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Versions: 00 01 02 03 04 05 06 07 08 draft-ietf-mpls-pim-sm-over-mldp

Network Working Group                                      Yakov Rekhter
Internet Draft                                          Juniper Networks
Intended status: Standards Track
Expires: August 2014                                      Rahul Aggarwal
                                                                  Arktan

                                                         Nicolai Leymann
                                                        Deutsche Telekom

                                                          Wim Henderickx
                                                          Alcatel-Lucent

                                                            Quintin Zhao
                                                                  Huawei

                                                              Richard Li
                                                                  Huawei

                                                         February 7 2014


         Carrying PIM-SM in ASM mode Trees over P2MP mLDP LSPs


               draft-rekhter-mpls-pim-sm-over-mldp-08.txt

Status of this Memo

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Copyright Notice

   Copyright (c) 2013 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
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   described in the Simplified BSD License.


Abstract

   When IP multicast trees created by PIM-SM in Any Source Multicast
   (ASM) mode need to pass through an MPLS domain, it may be desirable
   to map such trees to Point-to-Multipoint Label Switched Paths. This
   document describes how to accomplish this in the case where such
   Point-to-Multipoint Label Switched Paths are established using mLDP.




























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Table of Contents

 1          Specification of Requirements  .........................   3
 2          Introduction  ..........................................   3
 3          Option 1 - Non-transitive mapping of IP multicast shared tree  5
 3.1        Originating Source Active auto-discovery routes (Option 1)  5
 3.2        Receiving BGP Source Active auto-discovery route by LSR  ...6
 3.3        Handling (S, G, RPT-bit) state  ........................   6
 4          Option 2 - Transitive mapping of IP multicast shared tree  .6
 4.1        In-band signaling for IP Multicast Shared Tree  ........   7
 4.2        Originating Source Active auto-discovery routes (Option 2)  8
 4.3        Receiving BGP Source Active auto-discovery route  ......   9
 4.4        Pruning Sources off the Shared Tree  ...................   9
 4.5        More on handling (S,G,RPT-bit) state  ..................  10
 5          IANA Considerations  ...................................  10
 6          Security Considerations  ...............................  10
 7          Acknowledgements  ......................................  10
 8          Normative References  ..................................  11
 9          Informative References  ................................  11
10          Authors' Addresses  ....................................  11






1. Specification of Requirements

   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].


2. Introduction

   [RFC6826] describes how to map Point-to-Multipoint Label Switched
   Paths (P2MP LSPs) created by mLDP [mLDP] to multicast trees created
   by PIM-SM in SSM mode [RFC4607]. This document describes how to map
   mLDP P2MP trees to multicast trees created by PIM-SM in ASM mode. It
   describes two possible options for doing this.

   An implementation MAY support Option 1, as described in Section 3 of
   this document. An implementation MUST support Option 2, as described



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   in Section 4 of this document.

   Note that from a deployment point of view these two options are
   mutually exclusive. That is on the same network one could either
   deploy Option 1, or Option 2, but not both.

   The reader of this document is expected to be familiar with PIM-SM
   [RFC4601] and mLDP [mLDP].

   This document relies on the procedures in [RFC6826] to support Source
   Trees. E.g., following these procedures an LSR may initiate a mLDP
   Label Map with the Transit IPv4/IPv6 Source TLV for (S, G) when
   receiving PIM (S,G) Join.



   This document uses BGP Source Active auto-discovery routes, as
   defined in [MVPN-BGP].

   In a deployment scenario where the service provider has provisioned
   the network in such a way that the RP for a particular ASM group G is
   always between the receivers and the sources. If the network is
   provisioned in this manner, the ingress PE for (S,G) is always the
   same as the ingress PE for the RP, and thus the Source Active A-D
   routes are never needed. If it is known a priori that the network is
   provisioned in this manner, mLDP in-band signaling can be supported
   using a different set of procedures, as specified in [draft-
   wijnands].  A service provider will provision the PE routers either
   to use [draft-wijnands] procedures or to use the procedures of this
   document.

   Like [RFC6826], each IP multicast tree is mapped one-to-one to a P2MP
   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.

   It is to be noted that the existing BGP MVPN [MVPN-BGP] procedures
   may be used to map Internet IP multicast trees to P2MP LSPs. These
   procedures would accomplish this for IP multicast trees created by
   PIM-SM in SSM mode as well as for IP multicast trees created by PIM-
   SM in ASM mode. Furthermore, these procedures would also support the
   ability to aggregate multiple IP multicast trees to one P2MP LSP in
   the MPLS network. The details of this particular approach are out of
   scope of this document.

   This document assumes that a given LSR may have some of its
   interfaces IP multicast capable, while other interfaces being MPLS



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   capable.



3. Option 1 - Non-transitive mapping of IP multicast shared tree

   This option does not transit IP multicast shared trees over the MPLS
   network. Therefore, when an LSR creates (*, G) state (as a result of
   receiving PIM messages on one of its IP multicast interfaces), the
   LSR does not propagate this state in mLDP.


3.1. Originating Source Active auto-discovery routes (Option 1)

   Whenever (as a result of receiving either PIM Register or MSDP
   messages) a Rendezvous Point (RP) discovers a new multicast source,
   the RP SHOULD originate a BGP Source Active auto-discovery route.
   The route carries a single MCAST-VPN NLRI [MVPN-BGP] constructed as
   follows:

     + The Route Distinguisher (RD) in this NLRI is set to 0.

     + The Multicast Source field MUST be set to S. This could be either
       an IPv4 or an IPv6 address. The Multicast Source Length field is
       set appropriately to reflect this.

     + The Multicast Group field MUST be set to G. This could be either
       an IPv4 or an IPv6 address. The Multicast Group Length field is
       set appropriately to reflect this.


   To constrain distribution of the Source Active auto-discovery route
   to the AS of the advertising RP this route SHOULD carry the NO_EXPORT
   Community ([RFC1997]).

   Using the normal BGP procedures the Source Active auto-discovery
   route is propagated to all other LSRs within the AS.

   Whenever the RP discovers that the source is no longer active, the RP
   MUST withdraw the Source Active auto-discovery route, if such a route
   was previously advertised by the RP.










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3.2. Receiving BGP Source Active auto-discovery route by LSR

   Consider an LSR that has some of its interfaces capable of IP
   multicast and some capable of MPLS multicast.

   When as a result of receiving PIM messages on one of its IP multicast
   interfaces such LSR creates in its Tree Information Base (TIB) a new
   (*, G) entry with a non-empty outgoing interface list that contains
   one or more IP multicast interfaces, the LSR MUST check if it has any
   Source Active auto-discovery routes for that G. If there is such a
   route, S of that route is reachable via an MPLS interface, and the
   LSR does not have (S, G) state in its TIB for (S, G) carried in the
   route, then the LSR originates the mLDP Label Map with the Transit
   IPv4/IPv6 Source TLV carrying (S,G), as specified in [RFC6826].

   When an LSR receives a new Source Active auto-discovery route, the
   LSR MUST check if its TIB contains an (*, G) entry with the same G as
   carried in the Source Active auto-discovery route. If such an entry
   is found, S is reachable via an MPLS interface, and the LSR does not
   have (S, G) state in its TIB for (S, G) carried in the route, then
   the LSR originates an mLDP Label Map with the Transit IPv4/IPv6
   Source TLV carrying (S,G), as specified in [RFC6826].


3.3. Handling (S, G, RPT-bit) state

   Creation and deletion of (S, G, RPT-bit) PIM state ([RFC4601]) on a
   LSR that resulted from receiving PIM messages on one of its IP
   multicast interfaces does not result in any mLDP and/or BGP actions
   by the LSR.


4. Option 2 - Transitive mapping of IP multicast shared tree

   This option enables transit of IP multicast shared trees over the
   MPLS network. Therefore, when an LSR creates (*, G) state as a result
   of receiving PIM messages on one of its IP multicast interfaces, the
   LSR does propagate this state in mLDP, as described below.

   Note that in the deployment scenarios where for a given G none of the
   PEs originate an (S, G) mLDP Label Map with the Transit IPv4/IPv6
   Source TLV, no Source Active auto-discovery routes will be used.  One
   other scenario where no Source Active auto-discovery routes will be
   used is described in section "Originating Source Active auto-
   discovery routes (Option 2)". In all these scenarios the only part of
   Option 2 that will be used is the in-band signaling for IP Multicast
   Shared Tree, as described in the next section.




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4.1. In-band signaling for IP Multicast Shared Tree

   To provide support for in-band mLDP signaling of IP multicast shared
   trees this document defines two new mLDP TLVs: Transit IPv4 Shared
   Tree TLV, and Transit IPv6 Shared Tree TLV.

   These two TLVs have exactly the same encoding/format as the IPv4/IPv6
   Source Tree TLVs defined in [RFC6826], except that instead of the
   Source field they have the RP field, and this field carries the
   address of the RP, as follows:

       Transit IPv4 Shared Tree 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                        | RP
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                                        | Group
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                                        |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


      Type:  TBD (to be assigned by IANA).

      Length:  8

      RP:  IPv4 RP address, 4 octets.

      Group:  IPv4 multicast group address, 4 octets.


      Transit IPv6 Shared Tree 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                        | RP            ~
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        ~                                               | Group         ~
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        ~                                               |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


      Type:  TBD (to be assigned by IANA).




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      Length:  32

      RP:  IPv6 RP address, 16 octets.

      Group:  IPv6 multicast group address, 16 octets.


   Procedures for in-band signaling for IP multicast shared trees with
   mLDP follow the same procedures as for in-band signaling for IP
   multicast source trees specified in [RFC6826], except that while the
   latter signals (S,G) state using Transit IPv4/IPv6 Source TLVs, the
   former signals (*,G) state using Transit IPv4/IPv6 Shared Tree TLVs.


4.2. Originating Source Active auto-discovery routes (Option 2)

   Consider an LSR that has some of its interfaces capable of IP
   multicast and some capable of MPLS multicast.

   Whenever such LSR creates an (S, G) state as a result of receiving an
   mLDP Label Map with the Transit IPv4/IPv6 Source TLV for (S, G), if
   all of the following are true:

     + S is reachable via one of the IP multicast capable interfaces,

     + the LSR determines that G is in the PIM-SM in ASM mode range, and

     + the LSR does not have an (*, G) state with one of the IP
       multicast capable interfaces as an incoming interface (iif) for
       that state


   the LSR MUST originate a BGP Source Active auto-discovery route.

   The route carries a single MCAST-VPN NLRI constructed as follows:


     + The RD in this NLRI is set to 0.

     + The Multicast Source field MUST be set to S. The Multicast Source
       Length field is set appropriately to reflect this.

     + The Multicast Group field MUST be set to G. The Multicast Group
       Length field is set appropriately to reflect this.


   To constrain distribution of the Source Active auto-discovery route
   to the AS of the advertising LSR this route SHOULD carry the



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   NO_EXPORT Community ([RFC1997]).

   Using the normal BGP procedures the Source Active auto-discovery
   route is propagated to all other LSRs within the AS.

   Whenever the LSR deletes the (S,G) state that was previously created
   as a result of receiving an mLDP Label Map with the Transit IPv4/IPv6
   Source TLV for (S,G), the LSR that deletes the state MUST also
   withdraw the Source Active auto-discovery route, if such a route was
   advertised when the state was created.

   Note that whenever an LSR creates an (S,G) state as a result of
   receiving an mLDP Label Map with the Transit IPv4/IPv6 Source TLV for
   (S,G) with S reachable via one of the IP multicast capable
   interfaces, and the LSR already has a (*,G) state with RP reachable
   via one of the IP multicast capable interfaces as a result of
   receiving an mLDP Label Map with the Transit IPv4/IPv6 Shared Tree
   TLV for (*,G), the LSR does not originate a Source Active auto-
   discovery route.


4.3. Receiving BGP Source Active auto-discovery route

   Procedures for receiving BGP Source Active auto-discovery routes are
   the same as with Option 1.


4.4. Pruning Sources off the Shared Tree

   If after receiving a new Source Active auto-discovery route for (S,G)
   the LSR determines that (a) it has the (*, G) entry in its TIB, (b)
   the incoming interface list (iif) for that entry contains one of the
   IP interfaces, (c) at least one of the MPLS interfaces is in the
   outgoing interface list (oif) for that entry, and (d) the LSR does
   not originate an mLDP Label Mapping message for (S,G) with the
   Transit IPv4/IPv6 Source TLV, then the LSR MUST transition the
   (S,G,RPT-bit) downstream state to the Prune state. [Conceptually the
   PIM state machine on the LSR will act "as if" it had received
   Prune(S,G,rpt) on one of its MPLS interfaces, without actually having
   received one.] Depending on the (S,G,RPT-bit) state on the iif, this
   may result in the LSR using PIM procedures to prune S off the Shared
   (*,G) tree.

   The LSR MUST keep the (S,G,RPT-bit) downstream state machine in the
   Prune state for as long as (a) the outgoing interface list (oif) for
   (*, G) contains one of the MPLS interfaces, and (b) the LSR has at
   least one Source Active auto-discovery route for (S,G), and (c) the
   LSR does not originate the mLDP Label Mapping message for (S,G) with



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   the Transit IPv4/IPv6 Source TLV. Once either of these conditions
   become no longer valid, the LSR MUST transition the (S,G,RPT-bit)
   downstream state machine to the NoInfo state.

   Note that except for the scenario described in the first paragraph of
   this section, in all other scenarios relying solely on PIM procedures
   on the LSR is sufficient to ensure the correct behavior when pruning
   sources off the shared tree.


4.5. More on handling (S,G,RPT-bit) state

   Creation and deletion of (S,G,RPT-bit) state on a LSR that resulted
   from receiving PIM messages on one of its IP multicast interfaces
   does not result in any mLDP and/or BGP actions by the LSR.


5. IANA Considerations

   This document requires allocation from the LDP MP Opaque Value
   Element type name space managed by IANA the following two new mLDP
   TLVs: Transit IPv4 Shared Tree TLV, and Transit IPv6 Shared Tree TLV.


6. Security Considerations

   All the security considerations for mLDP ([mLDP]) apply here.


7. Acknowledgements

   Use of Source Active auto-discovery routes was borrowed from [MVPN-
   BGP]. Some text in this document was borrowed from [MVPN-BGP].

   Some of the text in this document was borrowed from [RFC6826].

   We would like to acknowledge Arkadiy Gulko for his review and
   comments.

   We would also like to thank Xuxiaohu, Gregory Mirsky, and Rajiv Asati
   for their review and comments.










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8. Normative References

   [mLDP] Minei, I., "Label Distribution Protocol Extensions for Point-
   to- Multipoint and Multipoint-to-Multipoint Label Switched Paths",
   RFC6388, November 2011.

   [RFC6826] "In-band signaling for Point-to-Multipoint and Multipoint-
   to-Multipoint Label Switched Paths", I. Wijnands et al., RFC6826,
   January 2013

   [MVPN-BGP] "BGP Encodings and Procedures for Multicast in MPLS/BGP IP
   VPNs", R. Aggarwal et al., RFC6514, February 2012

   [RFC1997] R. Chandra, P. Traina, T. Li, "BGP Communities Attribute",
   RFC1997, August 1996.

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


9. 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.

   [draft-wijnands] Wijnands IJ, et. al., "mLDP In-Band Signaling with
   Wildcards", draft-wijnands-mpls-mldp-in-band-wildcard-encoding, work
   in progress



10. Authors' Addresses

   Yakov Rekhter
   Juniper Networks, Inc.
   e-mail: yakov@juniper.net

   Rahul Aggarwal
   e-mail: raggarwa_1@yahoo.com

   Nicolai Leymann
   Deutsche Telekom
   Winterfeldtstrasse 21
   Berlin  10781



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   Germany
   e-mail: nicolai.leymann@t-systems.com

   Wim Henderickx
   Alcatel-Lucent
   Email: wim.henderickx@alcatel-lucent.com

   Richard Li
   Huawei
   Email: renwei.li@huawei.com

   Quintin Zhao
   Huawei
   Email: quintin.zhao@huawei.com





































Rekhter                                                        [Page 12]


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