Aggarwal [Editors], "Multicast in MPLS/BGP IP
   VPNs", draft-ietf-l3vpn-2547bis-mcast-10.txt, January 2010

   [MVPN-BGP], "BGP Encodings and Procedures for Multicast in MPLS/BGP
   IP VPNs", Rahul Aggarwal, Eric Rosen, Thomas Morin, Yakov Rekhter,
   draft-ietf-l3vpn-2547bis-mcast-bgp-08.txt, October 2009

   [RFC2119] "Key words for use in RFCs to Indicate Requirement
   Levels.", Bradner, March 1997




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10. Informational References

   [RFC4291] "IP Version 6 Addressing Architecture", R. Hinden, S.
   Deering, RFC 4291, February 2006.

   [RFC4364] "BGP/MPLS IP Virtual Private Networks (VPNs)", E. Rosen, Y.
   Rekhter, RFC4364, February 2006

   [RFC4659] "BGP-MPLS IP Virtual Private Network (VPN) Extension for
   IPv6 VPN", J. De Clercq, D. Ooms, M. Carugi, F. Le Faucheur. RFC
   4659, September 2006

   [RFC4798] "Connecting IPv6 Islands over IPv4 MPLS Using IPv6 Provider
   Edge Routers (6PE)", J. De Clercq, D. Ooms, S. Prevost, F. Le
   Faucheur.  RFC 4798, February 2007

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

   [RFC5549] "Advertising IPv4 Network Layer Reachability Information
   with an IPv6 Next Hop" F. Le Faucheur, E. Rosen. RFC 5549, May 2009

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
























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