Multipoint Label Distribution Protocol In-Band Signaling in a VRF Context
draft-ietf-l3vpn-mldp-vrf-in-band-signaling-00

Network Working Group                                  IJ. Wijnands, Ed.
Internet-Draft                                             Cisco Systems
Intended status: Standards Track                              P. Hitchen
Expires: June 23, 2013                                                BT
                                                              N. Leymann
                                                        Deutsche Telekom
                                                           W. Henderickx
                                                          Alcatel-Lucent
                                                                A. Gulko
                                                         Thomson Reuters
                                                       December 20, 2012

                 Multipoint Label Distribution Protocol
                   In-Band Signaling in a VRF Context
             draft-ietf-l3vpn-mldp-vrf-in-band-signaling-00

Abstract

   Sometimes an IP multicast distribution tree (MDT) traverses both
   MPLS-enabled and non-MPLS-enabled regions of a network.  Typically
   the MDT begins and ends in non-MPLS regions, but travels through an
   MPLS region.  In such cases, it can be useful to begin building the
   MDT as a pure IP MDT, then convert it to an MPLS Multipoint LSP
   (Label Switched Path) when it enters an MPLS-enabled region, and then
   convert it back to a pure IP MDT when it enters a non-MPLS-enabled
   region.  Other documents specify the procedures for building such a
   hybrid MDT, using Protocol Independent Multicast (PIM) in the non-
   MPLS region of the network, and using Multipoint Extensions to Label
   Distribution Protocol (mLDP) in the MPLS region.  This document
   extends those procedures to handle the case where the link connecting
   the two regions is a "Virtual Routing and Forwarding Table" (VRF)
   link, as defined in the "BGP IP/MPLS VPN" specifications.  However,
   this document is primarily aimed at particular use cases where VRFs
   are used to support multicast applications other than Multicast VPN.

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/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any

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   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on June 23, 2013.

Copyright Notice

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   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Conventions used in this document  . . . . . . . . . . . .  5
     1.2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  5
   2.  VRF In-band signaling for MP LSPs  . . . . . . . . . . . . . .  6
   3.  Encoding the Opaque Value of an LDP MP FEC . . . . . . . . . .  7
     3.1.  Transit VPNv4 Source TLV . . . . . . . . . . . . . . . . .  7
     3.2.  Transit VPNv6 Source TLV . . . . . . . . . . . . . . . . .  8
     3.3.  Transit VPNv4 bidir TLV  . . . . . . . . . . . . . . . . .  9
     3.4.  Transit VPNv6 bidir TLV  . . . . . . . . . . . . . . . . . 10
   4.  Security Considerations  . . . . . . . . . . . . . . . . . . . 11
   5.  IANA considerations  . . . . . . . . . . . . . . . . . . . . . 11
   6.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 11
   7.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     7.1.  Normative References . . . . . . . . . . . . . . . . . . . 11
     7.2.  Informative References . . . . . . . . . . . . . . . . . . 12
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12

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1.  Introduction

   Sometimes an IP multicast distribution tree (MDT) traverses both
   MPLS-enabled and non-MPLS-enabled regions of a network.  Typically
   the MDT begins and ends in non-MPLS regions, but travels through an
   MPLS region.  In such cases, it can be useful to begin building the
   MDT as a pure IP MDT, then convert it to an MPLS Multipoint LSP
   (Label Switched Path) when it enters an MPLS-enabled region, and then
   convert it back to a pure IP MDT when it enters a non-MPLS-enabled
   region.  Other documents specify the procedures for building such a
   hybrid MDT, using Protocol Independent Multicast (PIM) in the non-
   MPLS region of the network, and using Multipoint Extensions to Label
   Distribution Protocol (mLDP) in the MPLS region.  This document
   extends those procedures to handle the case where the link connecting
   the two regions is a "Virtual Routing and Forwarding Table" (VRF)
   link, as defined in the "BGP IP/MPLS VPN" specifications.  However,
   this document is primarily aimed at particular use cases where VRFs
   are used to support multicast applications other than Multicast VPN.

   In PIM, a tree is identified by a source address (or in the case of
   bidirectional trees [RFC5015], a rendezvous point address or "RPA")
   and a group address.  The tree is built from the leaves up, by
   sending PIM control messages in the direction of the source address
   or the RPA.  In mLDP, a tree is identified by a root address and an
   "opaque value", and is built by sending mLDP control messages in the
   direction of the root.  The procedures of
   [I-D.ietf-mpls-mldp-in-band-signaling] explain how to convert a PIM
   <source address or RPA, group address> pair into an mLDP <root node,
   opaque value> pair;, and how to convert the mLDP <root node, opaque
   value> pair back into the original PIM <source address or RPA, group
   address> pair.

   However, those procedures assume that the routers doing the PIM/mLDP
   conversion have routes to the source address or RPA in their global
   routing tables.  Thus the procedures cannot be applied exactly as
   specified when the interfaces connecting the non-MPLS-enabled region
   to the MPLS-enabled region are interfaces that belong to a VRF as
   described in [RFC4364].  This specification extends the procedures of
   [I-D.ietf-mpls-mldp-in-band-signaling] so that they may be applied in
   the VRF context.

   As in [I-D.ietf-mpls-mldp-in-band-signaling], the scope of this
   document is limited to the case where the multicast content is
   distributed in the non-MPLS-enabled regions via PIM-created Source-
   Specific or Bidirectional trees.  Bidirectional trees are always
   mapped onto Multipoint-to-Multipoint LSPs, and source-specific trees
   are always mapped onto Point-to-Multipoint LSPs.

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   Note that the procedures described herein do not support non-
   bidirectional PIM ASM groups, do not support the use of multicast
   trees other than mLDP multipoint LSPs in the core, and do not provide
   the capability to aggregate multiple PIM trees onto a single
   multipoint LSP.  If any of those features are needed, they can be
   provided by the procedures of [RFC6513] and [RFC6514].  However,
   there are cases where multicast services are offered through VRF
   interfaces, and where mLDP is used in the core, but where aggregation
   is not desired.  For example, some service providers offer multicast
   content to their customers, but have chosen to use VRFs to isolate
   the various customers and services.  This is a simpler scenario that
   one in which the customers provide their own multicast content, out
   of the control of the service provider, and can be handled with a
   simpler solution.  Also, when PIM trees are mapped one-to-one to
   multipoint LSPs, it is helpful for troubleshooting purposes to have
   the PIM source/group addresses encoded into the mLDP FEC element.

   In order to use the mLDP in-band signaling procedures for a
   particular group address in the context of a particular set of VRFs,
   those VRFs MUST be configured with a range of multicast group
   addresses for which mLDP in-band signaling is to be enabled.  This
   configuration is per VRF ("Virtual Routing and Forwarding table",
   defined in [RFC4364]).  For those groups, and those groups only, the
   procedures of this document are used.  For other groups the general
   purpose Multicast VPN procedures MAY be used, although it is more
   likely this VRF is dedicated to mLDP in-band signaling procedures and
   all other groups are discarded.  The configuration must be present in
   all PE routers that attach to sites containing senders or receivers
   for the given set of group addresses.  Note, since the provider most
   likely owns the multicast content and how it is transported across
   the network is transparent to the end-user, no co-oordination needs
   to happen between the end-user and the provider.

1.1.  Conventions used in this document

   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].

1.2.  Terminology

   IP multicast tree :  An IP multicast distribution tree identified by
      an source IP address and/or IP multicast destination address, also
      referred to as (S,G) and (*,G).

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   mLDP :  Multicast LDP.

   In-band signaling :  Using the opaque value of a mLDP FEC element to
      encode the (S,G) or (*,G) identifying a particular IP multicast
      tree.

   P2MP LSP:  An LSP that has one Ingress LSR and one or more Egress
      LSRs (see [RFC6388]).

   MP2MP LSP:  An LSP that connects a set of leaf nodes, acting
      indifferently as ingress or egress (see [RFC6388]).

   MP LSP:  A multipoint LSP, either a P2MP or an MP2MP LSP.

   Ingress LSR:  Source of a P2MP LSP, also referred to as root node.

   VRF:  Virtual Routing and Forwarding table.

2.  VRF In-band signaling for MP LSPs

   Suppose that a PE router, PE1, receives a PIM Join(S,G) message over
   one of its VRF interfaces.  Following the procedure of section 5.1 of
   [RFC6513], PE1 determines the "upstream RD", the "upstream PE", and
   the "upstream multicast hop" (UMH) for the source address S. Please
   note that sections 5.1.1 and 5.1.2 of [RFC6513] are applicable.

   In order to transport the multicast tree via a MP LSP using VRF in-
   band signaling, an mLDP Label Mapping Message is sent by PE1.  This
   message will contain either a P2MP FEC or an MP2MP FEC (see
   [RFC6388], depending upon whether the PIM tree being transported is a
   source-specific tree, or a bidirectional tree, respectively.  The FEC
   contains a "root" and an "opaque value".

   If the UMH and the upstream PE have the same IP address (i.e., the
   Upstream PE is the UMH), then the root of the Multipoint FEC is set
   to the IP address of the Upstream PE.  If, in the context of this
   VPN, (S,G) refers to a source-specific MDT, then the values of S, G,
   and the upstream RD are encoded into the opaque value.  If, in the
   context of this VPN, G is a bidirectional group address, then S is
   replaced with the value of the RPA associated with G. The coding
   details are specified in Section 3.  Conceptually, the Multipoint FEC

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   can be thought of as an ordered pair: <root=Upstream-PE,
   opaque_value=<S or RPA ,G ,Upstream-RD>.  The mLDP Label Mapping
   Message is then sent by PE1 on its LDP session to the "next hop" on
   its path to the upstream PE.  The "next hop" is usually the IGP next
   hop, but see [I-D.ietf-mpls-targeted-mldp] for cases in which the
   next hop is not the IGP next hop.

   If the UMH and the upstream PE do not have the same IP address, the
   procedures of section 2 of [RFC6512] should be applied.  The root
   node of the multipoint FEC is set to the UMH.  The recursive opaque
   value is then set as follows: the root node is set to the upstream
   PE, and the opaque value is set to the multipoint FEC described in
   the previous paragraph.  That is, the multipoint FEC can be thought
   of as the following recursive ordered pair: <root=UMH,
   opaque_value=<root=Upstream-PE, opaque_value =<S or RPA, G,
   Upstream-RD>>.

   The encoding of the multipoint FEC also specifies the "type" of PIM
   MDT being spliced onto the multipoint LSP.  Four types of MDT are
   defined: IPv4 source-specific tree, IPv6 source-specific tree, IPv4
   bidirectional tree, and IPv6 bidirectional tree.

   When a PE router receives an mLDP message with a P2MP or MP2MP FEC,
   where the PE router itself is the root node, and the opaque value is
   one of the types defined in Section 3, then it uses the RD encoded in
   the opaque value field to determine the VRF context.  (This RD will
   be associated with one of the PEs VRFs.)  Then, in the context of
   that VRF, the PE follows the procedure specified in section 2 of
   [I-D.ietf-mpls-mldp-in-band-signaling].

3.  Encoding the Opaque Value of an LDP MP FEC

   This section documents the different transit opaque encodings.

3.1.  Transit VPNv4 Source TLV

   This opaque value type is used when transporting a source-specific
   mode multicast tree whose source and group addresses are IPv4
   addresses.

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      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Type          | Length                        | Source
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                                     | Group
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                                     |               ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ~                   RD                          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type:  (to be assigned by IANA).

   Length:  16

   Source:  IPv4 multicast source address, 4 octets.

   Group:  IPv4 multicast group address, 4 octets.

   RD:  Route Distinguisher, 8 octets.

3.2.  Transit VPNv6 Source TLV

   This opaque value type is used when transporting a source-specific
   mode multicast tree whose source and group addresses are IPv6
   addresses.

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Type          | Length                        | Source        ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ~                                               | Group         ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ~                                               |               ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ~                 RD                            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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   Type:  (to be assigned by IANA).

   Length:  40

   Source:  IPv6 multicast source address, 16 octets.

   Group:  IPv6 multicast group address, 16 octets.

   RD:  Route Distinguisher, 8 octets.

3.3.  Transit VPNv4 bidir TLV

   This opaque value type is used when transporting a bidirectional
   multicast tree whose group address is an IPv4 address.  The RP
   address is also an IPv4 address in this case.

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Type          | Length                        | Mask Len      |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                              RP                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                            Group                              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ~                              RD                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type:  (to be assigned by IANA).

   Length:  17

   Mask Len:  The number of contiguous one bits that are left justified
      and used as a mask, 1 octet.

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   RP:  Rendezvous Point (RP) IPv4 address used for encoded Group, 4
      octets.

   Group:  IPv4 multicast group address, 4 octets.

   RD:  Route Distinguisher, 8 octets.

3.4.  Transit VPNv6 bidir TLV

   This opaque value type is used when transporting a bidirectional
   multicast tree whose group address is an IPv6 address.  The RP
   address is also an IPv6 address in this case.

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Type          | Length                        | Mask Len      |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                              RP                               ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ~                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                            Group                              ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ~                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ~                              RD                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type:  (to be assigned by IANA).

   Length:  41

   Mask Len:  The number of contiguous one bits that are left justified
      and used as a mask, 1 octet.

   RP:  Rendezvous Point (RP) IPv6 address used for encoded group, 16
      octets.

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   Group:  IPv6 multicast group address, 16 octets.

   RD:  Route Distinguisher, 8 octets.

4.  Security Considerations

   The same security considerations apply as for the base LDP
   specification, described in [RFC5036], and the base mLDP
   specification, described in [RFC6388]

5.  IANA considerations

   [RFC6388] defines a registry for "The LDP MP Opaque Value Element
   Basic Type".  This document requires the assignment of four new code
   points in this registry:

      Transit VPNv4 Source TLV type

      Transit VPNv6 Source TLV type

      Transit VPNv4 Bidir TLV type

      Transit VPNv6 Bidir TLV type

6.  Acknowledgments

   Thanks to Eric Rosen, Andy Green and Yakov Rekhter for their comments
   on the draft.

7.  References

7.1.  Normative References

   [RFC4364]  Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
              Networks (VPNs)", RFC 4364, February 2006.

   [RFC5015]  Handley, M., Kouvelas, I., Speakman, T., and L. Vicisano,
              "Bidirectional Protocol Independent Multicast (BIDIR-
              PIM)", RFC 5015, October 2007.

   [RFC5036]  Andersson, L., Minei, I., and B. Thomas, "LDP
              Specification", RFC 5036, October 2007.

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

   [RFC6388]  Wijnands, IJ., Minei, I., Kompella, K., and B. Thomas,
              "Label Distribution Protocol Extensions for Point-to-
              Multipoint and Multipoint-to-Multipoint Label Switched
              Paths", RFC 6388, November 2011.

   [RFC6512]  Wijnands, IJ., Rosen, E., Napierala, M., and N. Leymann,
              "Using Multipoint LDP When the Backbone Has No Route to
              the Root", RFC 6512, February 2012.

   [I-D.ietf-mpls-mldp-in-band-signaling]
              Wijnands, I., Eckert, T., Leymann, N., and M. Napierala,
              "Multipoint LDP in-band signaling for Point-to-Multipoint
              and Multipoint- to-Multipoint Label Switched Paths",
              draft-ietf-mpls-mldp-in-band-signaling-06 (work in
              progress), June 2012.

7.2.  Informative References

   [I-D.ietf-mpls-targeted-mldp]
              Napierala, M. and E. Rosen, "Using LDP Multipoint
              Extensions on Targeted LDP Sessions",
              draft-ietf-mpls-targeted-mldp-00 (work in progress),
              August 2012.

   [RFC6513]  Rosen, E. and R. Aggarwal, "Multicast in MPLS/BGP IP
              VPNs", RFC 6513, February 2012.

   [RFC6514]  Aggarwal, R., Rosen, E., Morin, T., and Y. Rekhter, "BGP
              Encodings and Procedures for Multicast in MPLS/BGP IP
              VPNs", RFC 6514, February 2012.

Authors' Addresses

   IJsbrand Wijnands (editor)
   Cisco Systems
   De kleetlaan 6a
   Diegem  1831
   Belgium

   Email: ice@cisco.com

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   Paul Hitchen
   BT
   BT Adastral Park
   Ipswich  IP53RE
   UK

   Email: paul.hitchen@bt.com

   Nicolai Leymann
   Deutsche Telekom
   Winterfeldtstrasse 21
   Berlin  10781
   Germany

   Email: n.leymann@telekom.de

   Wim Henderickx
   Alcatel-Lucent
   Copernicuslaan 50
   Antwerp  2018
   Belgium

   Email: wim.henderickx@alcatel-lucent.com

   Arkadiy Gulko
   Thomson Reuters
   195 Broadway
   New York  NY 10007
   USA

   Email: arkadiy.gulko@thomsonreuters.com

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