EVPN BUM over BIER: EVPN Broadcast, Unknown Unicast, or Multicast (BUM) Using Bit Index Explicit Replication (BIER)

Internet Engineering Task Force (IETF)                          Z. Zhang
Request for Comments: 9624                                 T. Przygienda
Category: Standards Track                               Juniper Networks
ISSN: 2070-1721                                               A. Sajassi
                                                           Cisco Systems
                                                              J. Rabadan
                                                                   Nokia
                                                             August 2024


  EVPN Broadcast, Unknown Unicast, or Multicast (BUM) Using Bit Index
                      Explicit Replication (BIER)

Abstract

   This document specifies protocols and procedures for forwarding
   Broadcast, Unknown Unicast, or Multicast (BUM) traffic of Ethernet
   VPNs (EVPNs) using Bit Index Explicit Replication (BIER).

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc9624.

Copyright Notice

   Copyright (c) 2024 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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Table of Contents

   1.  Introduction
     1.1.  Terminology
     1.2.  Requirements Language
   2.  Use of the PMSI Tunnel Attribute
     2.1.  IP-Based Tunnel and BIER PHP
     2.2.  Explicit Tracking
       2.2.1.  Using IMET/SMET Routes
       2.2.2.  Using S-PMSI/Leaf A-D Routes
     2.3.  MPLS Label in the PTA
   3.  Multihoming Split Horizon
   4.  Data Plane
     4.1.  Encapsulation and Transmission
       4.1.1.  At a BFIR That Is an Ingress PE
       4.1.2.  At a BFIR That Is a P-Tunnel Segmentation Point
     4.2.  Disposition
       4.2.1.  At a BFER That Is an Egress PE
       4.2.2.  At a BFER That Is a P-Tunnel Segmentation Point
   5.  IANA Considerations
   6.  Security Considerations
   7.  References
     7.1.  Normative References
     7.2.  Informative References
   Acknowledgements
   Authors' Addresses

1.  Introduction

   [RFC7432] and [RFC8365] specify the protocols and procedures for
   Ethernet VPNs (EVPNs).  For Broadcast, Unknown Unicast, or Multicast
   (BUM) traffic, provider/underlay tunnels are used to carry the BUM
   traffic.  Several kinds of tunnel technologies can be used as
   specified in [RFC7432] and [RFC8365], and this document specifies the
   protocols and procedures to use Bit Index Explicit Replication (BIER)
   [RFC8279] as provider tunnels for EVPN BUM traffic.

   BIER is an architecture that provides optimal multicast forwarding
   through a "multicast domain" without requiring intermediate routers
   to maintain any per-flow state or to engage in an explicit tree-
   building protocol.

   The EVPN BUM procedures specified in [RFC7432] and extended in
   [RFC9572], [RFC9251], and [CMCAST-ENHANCEMENTS] are much aligned with
   Multicast VPN (MVPN) procedures [RFC6514], and an EVPN Broadcast
   Domain (BD) corresponds to a VPN in MVPN.  As such, this document is
   also very much aligned with [RFC8556], which specifies MVPN with
   BIER.  For terseness, some background, terms, and concepts are not
   repeated here.  Additionally, some text is borrowed verbatim from
   [RFC8556].

1.1.  Terminology

   ES:  Ethernet Segment

   ESI:  Ethernet Segment Identifier

   BFR:  Bit-Forwarding Router

   BFIR:  Bit-Forwarding Ingress Router

   BFER:  Bit-Forwarding Egress Router

   BFR-Prefix:  An IP address that uniquely identifies a BFR and is
      routable in a BIER domain.

   C-S:  A multicast source address identifying a multicast source
      located at an EVPN customer site.  "C-" stands for "Customer-".

   C-G:  A multicast group address used by an EVPN customer.

   C-flow:  A customer multicast flow.  Each C-flow is identified by the
      ordered pair (source address, group address), where each address
      is in the customer's address space.  The identifier of a
      particular C-flow is usually written as (C-S, C-G).  Sets of
      C-flows can be denoted by the use of the "C-*" wildcard (see
      [RFC6625]), e.g., (C-*, C-G).

   P-tunnel:  A multicast tunnel through the network of one or more
      service providers used to transport C-flows.  "P-" stands for
      "Provider-".

   IMET A-D Route:  Inclusive Multicast Ethernet Tag Auto-Discovery
      route.  Carried in BGP Update messages, these routes are used to
      advertise the "default" P-tunnel for a particular BD.

   SMET A-D Route:  Selective Multicast Ethernet Tag Auto-Discovery
      route.  Carried in BGP Update messages, these routes are used to
      advertise the C-flows that the advertising Provider Edge (PE) is
      interested in.

   PMSI:  Provider Multicast Service Interface [RFC6513].  A conceptual
      interface used by a PE to send customer multicast traffic to all
      or some PEs in the same VPN.

   I-PMSI:  Inclusive PMSI.  For all PEs in the same VPN.

   S-PMSI:  Selective PMSI.  For some of the PEs in the same VPN.

   I-PMSI A-D Route:  Inclusive PMSI Auto-Discovery route used to
      advertise the tunnels that instantiate an I-PMSI.

   S-PMSI A-D Route:  Selective PMSI Auto-Discovery route used to
      advertise that particular C-flows are bound to (i.e., are
      traveling through) particular P-tunnels.

   PTA:  PMSI Tunnel Attribute.  A BGP attribute used to identify a
      particular P-tunnel.

   VXLAN:  Virtual eXtensible Local Area Network [RFC7348]

   NVGRE:  Network Virtualization Using Generic Routing Encapsulation
      [RFC7637]

   GENEVE:  Generic Network Virtualization Encapsulation [RFC8926]

   VNI:  VXLAN Network Identifier

   VSID:  Virtual Subnet Identifier

   RSVP-TE P2MP:  Resource Reservation Protocol for Point-to-Multipoint
      TE Label Switched Paths (LSPs) [RFC4875]

   mLDP P2MP:  Multipoint Label Distribution Protocol extensions for
      Point-to-Multipoint LSPs [RFC6388]

1.2.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

2.  Use of the PMSI Tunnel Attribute

   [RFC7432] specifies that Inclusive Multicast Ethernet Tag (IMET)
   routes carry a PMSI Tunnel Attribute (PTA) to identify the particular
   P-tunnel to which one or more BUM flows are being assigned, which is
   the same as specified in [RFC6514] for MVPN.  [RFC8556] specifies the
   encoding of the PTA for the use of BIER with MVPN.  Much of that
   specification is reused for the use of BIER with EVPN, and much of
   the text below is borrowed verbatim from [RFC8556].

   The PTA contains the following fields:

   *  Tunnel Type.  The same codepoint 0x0B that IANA has assigned for
      BIER for MVPN [RFC8556] is used for EVPN as well.

   *  Tunnel Identifier.  This field contains three subfields for BIER.
      The text below is exactly as in [RFC8556].

      1.  The first subfield is a single octet, containing a BIER sub-
          domain-id (see [RFC8279]).  This indicates that packets sent
          on the PMSI will be sent on the specified BIER sub-domain.
          How that sub-domain is chosen is outside the scope of this
          document.

      2.  The second subfield is a two-octet field containing the BFR-id
          in the sub-domain identified in the first subfield of the
          router that is constructing the PTA.

      3.  The third subfield is the BFR-Prefix (see [RFC8279]) of the
          router (a BFIR) that is constructing the PTA.  The BFR-Prefix
          will either be a /32 IPv4 address or a /128 IPv6 address.
          Whether the address is IPv4 or IPv6 can be inferred from the
          total length of the PTA.

          The BFR-Prefix need not be the same IP address that is carried
          in any other field of the x-PMSI A-D route, even if the BFIR
          is the originating router of the x-PMSI A-D route.

   *  MPLS Label.  For EVPN-MPLS [RFC7432], this field contains an
      upstream-assigned MPLS label.  It is assigned by the BFIR.
      Constraints on how the originating router selects this label are
      discussed in Section 2.3.  For EVPN-VXLAN/NVGRE/GENEVE [RFC8365]
      [RFC7348] [RFC7637] [RFC8926], this field is a 24-bit VNI/VSID of
      global significance.

   *  Flags.  When the tunnel type is BIER, two of the flags in the PTA
      Flags field are meaningful.  Details about the use of these flags
      can be found in Section 2.2.

      -  Leaf Info Required per Flow (LIR-pF) [RFC8534]

      -  Leaf Info Required (LIR)

   Note that if a PTA specifying "BIER" is attached to an IMET, S-PMSI
   A-D, or per-region I-PMSI A-D route, the route MUST NOT be
   distributed beyond the boundaries of a BIER domain.  That is, any
   routers that receive the route must be in the same BIER domain as the
   originator of the route.  If the originator is in more than one BIER
   domain, the route must be distributed only within the BIER domain in
   which the BFR-Prefix in the PTA uniquely identifies the originator.
   As with all MVPN routes, the distribution of these routes is
   controlled by the provisioning of Route Targets.

2.1.  IP-Based Tunnel and BIER PHP

   When VXLAN/NVGRE/GENEVE is used for EVPN, by default, the outer IP
   header (and UDP header in the case of VXLAN/GENEVE) is not included
   in the BIER payload, except when it is known a priori that BIER
   Penultimate Hop Popping (PHP) [BIER-PHP] is used in the BIER domain
   and the encapsulation (after the BIER header is popped) between the
   BIER Penultimate Hop and the egress PE does not have a way to
   indicate the next header is VXLAN/NVGRE/GENEVE.  In that case, the
   full VXLAN/NVGRE/GENEVE encapsulation MUST be used.  In the outer IP
   header, a well-known IP multicast address (224.0.0.122 in the case of
   IPv4 or FF02:0:0:0:0:0:0:14 in the case of IPv6) is used as the
   destination address, and the egress PEs MUST be set up to receive and
   process packets addressed to the destination address.  The address is
   used for all BDs, and the inner VXLAN/NVGRE/GENEVE header will be
   used to identify BDs.

2.2.  Explicit Tracking

   When using BIER to transport an EVPN BUM data packet through a BIER
   domain, an ingress PE functions as a BFIR (see [RFC8279]).  The BFIR
   must determine the set of BFERs to which the packet needs to be
   delivered.  This can be done in either of two ways as described in
   the following two sections.

2.2.1.  Using IMET/SMET Routes

   Both IMET and SMET routes provide explicit tracking functionality.

   For an inclusive PMSI, the set of BFERs (egress PEs) includes the
   originators of all IMET routes for a BD.  For a selective PMSI, the
   set of BFERs (egress PEs) includes the originators of corresponding
   SMET routes.

   The SMET routes do not carry a PTA.  When an ingress PE sends traffic
   on a selective tunnel using BIER, it uses the upstream-assigned label
   that is advertised in its IMET route.

   When only selective forwarding is used for all flows and without
   tunnel segmentation, SMET routes are used without the need for S-PMSI
   A-D routes.  Otherwise, the procedures in the following section
   apply.

2.2.2.  Using S-PMSI/Leaf A-D Routes

   There are two cases where S-PMSI/Leaf A-D routes are used as
   discussed in the following two sections.

2.2.2.1.  Selective Forwarding Only for Some Flows

   With the SMET procedure, a PE advertises a SMET route for each (C-S,
   C-G) or (C-*, C-G) state that it learns on its Attachment Circuits
   (ACs), and each SMET route is tracked by every PE in the same BD.  It
   may be desired that SMET routes are not used in order to reduce the
   burden of explicit tracking.

   In this case, most multicast traffic will follow the I-PMSI
   (advertised via the IMET route) and only some flows will follow
   S-PMSIs.  To achieve that, S-PMSI/Leaf A-D routes can be used, as
   specified in [RFC9572].

   The rules specified in Sections 2.2.1 and 2.2.2 of [RFC8556] apply.

2.2.2.2.  Tunnel Segmentation

   Another case where S-PMSI/Leaf A-D routes are necessary is tunnel
   segmentation, which is also specified in [RFC9572] and further
   clarified in [CMCAST-ENHANCEMENTS] for segmentation with SMET routes.
   This is only applicable to EVPN-MPLS.

   The rules specified in Section 2.2.1 of [RFC8556] apply.
   Section 2.2.2 of [RFC8556] does not apply, because like in MVPN, the
   LIR-pF flag cannot be used with segmentation.

2.2.2.3.  Applicability of Additional MVPN Specifications

   As with the MVPN case, "Use of the PMSI Tunnel Attribute in Leaf A-D
   Routes" (Section 3 of [RFC8556]) applies.

   Notice that [RFC8556] refers to procedures specified in [RFC6625] and
   [RFC8534].  Those two documents were specified for MVPN but apply to
   IP multicast payload in EVPN as well.

2.3.  MPLS Label in the PTA

   Rules in Section 2.1 of [RFC8556] apply, EXCEPT the following three
   bullets (they do NOT apply to EVPN) in that section:

   *  If the two routes do not have the same Address Family Identifier
      (AFI) value, then their respective PTAs MUST contain different
      MPLS label values.  This ensures that when an egress PE receives a
      data packet with the given label, the egress PE can infer from the
      label whether the payload is an IPv4 packet or an IPv6 packet.

   *  If the BFIR is an ingress PE supporting MVPN extranet [RFC7900]
      functionality, and if the two routes originate from different VRFs
      on this ingress PE, then the respective PTAs of the two routes
      MUST contain different MPLS label values.

   *  If the BFIR is an ingress PE supporting the "Extranet Separation"
      feature of MVPN extranet (see Section 7.3 of [RFC7900]), and if
      one of the routes carries the "Extranet Separation" extended
      community but the other does not, then the respective PTAs of the
      two routes MUST contain different MPLS label values.

3.  Multihoming Split Horizon

   For EVPN-MPLS, [RFC7432] specifies the use of ESI labels to identify
   the ES from which a BUM packet originates.  A PE receiving that
   packet from the core side will not forward it to the same ES.  The
   procedure works for both Ingress Replication (IR) and RSVP-TE/mLDP
   P2MP tunnels, using downstream- and upstream-assigned ESI labels,
   respectively.  For EVPN-VXLAN/NVGRE/GENEVE, [RFC8365] specifies local
   bias procedures, where a PE receiving a BUM packet from the core side
   knows the ingress PE due to encapsulation; therefore, the PE does not
   forward the packet to any multihoming ESes that the ingress PE is on.
   This is because the ingress PE already forwarded the packet to those
   ESes, regardless of whether the ingress PE is a Designated Forwarder
   for those ESes.

   With BIER, the local bias procedure still applies for EVPN-
   VXLAN/NVGRE/GENEVE, as the BFIR-id in the BIER header identifies the
   ingress PE.  For EVPN-MPLS, ESI label procedures also still apply,
   though two upstream-assigned labels will be used (one for identifying
   the BD and one for identifying the ES) -- the same as in the case of
   using a single P2MP tunnel for multiple BDs.  The BFIR-id in the BIER
   header identifies the ingress PE that assigned those two labels.

4.  Data Plane

   Like MVPN, the EVPN application plays the role of the "multicast flow
   overlay" as described in [RFC8279].

4.1.  Encapsulation and Transmission

   A BFIR could be either an ingress PE or a P-tunnel segmentation
   point.  The procedures are slightly different as described below.

4.1.1.  At a BFIR That Is an Ingress PE

   To transmit a BUM data packet, an ingress PE first determines the
   route matched for transmission and routes for tracking leaves
   according to the following rules.

   1.  If selective forwarding is not used or is not an IP multicast
       packet after the Ethernet header, the IMET route originated for
       the BD by the ingress PE is the route matched for transmission.
       Leaf-tracking routes are all other received IMET routes for the
       BD.

   2.  Otherwise, if selective forwarding is used for all IP multicast
       traffic based on SMET routes, the IMET route originated for the
       BD by the ingress PE is the route matched for transmission.
       Received SMET routes for the BD, whose source and destination
       address fields match the packet's source and destination IP
       address, are leaf-tracking routes.

   3.  Otherwise, the route matched for transmission is the S-PMSI A-D
       route originated by the ingress PE for the BD, whose source and
       destination address fields match the packet's source and
       destination IP address and have a PTA specifying a valid tunnel
       type that is not "no tunnel info".  Leaf-tracking routes are
       determined as follows:

       a.  If the match for the transmission route carries a PTA that
           has the LIR flag set but does not have the LIR-pF flag set,
           the routes matched for tracking are Leaf A-D routes whose
           Route Key field is identical to the NLRI of the S-PMSI A-D
           route.

       b.  If the match for the transmission route carries a PTA that
           has the LIR-pF flag, the leaf-tracking routes are Leaf A-D
           routes whose Route Key field is derived from the NLRI of the
           S-PMSI A-D route according to the procedures described in
           Section 5.2 of [RFC8534].

       Note that in both cases, SMET routes may be used in lieu of Leaf
       A-D routes, as a PE may omit the Leaf A-D route in response to an
       S-PMSI A-D route with the LIR or LIR-pF bit set if a SMET route
       with the corresponding Tag, Source, and Group fields is already
       originated [RFC9572].  In particular, in the second case above,
       even though the SMET route does not have a PTA attached, it is
       still considered a Leaf A-D route in response to a wildcard
       S-PMSI A-D route with the LIR-pF bit set.

   4.  Otherwise, the route matched for transmission and leaf-tracking
       routes are determined as in rule 1.

   If no route is matched for transmission, the packet is not forwarded
   onto a P-tunnel.  If the tunnel that the ingress determines to use
   based on the route matched for transmission (and considering
   interworking with PEs that do not support certain tunnel types per
   procedures in [RFC9251]) requires leaf tracking (e.g., Ingress
   Replication, RSVP-TE P2MP tunnel, or BIER) but there are no leaf-
   tracking routes, the packet will not be forwarded onto a P-tunnel
   either.

   The following text assumes that BIER is the determined tunnel type.
   The ingress PE pushes an upstream-assigned ESI label per [RFC7432] if
   the following conditions are all met:

   *  The packet is received on a multihomed ES.

   *  It is EVPN-MPLS.

   *  The ESI label procedure is used for split horizon.

   The MPLS label from the PTA of the route matched for transmission is
   then pushed onto the packet's label stack for EVPN-MPLS.  For EVPN-
   VXLAN/NVGRE/GENEVE, a VXLAN/NVGRE/GENEVE header is prepended to the
   packet with the VNI/VSID set to the value in the PTA's Label field,
   and then an IP/UDP header is prepended if needed (e.g., for PHP
   purposes).

   Then, the packet is encapsulated in a BIER header and forwarded
   according to the procedures of [RFC8279] and [RFC8296].
   Specifically, see "Imposing and Processing the BIER Encapsulation"
   (Section 3 of [RFC8296]).  The Proto field in the BIER header is set
   to 2 in the case of EVPN-MPLS, 7/8/9 in the case of EVPN-VXLAN/NVGRE/
   GENEVE (Section 5) when an IP header is not used, or 4/6 if an IP
   header is used for EVPN-VXLAN/NVGRE/GENEVE.

   To create the proper BIER header for a given packet, the BFIR must
   know all the BFERs that need to receive that packet.  This is
   determined from the set of leaf-tracking routes.

4.1.2.  At a BFIR That Is a P-Tunnel Segmentation Point

   In this case, the encapsulation for the upstream segment of the
   P-tunnel includes (among other things) a label that identifies the
   x-PMSI or IMET A-D route that is the match for reception on the
   upstream segment.  The segmentation point re-advertised the route
   into one or more downstream regions.  Each instance of the re-
   advertised route for a downstream region has a PTA that specifies the
   tunnel for that region.  For any particular downstream region, the
   route matched for transmission is the re-advertised route, and the
   leaf-tracking routes are determined as follows, if needed, for the
   tunnel type:

   *  If the route matched for transmission is an x-PMSI route, it must
      have the LIR flag set in its PTA, and the leaf-tracking routes are
      all the matching Leaf A-D and SMET routes received in the
      downstream region.

   *  If the route matched for transmission is an IMET route, the leaf-
      tracking routes are all the IMET routes for the same BD received
      in the downstream region.

   If the downstream region uses BIER, the packet is forwarded as
   follows: the upstream segmentation's encapsulation is removed and the
   above-mentioned label is swapped to the upstream-assigned label in
   the PTA of the route matched for transmission, and then a BIER header
   is imposed as in Section 4.1.1.

4.2.  Disposition

   The same procedures in Section 4.2 of [RFC8556] are followed for
   EVPN-MPLS, except for some EVPN specifics that are discussed in the
   following two subsections of this document.

   For EVPN-VXLAN/NVGRE/GENEVE, the only differences are that the
   payload is VXLAN/NVGRE/GENEVE (with or without an IP header) and the
   VNI/VSID field in the VXLAN/NVGRE/GENEVE header is used to determine
   the corresponding BD.

4.2.1.  At a BFER That Is an Egress PE

   Once the corresponding BD is determined from the upstream-assigned
   label or VNI/VSID, EVPN forwarding procedures per [RFC7432] or
   [RFC8365] are followed.  In the case of EVPN-MPLS, if there is an
   inner label in the label stack following the BIER header, that inner
   label is considered the upstream-assigned ESI label for split-horizon
   purposes.

4.2.2.  At a BFER That Is a P-Tunnel Segmentation Point

   This is only applicable to EVPN-MPLS.  The same procedures in
   Section 4.2.2 of [RFC8556] are followed, subject to multihoming
   procedures specified in [RFC9572].

5.  IANA Considerations

   Per this document, IANA has registered the following three values in
   the "BIER Next Protocol Identifiers" registry:

          +=======+================================+===========+
          | Value | Description                    | Reference |
          +=======+================================+===========+
          | 7     | Payload is VXLAN encapsulated  | RFC 9624  |
          |       | (no IP/UDP header)             |           |
          +-------+--------------------------------+-----------+
          | 8     | Payload is NVGRE encapsulated  | RFC 9624  |
          |       | (no IP header)                 |           |
          +-------+--------------------------------+-----------+
          | 9     | Payload is GENEVE encapsulated | RFC 9624  |
          |       | (no IP/UDP header)             |           |
          +-------+--------------------------------+-----------+

             Table 1: BIER Next Protocol Identifiers Registry

   IANA has also assigned an IPv4 and an IPv6 multicast address for the
   case discussed in Section 2.1.

   The following entry has been added to the "Local Network Control
   Block (224.0.0.0 - 224.0.0.255 (224.0.0/24))" registry for IPv4:

   Address(es):  224.0.0.122
   Description:  Network Virtualization Overlay (NVO) BUM Traffic
   Reference:  RFC 9624

   The following entry has been added to the "Link-Local Scope Multicast
   Addresses" registry for IPv6:

   Address(es):  FF02:0:0:0:0:0:0:14
   Description:  Network Virtualization Overlay (NVO) BUM Traffic
   Reference:  RFC 9624

6.  Security Considerations

   This document is about using BIER as provider tunnels for EVPN.  It
   is very similar to using BIER as MVPN provider tunnels and does not
   introduce additional security implications beyond what have been
   discussed in the EVPN base protocol specification [RFC7432] and MVPN
   using BIER [RFC8556].

7.  References

7.1.  Normative References

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

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

   [RFC6514]  Aggarwal, R., Rosen, E., Morin, T., and Y. Rekhter, "BGP
              Encodings and Procedures for Multicast in MPLS/BGP IP
              VPNs", RFC 6514, DOI 10.17487/RFC6514, February 2012,
              <https://www.rfc-editor.org/info/rfc6514>.

   [RFC6625]  Rosen, E., Ed., Rekhter, Y., Ed., Hendrickx, W., and R.
              Qiu, "Wildcards in Multicast VPN Auto-Discovery Routes",
              RFC 6625, DOI 10.17487/RFC6625, May 2012,
              <https://www.rfc-editor.org/info/rfc6625>.

   [RFC7432]  Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A.,
              Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based
              Ethernet VPN", RFC 7432, DOI 10.17487/RFC7432, February
              2015, <https://www.rfc-editor.org/info/rfc7432>.

   [RFC7900]  Rekhter, Y., Ed., Rosen, E., Ed., Aggarwal, R., Cai, Y.,
              and T. Morin, "Extranet Multicast in BGP/IP MPLS VPNs",
              RFC 7900, DOI 10.17487/RFC7900, June 2016,
              <https://www.rfc-editor.org/info/rfc7900>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8279]  Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A.,
              Przygienda, T., and S. Aldrin, "Multicast Using Bit Index
              Explicit Replication (BIER)", RFC 8279,
              DOI 10.17487/RFC8279, November 2017,
              <https://www.rfc-editor.org/info/rfc8279>.

   [RFC8296]  Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A.,
              Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation
              for Bit Index Explicit Replication (BIER) in MPLS and Non-
              MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, January
              2018, <https://www.rfc-editor.org/info/rfc8296>.

   [RFC8365]  Sajassi, A., Ed., Drake, J., Ed., Bitar, N., Shekhar, R.,
              Uttaro, J., and W. Henderickx, "A Network Virtualization
              Overlay Solution Using Ethernet VPN (EVPN)", RFC 8365,
              DOI 10.17487/RFC8365, March 2018,
              <https://www.rfc-editor.org/info/rfc8365>.

   [RFC8534]  Dolganow, A., Kotalwar, J., Rosen, E., Ed., and Z. Zhang,
              "Explicit Tracking with Wildcard Routes in Multicast VPN",
              RFC 8534, DOI 10.17487/RFC8534, February 2019,
              <https://www.rfc-editor.org/info/rfc8534>.

   [RFC8556]  Rosen, E., Ed., Sivakumar, M., Przygienda, T., Aldrin, S.,
              and A. Dolganow, "Multicast VPN Using Bit Index Explicit
              Replication (BIER)", RFC 8556, DOI 10.17487/RFC8556, April
              2019, <https://www.rfc-editor.org/info/rfc8556>.

   [RFC8926]  Gross, J., Ed., Ganga, I., Ed., and T. Sridhar, Ed.,
              "Geneve: Generic Network Virtualization Encapsulation",
              RFC 8926, DOI 10.17487/RFC8926, November 2020,
              <https://www.rfc-editor.org/info/rfc8926>.

   [RFC9251]  Sajassi, A., Thoria, S., Mishra, M., Patel, K., Drake, J.,
              and W. Lin, "Internet Group Management Protocol (IGMP) and
              Multicast Listener Discovery (MLD) Proxies for Ethernet
              VPN (EVPN)", RFC 9251, DOI 10.17487/RFC9251, June 2022,
              <https://www.rfc-editor.org/info/rfc9251>.

   [RFC9572]  Zhang, Z., Lin, W., Rabadan, J., Patel, K., and A.
              Sajassi, "Updates to EVPN Broadcast, Unknown Unicast, or
              Multicast (BUM) Procedures", RFC 9572,
              DOI 10.17487/RFC9572, May 2024,
              <https://www.rfc-editor.org/info/rfc9572>.

7.2.  Informative References

   [BIER-PHP] Zhang, Z., "BIER Penultimate Hop Popping", Work in
              Progress, Internet-Draft, draft-ietf-bier-php-11, 6
              February 2024, <https://datatracker.ietf.org/doc/html/
              draft-ietf-bier-php-11>.

   [CMCAST-ENHANCEMENTS]
              Zhang, Z., Kebler, R., Lin, W., and E. Rosen, "MVPN/EVPN
              C-Multicast Routes Enhancements", Work in Progress,
              Internet-Draft, draft-zzhang-bess-mvpn-evpn-cmcast-
              enhancements-04, 17 March 2024,
              <https://datatracker.ietf.org/doc/html/draft-zzhang-bess-
              mvpn-evpn-cmcast-enhancements-04>.

   [RFC4875]  Aggarwal, R., Ed., Papadimitriou, D., Ed., and S.
              Yasukawa, Ed., "Extensions to Resource Reservation
              Protocol - Traffic Engineering (RSVP-TE) for Point-to-
              Multipoint TE Label Switched Paths (LSPs)", RFC 4875,
              DOI 10.17487/RFC4875, May 2007,
              <https://www.rfc-editor.org/info/rfc4875>.

   [RFC6388]  Wijnands, IJ., Ed., Minei, I., Ed., Kompella, K., and B.
              Thomas, "Label Distribution Protocol Extensions for Point-
              to-Multipoint and Multipoint-to-Multipoint Label Switched
              Paths", RFC 6388, DOI 10.17487/RFC6388, November 2011,
              <https://www.rfc-editor.org/info/rfc6388>.

   [RFC7348]  Mahalingam, M., Dutt, D., Duda, K., Agarwal, P., Kreeger,
              L., Sridhar, T., Bursell, M., and C. Wright, "Virtual
              eXtensible Local Area Network (VXLAN): A Framework for
              Overlaying Virtualized Layer 2 Networks over Layer 3
              Networks", RFC 7348, DOI 10.17487/RFC7348, August 2014,
              <https://www.rfc-editor.org/info/rfc7348>.

   [RFC7637]  Garg, P., Ed. and Y. Wang, Ed., "NVGRE: Network
              Virtualization Using Generic Routing Encapsulation",
              RFC 7637, DOI 10.17487/RFC7637, September 2015,
              <https://www.rfc-editor.org/info/rfc7637>.

Acknowledgements

   The authors thank Eric Rosen for his review and suggestions.
   Additionally, much of the text is borrowed verbatim from [RFC8556].

Authors' Addresses

   Zhaohui Zhang
   Juniper Networks
   Email: zzhang@juniper.net


   Tony Przygienda
   Juniper Networks
   Email: prz@juniper.net


   Ali Sajassi
   Cisco Systems
   Email: sajassi@cisco.com


   Jorge Rabadan
   Nokia
   Email: jorge.rabadan@nokia.com