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Versions: (draft-wijnands-mpls-mldp-in-band-signaling) 00 01 02 03 04 05 06 07 08 RFC 6826

Network Working Group                                  IJ. Wijnands, Ed.
Internet-Draft                                                 T. Eckert
Intended status: Standards Track                     Cisco Systems, Inc.
Expires: August 12, 2011                                      N. Leymann
                                                        Deutsche Telekom
                                                            M. Napierala
                                                               AT&T Labs
                                                        February 8, 2011


mLDP based in-band signaling for Point-to-Multipoint and Multipoint-to-
                    Multipoint Label Switched Paths
               draft-ietf-mpls-mldp-in-band-signaling-03

Abstract

   Suppose an IP multicast tree, constructed by Protocol Independent
   Multicast (PIM), needs to pass through an MPLS domain in which
   Multipoint LDP (mLDP) Point-to-Multipoint and/or Multipoint-to-
   Multipoint Labels Switched Paths (LSPs) can be created.  The part of
   the IP multicast tree that traverses the MPLS domain can be
   instantiated as a multipoint LSP.  When a PIM Join message is
   received at the border of the MPLS domain, information from that
   message is encoded into mLDP messages.  When the mLDP messages are
   received at the border of the next IP domain, the encoded information
   is used to generate PIM messages that can be sent through the IP
   domain.  The result is an IP multicast tree consisting of a set of IP
   multicast sub-trees that are spliced together with a multipoint LSP.

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
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   Drafts.

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   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



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   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on August 12, 2011.

Copyright Notice

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Conventions used in this document  . . . . . . . . . . . .  3
     1.2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  In-band signaling for MP LSPs  . . . . . . . . . . . . . . . .  4
     2.1.  Transiting Unidirectional IP multicast Shared Trees  . . .  5
     2.2.  Transiting IP multicast source trees . . . . . . . . . . .  5
     2.3.  Transiting IP multicast bidirectional trees  . . . . . . .  6
   3.  LSP opaque encodings . . . . . . . . . . . . . . . . . . . . .  7
     3.1.  Transit IPv4 Source TLV  . . . . . . . . . . . . . . . . .  7
     3.2.  Transit IPv6 Source TLV  . . . . . . . . . . . . . . . . .  7
     3.3.  Transit IPv4 bidir TLV . . . . . . . . . . . . . . . . . .  8
     3.4.  Transit IPv6 bidir TLV . . . . . . . . . . . . . . . . . .  8
   4.  Security Considerations  . . . . . . . . . . . . . . . . . . .  9
   5.  IANA considerations  . . . . . . . . . . . . . . . . . . . . .  9
   6.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 10
   7.  Contributing authors . . . . . . . . . . . . . . . . . . . . . 10
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 11
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 11
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12





























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1.  Introduction

   The mLDP specification [I-D.ietf-mpls-ldp-p2mp] describes mechanisms
   for creating point-to-multipoint (P2MP) and multipoint-to-multipoint
   MP2MP LSPs.  These LSPs are typically used for transporting enduser
   multicast packets.  However, the mLDP specification
   [I-D.ietf-mpls-ldp-p2mp] does not provide any rules for associating
   particular enduser multicast packets with any particular LSP.  Other
   drafts, like [I-D.ietf-l3vpn-2547bis-mcast], describe applications in
   which out-of-band signaling protocols, such as PIM and BGP, are used
   to establish the mapping between an LSP and the multicast packets
   that need to be forwarded over the LSP.

   This draft describes an application in which the information needed
   to establish the mapping between an LSP and the set of multicast
   packets to be forwarded over it is carried in the "opaque value"
   field of an mLDP FEC element.  When an IP multicast tree (either a
   source-specific tree or a bidirectional tree) enters the MPLS network
   the (S,G) or (*,G) information from the IP multicast control plane
   state is carried in the opaque value field of the mLDP FEC message.
   As the tree leaves the MPLS network, this information is extracted
   from the FEC element and used to build the IP multicast control
   plane.  PIM messages can be sent outside the MPLS domain.  Note that
   although the PIM control messages are sent periodically, the mLDP
   messages are not.

   Each IP multicast tree is mapped one-to-one to a P2MP or MP2MP LSP in
   the MPLS network.  This type of service works well if the number of
   LSPs that are created is under control of the MPLS network operator,
   or if the number of LSPs for a particular service are known to be
   limited in number.

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
      refered to as (S,G) and (*,G).







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   mLDP :  Multicast LDP.


   Transit LSP :  An P2MP or MP2MP LSP whose FEC element contains the
      (S,G) or (*,G) identifying a particular IP multicast distribution
      tree.


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


   P2MP LSP:  An LSP that has one Ingress LSR and one or more Egress
      LSRs.


   MP2MP LSP:  An LSP that connects a set of leaf nodes, acting
      indifferently as ingress or egress.


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


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


   Egress LSR:  One of potentially many destinations of an LSP, also
      referred to as leaf node in the case of P2MP and MP2MP LSPs.


   Transit LSR:  An LSR that has one or more directly connected
      downstream LSRs.


2.  In-band signaling for MP LSPs

   Suppose an LSR, call it D, is attached to a network that is capable
   of MPLS multicast and IP multicast, and D has the desire to create IP
   multicast tree due to a certain IP multicast event, like a PIM Join,
   MSDP Source Announcement (SA) [RFC3618], BGP Source Active auto-
   discovery route [I-D.rekhter-pim-sm-over-mldp] or RP discovery.
   Suppose that D can determine that the IP multicast tree needs to
   travel through the MPLS network until it reaches some other LSR, U.
   For instance, when D looks up the route to the Source or Rendezvous
   Point (RP) [RFC4601] of the IP multicast tree, it may discover that
   the route is a BGP route with U as the BGP next hop.  Then D may
   chose to set up a P2MP or MP2MP LSP, with U as root, and to make that



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   LSP become part of the IP multicast distribution tree.  Note that
   other methods are possible to determine that an IP multicast tree is
   to be transported across an MPLS network using P2MP or MP2MP LSPs,
   these methods are outside the scope of this document.

   Source or RP addresses that are reachable in a VPN context are
   outside the scope of this document.

   Multicast groups that operate in PIM Dense-Mode are outside the scope
   of this document.

   In order to transport the multicast tree via a P2MP or MP2MP LSP
   using in-band signaling the source and the group will be encoded into
   an mLDP opaque TLV encoding [I-D.ietf-mpls-ldp-p2mp].  The type of
   encoding depends on the IP version.  The tree type (P2MP or MP2MP)
   depends on whether this is a source specific or a bidirectional
   multicast tree.  The root of the tree is the BGP next-hop that was
   found during the route lookup on the source or RP.  Using this
   information a mLDP FEC is created and the LSP is build towards the
   root of the LSP.

   When an LSR receives a label mapping or withdraw and discovers it is
   the root of the identified P2MP or MP2MP LSP, then the following
   procedure is executed.  If the opaque encoding of the FEC indicates
   this is a Transit LSP (indicated by the opaque type), the opaque TLV
   is decoded and the multicast source and group is passed to the
   multicast code.  If the multicast tree information is received via a
   label mapping, the multicast code will adds the downstream LDP
   neighbor to the olist of the corresponding (S,G) or (*,G) state,
   creating such state if it does not already exist.  If it is due to a
   label withdraw, the multicast code will remove the downstream LDP
   neighbor from the olist of the corresponding (S,G) or (*,G) state.
   From this point on normal PIM processing will occur.

2.1.  Transiting Unidirectional IP multicast Shared Trees

   Nothing prevents PIM shared trees, used by PIM-SM in the ASM service
   model, from being transported across a MPLS core.  However, it is not
   possible to prune individual sources from the shared tree without the
   use of an additional out-of-band signaling protocol, like PIM or BGP
   [I-D.rekhter-pim-sm-over-mldp].  For that reason transiting Shared
   Trees across a Transit LSP is outside the scope of this draft.

2.2.  Transiting IP multicast source trees

   IP multicast source trees can either be created via PIM operating in
   SSM mode [RFC4607] or ASM mode [RFC4601].  When PIM-SM is used in ASM
   mode, the usual means of discovering active sources is to join a



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   sparse mode shared tree.  However, this document does not provide any
   method of transporting a sparse mode shared tree across an MPLS
   network.  To apply the technique of this document to PIM-SM in ASM
   mode, there must be some other means of discovering the active
   sources.  One possible means is the use of MSDP [RFC3618].  Another
   possible means is to use BGP Source Active auto-discovery routes, as
   documented in [I-D.rekhter-pim-sm-over-mldp].  However, the method of
   discovering the active sources is outside the scope of this document,
   and as a result this document does not specify everything that is
   needed to support the ASM service model using in-band signaling.

   The source and group addresses are encoded into the a transit TLV as
   specified in Section 3.1 and Section 3.2.

2.3.  Transiting IP multicast bidirectional trees

   Bidirectional IP multicast trees [RFC5015] MUST be transported across
   a MPLS network using MP2MP LSPs.  A bidirectional tree does not have
   a specific source address; the group address, subnet mask and RP are
   relevant for multicast forwarding.  This document does not provide
   procedures to discover RP to group mappings dynamically across an
   MPLS network and assumes the RP is statically defined.  Support of
   dynamic RP mappings in combination with in-band signaling is outside
   the scope of his document.

   The RP for the group is used to select the ingress PE and root of the
   LSP.  The group address is encoded according to the rules of
   Section 3.3 or Section 3.4, depending on the IP version.  The subnet
   mask associated with the bidirectional group is encoded in the
   Transit TLV.  There are two types of bidirectional states in IP
   multicast, the group specific state and the RPA state.  The first
   type is typically created due to receiving a PIM join and has a
   subnet mask of 32 for IPv4 and 128 for IPv6.  The latter is typically
   created via the static RP mapping and has a variable subnet mask.
   The RPA state is used to build a tree to the RP and used for sender
   only branches.  Each state (group specific and RPA state) will result
   in a separate MP2MP LSP.  The merging of the two MP2MP LSPs will be
   done by PIM on the root LSR.  No speccial procedures are nessesary
   for PIM to merge the two LSPs, each LSP is effectively treated as a
   PIM enabled interface.  Please see [RFC5015] for more details.

   In order transport the packets of sender only branch to the root of
   the LSP a MP2MP is created.  This will cause the sender only branches
   to receive each others packets.  These packets will be dropped and
   not forwarded, if that affect is undesireable some other means of
   transport has to be established to forward packets to the root of the
   tree, like a Multi-Point to Point LSP for example.  A technique to
   unicast packets to the root of a P2MP or MP2MP LSP is documented in



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   [I-D.rosen-l3vpn-mvpn-mspmsi] section 3.2.2.1 and
   [I-D.ietf-mpls-ldp-p2mp] section 3.


3.  LSP opaque encodings

   This section documents the different transit opaque encodings.

3.1.  Transit IPv4 Source TLV



     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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                                     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Type:  3 (to be assigned by IANA).


   Length:  8


   Source:  IPv4 multicast source address, 4 octets.


   Group:  IPv4 multicast group address, 4 octets.

3.2.  Transit IPv6 Source TLV



     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         ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ~                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+




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   Type:  4 (to be assigned by IANA).


   Length:  32


   Source:  IPv6 multicast source address, 16 octets.


   Group:  IPv6 multicast group address, 16 octets.

3.3.  Transit IPv4 bidir TLV



     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                              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Type:  5 (to be assigned by IANA).


   Length:  9


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


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


   Group:  IPv4 multicast group address, 4 octets.

3.4.  Transit IPv6 bidir TLV








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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                        | Mask Len      |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                             RP                               ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ~                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                            Group                              ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ~                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Type:  6 (to be assigned by IANA).


   Length:  33


   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.


   Group:  IPv6 multicast group address, 16 octets.


4.  Security Considerations

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


5.  IANA considerations

   This document requires allocation from the LDP MP Opaque Value
   Element type name space managed by IANA.  The values requested are:

      Transit IPv4 Source TLV type - requested 3

      Transit IPv6 Source TLV type - requested 4





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      Transit IPv4 Bidir TLV type - requested 5

      Transit IPv6 Bidir TLV type - requested 6


6.  Acknowledgments

   Thanks to Eric Rosen for his valuable comments on this draft.  Also
   thanks to Yakov Rekhter, Adrial Farrel and Uwe Joorde for providing
   comments on this draft.


7.  Contributing authors

   Below is a list of the contributing authors in alphabetical order:

     Toerless Eckert
     Cisco Systems, Inc.
     170 Tasman Drive
     San Jose, CA, 95134
     USA
     E-mail: eckert@cisco.com


     Nicolai Leymann
     Deutsche Telekom
     Winterfeldtstrasse 21
     Berlin, 10781
     Germany
     E-mail: n.leymann@telekom.de


     Maria Napierala
     AT&T Labs
     200 Laurel Avenue
     Middletown, NJ 07748
     USA
     E-mail: mnapierala@att.com


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





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8.  References

8.1.  Normative References

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

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

   [I-D.ietf-mpls-ldp-p2mp]
              Minei, I., Kompella, K., Wijnands, I., and B. Thomas,
              "Label Distribution Protocol Extensions for Point-to-
              Multipoint and Multipoint-to-Multipoint Label Switched
              Paths", draft-ietf-mpls-ldp-p2mp-11 (work in progress),
              October 2010.

8.2.  Informative References

   [RFC4601]  Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas,
              "Protocol Independent Multicast - Sparse Mode (PIM-SM):
              Protocol Specification (Revised)", RFC 4601, August 2006.

   [RFC4607]  Holbrook, H. and B. Cain, "Source-Specific Multicast for
              IP", RFC 4607, August 2006.

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

   [RFC3618]  Fenner, B. and D. Meyer, "Multicast Source Discovery
              Protocol (MSDP)", RFC 3618, October 2003.

   [I-D.ietf-l3vpn-2547bis-mcast]
              Aggarwal, R., Bandi, S., Cai, Y., Morin, T., Rekhter, Y.,
              Rosen, E., Wijnands, I., and S. Yasukawa, "Multicast in
              MPLS/BGP IP VPNs", draft-ietf-l3vpn-2547bis-mcast-10 (work
              in progress), January 2010.

   [I-D.rekhter-pim-sm-over-mldp]
              Rekhter, Y., Aggarwal, R., and N. Leymann, "Carrying
              PIM-SM in ASM mode Trees over P2MP mLDP LSPs",
              draft-rekhter-pim-sm-over-mldp-02 (work in progress),
              August 2010.

   [I-D.rosen-l3vpn-mvpn-mspmsi]
              Boers, A., Cai, Y., Napierala, M., Rosen, E., and I.
              Wijnands, "MVPN: Optimized use of PIM via MS-PMSIs",



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              draft-rosen-l3vpn-mvpn-mspmsi-08 (work in progress),
              January 2011.


Authors' Addresses

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

   Email: ice@cisco.com


   Toerless Eckert
   Cisco Systems, Inc.
   170 Tasman Drive
   San Jose  CA, 95134
   USA

   Email: eckert@cisco.com


   Nicolai Leymann
   Deutsche Telekom
   Winterfeldtstrasse 21
   Berlin  10781
   Germany

   Email: nicolai.leymann@t-systems.com


   Maria Napierala
   AT&T Labs
   200 Laurel Avenue
   Middletown  NJ 07748
   USA

   Email: mnapierala@att.com











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