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Versions: (draft-przygienda-bier-isis-ranges) 00 01 02 03 04 05 06 07 08 09 10 11 RFC 8401

Internet Engineering Task Force                         L. Ginsberg, Ed.
Internet-Draft                                             Cisco Systems
Intended status: Standards Track                           A. Przygienda
Expires: April 19, 2016                                         Ericsson
                                                               S. Aldrin
                                                                  Google
                                                                J. Zhang
                                                  Juniper Networks, Inc.
                                                        October 17, 2015


                         BIER support via ISIS
                   draft-ietf-bier-isis-extensions-01

Abstract

   Specification of an ISIS extension to support BIER domains and sub-
   domains.

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] .

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 April 19, 2016.

Copyright Notice

   Copyright (c) 2015 IETF Trust and the persons identified as the
   document authors.  All rights reserved.





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   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
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   4.  Concepts  . . . . . . . . . . . . . . . . . . . . . . . . . .   4
     4.1.  BIER Domains and Sub-Domains  . . . . . . . . . . . . . .   4
   5.  Procedures  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     5.1.  Enabling a BIER Sub-Domain  . . . . . . . . . . . . . . .   5
     5.2.  Multi Topology and Sub-Domain . . . . . . . . . . . . . .   5
     5.3.  Encapsulation . . . . . . . . . . . . . . . . . . . . . .   5
     5.4.  Tree Type . . . . . . . . . . . . . . . . . . . . . . . .   5
     5.5.  Label Advertisements for MPLS encapsulated BIER sub-
           domains . . . . . . . . . . . . . . . . . . . . . . . . .   5
       5.5.1.  Special Consideration . . . . . . . . . . . . . . . .   6
     5.6.  BFR-id Advertisements . . . . . . . . . . . . . . . . . .   6
     5.7.  Flooding  . . . . . . . . . . . . . . . . . . . . . . . .   6
   6.  Packet Formats  . . . . . . . . . . . . . . . . . . . . . . .   6
     6.1.  BIER Info sub-TLV . . . . . . . . . . . . . . . . . . . .   7
     6.2.  BIER MPLS Encapsulation sub-sub-TLV . . . . . . . . . . .   8
     6.3.  Optional BIER sub-domain Tree Type sub-sub-TLV  . . . . .   9
     6.4.  Optional BIER sub-domain BSL conversion sub-sub-TLV . . .  10
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  11
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  11
   9.  Normative References  . . . . . . . . . . . . . . . . . . . .  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

1.  Introduction

   Bit Index Explicit Replication (BIER)
   [I-D.draft-ietf-bier-architecture-02] defines an architecture where
   all intended multicast receivers are encoded as bitmask in the
   Multicast packet header within different encapsulations such as
   [I-D.draft-ietf-bier-mpls-encapsulation-02].  A router that receives
   such a packet will forward the packet based on the Bit Position in
   the packet header towards the receiver(s), following a precomputed
   tree for each of the bits in the packet.  Each receiver is
   represented by a unique bit in the bitmask.



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   This document presents necessary extensions to the currently deployed
   ISIS for IP [RFC1195] protocol to support distribution of information
   necessary for operation of BIER domains and sub-domains.  This
   document defines a new TLV to be advertised by every router
   participating in BIER signaling.

2.  Terminology

   Some of the terminology specified in
   [I-D.draft-ietf-bier-architecture-02] is replicated here and extended
   by necessary definitions:

   BIER:  Bit Index Explicit Replication (The overall architecture of
      forwarding multicast using a Bit Position).

   BIER-OL:  BIER Overlay Signaling.  (The method for the BFIR to learn
      about BFER's).

   BFR:  Bit Forwarding Router (A router that participates in Bit Index
      Multipoint Forwarding).  A BFR is identified by a unique BFR-
      prefix in a BIER domain.

   BFIR:  Bit Forwarding Ingress Router (The ingress border router that
      inserts the BM into the packet).

   BFER:  Bit Forwarding Egress Router.  A router that participates in
      Bit Index Forwarding as leaf.  Each BFER must be a BFR.  Each BFER
      must have a valid BFR-id assigned.

   BFT:  Bit Forwarding Tree used to reach all BFERs in a domain.

   BIFT:  Bit Index Forwarding Table.

   BMS:  Bit Mask Set. Set containing bit positions of all BFER
      participating in a set.

   BMP:  Bit Mask Position, a given bit in a BMS.

   Invalid BMP:  Unassigned Bit Mask Position, consisting of all 0s.

   IGP signalled BIER domain:  A BIER underlay where the BIER
      synchronization information is carried in IGP.  Observe that a
      multi-topology is NOT a separate BIER domain in IGP.

   BIER sub-domain:  A further distinction within a BIER domain
      identified by its unique sub-domain identifier.  A BIER sub-domain
      can support multiple BitString Lengths.




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   BFR-id:  An optional, unique identifier for a BFR within a BIER sub-
      domain.

   Invalid BFR-id:  Unassigned BFR-id, consisting of all 0s.

3.  IANA Considerations

   This document adds the following new sub-TLVs to the registry of sub-
   TLVs for TLVs 235, 237 [RFC5120] and TLVs 135,236
   [RFC5305],[RFC5308].

   Value: 32 (suggested - to be assigned by IANA)

   Name: BIER Info

4.  Concepts

4.1.  BIER Domains and Sub-Domains

   An ISIS signalled BIER domain is aligned with the scope of
   distribution of BFR-prefixes that identify the BFRs within ISIS.
   ISIS acts in such a case as the according BIER underlay.

   Within such a domain, ISIS extensions are capable of carrying BIER
   information for multiple BIER sub-domains.  Each sub-domain is
   uniquely identified by its subdomain-id and each subdomain can reside
   in any of the ISIS topologies [RFC5120].  The mapping of sub-domains
   to topologies is a local decision of each BFR currently but is
   advertised throughout the domain to ensure routing consistency.

   Each BIER sub-domain has as its unique attributes the encapsulation
   used and the type of tree it is using to forward BIER frames
   (currently always SPF).  Additionally, per supported bitstring length
   in the sub-domain, each router will advertise the necessary label
   ranges to support it.

   This RFC introduces a sub-TLV in the extended reachability TLVs to
   distribute such information about BIER sub-domains.  To satisfy the
   requirements for BIER prefixes per
   [I-D.draft-ietf-bier-architecture-02] additional information will be
   carried in [I-D.draft-ietf-isis-prefix-attributes-01].

5.  Procedures








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5.1.  Enabling a BIER Sub-Domain

   A given sub-domain with identifier SD with supported bitstring
   lengths MLs in a multi-topology MT [RFC5120] is denoted further as
   <MT,SD,MLs> and dos not have to be advertised by by default by BFRs
   to preserve the scaling of the protocol (i.e.  ISIS carries no TLVs
   containing any of the elements related to <MT,SD>).  The
   advertisement may be triggered e.g. by a first BIER sub-TLV
   (Section 6.1) containing <MT,SD> advertised into the area.  The
   specific trigger itself is outside the scope of this RFC but can be
   for example a VPN desiring to initiate a BIER sub-domain as MI-PMSI
   [RFC6513] tree or a pre-configured BFER (since BFERs will always
   advertise the BIER sub-TLV to make sure they can be reached).  It is
   outside the scope of this document to describe what trigger for a
   router capable of participating in <MT,SD> is used to start the
   origination of the necessary information to join into it.

5.2.  Multi Topology and Sub-Domain

   All routers in the flooding scope of the BIER sub-TLVs MUST advertise
   a sub-domain within the same multi-topology.  A router discovering a
   sub-domain advertised within a topology that is different from its
   own MUST report a misconfiguration of a specific sub-domain.  Each
   router MUST compute BFTs for a sub-domain using only routers
   advertising it in the same multi-topology.

5.3.  Encapsulation

   All routers in the flooding scope of the BIER TLVs MUST advertise the
   same encapsulation for a given <MT,SD>.  A router discovering
   encapsulation advertised that is different from its own MUST report a
   misconfiguration of a specific <MT,SD>.  Each router MUST compute
   BFTs for <MT,SD> using only routers having the same encapsulation as
   its own advertised encapsulation in BIER sub-TLV for <MT,SD>.

5.4.  Tree Type

   All routers in the flooding scope of the BIER TLVs MUST advertise the
   same tree type for a given <MT,SD>.  In case of mismatch the behavior
   is analogous to Section 5.3.

5.5.  Label Advertisements for MPLS encapsulated BIER sub-domains

   Each router MAY advertise within the BIER MPLS Encapsulation sub-sub-
   TLV (Section 6.2) of a BIER Info sub-TLV (Section 6.1) for <MT,SD>
   (denoted as TLV<MT,SD>) for every supported bitstring length a valid
   starting label value and a non-zero range length.  It MUST advertise
   at least one valid label value and a non-zero range length for the



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   required bitstring lengths per [I-D.draft-ietf-bier-architecture-02]
   in case it has computed itself as being on the BFT rooted at any of
   the BFRs with valid BFR-ids (except itself if it does NOT have a
   valid BFR-id) participating in <MT,SD>.

   A router MAY decide to not advertise the BIER Info sub-TLV
   (Section 6.1) for <MT,SD> if it does not want to participate in the
   sub-domain due to resource constraints, label space optimization,
   administrative configuration or any other reasons.

5.5.1.  Special Consideration

   A router that desires to participate in <MT,SD> MUST advertise for
   each bitstring length it supports in <MT,SD> a label range size that
   guarantees to cover the maximum BFR-id injected into <MT,SD> (which
   implies a certain maximum set id per bitstring length as described in
   [I-D.draft-ietf-bier-architecture-02]).  Any router that violates
   this condition MUST be excluded from BIER BFTs for <MT,SD>.

5.6.  BFR-id Advertisements

   Each BFER MAY advertise with its TLV<MT,SD> the BFR-id that it has
   administratively chosen.

   If a router discovers that two BFRs it can reach advertise the same
   value for BFR-id for <MT,SD>, it MUST report a misconfiguration and
   disregard those routers for all BIER calculations and procedures for
   <MT,SD> to align with [I-D.draft-ietf-bier-architecture-02].  It is
   worth observing that based on this procedure routers with colliding
   BFR-id assignments in <MT,SD> MAY still act as BFIRs in <MT,SD> but
   will be never able to receive traffic from other BFRs in <MT,SD>.

5.7.  Flooding

   BIER domain information SHOULD change and force flooding
   infrequently.  Especially, the router SHOULD make every possible
   attempt to bundle all the changes necessary to sub-domains and ranges
   advertised with those into least possible updates.

6.  Packet Formats

   All ISIS BIER information is carried within the TLVs 235, 237
   [RFC5120] and TLVs 135,236 [RFC5305], [RFC5308].








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6.1.  BIER Info sub-TLV

   This sub-TLV carries the information for the BIER sub-domains that
   the router participates in as BFR.  It can repeat multiple times for
   different multi-topology and sub-domain <MT,SD> combinations.

   The sub-TLV carries a single <MT,SD> combination followed by optional
   sub-sub-TLVs specified within its context such as e.g.  BIER MPLS
   Encapsulation per Section 6.2.  If the same <MT,SD> combination is
   advertised more than once, only the first occurence of the sub-TLV
   MUST be used.

   On violation of any of the following conditions, the receiving router
   SHOULD signal a misconfiguration condition.  Further results are
   unspecified unless described in the according section of this RFC:

   o  The subdomain-id MUST be included only within a single topology.





        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      |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |   Reserved    | subdomain-id  |   BFR-id                      |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+




   Type:  as indicated in IANA section.

   Length:  1 octet.

   Reserved:  reserved, must be 0 on transmission, ignored on reception.
      May be used in future versions. 8 bits

   subdomain-id:  Unique value identifying the BIER sub-domain. 1 octet

   BFR-id:  A 2 octet field encoding the BFR-id, as documented in
      [I-D.draft-ietf-bier-architecture-02].  If set to the invalid BFR-
      id advertising router is not owning a BFR-id in the sub-domain.






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6.2.  BIER MPLS Encapsulation sub-sub-TLV

   This sub-sub-TLV carries the information for the BIER MPLS
   encapsulation and the necessary label ranges per bitstring length for
   a certain <MT,SD> and is carried within the BIER Info sub-TLV
   (Section 6.1) that the router participates in as BFR.

   On violation of any of the following conditions, the receiving router
   SHOULD signal a misconfiguration condition.  Further results are by
   default unspecified unless explicitly described:

   o  The sub-sub-TLV MUST be included once AND ONLY once within the
      sub-TLV.  If such a sub-sub-TLV is included more than once, only
      the first instance MUST be processed.

   o  Label ranges within the sub-sub-TLV MUST NOT overlap, otherwise
      the whole sub-sub-TLV MUST be disregarded and the violating
      routers are treated per further procedures in Section 5.3.

   o  Bitstring lengths within the sub-sub-TLV MUST NOT repeat,
      otherwise the whole sub-sub-TLV MUST be disregarded and the
      violating routers are treated per further procedures in
      Section 5.3.

   o  The sub-sub-TLV MUST include the required bitstring lengths
      encoded in precisely the same way as in
      [I-D.draft-ietf-bier-architecture-02].

   o  All label range sizes MUST be greater than 0.

   o  All labels MUST represent valid label values, otherwise the whole
      sub-sub-TLV MUST be disregarded and the violating routers are
      treated per further procedures in Section 5.3.


















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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      |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | Lbl Range Size|BS Len |                    Label              |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
               ~~ (number repetitions derived from TLV length) ~~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | Lbl Range Size|BS Len |                    Label              |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+




   Type:  value of 0 indicating MPLS encapsulation.

   Length:  1 octet.

   Local BitString Length (BS Len):  Bitstring length for the label
      range that this router is advertising per
      [I-D.draft-ietf-bier-mpls-encapsulation-02]. 4 bits.

   Label Range Size:  Number of labels in the range used on
      encapsulation for this BIER sub-domain for this bitstring length,
      1 octet.  This MUST never be advertised as 0 (zero) and otherwise,
      this sub-sub-TLV must be treated as if not present for BFT
      calculations and a misconfiguration SHOULD be reported by the
      receiving router.

   Label:  First label of the range used on encapsulation for this BIER
      sub-domain for this bitstring length, 20 bits.  The label is used
      for example by [I-D.draft-ietf-bier-mpls-encapsulation-02] to
      forward traffic to sets of BFERs.

6.3.  Optional BIER sub-domain Tree Type sub-sub-TLV

   This sub-sub-TLV carries the information of the BIER tree type for a
   <MT,SD> combination.  It is carried within the BIER Info sub-TLV
   (Section 6.1) that the router participates in as BFR.  This sub-sub-
   TLV is optional and its absence has the same semantics as its
   presence with Tree Type value 0 (SPF).  BIER implementation following
   this version of the RFC SHOULD NOT advertise this TLV.

   On violation of any of the following conditions, the receiving router
   implementing this RFC SHOULD signal a misconfiguration condition.
   Further results are unspecified unless described further:




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   o  The sub-sub-TLV MUST NOT be included more than once.

   o  The Tree Type MUST be 0 (SPF).



         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      |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        | Tree Type     |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        | Tree Type specific opaque data|
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
           ~~ up to TLV Length ~~
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        | Tree Type specific opaque data|
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



   Type:  value of 1 indicating BIER Tree Type.

   Length:  1 octet.

   Tree Type:  The only supported value in this specification is 0 and
      indicates that BIER uses normal SPF computed reachability to
      construct BIFT.  BIER implementation following this RFC MUST
      ignore the node for purposes of the sub-domain <MT,SD> if this
      field has any value except 0.

   Tree type specific opaque data:  Opaque data up to the length of the
      TLV carrying tree type specific parameters.  For Tree Type 0 (SPF)
      no such data is included and therefore TLV Length is 1.

6.4.  Optional BIER sub-domain BSL conversion sub-sub-TLV

   This sub-sub-TLV indicates whether the BFR is capable of imposing a
   different Bit String Length (BSL) than the one it received in a BIER
   encapsulated packet.  Such a capability may allow future, advanced
   tree types which ensure simple migration procedures from one BSL to
   another in a given <MT,SD> or prevent stable blackholes in scenarios
   where not all routers support the same set of BSLs in a given
   <MT,SD>.  It is carried within the BIER Info sub-TLV (Section 6.1).
   This sub-sub-TLV is optional and its absence indicates that the
   router is NOT capable of imposing different BSLs but will always
   forward the packet with the BSL unchanged.



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   On violation of any of the following conditions, the receiving router
   implementing this RFC SHOULD signal a misconfiguration condition.
   Further results are unspecified unless described further:

   o  The sub-sub-TLV MUST NOT be included more than once.



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



   Type:  value of 2 indicating BIER BSL conversion.

   Length:  1 octet.

7.  Security Considerations

   Implementations must assure that malformed TLV and Sub-TLV
   permutations do not result in errors which cause hard protocol
   failures.

8.  Acknowledgements

   The RFC is aligned with the
   [I-D.draft-ietf-bier-ospf-bier-extensions-00] draft as far as the
   protocol mechanisms overlap.

   Many thanks for comments from (in no particular order) Hannes
   Gredler, Ijsbrand Wijnands, Peter Psenak and Chris Bowers.

9.  Normative References

   [I-D.draft-ietf-bier-architecture-02]
              Wijnands et al., IJ., "Stateless Multicast using Bit Index
              Explicit Replication Architecture", internet-draft draft-
              ietf-bier-architecture-02.txt, July 2015.

   [I-D.draft-ietf-bier-mpls-encapsulation-02]
              Wijnands et al., IJ., "Bit Index Explicit Replication
              using MPLS encapsulation", internet-draft draft-ietf-bier-
              mpls-encapsulation-02.txt, Aug 2015.





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   [I-D.draft-ietf-bier-ospf-bier-extensions-00]
              Psenak et al., P., "OSPF Extension for Bit Index Explicit
              Replication", internet-draft draft-ietf-bier-ospf-bier-
              extensions-00.txt, October 2014.

   [I-D.draft-ietf-isis-prefix-attributes-01]
              Ginsberg et al., U., "IS-IS Prefix Attributes for Extended
              IP and IPv6 Reachability", internet-draft draft-ietf-isis-
              prefix-attributes-01.txt, June 2015.

   [RFC1195]  Callon, R., "Use of OSI IS-IS for routing in TCP/IP and
              dual environments", RFC 1195, DOI 10.17487/RFC1195,
              December 1990, <http://www.rfc-editor.org/info/rfc1195>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC5120]  Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
              Topology (MT) Routing in Intermediate System to
              Intermediate Systems (IS-ISs)", RFC 5120,
              DOI 10.17487/RFC5120, February 2008,
              <http://www.rfc-editor.org/info/rfc5120>.

   [RFC5305]  Li, T. and H. Smit, "IS-IS Extensions for Traffic
              Engineering", RFC 5305, DOI 10.17487/RFC5305, October
              2008, <http://www.rfc-editor.org/info/rfc5305>.

   [RFC5308]  Hopps, C., "Routing IPv6 with IS-IS", RFC 5308,
              DOI 10.17487/RFC5308, October 2008,
              <http://www.rfc-editor.org/info/rfc5308>.

   [RFC6513]  Rosen, E., Ed. and R. Aggarwal, Ed., "Multicast in MPLS/
              BGP IP VPNs", RFC 6513, DOI 10.17487/RFC6513, February
              2012, <http://www.rfc-editor.org/info/rfc6513>.

Authors' Addresses

   Les Ginsberg (editor)
   Cisco Systems
   510 McCarthy Blvd.
   Milpitas, CA  95035
   USA

   Email: ginsberg@cisco.com





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   Tony Przygienda
   Ericsson
   300 Holger Way
   San Jose, CA  95134
   USA

   Email: antoni.przygienda@ericsson.com


   Sam Aldrin
   Google
   1600 Amphitheatre Parkway
   Mountain View, CA
   USA

   Email: aldrin.ietf@gmail.com


   Jeffrey (Zhaohui) Zhang
   Juniper Networks, Inc.
   10 Technology Park Drive
   Westford, MA  01886
   USA

   Email: zzhang@juniper.net


























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