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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                                             Eric C. Rosen
Intended Status: Proposed Standard                   Cisco Systems, Inc.
Updates: 6514
Expires: November 20, 2014                                    Uwe Joorde
                                                        Deutsche Telekom

                                                            May 20, 2014


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


                 draft-ietf-l3vpn-mvpn-mldp-nlri-05.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.


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
 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  ...............................   9
 7          Acknowledgments  .......................................   9
 8          Authors' Addresses  ....................................   9
 9          Normative References  ..................................  10
10          Informative References  ................................  10













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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" (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 Equivalance 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 mLDP as the C-multicast
       control protocol.






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     - S-PMSI A-D route for mLDP as the C-multicast control protocol.

     - Leaf A-D route for mLDP as the C-multicast control protocol.

   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 bit 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 mLDP, the S-PMSI A-D route for mLDP, and the Leaf A-D route
   for 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 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 mLDP will
   consist of a Route Distinguisher, followed by the Source AS, followed
   by the mLDP FEC.

   In a Leaf A-D route for mLDP that has been derived from an S-PMSI A-D
   route for 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 mLDP that has not been derived from an S-PMSI
   A-D route for mLDP, 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 4.3 ("Typed NLRI") is applicable
   if the Route Type field of the NLRI of a received MCAST-VPN route
   contains an unrecognized value.

   An mLDP FEC element contains an "address family" field whose value is
   from IANA's "Address Family Numbers" registry.  The value of the



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   "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 should create a registry called "MCAST-VPN Route
   Types", referencing this document and [MVPN-BGP].  The allocation
   policy should be "Standards Action".  Values may be 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 is the C-multicast control protocol, or when
       the the NLRI format associated with the route type is independent
       of the C-multicast control protocol.



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     - Range 0x41-0x7f: 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 for future use; values
       should not be assigned from this range.

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

     - 0x00: Reserved (not to be assigned)

     - 0x01: Intra-AS I-PMSI A-D route (reference: [MVPN-BGP])

     - 0x02: Inter-AS I-PMSI A-D route (reference: [MVPN-BGP])

     - 0x03: S-PMSI A-D route for PIM as the C-Multicast control
       protocol (reference: [MVPN-BGP])

     - 0x04: Leaf A-D route for PIM as the C-Multicast control protocol
       (reference: [MVPN-BGP])

     - 0x05: Source Active A-D route for PIM as the C-Multicast control
       protocol (reference: [MVPN-BGP])

     - 0x06: Shared Tree Join route for PIM as the C-Multicast control
       protocol (reference: [MVPN-BGP])

     - 0x07: Source Tree Join route for PIM as the C-Multicast control
       protocol (reference: [MVPN-BGP])

     - 0x40-0x42: Reserved (not to be assigned)

     - 0x43: S-PMSI A-D route for mLDP as the C-Multicast control
       protocol (reference: this document)

     - 0x44: Leaf A-D route for mLDP as the C-Multicast control protocol
       (reference: this document)

     - 0x45-0x46: Reserved (not to be assigned)

     - 0x47: Source Tree Join route for mLDP as the C-Multicast control
       protocol (reference: this document)

   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 5 bits.  If one of the two codepoints



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   is not actually needed, it should be registered anyway, and marked as
   "reserved (not to be assigned)".


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 think 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
   Belgium
   E-mail: ice@cisco.com


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


   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-09.txt, May
   2014

   [GTM] "Global Table Multicast with BGP-MVPN Procedures", Zhang,
   Giuliano, Rosen, Subramanian, Pacella, Schiller, draft-zzhang-l3vpn-
   mvpn-global-table-mcast-04.txt, May 2014

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

   [LDP-MT] "LDP Extensions for Multi-Topology Routing", Zhao, et. al.,
   draft-ietf-mpls-ldp-multi-topology-12.txt, April 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-09.txt, December 2013










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