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Versions: (draft-rosen-l3vpn-mvpn-mldp-nlri) 00 01 02 03 04 05 06 07 08 09 10 RFC 7441

L3VPN Working Group                                    IJsbrand Wijnands
Internet Draft                                       Cisco Systems, Inc.
Intended Status: Proposed Standard
Updates: 6514                                              Eric C. Rosen
Expires: May 25, 2015                             Juniper Networks, Inc.

                                                              Uwe Joorde
                                                        Deutsche Telekom

                                                       November 25, 2014


         Encoding mLDP FECs in the NLRI of BGP MCAST-VPN Routes


                 draft-ietf-l3vpn-mvpn-mldp-nlri-10.txt

Abstract

   Many service providers offer "BGP/MPLS IP VPN" service to their
   customers.  Existing IETF standards specify the procedures and
   protocols that a service provider uses in order to offer this service
   to customers who have IP unicast and IP multicast traffic in their
   VPNs.  It is also desirable to be able to support customers who have
   MPLS multicast traffic in their VPNs.  This document specifies the
   procedures and protocol extensions that are needed to support
   customers who use the Multicast Extensions to Label Distribution
   Protocol (mLDP) as the control protocol for their MPLS multicast
   traffic.  Existing standards do provide some support for customers
   who use mLDP, but only under a restrictive set of circumstances.
   This document generalizes the existing support to include all cases
   where the customer uses mLDP, without any restrictions.  This
   document updates RFC 6514.


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



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   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.


Copyright and License Notice

   Copyright (c) 2014 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
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   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.



Table of Contents

 1          Introduction  ..........................................   3
 2          Why This Document is Needed  ...........................   4
 3          Encoding an mLDP FEC in the MCAST-VPN NLRI  ............   5
 4          Wildcards  .............................................   7
 5          IANA Considerations  ...................................   7
 6          Security Considerations  ...............................  10
 7          Acknowledgments  .......................................  10
 8          Authors' Addresses  ....................................  10
 9          Normative References  ..................................  11
10          Informative References  ................................  11















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1. Introduction

   Many service providers (SPs) offer "BGP/MPLS IP VPN" service to their
   customers.  When a customer has IP multicast traffic in its VPN, the
   service provider needs to signal the customer multicast states across
   the backbone.  A customer with IP multicast traffic is typically
   using PIM ("Protocol Independent Multicast") [PIM] and/or IGMP
   ("Internet Group Management Protocol") [IGMP] as the multicast
   control protocol in its VPN.  The IP multicast states of these
   protocols are commonly denoted as "(S,G)" and/or "(*,G)" states,
   where "S" is a multicast source address and "G" is a multicast group
   address.  [MVPN-BGP] specifies the way an SP may use BGP to signal a
   customer's IP multicast states across the SP backbone.  This is done
   by using "Multiprotocol BGP" Updates whose "Subsequent Address Family
   Identifier" (SAFI) value is "MCAST-VPN" (5).  The NLRI ("Network
   Layer Reachability Information") field of these Updates includes a
   customer Multicast Source field and a customer Multicast Group field,
   thus enabling the customer's (S,G) or (*,G) states to be encoded in
   the NLRI.

   It is also desirable for the BGP/MPLS IP VPN service to be able to
   support customers who are using MPLS multicast, either instead of, or
   in addition to, IP multicast.  This document specifies the procedures
   and protocol extensions needed to support customers who use mLDP
   ("Multicast Extensions to Label Distribution Protocol") [mLDP] to
   create and maintain Point-to-Multipoint (P2MP) and/or Multipoint-to-
   Multipoint (MP2MP) Label Switched Paths (LSPs).  While mLDP is not
   the only protocol that can be used to create and maintain multipoint
   LSPs, consideration of other MPLS multicast control protocols is
   outside the scope of this document.

   When a customer is using mLDP in its VPN, the customer multicast
   states associated with mLDP are denoted by an mLDP "FEC Element"
   ("Forwarding Equivalence Class element", see [mLDP]), instead of by
   an (S,G) or (*,G).  Thus it is necessary to have a way to encode a
   customer's mLDP FEC Elements in the NLRI field of the BGP MCAST-VPN
   routes.

   While [MVPN-BGP] does specify a way of encoding an mLDP FEC Element
   in the MCAST-VPN NLRI field, the encoding specified therein makes a
   variety of restrictive assumptions about the customer's use of mLDP.
   (These assumptions are described in section 2 of this document.)  The
   purpose of this document is to update [MVPN-BGP] so that customers
   using mLDP in their VPNs can be supported even when those assumptions
   do not hold.

   Some SPs use the MVPN procedures to provide "global table multicast"
   service (i.e., multicast service that is not in the context of a VPN)



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   to customers.  Methods for doing this are specified in [GTM] and in
   [SEAMLESS-MCAST].  The procedures described in this document can be
   used along with the procedures of [GTM] or [SEAMLESS-MCAST] to
   provide global table multicast service to customers that use MPLS
   multicast in a global table context.

   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].


2. Why This Document is Needed

   An mLDP FEC Element consists of a FEC Type, a Root Node, and an
   Opaque Value.  mLDP uses several FEC types, and in particular, uses
   the FEC type to distinguish between P2MP LSPs and MP2MP LSPs.

   Section 11.1.2 of [MVPN-BGP] ("Originating routes: mLDP as the C-
   multicast control protocol") states:

       Whenever a PE ("Provider Edge" router) receives from one of its
       CEs ("Customer Edge" routers) a P2MP Label Map <X, Y, L> over
       interface I, where X is the Root Node Address, Y is the Opaque
       Value, and L is an MPLS label ... the PE constructs a Source Tree
       Join C-multicast route whose MCAST-VPN NLRI contains X as the
       Multicast Source field, and Y as the Multicast Group field.

   In other words, the Root Node of the mLDP FEC Element appears in the
   Multicast Source Field, and the Opaque Value of the mLDP FEC Element
   appears in the Multicast Group field.

   This method of encoding an mLDP FEC in an MCAST-VPN NLRI can only be
   used if all of the following conditions hold:

      1. A customer using mLDP is not also using PIM/IGMP.

         The encoding in [MVPN-BGP] does not specify any way in which
         one can determine, upon receiving a BGP Update, whether the
         Multicast Group field contains an IP address or whether it
         contains an mLDP FEC Element Opaque Value.  Therefore it might
         not uniquely identify a customer multicast state if the
         customer is using both PIM/IGMP and mLDP in its VPN.

      2. A customer using mLDP is using only the mLDP P2MP FEC Element,
         and is not using the mLDP MP2MP FEC Element.

         The encoding in [MVPN-BGP] does not specify any way to encode
         the type of the mLDP FEC Element; it just assumes it to be a



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         P2MP FEC Element.

      3. A customer using mLDP is using only an mLDP Opaque Value type
         for which the Opaque Value is exactly 32 bits or 128 bits long.

         The use of Multicast Group fields that have other lengths is
         declared by [MVPN-BGP] to be "out of scope" of that document
         (see, e.g., section 4.3 of that document).

         This condition holds if the customer uses only the mLDP
         "Generic LSP Identifier" Opaque Value type (defined in [mLDP]).
         However, mLDP supports many other Opaque Value types whose
         length is not restricted to be 32 or 128 bits.

   The purpose of this document is to update [MVPN-BGP] so that
   customers using mLDP can be supported, even when these conditions do
   not hold.


3. Encoding an mLDP FEC in the MCAST-VPN NLRI

   When mLDP is used as the customer multicast control protocol, [MVPN-
   BGP] presupposes that an mLDP FEC element will be encoded in the NLRI
   of the following three MCAST-VPN route types:

     - C-multicast Source Tree Join,

     - S-PMSI A-D route, and

     - Leaf A-D route.

   The other four MCAST-VPN route types defined in [MVPN-BGP] do not
   ever need to carry mLDP FEC Elements. The C-multicast Shared Tree
   Join route and the Source Active A-D route are used to communicate
   state about unidirectional shared trees; since mLDP does not have
   unidirectional shared trees, these routes are not used to signal mLDP
   states.  The Intra-AS I-PMSI A-D route and the Inter-AS I-PMSI A-D
   route do not identify specific customer multicast states, and hence
   do not carry any information that is specific to the customer's
   multicast control protocol.

   This document defines three new route types:

     - C-Multicast Source Tree Join route for C-multicast mLDP







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     - S-PMSI A-D route for C-multicast mLDP

     - Leaf A-D route for C-multicast mLDP.

   The term "C-multicast mLDP" in the names of these route types is
   intended to indicate that the NLRI of these routes contains mLDP FEC
   elements.

   Each of these route types corresponds to a route type defined in
   [MVPN-BGP].  IANA has been requested to allocate codepoints for these
   three route types such that (a) the high order two bits have the
   value 0x01, and (b) the low order six bits have the same value as
   the codepoints for the corresponding route types from [MVPN-BGP].

   In general, the procedures defined in other MVPN specifications for
   the C-Multicast Source Tree Join route, the S-PMSI A-D route, and the
   Leaf A-D route apply as well to the C-Multicast Source Tree Join
   route for C-multicast mLDP, the S-PMSI A-D route for C-multicast
   mLDP, and the Leaf A-D route for C-multicast mLDP, respectively.
   However, the NLRI of these three new route types is constructed
   differently than the NLRI of the corresponding routes from [MVPN-
   BGP]: the "Multicast Source Length", "Multicast Source", "Multicast
   Group Length", and "Multicast Group" fields are omitted, and in their
   place is a single mLDP FEC Element, as defined in [mLDP].  (See
   section 2.2 of [mLDP] for a diagram of the mLDP FEC element.)

   As a result, the NLRI of an S-PMSI A-D route for C-multicast mLDP
   will consist of a Route Distinguisher, followed by the mLDP FEC,
   followed by the "Originating Router's IP Address Field".

   The NLRI of a C-multicast Source Tree Join route for C-multicast mLDP
   will consist of a Route Distinguisher, followed by the Source AS,
   followed by the mLDP FEC.

   In a Leaf A-D route for C-multicast mLDP that has been derived from
   an S-PMSI A-D route for C-multicast mLDP, the "route key" field
   remains the NLRI of the S-PMSI A-D route from which it was derived.

   In a Leaf A-D route for C-multicast mLDP that has not been derived
   from an S-PMSI A-D, the "route key" field is as specified in
   [SEAMLESS-MCAST], except that the "Multicast Source Length",
   "Multicast Source", "Multicast Group Length", and "Multicast Group"
   fields are omitted, and in their place is a single mLDP FEC Element.
   Thus the route key field consists of a Route Distinguisher, an MLDP
   FEC element, and the IP address of the Ingress PE router.

   Please note that [BGP-ERR] section 5.4 ("Typed NLRI") is applicable
   if the Route Type field of the NLRI of a received MCAST-VPN route



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   contains an unrecognized value.  Any such routes will be discarded.

   An mLDP FEC element contains an "address family" field whose value is
   from IANA's "Address Family Numbers" registry.  The value of the
   "address family" field identifies the address family of the "root
   node address" field of the FEC element.  When an mLDP FEC element is
   encoded into the NLRI of an a BGP update whose SAFI is MCAST-VPN, the
   address family of the root node address (as indicated in the FEC
   element) MUST "correspond to" the address family that is identified
   in the "Address Family Identifier" (AFI) field of that BGP update.
   These two "address family" fields are considered to "correspond" to
   each other under the following conditions:

     - they contain identical values, or

     - the BGP update's AFI field identifies IPv4 as the address family,
       and the mLDP FEC element identifies "Multi-Topology IPv4" as the
       address family of the root node, or

     - the BGP update's AFI field identifies IPv6 as the address family,
       and the mLDP FEC element identifies "Multi-Topology IPv6" as the
       address family of the root node.

   For more information about the "multi-topology" address families, see
   [LDP-MT] and [mLDP-MT].


4. Wildcards

   [MVPN-WILDCARDS] specifies encodings and procedures that allow
   "wildcards" to be specified in the NLRI of S-PMSI A-D routes.  A set
   of rules are given that specify when a customer multicast flow
   "matches" a given S-PMSI A-D route whose NLRI contains wildcards.
   However, the use of these wildcards is defined only for the case
   where the customer is using PIM as its multicast control protocol.
   The use of wildcards when the customer is using mLDP as its multicast
   control protocol is outside the scope of this document.

5. IANA Considerations

   [MVPN-BGP] does not create a registry for the allocation of new
   MCAST-VPN Route Type values.  In retrospect, it seems that it should
   have done so.  IANA is requested to create a new registry called "BGP
   MCAST-VPN Route Types", referencing this document and [MVPN-BGP].
   The registry should be created under the "top-level" registry:
   "Border Gateway Protocol (BGP) Parameters
   http://www.iana.org/assignments/bgp-parameters/bgp-parameters".  The
   allocation policy should be "Standards Action".  Values may be



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   assigned from one of several ranges:

     - Range 0x01-0x3f: Generic/PIM Range.  Values are assigned from
       this range when the NLRI format associated with the route type
       presupposes that PIM or IGMP is the C-multicast control protocol,
       or when the NLRI format associated with the route type is
       independent of the C-multicast control protocol.

     - Range 0x43-0x7f: mLDP Range.  Values are assigned from this range
       when the NLRI format associated with the route type presupposes
       that mLDP is the C-multicast control protocol.

     - Range 0x80-0xff: This range is reserved; values should not be
       assigned from this range.

   In general, whenever an assignment is requested from this registry,
   two codepoints should be requested at the same time: one from the
   Generic/PIM range and one from the mLDP range.  The two codepoints
   should have the same low-order 6 bits.  If one of the two codepoints
   is not actually needed, it should be registered anyway, and marked as
   "reserved".

   When the BGP MCAST-VPN Route Types registry is created, it should
   contain the following assignments:



























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    Value       Meaning                              Reference
    0x00        Reserved                             This RFC

    0x01        Intra-AS I-PMSI A-D route            This RFC, RFC6514

    0x02        Inter-AS I-PMSI A-D route            This RFC, RFC6514

    0x03        S-PMSI A-D route                     This RFC, RFC6514

    0x04        Leaf A-D route                       This RFC, RFC6514

    0x05        Source Active A-D route              This RFC, RFC6514

    0x06        Shared Tree Join route               This RFC, RFC6514



    0x07        Source Tree Join route               This RFC, RFC6514

    0x08-0x3f   Unassigned (Generic/PIM range)       This RFC

    0x40-0x42   Reserved                             This RFC

    0x43        S-PMSI A-D route for
                C-multicast mLDP                     This RFC

    0x44        Leaf A-D route for C-multicast mLDP  This RFC

    0x45-0x46   Reserved                             This RFC

    0x47        Source Tree Join route for
                C-multicast mLDP                     This RFC

    0x48-0x7f   Unassigned (mLDP range)              This RFC

    0x80-0xff   Reserved                             This RFC















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6. Security Considerations

   This document specifies a method of encoding an mLDP FEC element in
   the NLRI of some of the BGP Update messages that are specified in
   [MVPN-BGP].  The security considerations of [mLDP] and of [MVPN-BGP]
   are applicable, but no new security considerations are raised.


7. Acknowledgments

   The authors wish to thank Pradosh Mohapatra and Saquib Najam for
   their ideas and comments.  We also thank Yakov Rekhter and Martin
   Vigoureux for their comments.



8. Authors' Addresses

   IJsbrand Wijnands
   Cisco Systems, Inc.
   De kleetlaan 6a Diegem 1831
   BE
   E-mail: ice@cisco.com


   Eric C. Rosen
   Juniper Networks, Inc.
   10 Technology Park Drive
   Westford, Massachusetts  01886
   US
   E-mail: erosen@juniper.net


   Uwe Joorde
   Deutsche Telekom
   Hammer Str. 216-226
   D-48153 Muenster, Germany
   E-mail: Uwe.Joorde@telekom.de













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9. Normative References

   [mLDP] "Label Distribution Protocol Extensions for Point-to-
   Multipoint and Multipoint-to-Multipoint Label Switched Paths",
   Wijnands, Minei, Kompella, Thomas, RFC 6388, November 2011

   [MVPN-BGP] "BGP Encodings and Procedures for Multicast in MPLS/BGP IP
   VPNs", Aggarwal, Rosen, Morin, Rekhter, RFC 6514, February 2012

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


10. Informative References

   [BGP-ERR] "Revised Error Handling for BGP UPDATE Messages", Chen,
   Scudder, Mohapatra, Patel, draft-ietf-idr-error-handling-16.txt,
   November 2014

   [GTM] "Global Table Multicast with BGP-MVPN Procedures", Zhang,
   Giuliano, Rosen, Subramanian, Pacella, Schiller, draft-ietf-l3vpn-
   mvpn-global-table-mcast-00.txt, June 2014

   [IGMP] "Internet Group Management Protocol, Version 3", Cain,
   Deering, Kouvelas, Fenner, Thyagarajan, RFC 3376, October 2002

   [LDP-MT] "LDP Extensions for Multi-Topology", Zhao, et. al., RFC
   7307, July 2014

   [mLDP-MT] "mLDP Extensions for Multi Topology Routing", Wijnands,
   Raza, draft-iwijnand-mpls-mldp-multi-topology-03.txt, June 2013

   [MVPN-WILDCARDS], "Wildcards in Multicast VPN Auto-Discovery Routes",
   Rosen, Rekhter, Hendrickx, Qiu, RFC 6625, May 2012

   [PIM] "Protocol Independent Multicast - Sparse Mode (PIM-SM)",
   Fenner, Handley, Holbrook, Kouvelas, August 2006, RFC 4601

   [SEAMLESS-MCAST] "Inter-Area P2MP Segmented LSPs", Rekhter, Aggarwal,
   Morin, Grosclaude, Leymann, Saad, draft-ietf-mpls-seamless-
   mcast-14.txt, July 2014










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