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Internet Engineering Task Force                             D. Farinacci
Internet-Draft                                               lispers.net
Intended status: Experimental                               M. Napierala
Expires: March 18, 2014                                             AT&T
                                                      September 14, 2013


                 LISP Control-Plane Multicast Signaling
                  draft-farinacci-lisp-mr-signaling-03

Abstract

   This document describes an alternate method to signal multicast tree
   building among xTRs in multicast capable LISP sites.  This approach
   avoids the need to run a multicast routing protocol on the LISP
   overlay.

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
   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 March 18, 2014.

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
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   (http://trustee.ietf.org/license-info) in effect on the date of
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.



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Table of Contents

   1.  Requirements Language  . . . . . . . . . . . . . . . . . . . .  3
   2.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Definition of Terms  . . . . . . . . . . . . . . . . . . . . .  6
   4.  Overview . . . . . . . . . . . . . . . . . . . . . . . . . . .  7
   5.  Join-Request/Leave-Request Encoding Formats  . . . . . . . . .  9
   6.  Replication Considerations . . . . . . . . . . . . . . . . . . 11
   7.  Interworking Considerations  . . . . . . . . . . . . . . . . . 12
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 13
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 14
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
     10.1.  Normative References  . . . . . . . . . . . . . . . . . . 15
     10.2.  Informative References  . . . . . . . . . . . . . . . . . 15
   Appendix A.  Acknowledgments . . . . . . . . . . . . . . . . . . . 16
   Appendix B.  Document Change Log . . . . . . . . . . . . . . . . . 17
     B.1.   Changes to draft-farinacci-lisp-mr-signaling-03.txt . . . 17
     B.2.   Changes to draft-farinacci-lisp-mr-signaling-02.txt . . . 17
     B.3.   Changes to draft-farinacci-lisp-mr-signaling-01.txt . . . 17
     B.4.   Changes to draft-farinacci-lisp-mr-signaling-00.txt . . . 17
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18






























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1.  Requirements Language

   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].














































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2.  Introduction

   The Locator/ID Separation Architecture [RFC6830] provides a mechanism
   to separate out Identification and Location semantics from the
   current definition of an IP address.  By creating two namespaces, an
   Endpoint ID (EID) namespace used by sites and a Routing Locator
   (RLOC) namespace used by core routing, the core routing
   infrastructure can scale by doing topological aggregation of routing
   information.

   Since LISP creates a new namespace, a mapping function must exist to
   map a site's EID prefixes to its associated locators.  For unicast
   packets, both the source address and destination address must be
   mapped.  For multicast packets, only the source address needs to be
   mapped.  The destination group address doesn't need to be mapped
   because the semantics of an IPv4 or IPv6 group address are logical in
   nature and not topology-dependent.  Therefore, this specification
   focuses on the procedures of how to map a source EID address and
   destination group address of a multicast flow during distribution
   tree setup and packet delivery.

   The LISP Multicast specification [RFC6831] addresses the following
   procedures:

   1.  How a multicast source host in a LISP site sends multicast
       packets to receivers inside of its site as well as to receivers
       in other sites that are LISP enabled.

   2.  How inter-domain (or inter-LISP sites) multicast distribution
       trees are built and how forwarding of multicast packets leaving a
       source site toward receivers sites is performed.

   3.  What protocols are affected and what changes are required to such
       multicast protocols.

   4.  How ASM-mode (Any Source Multicast), SSM-mode (Single Source
       Multicast), and Bidir-mode (Bidirectional Shared Trees) service
       models will operate.

   5.  How multicast packet flow will occur for multiple combinations of
       LISP and non-LISP capable source and receiver sites.

   The distribution tree mechanism in [RFC6831] specifies the use of the
   PIM multicast routing protocol and how PIM is used between xTRs
   connecting multicast capable source sites and receiver sites
   together.

   This specification will describe an alternate method for connecting



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   multicast capable sites together by using Map-Requests instead of the
   PIM protocol.  The advantages this brings is a single LISP control-
   plane mechanism used for both unicast and multicast packet flow.

   This specification does not describe how (S-EID,G) multicast
   distribution tree state is built in multicast receiver sites and in
   multicast source sites.  This specification also does not describe
   how (S-RLOC,G) or (S-RLOC,DG) multicast distribution tree state is
   built in the core network.  This specification defines how (S-EID,G)
   state is propagated from multicast receiver site resident ETRs to
   multicast ITRs.  This signaling is needed so the (S-EID,G) state can
   be propagated from the ITR to the source host in the multicast source
   site.






































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3.  Definition of Terms

   Note that all the definitions that apply in [RFC6831] apply in this
   specification as well.  And the following definitions are specific to
   this specification.

   Join-Request:   This is a reference to a Map-Request that allows the
      joining to a multicast tree by an ETR to an ITR (or PITR) for a
      given (S-EID,G) entry.

   Leave-Request:   This is a reference to a Map-Request that allows the
      leaving from a multicast tree by an ETR to an ITR (or PITR) for a
      given (S-EID,G) entry.

   LISP-RE:   RE stands for "Replication Engineering" which is a term
      used to design algorithms, protocols, and networks to optimize
      where multicast packet replication is performed in the network.

   Unicast Replication:   Is the notion of replicating a multicast
      packet at an ITR (or PITR) by encapsulating it into a unicast
      packet.  That is, the oif-list of a multicast routing table entry
      can not only have interfaces present for link-layer replication
      and for multicast encapsulation but also for unicast
      encapsulation.

   Delivery Group:   This is the outer packet's (or encapsulating
      header's) destination address when encapsulating a multicast
      packet inside of a multicast packet.  There is a one-to-one and
      one-to-many relationship between the inner header's destination
      group address and the outer header's destination group address.
      Notation for a delivery group entry is (S-RLOC,DG).

   (S-EID,G):  This is multicast state notation which is signaled from
      ETR to ITR in Map-Request messages.  'G' is the group address
      multicast hosts send and/or join to.  'S-EID' can be a host EID
      that sends multicast packets.  'S-EID' can be a Rendezvous Point
      (RP) that resides in the LISP multicast site so (*,G) state can be
      signaled from ETR to ITR.  All of PIM (S,G), (*,G), and (S,G,RP-
      bit) state can be conveyed via the Multicast Info Type format
      [LISP-LCAF] in Map-Request messages.

   (S-RLOC,DG):  This is multicast state notation which is kept by the
      multicast core network.  An (S-EID,G) packet originated by a
      multicast source is encapsulated by an ITR (or PITR) which maps
      the source EID (S-EID) to a source RLOC (S-RLOC) and the
      destination group address G to a Delivery Group address (DG).





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4.  Overview

   In [RFC6831], there is a two step approach for an ETR to join the
   distribution tree (S-EID,G) at an ITR where that distribution tree
   connects to a core distribution tree.  In the first step, the ETR
   must look up which ITR is associated with S-EID.  That is performed
   with a mapping database lookup and having the ETR select an ITR from
   the list of high priority RLOCs.  In the second step, a unicast PIM
   join must be sent by the ETR to the ITR.

   In the design here within, we transmit the join and leave semantic in
   a Map-Request message.  In this case, both the S-EID lookup and the
   the fact the ETR wants to join the distribution tree S-EID for a
   particular multicast group can be conveyed in one message exchange.
   The advantages of this are:

   1.  Less message overhead used for signaling.

   2.  State signaling comes together in a single message.  If an ETR
       has a map-cache entry for the S-EID, it also knows that the Join
       for (S-EID,G) reliably made it to the ITR.  If there is message
       loss both pieces of state fate-share the loss.

   3.  The Map-Reply is used as an acknowledgement where as with unicast
       PIM Join-Prune messages, they must be sent periodically which may
       create scalability problems in networks with a lot of multicast
       state.

   Here is the basic procedure that a multicast ETR or multicast PETR
   uses to convey (S-EID,G) join state to a multicast ITR or multicast
   PITR:

   1.  When an ETR creates (S-EID,G) from a site based PIM Join message
       and the oif-list goes non-empty, a Join-Request is sent.  If a
       map-cache entry exists for S-EID, then the Map-Request is sent to
       the highest multicast priority RLOC.  If a map-cache entry does
       not exist, the Map-Request is sent to the mapping database
       system.

   2.  When a Map-Reply is not returned, the Map-Request is
       retransmitted.  When a Map-Reply is returned, the ETR can be
       assured that the ITR will replicate packets to the ETR.

   3.  When unicast replication is performed, no additional action needs
       to be performed by the ETR.

   4.  When multicast replication is performed, the ETR must send a PIM
       Join message for (S-RLOC,G) or (S-RLOC,DG) into the core as



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       specified in [RFC6831].  See Section 6 for details when ITR
       unicast and/or multicast replication is done and how it is
       decided.

   An ETR must detect when an ITR has reloaded or cleared its state so
   that the ETR can resend Join-Requests for all the (S-EID,G) state it
   has cached.  Procedures for how to achieve this will be discussed in
   future versions of this specification.

   Here is the basic procedure a multicast ETR or multicast PETR uses to
   convey (S-EID,G) leave state to a multicast ITR or multicast PITR:

   1.  When an ETR (S-EID,G) oif-list state goes empty, a Leave-Request
       is sent.  If a map-cache entry exists for S-EID, then the Map-
       Request is sent to the highest multicast priority RLOC.  If a
       map-cache entry does not exist, the Map-Request is sent to the
       mapping database system.

   2.  When a Map-Reply is not returned, the Map-Request is
       retransmitted.  When a Map-Reply is returned, the ETR can be
       assured that the ITR will no longer replicate packets to the ETR.

   3.  When unicast replication is performed, no additional action needs
       to be performed by the ETR.

   4.  When multicast replication is performed, the ETR must send a PIM
       Leave message for (S-RLOC,G) or (S-RLOC,DG) into the core network
       as specified in [RFC6831].























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5.  Join-Request/Leave-Request Encoding Formats

   A Join-Request and Leave-Request are encoded as follows:

   o  (S-EID,G) is encoded in the destination EID-prefix field of a Map-
      Request [RFC6830].

   o  The encoding format of the destination EID-prefix is in LCAF
      format Type 'Multicast Info' [LISP-LCAF].  The J-bit and L-bit
      indicate if the Map-Request is a Join-Request or a Leave-Request,
      respectively.

   o  (S-RLOC,DG) is encoded in the Source EID Address field of the Map-
      Request.  It is also encoded in the same LCAF Type 'Multicast
      Info'.

   o  If S-RLOC is not known, then AFI=0 is encoded in the Source
      Address field of the LCAF type.

   o  If S-RLOC is known, then the RLOC of the ITR is encoded in the
      Source Address field of the LCAF type.

   o  If a Delivery Group is being requested by the ETR, then DG is
      encoded in the Group Address field of the LCAF type.

   o  If a unicast replication is being requested by the ETR, then ETR
      encodes a unicast RLOC address in the Group Address field of the
      LCAF type.

   A Map-Reply is returned for a Join-Request or a Leave-Request with
   the following format encoding:

   1.  The destination EID-prefix encoding in the Map-Request is copied
       and encoded in the Source EID Address field of the Map-Reply.
       This is so the ETR can match Map-Replies with Map-Requests.  The
       nonce field may be used for this purpose as well.  The address
       encoding is (S-EID,G).

   2.  The destination EID-prefix in the Map-Reply is the multicast
       information the ITR is conveying to ETR.  It can be (ITR-RLOC,DG)
       or (ITR-RLOC,ETR-RLOC).

   3.  When the ETR requested unicast replication, then the returned
       destination EID-prefix contains (ITR-RLOC,ETR-RLOC)

   4.  When the ETR requested a DG for multicast replication, then the
       returned destination EID-prefix contains (ITR-RLOC,DG).




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   5.  When the ITR overrides a requested (ITR-RLOC,ETR-RLOC) with a
       returned (ITR-RLOC,DG), then the ETR must send a join (or leave)
       for (ITR-RLOC,DG) into the core network.

   6.  When the ITR overrides a join-requested (ITR-RLOC,DG1) with a
       returned value of (ITR-RLOC,DG2), then the ETR must send a Join-
       Request for (ITR-RLOC,DG2) and send a Leave-Request for (ITR-
       RLOC,DG1) into the core network.

   7.  When the ITR with RLOC 'RLOC-ITR1' returns (RLOC-ITR2,DG) in a
       Map-Reply, the ETR must send a Join-Request to RLOC-ITR2 and send
       a Leave-Request to RLOC-ITR1 for (RLOC-ITR1,DG).  Same action is
       performed when (RLOC-ITR2,ETR-RLOC) is returned for a join-
       requested value of (RLOC-ITR1,ETR-RLOC).





































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6.  Replication Considerations

   When an ITR processes a received multicast packet sourced by a host
   in its site, the oif-list for the (S-EID,G) entry it maintains can
   have the following entries:

   1.  An interface entry that leads to multicast receivers inside of
       the site.

   2.  An encapsulation entry that can be targeted to a Delivery Group
       or a unicast RLOC.  The Delivery Group can either be the same or
       map from the group address of the packet originated by the
       multicast source host.

   The oif-list entries can be created by the signaling mechanisms
   defined in [RFC6831] using the PIM protocol or by the signaling
   mechanisms in this specification using Map-Requests.

   Another option is to have an external orchestration system program
   the mapping database explicitly so ETR signaling to the ITR can be
   reduced or even eliminated.  Also by the use of Explicit-Locator-
   Paths (ELPs) [LISP-TE], LISP-RE capabilities can be explored.  For
   more details see [LISP-RE].

   Since an oif-list can contain either a Delivery Group or a unicast
   RLOC as a destination address for the outer header, a question is
   raised where the decision is made to use one or the other, or both.

   It is desirable to use multicast routing in the core network where it
   is available.  However, if ETRs are attached to a multicast capable
   core network, the ITR may not be.  In this case, unicast RLOC
   encapsulation will be necessary to deliver multicast packets directly
   to the ETR.  It will left to the network administrator to configure
   the decision on Delivery Group versus unicast RLOCs is done by the
   ETRs, the ITR, or an orchestration system directly programming the
   mapping database.  This specification allows and permits for the ETR
   to request the encapsulation destination address as well as allowing
   the ITR to override it.













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7.  Interworking Considerations

   The Map-Request multicast signaling between ETR(s) and an ITR
   described in this specification is also used by ETR(s) to multicast
   PITRs which are deployed to support non-LISP multicast source sites.
   This is true for multicast PETRs that signal to an ITR or mPITR which
   support non-LISP multicast receiver sites.












































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8.  Security Considerations

   The security concerns for LISP multicast are mainly the same as for
   the base LISP specification [RFC6830] and the LISP multicast
   specification [RFC6831], including PIM-ASM [RFC4601].

   Where there are security concerns with respect to unicast PIM
   messages, as discussed in [RFC6831], the same may also be true for
   multicast signaling with Map-Request messages.










































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9.  IANA Considerations

   At this time there are no requests for IANA.
















































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10.  References

10.1.  Normative References

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

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

   [RFC6830]  Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The
              Locator/ID Separation Protocol (LISP)", RFC 6830,
              January 2013.

   [RFC6831]  Farinacci, D., Meyer, D., Zwiebel, J., and S. Venaas, "The
              Locator/ID Separation Protocol (LISP) for Multicast
              Environments", RFC 6831, January 2013.

10.2.  Informative References

   [LISP-LCAF]
              Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical
              Address Format", draft-ietf-lisp-lcaf-00.txt (work in
              progress).

   [LISP-RE]  Coras, F., Cabellos-Aparicio, A., Domingo-Pascual, J.,
              Maino, F., and D. Farinacci, "LISP Replication
              Engineering", draft-coras-lisp-re-01.txt (work in
              progress).

   [LISP-TE]  Farinacci, D., Lahiri, P., and M. Kowal, "LISP Traffic
              Engineering Use-Cases", draft-farinacci-lisp-te-02.txt
              (work in progress).

















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Appendix A.  Acknowledgments

   The authors would like to thank the following people for their
   participation in conversations on the topic.  They are Gregg Schudel,
   Florin Coras, Darrel Lewis, Fabio Maino, and Noel Chiappa.














































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Appendix B.  Document Change Log

B.1.  Changes to draft-farinacci-lisp-mr-signaling-03.txt

   o  Posted September 2013.

   o  Add clarificaiton text through out to reflect comments from Noel
      Chiappa.

B.2.  Changes to draft-farinacci-lisp-mr-signaling-02.txt

   o  Refreshing references and document timer.

B.3.  Changes to draft-farinacci-lisp-mr-signaling-01.txt

   o  Refreshing references and document timer.

B.4.  Changes to draft-farinacci-lisp-mr-signaling-00.txt

   o  Initial draft posted July 2012.































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Authors' Addresses

   Dino Farinacci
   lispers.net
   San Jose, California
   USA

   Phone: 408-718-2001
   Email: farinacci@gmail.com


   Maria Napierala
   AT&T
   Middletown, NJ
   USA

   Email: mnapierala@att.com


































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