Internet DRAFT - draft-wijnands-mpls-mldp-in-band-signaling

draft-wijnands-mpls-mldp-in-band-signaling






Network Working Group                               I. Wijnands (Editor)
Internet-Draft                                                 T. Eckert
Intended status: Standards Track                     Cisco Systems, Inc.
Expires: April 27, 2010                                       N. Leymann
                                                        Deutsche Telekom
                                                            M. Napierala
                                                               AT&T Labs
                                                        October 24, 2009


mLDP based in-band signaling for Point-to-Multipoint and Multipoint-to-
                    Multipoint Label Switched Paths
             draft-wijnands-mpls-mldp-in-band-signaling-02

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Copyright Notice



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   Copyright (c) 2009 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 in effect on the date of
   publication of this document (http://trustee.ietf.org/license-info).
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.

Abstract

   When an IP multicast tree needs to pass through an MPLS domain, it is
   advantageous to map the tree to a Point-to-Multipoint or Multipoint-
   to-Multipoint Label Switched Path.  This document specifies a way to
   provide a one-one mapping between IP multicast trees and Label
   Switched Paths using mLDP signaling.  The IP multicast control
   messages are translated into MPLS control messages when they enter
   the MPLS domain, and are translated back into IP multicast control
   messages at the far end of the MPLS domain.  The IP multicast control
   information is coded into the MPLS control information in such a way
   as to ensure that a single Multipoint Label Switched Path gets set up
   for each IP multicast tree.





























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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Conventions used in this document  . . . . . . . . . . . .  4
     1.2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  In-band signaling for MP LSPs  . . . . . . . . . . . . . . . .  5
     2.1.  Transiting IP multicast source trees . . . . . . . . . . .  6
     2.2.  Transiting IP multicast bidirectional trees  . . . . . . .  6
     2.3.  Transiting IP multicast shared Trees . . . . . . . . . . .  7
   3.  LSP opaque encodings . . . . . . . . . . . . . . . . . . . . .  7
     3.1.  Transit IPv4 Source TLV  . . . . . . . . . . . . . . . . .  7
     3.2.  Transit IPv6 Source TLV  . . . . . . . . . . . . . . . . .  8
     3.3.  Transit IPv4 bidir TLV . . . . . . . . . . . . . . . . . .  8
     3.4.  Transit IPv6 bidir TLV . . . . . . . . . . . . . . . . . .  9
   4.  Security Considerations  . . . . . . . . . . . . . . . . . . . 10
   5.  IANA considerations  . . . . . . . . . . . . . . . . . . . . . 10
   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 IP multicast control messages used to set up the tree
   are translated into mLDP messages.  The (S,G) or (*,G) information
   from the IP multicast control messages 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 messages that are sent outside the MPLS
   domain.  Note that although the IP multicast 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
      signal multicast route information.


   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] 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 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



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   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.

   In order to send the multicast stream 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 stream.  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 will be executed.  If the opaque encoding of the FEC
   indicates this is an Transit LSP (indicated by the opaque type), the
   opaque TLV will be decoded and the multicast source and group is
   passed to the multicast code.  If the multicast tree information was
   received via a label mapping, the multicast code will effectively
   treat this as a positif indication to create a IP multicast tree
   based on the received information.  If it was due to a label
   withdraw, the multicast code will effectively treat this as having
   received a negative indication and it will remove the tree
   indentified by the encoded information.  From this point on normal
   PIM processing will occur.

2.1.  Transiting IP multicast source trees

   IP multicast source trees can either be created via PIM operating in
   SSM mode [RFC4607] or ASM mode [RFC4601] (for example via last hop
   behavior or MSDP [RFC3618]) and MUST be transporting across the MPLS
   network using a P2MP LSP.  A Transit LSP may be setup to forward the
   IP multicast traffic across an MPLS core.  If the multicast source is
   reachable in a global table the source and group addresses are
   encoded into the a transit TLV.  Depending on the IP version it is
   either Section 3.1 or Section 3.2.

2.2.  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; only the group address and subnet mask are
   relevant for multicast forwarding.  The RP for the group already
   known by IP multicast is used to select the ingress PE and root of



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   the LSP.  The group address is encoded in either 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 bidirection states in IP multicast, the group
   specific state and the RPA state.  The first type is typlically
   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 RP
   mapping protocol and has a variable subnet mask.  The RPA state is
   used to build a tree to the RP and used for sender only branches.
   Please see [RFC5015] for more details.

2.3.  Transiting IP multicast shared Trees

   Nothing prevents PIM shared trees from being transported across a
   MPLS core.  However, it is not possible to prune of individual
   sources from the shared tree without the use of an additional out-of-
   band signaling protocol, like PIM.  For that reason transiting Shared
   Trees across a Transit LSP is outside the scope of this draft.


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:  2 (to be assigned by IANA).


   Length:  8








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


   Type:  3 (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                              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+







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   Type:  4 (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



     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:  4 (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.








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   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 2

      Transit IPv6 Source TLV type - requested 3

      Transit IPv4 Bidir TLV type - requested 4

      Transit IPv6 Bidir TLV type - requested 5


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







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     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


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., "Label Distribution Protocol Extensions for
              Point-to-Multipoint and  Multipoint-to-Multipoint Label
              Switched Paths", draft-ietf-mpls-ldp-p2mp-05 (work in
              progress), June 2008.

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.



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   [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-07 (work
              in progress), July 2008.


Authors' Addresses

   IJsbrand Wijnands
   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










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

   Email: mnapierala@att.com












































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