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IGMP and MLD Proxy for EVPN
draft-ietf-bess-evpn-igmp-mld-proxy-21

Document Type Active Internet-Draft (bess WG)
Authors Ali Sajassi , Samir Thoria , Mankamana Prasad Mishra , John Drake , Wen Lin
Last updated 2022-05-19 (Latest revision 2022-03-22)
Replaces draft-sajassi-bess-evpn-igmp-mld-proxy
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OPSDIR Last Call Review Incomplete, due 2021-09-07
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Details
draft-ietf-bess-evpn-igmp-mld-proxy-21
BESS WorkGroup                                                A. Sajassi
Internet-Draft                                                 S. Thoria
Intended status: Standards Track                               M. Mishra
Expires: September 23, 2022                                Cisco Systems
                                                                K. Patel
                                                                  Arrcus
                                                                J. Drake
                                                                  W. Lin
                                                        Juniper Networks
                                                          March 22, 2022

                      IGMP and MLD Proxy for EVPN
                 draft-ietf-bess-evpn-igmp-mld-proxy-21

Abstract

   This document describes how to support efficiently endpoints running
   IGMP(Internet Group Management Protocol) or MLD (Multicast Listener
   Discovery) for the multicast services over an EVPN network by
   incorporating IGMP/MLD proxy procedures on EVPN (Ethernet VPN) PEs.

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 https://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 September 23, 2022.

Copyright Notice

   Copyright (c) 2022 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
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents

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   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  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Specification of Requirements . . . . . . . . . . . . . . . .   4
   3.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  IGMP/MLD Proxy  . . . . . . . . . . . . . . . . . . . . . . .   6
     4.1.  Proxy Reporting . . . . . . . . . . . . . . . . . . . . .   6
       4.1.1.  IGMP/MLD Membership Report Advertisement in BGP . . .   7
       4.1.2.  IGMP/MLD Leave Group Advertisement in BGP . . . . . .   9
     4.2.  Proxy Querier . . . . . . . . . . . . . . . . . . . . . .   9
   5.  Operation . . . . . . . . . . . . . . . . . . . . . . . . . .  10
     5.1.  PE with only attached hosts for a given subnet  . . . . .  11
     5.2.  PE with a mix of attached hosts and multicast source  . .  12
     5.3.  PE with a mix of attached hosts, a multicast source and a
           router  . . . . . . . . . . . . . . . . . . . . . . . . .  12
   6.  All-Active Multi-Homing . . . . . . . . . . . . . . . . . . .  12
     6.1.  Local IGMP/MLD Membership Report Synchronization  . . . .  12
     6.2.  Local IGMP/MLD Leave Group Synchronization  . . . . . . .  13
       6.2.1.  Remote Leave Group Synchronization  . . . . . . . . .  14
       6.2.2.  Common Leave Group Synchronization  . . . . . . . . .  14
     6.3.  Mass Withdraw of Multicast Membership Report Sync route
           in case of failure  . . . . . . . . . . . . . . . . . . .  15
   7.  Single-Active Multi-Homing  . . . . . . . . . . . . . . . . .  15
   8.  Selective Multicast Procedures for IR tunnels . . . . . . . .  15
   9.  BGP Encoding  . . . . . . . . . . . . . . . . . . . . . . . .  16
     9.1.  Selective Multicast Ethernet Tag Route  . . . . . . . . .  16
       9.1.1.  Constructing the Selective Multicast Ethernet Tag
               route . . . . . . . . . . . . . . . . . . . . . . . .  18
       9.1.2.  Reconstructing IGMP / MLD Membership Reports from
               Selective Multicast Route . . . . . . . . . . . . . .  19
       9.1.3.  Default Selective Multicast Route . . . . . . . . . .  20
     9.2.  Multicast Membership Report Synch Route . . . . . . . . .  21
       9.2.1.  Constructing the Multicast Membership Report Synch
               Route . . . . . . . . . . . . . . . . . . . . . . . .  22
       9.2.2.  Reconstructing IGMP / MLD Membership Reports from
               Multicast Membership Report Sync Route  . . . . . . .  23
     9.3.  Multicast Leave Synch Route . . . . . . . . . . . . . . .  24
       9.3.1.  Constructing the Multicast Leave Synch Route  . . . .  26
       9.3.2.  Reconstructing IGMP / MLD Leave from Multicast Leave
               Sync Route  . . . . . . . . . . . . . . . . . . . . .  27
     9.4.  Multicast Flags Extended Community  . . . . . . . . . . .  28
     9.5.  EVI-RT Extended Community . . . . . . . . . . . . . . . .  29

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     9.6.  Rewriting of RT ECs and EVI-RT ECs by ASBRs . . . . . . .  31
     9.7.  BGP Error Handling  . . . . . . . . . . . . . . . . . . .  32
   10. IGMP Version 1 Membership Report  . . . . . . . . . . . . . .  32
   11. Security Considerations . . . . . . . . . . . . . . . . . . .  32
   12. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  32
     12.1.  EVPN Extended Community Sub-Types Registrations  . . . .  32
     12.2.  EVPN Route Type Registration . . . . . . . . . . . . . .  33
     12.3.  Multicast Flags Extended Community Registry  . . . . . .  33
   13. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . .  33
   14. Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  34
   15. References  . . . . . . . . . . . . . . . . . . . . . . . . .  34
     15.1.  Normative References . . . . . . . . . . . . . . . . . .  34
     15.2.  Informative References . . . . . . . . . . . . . . . . .  35
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  35

1.  Introduction

   In DC applications, a point of delivery (POD) can consist of a
   collection of servers supported by several top of rack (ToR) and
   spine switches.  This collection of servers and switches are self
   contained and may have their own control protocol for intra-POD
   communication and orchestration.  However, EVPN is used as standard
   way of inter-POD communication for both intra-DC and inter-DC.  A
   subnet can span across multiple PODs and DCs.  EVPN provides a robust
   multi-tenant solution with extensive multi-homing capabilities to
   stretch a subnet (VLAN) across multiple PODs and DCs.  There can be
   many hosts (several hundreds) attached to a subnet that is stretched
   across several PODs and DCs.

   These hosts express their interests in multicast groups on a given
   subnet/VLAN by sending IGMP/MLD Membership Reports for their
   interested multicast group(s).  Furthermore, an IGMP/MLD router
   periodically sends membership queries to find out if there are hosts
   on that subnet that are still interested in receiving multicast
   traffic for that group.  The IGMP/MLD Proxy solution described in
   this document accomplishes three objectives:

   1.  Reduce flooding of IGMP/MLD messages: just like the ARP/ND
       suppression mechanism in EVPN to reduce the flooding of ARP
       messages over EVPN, it is also desired to have a mechanism to
       reduce the flooding of IGMP/MLD messages (both Queries and
       Membership Reports) in EVPN.

   2.  Distributed anycast multicast proxy: it is desirable for the EVPN
       network to act as a distributed anycast multicast router with
       respect to IGMP/MLD proxy function for all the hosts attached to
       that subnet.

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   3.  Selective Multicast: to forward multicast traffic over EVPN
       network such that it only gets forwarded to the PEs that have
       interest in the multicast group(s).  This document shows how this
       objective may be achieved when Ingress Replication is used to
       distribute the multicast traffic among the PEs.  Procedures for
       supporting selective multicast using P2MP tunnels can be found in
       [I-D.ietf-bess-evpn-bum-procedure-updates]

   The first two objectives are achieved by using IGMP/MLD proxy on the
   PE.  The third objective is achieved by setting up a multicast tunnel
   only among the PEs that have interest in that multicast group(s)
   based on the trigger from IGMP/MLD proxy processes.  The proposed
   solutions for each of these objectives are discussed in the following
   sections.

2.  Specification of Requirements

   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.

3.  Terminology

   o  AC: Attachment Circuit.

   o  All-Active Redundancy Mode: When all PEs attached to an Ethernet
      segment are allowed to forward known unicast traffic to/from that
      Ethernet segment for a given VLAN, then the Ethernet segment is
      defined to be operating in All-Active redundancy mode.

   o  BD: Broadcast Domain.  As per [RFC7432], an EVI consists of a
      single or multiple BDs.  In case of VLAN-bundle and VLAN-aware
      bundle service model, an EVI contains multiple BDs.  Also, in this
      document, BD and subnet are equivalent terms.

   o  DC: Data Center

   o  Ethernet Segment (ES): When a customer site (device or network) is
      connected to one or more PEs via a set of Ethernet links.

   o  Ethernet Segment Identifier (ESI): A unique non-zero identifier
      that identifies an Ethernet Segment.

   o  Ethernet Tag: It identifies a particular broadcast domain, e.g., a
      VLAN.  An EVPN instance consists of one or more broadcast domains.

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   o  EVI: An EVPN instance spanning the Provider Edge (PE) devices
      participating in that EVPN

   o  EVPN: Ethernet Virtual Private Network

   o  IGMP: Internet Group Management Protocol

   o  IR: Ingress Replication

   o  MLD: Multicast Listener Discovery

   o  OIF: Outgoing Interface for multicast.  It can be physical
      interface, virtual interface or tunnel.

   o  PE: Provider Edge.

   o  POD: Point of Delivery

   o  S-PMSI: Selective P-Multicast Service Interface - a conceptual
      interface for a PE to send customer multicast traffic to some of
      the PEs in the same VPN.

   o  Single-Active Redundancy Mode: When only a single PE, among all
      the PEs attached to an Ethernet segment, is allowed to forward
      traffic to/from that Ethernet segment for a given VLAN, then the
      Ethernet segment is defined to be operating in Single-Active
      redundancy mode.

   o  SMET: Selective Multicast Ethernet Tag

   o  ToR: Top of Rack

   This document also assumes familiarity with the terminology of
   [RFC7432], [RFC3376], [RFC2236] . Though most of the place this
   document uses term IGMP Membership Report, the text applies equally
   for MLD Membership Report too.  Similarly, text for IGMPv2 applies to
   MLDv1 and text for IGMPv3 applies to MLDv2.  IGMP / MLD version
   encoding in BGP update is stated in Section 9

   It is important to note when there is text considering whether a PE
   indicates support for IGMP proxying, the corresponding behavior has a
   natural analogue for indication of support for MLD proxying, and the
   analogous requirements apply as well.

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4.  IGMP/MLD Proxy

   The IGMP Proxy mechanism is used to reduce the flooding of IGMP
   messages over an EVPN network similar to ARP proxy used in reducing
   the flooding of ARP messages over EVPN.  It also provides a
   triggering mechanism for the PEs to setup their underlay multicast
   tunnels.  The IGMP Proxy mechanism consists of two components:

   1.  Proxy for IGMP Membership Reports.

   2.  Proxy for IGMP Membership Queries.

   The goal of IGMP and MLD proxying is to make the EVPN behave
   seamlessly for the tenant systems with respect to multicast
   operations, while using a more efficient delivery system for
   signaling and delivery across the VPN.  Accordingly, group state must
   be tracked synchronously among the PEs serving the VPN, with join and
   leave events propagated to the peer PEs, and each PE tracking the
   state of each of its peer PEs with respect whether there are locally
   attached group members (and in some cases, senders), what version(s)
   of IGMP/MLD are in use for those locally attached group members, etc.
   In order to perform this translation, each PE acts as an IGMP router
   for the locally attached domain, and maintains the requisite state on
   locally attached nodes, sends periodic membership queries, etc.  The
   role of EVPN SMET route propagation is to ensure that each PE's local
   state is propagated to the other PEs so that they share a consistent
   view of the overall IGMP Membership Request and Leave Group state.
   It is important to note that the need to keep such local state can be
   triggered by either local IGMP traffic or BGP EVPN signaling.  In
   most cases a local IGMP event will need to be signaled over EVPN,
   though state initiated by received EVPN traffic will not always need
   to be relayed to the locally attached domain.

4.1.  Proxy Reporting

   When IGMP protocol is used between hosts and their first hop EVPN
   router (EVPN PE), Proxy-reporting is used by the EVPN PE to summarize
   (when possible) reports received from downstream hosts and propagate
   them in BGP to other PEs that are interested in the information.
   This is done by terminating the IGMP Reports in the first hop PE, and
   translating and exchanging the relevant information among EVPN BGP
   speakers.  The information is again translated back to IGMP message
   at the recipient EVPN speaker.  Thus it helps create an IGMP overlay
   subnet using BGP.  In order to facilitate such an overlay, this
   document also defines a new EVPN route type NLRI, the EVPN Selective
   Multicast Ethernet Tag route, along with its procedures to help
   exchange and register IGMP multicast groups Section 9.

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4.1.1.  IGMP/MLD Membership Report Advertisement in BGP

   When a PE wants to advertise an IGMP Membership Report using the BGP
   EVPN route, it follows the following rules (BGP encoding stated in
   Section 9).  Where first four rules are applicable to originator PE
   and last three rules are applicable to remote PE processing SMET
   routes:

   Processing at BGP route originator:

   1.  When the first hop PE receives IGMP Membership Reports ,
       belonging to the same IGMP version, from different attached hosts
       for the same (*,G) or (S,G), it SHOULD send a single BGP message
       corresponding to the very first IGMP Membership Request (BGP
       update as soon as possible) for that (*,G) or (S,G).  This is
       because BGP is a stateful protocol and no further transmission of
       the same report is needed.  If the IGMP Membership Request is for
       (*,G), then multicast group address MUST be sent along with the
       corresponding version flag (v2 or v3) set.  In case of IGMPv3,
       the exclude flag MUST also be set to indicate that no source IP
       address must be excluded (include all sources "*").  If the IGMP
       Membership Report is for (S,G), then besides setting multicast
       group address along with the version flag v3, the source IP
       address and the IE flag MUST be set.  It should be noted that
       when advertising the EVPN route for (S,G), the only valid version
       flag is v3 (v2 flags MUST be set to zero).

   2.  When the first hop PE receives an IGMPv3 Membership Report for
       (S,G) on a given BD, it MUST advertise the corresponding EVPN
       Selective Multicast Ethernet Tag (SMET) route regardless of
       whether the source (S) is attached to itself or not in order to
       facilitate the source move in the future.

   3.  When the first hop PE receives an IGMP version-X Membership
       Report first for (*,G) and then later it receives an IGMP
       version-Y Membership Report for the same (*,G), then it MUST re-
       advertise the same EVPN SMET route with flag for version-Y set in
       addition to any previously-set version flag(s).  In other words,
       the first hop PE MUST NOT withdraw the EVPN route before sending
       the new route because the flag field is not part of BGP route key
       processing.

   4.  When the first hop PE receives an IGMP version-X Membership
       Report first for (*,G) and then later it receives an IGMPv3
       Membership Report for the same multicast group address but for a
       specific source address S, then the PE MUST advertise a new EVPN
       SMET route with v3 flag set (and v2 reset).  The IE flag also
       need to be set accordingly.  Since source IP address is used as

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       part of BGP route key processing it is considered as a new BGP
       route advertisement.  When different version of IGMP Membership
       Report are received, final state MUST be as per section 5.1 of
       [RFC3376].  At the end of route processing local and remote group
       record state MUST be as per section 5.1 of [RFC3376].

   Processing at BGP route receiver:

   1.  When a PE receives an EVPN SMET route with more than one version
       flag set, it will generate the corresponding IGMP report for
       (*,G) for each version specified in the flags field.  With
       multiple version flags set, there must not be source IP address
       in the received EVPN route.  If there is, then an error SHOULD be
       logged.  If the v3 flag is set (in addition to v2), then the IE
       flag MUST indicate "exclude".  If not, then an error SHOULD be
       logged.  The PE MUST generate an IGMP Membership Report for that
       (*,G) and each IGMP version in the version flag.

   2.  When a PE receives a list of EVPN SMET NLRIs in its BGP update
       message, each with a different source IP address and the same
       multicast group address, and the version flag is set to v3, then
       the PE generates an IGMPv3 Membership Report with a record
       corresponding to the list of source IP addresses and the group
       address along with the proper indication of inclusion/exclusion.

   3.  Upon receiving EVPN SMET route(s) and before generating the
       corresponding IGMP Membership Request(s), the PE checks to see
       whether it has any CE multicast router for that BD on any of its
       ES's . The PE provides such a check by listening for PIM Hello
       messages on that AC (i.e, ES,BD).  If the PE does have the
       router's ACs, then the generated IGMP Membership Request(s) are
       sent to those ACs.  If it doesn't have any of the router's AC,
       then no IGMP Membership Request(s) needs to be generated.  This
       is because sending IGMP Membership Requests to other hosts can
       result in unintentionally preventing a host from joining a
       specific multicast group using IGMPv2 - i.e., if the PE does not
       receive a Membership Report from the host it will not forward
       multicast data to it.  Per [RFC4541] , when an IGMPv2 host
       receives a Membership Report for a group address that it intends
       to join, the host will suppress its own membership report for the
       same group, and if the PE does not receive an IGMP Membership
       Report from the host it will not forward multicast data to it.
       In other words, an IGMPv2 Membership Report MUST NOT be sent on
       an AC that does not lead to a CE multicast router.  This message
       suppression is a requirement for IGMPv2 hosts.  This is not a
       problem for hosts running IGMPv3 because there is no suppression
       of IGMP Membership Reports.

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4.1.2.  IGMP/MLD Leave Group Advertisement in BGP

   When a PE wants to withdraw an EVPN SMET route corresponding to an
   IGMPv2 Leave Group or IGMPv3 "Leave" equivalent message, it follows
   the following rules, where first rule defines the procedure at
   originator PE and last two rules talk about procedures at remote PE:

   Processing at BGP route originator:

   1.  When a PE receives an IGMPv2 Leave Group or its "Leave"
       equivalent message for IGMPv3 from its attached host, it checks
       to see if this host is the last host that is interested in this
       multicast group by sending a query for the multicast group.  If
       the host was indeed the last one (i.e. no responses are received
       for the query), then the PE MUST re-advertises EVPN SMET
       Multicast route with the corresponding version flag reset.  If
       this is the last version flag to be reset, then instead of re-
       advertising the EVPN route with all version flags reset, the PE
       MUST withdraw the EVPN route for that (*,G).

   Processing at BGP route receiver:

   1.  When a PE receives an EVPN SMET route for a given (*,G), it
       compares the received version flags from the route with its per-
       PE stored version flags.  If the PE finds that a version flag
       associated with the (*,G) for the remote PE is reset, then the PE
       MUST generate IGMP Leave for that (*,G) toward its local
       interface (if any) attached to the multicast router for that
       multicast group.  It should be noted that the received EVPN route
       MUST at least have one version flag set.  If all version flags
       are reset, it is an error because the PE should have received an
       EVPN route withdraw for the last version flag.  Error MUST be
       considered as a BGP error and the PE MUST apply the "treat-as-
       withdraw" procedure of [RFC7606].

   2.  When a PE receives an EVPN SMET route withdraw, it removes the
       remote PE from its OIF list for that multicast group and if there
       are no more OIF entries for that multicast group (either locally
       or remotely), then the PE MUST stop responding to Membership
       Queries from the locally attached router (if any).  If there is a
       source for that multicast group, the PE stops sending multicast
       traffic for that source.

4.2.  Proxy Querier

   As mentioned in the previous sections, each PE MUST have proxy
   querier functionality for the following reasons:

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   1.  To enable the collection of EVPN PEs providing L2VPN service to
       act as distributed multicast router with Anycast IP address for
       all attached hosts in that subnet.

   2.  To enable suppression of IGMP Membership Reports and Membership
       Queries over MPLS/IP core.

5.  Operation

   Consider the EVPN network of Figure-1, where there is an EVPN
   instance configured across the PEs shown in this figure (namely PE1,
   PE2, and PE3).  Let's consider that this EVPN instance consists of a
   single bridge domain (single subnet) with all the hosts, sources, and
   the multicast router connected to this subnet.  PE1 only has
   hosts(host denoted by Hx) connected to it.  PE2 has a mix of hosts
   and a multicast source.  PE3 has a mix of hosts, a multicast source
   (source denoted by Sx), and a multicast router (router denoted by
   Rx).  Furthermore, let's consider that for (S1,G1), R1 is used as the
   multicast router.  The following subsections describe the IGMP proxy
   operation in different PEs with regard to whether the locally
   attached devices for that subnet are:

   o  only hosts

   o  mix of hosts and multicast source

   o  mix of hosts, multicast source, and multicast router

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                              +--------------+
                              |              |
                              |              |
                       +----+ |              | +----+
        H1:(*,G1)v2 ---|    | |              | |    |---- H6(*,G1)v2
        H2:(*,G1)v2 ---| PE1| |   IP/MPLS    | | PE2|---- H7(S2,G2)v3
        H3:(*,G1)v3 ---|    | |   Network    | |    |---- S2
        H4:(S2,G2)v3 --|    | |              | |    |
                       +----+ |              | +----+
                              |              |
                       +----+ |              |
        H5:(S1,G1)v3 --|    | |              |
                 S1 ---| PE3| |              |
                 R1 ---|    | |              |
                       +----+ |              |
                              |              |
                              +--------------+

      Figure 1: EVPN network

5.1.  PE with only attached hosts for a given subnet

   When PE1 receives an IGMPv2 Membership Report from H1, it does not
   forward this Membership Report to any of its other ports (for this
   subnet) because all these local ports are associated with the hosts.
   PE1 sends an EVPN Multicast Group route corresponding to this
   Membership Report for (*,G1) and setting v2 flag.  This EVPN route is
   received by PE2 and PE3 that are the members of the same BD (i.e.,
   same EVI in case of VLAN-based service or EVI,VLAN in case of VLAN-
   aware bundle service).  PE3 reconstructs the IGMPv2 Membership Report
   from this EVPN BGP route and only sends it to the port(s) with
   multicast routers attached to it (for that subnet).  In this example,
   PE3 sends the reconstructed IGMPv2 Membership Report for (*,G1) only
   to R1.  Furthermore, even though PE2 receives the EVPN BGP route, it
   does not send it to any of its ports for that subnet; viz, ports
   associated with H6 and H7.

   When PE1 receives the second IGMPv2 Membership Report from H2 for the
   same multicast group (*,G1), it only adds that port to its OIF list
   but it doesn't send any EVPN BGP route because there is no change in
   information.  However, when it receives the IGMPv3 Membership Report
   from H3 for the same (*,G1).  Besides adding the corresponding port
   to its OIF list, it re-advertises the previously sent EVPN SMET route
   with the v3 and exclude flag set.

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   Finally when PE1 receives the IGMPv3 Membership Report from H4 for
   (S2,G2), it advertises a new EVPN SMET route corresponding to it.

5.2.  PE with a mix of attached hosts and multicast source

   The main difference in this case is that when PE2 receives the IGMPv3
   Membership Report from H7 for (S2,G2), it does advertise it in BGP to
   support source move even though PE2 knows that S2 is attached to its
   local AC.  PE2 adds the port associated with H7 to its OIF list for
   (S2,G2).  The processing for IGMPv2 received from H6 is the same as
   the IGMPv2 Membership Report described in previous section.

5.3.  PE with a mix of attached hosts, a multicast source and a router

   The main difference in this case relative to the previous two
   sections is that IGMP v2/v3 Membership Report messages received
   locally need to be sent to the port associated with router R1.
   Furthermore, the Membership Reports received via BGP (SMET) need to
   be passed to the R1 port but filtered for all other ports.

6.  All-Active Multi-Homing

   Because the LAG flow hashing algorithm used by the CE is unknown at
   the PE, in an All-Active redundancy mode it must be assumed that the
   CE can send a given IGMP message to any one of the multi-homed PEs,
   either DF or non-DF; i.e., different IGMP Membership Request messages
   can arrive at different PEs in the redundancy group and furthermore
   their corresponding Leave messages can arrive at PEs that are
   different from the ones that received the Membership Report.
   Therefore, all PEs attached to a given ES must coordinate IGMP
   Membership Request and Leave Group (x,G) state, where x may be either
   '*' or a particular source S, for each BD on that ES.  Each PE has a
   local copy of that state and the EVPN signaling serves to synchronize
   state across PEs.  This allows the DF for that (ES,BD) to correctly
   advertise or withdraw a Selective Multicast Ethernet Tag (SMET) route
   for that (x,G) group in that BD when needed.  All-Active multihoming
   PEs for a given ES MUST support IGMP synchronization procedures
   described in this section if they need to perform IGMP proxy for
   hosts connected to that ES.

6.1.  Local IGMP/MLD Membership Report Synchronization

   When a PE, either DF or non-DF, receives on a given multihomed ES
   operating in All-Active redundancy mode, an IGMP Membership Report
   for (x,G), it determines the BD to which the IGMP Membership Report
   belongs.  If the PE doesn't already have local IGMP Membership
   Request (x,G) state for that BD on that ES, it MUST instantiate local
   IGMP Membership Request (x,G) state and MUST advertise a BGP IGMP

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   Membership Report Synch route for that (ES,BD).  Local IGMP
   Membership Request (x,G) state refers to IGMP Membership Request
   (x,G) state that is created as a result of processing an IGMP
   Membership Report for (x,G).

   The IGMP Membership Report Synch route MUST carry the ES-Import RT
   for the ES on which the IGMP Membership Report was received.  Thus it
   MUST only be imported by the PEs attached to that ES and not any
   other PEs.

   When a PE, either DF or non-DF, receives an IGMP Membership Report
   Synch route it installs that route and if it doesn't already have
   IGMP Membership Request (x,G) state for that (ES,BD), it MUST
   instantiate that IGMP Membership Request (x,G) state - i.e., IGMP
   Membership Request (x,G) state is the union of the local IGMP
   Membership Report (x,G) state and the installed IGMP Membership
   Report Synch route.  If the DF did not already advertise (originate)
   a SMET route for that (x,G) group in that BD, it MUST do so now.

   When a PE, either DF or non-DF, deletes its local IGMP Membership
   Request (x,G) state for that (ES,BD), it MUST withdraw its BGP IGMP
   Membership Report Synch route for that (ES,BD).

   When a PE, either DF or non-DF, receives the withdrawal of an IGMP
   Membership Report Synch route from another PE it MUST remove that
   route.  When a PE has no local IGMP Membership Request (x,G) state
   and it has no installed IGMP Membership Report Synch routes, it MUST
   remove IGMP Membership Request (x,G) state for that (ES,BD).  If the
   DF no longer has IGMP Membership Request (x,G) state for that BD on
   any ES for which it is DF, it MUST withdraw its SMET route for that
   (x,G) group in that BD.

   In other words, a PE advertises an SMET route for that (x,G) group in
   that BD when it has IGMP Membership Request (x,G) state in that BD on
   at least one ES for which it is DF and it withdraws that SMET route
   when it does not have IGMP Membership Request (x,G) state in that BD
   on any ES for which it is DF.

6.2.  Local IGMP/MLD Leave Group Synchronization

   When a PE, either DF or non-DF, receives, on a given multihomed ES
   operating in All-Active redundancy mode, an IGMP Leave Group message
   for (x,G) from the attached CE, it determines the BD to which the
   IGMPv2 Leave Group belongs.  Regardless of whether it has IGMP
   Membership Request (x,G) state for that (ES,BD), it initiates the
   (x,G) leave group synchronization procedure, which consists of the
   following steps:

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   1.  It computes the Maximum Response Time, which is the duration of
       (x,G) leave group synchronization procedure.  This is the product
       of two locally configured values, Last Member Query Count and
       Last Member Query Interval (described in Section 3 of [RFC2236]),
       plus a delta corresponding to the time it takes for a BGP
       advertisement to propagate between the PEs attached to the
       multihomed ES (delta is a consistently configured value on all
       PEs attached to the multihomed ES).

   2.  It starts the Maximum Response Time timer.  Note that the receipt
       of subsequent IGMP Leave Group messages or BGP Leave Synch routes
       for (x,G) do not change the value of a currently running Maximum
       Response Time timer and are ignored by the PE.

   3.  It initiates the Last Member Query procedure described in
       Section 3 of [RFC2236]; viz, it sends a number of Group-Specific
       Query (x,G) messages (Last Member Query Count) at a fixed
       interval (Last Member Query Interval) to the attached CE.

   4.  It advertises an IGMP Leave Synch route for that that (ES,BD).
       This route notifies the other multihomed PEs attached to the
       given multihomed ES that it has initiated an (x,G) leave group
       synchronization procedure; i.e., it carries the ES-Import RT for
       the ES on which the IGMP Leave Group was received.  It also
       contains the Maximum Response Time.

   5.  When the Maximum Response Timer expires, the PE that has
       advertised the IGMP Leave Synch route withdraws it.

6.2.1.  Remote Leave Group Synchronization

   When a PE, either DF or non-DF, receives an IGMP Leave Synch route it
   installs that route and it starts a timer for (x,G) on the specified
   (ES,BD) whose value is set to the Maximum Response Time in the
   received IGMP Leave Synch route.  Note that the receipt of subsequent
   IGMPv2 Leave Group messages or BGP Leave Synch routes for (x,G) do
   not change the value of a currently running Maximum Response Time
   timer and are ignored by the PE.

6.2.2.  Common Leave Group Synchronization

   If a PE attached to the multihomed ES receives an IGMP Membership
   Report for (x,G) before the Maximum Response Time timer expires, it
   advertises a BGP IGMP Membership Report Synch route for that (ES,BD).
   If it doesn't already have local IGMP Membership Request (x,G) state
   for that (ES,BD), it instantiates local IGMP Membership Request (x,G)
   state.  If the DF is not currently advertising (originating) a SMET
   route for that (x,G) group in that BD, it does so now.

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   If a PE attached to the multihomed ES receives an IGMP Membership
   Report Synch route for (x,G) before the Maximum Response Time timer
   expires, it installs that route and if it doesn't already have IGMP
   Membership Request (x,G) state for that BD on that ES, it
   instantiates that IGMP Membership Request (x,G) state.  If the DF has
   not already advertised (originated) a SMET route for that (x,G) group
   in that BD, it does so now.

   When the Maximum Response Timer expires a PE that has advertised an
   IGMP Leave Synch route, withdraws it.  Any PE attached to the
   multihomed ES, that started the Maximum Response Time and has no
   local IGMP Membership Request (x,G) state and no installed IGMP
   Membership Report Synch routes, it removes IGMP Membership Request
   (x,G) state for that (ES,BD).  If the DF no longer has IGMP
   Membership Request (x,G) state for that BD on any ES for which it is
   DF, it withdraws its SMET route for that (x,G) group in that BD.

6.3.  Mass Withdraw of Multicast Membership Report Sync route in case of
      failure

   A PE which has received an IGMP Membership Request would have synced
   the IGMP Membership Report by the procedure defined in section 6.1.
   If a PE with local Membership Report state goes down or the PE to CE
   link goes down, it would lead to a mass withdraw of multicast routes.
   Remote PEs (PEs where these routes were remote IGMP Membership
   Reports) SHOULD NOT remove the state immediately; instead General
   Query SHOULD be generated to refresh the states.  There are several
   ways to detect failure at a peer, e.g. using IGP next hop tracking or
   ES route withdraw.

7.  Single-Active Multi-Homing

   Note that to facilitate state synchronization after failover, the PEs
   attached to a multihomed ES operating in Single-Active redundancy
   mode SHOULD also coordinate IGMP Membership Report (x,G) state.  In
   this case all IGMP Membership Report messages are received by the DF
   and distributed to the non-DF PEs using the procedures described
   above.

8.  Selective Multicast Procedures for IR tunnels

   If an ingress PE uses ingress replication, then for a given (x,G)
   group in a given BD:

   1.  It sends (x,G) traffic to the set of PEs not supporting IGMP or
       MLD Proxy.  This set consists of any PE that has advertised an
       IMET route for the BD without a Multicast Flags extended
       community or with a Multicast Flags extended community in which

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       neither the IGMP Proxy support nor the MLD Proxy support flags
       are set.

   2.  It sends (x,G) traffic to the set of PEs supporting IGMP or MLD
       Proxy and having listeners for that (x,G) group in that BD.  This
       set consists of any PE that has advertised an IMET route for the
       BD with a Multicast Flags extended community in which the IGMP
       Proxy support and/or the MLD Proxy support flags are set and that
       has advertised a SMET route for that (x,G) group in that BD.

9.  BGP Encoding

   This document defines three new BGP EVPN routes to carry IGMP
   Membership Reports.  The route types are known as:

   + 6 - Selective Multicast Ethernet Tag Route

   + 7 - Multicast Membership Report Synch Route

   + 8 - Multicast Leave Synch Route

   The detailed encoding and procedures for these route types are
   described in subsequent sections.

9.1.  Selective Multicast Ethernet Tag Route

   A Selective Multicast Ethernet Tag route type specific EVPN NLRI
   consists of the following:

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                      +---------------------------------------+
                      |  RD (8 octets)                        |
                      +---------------------------------------+
                      |  Ethernet Tag ID (4 octets)           |
                      +---------------------------------------+
                      |  Multicast Source Length (1 octet)    |
                      +---------------------------------------+
                      |  Multicast Source Address (variable)  |
                      +---------------------------------------+
                      |  Multicast Group Length (1 octet)     |
                      +---------------------------------------+
                      |  Multicast Group Address (Variable)   |
                      +---------------------------------------+
                      |  Originator Router Length (1 octet)   |
                      +---------------------------------------+
                      |  Originator Router Address (variable) |
                      +---------------------------------------+
                      |  Flags (1 octet)                      |
                      +---------------------------------------+

   For the purpose of BGP route key processing, all the fields are
   considered to be part of the prefix in the NLRI except for the one-
   octet flag field.  The Flags fields are defined as follows:

                        0  1  2  3  4  5  6  7
                       +--+--+--+--+--+--+--+--+
                       | reserved  |IE|v3|v2|v1|
                       +--+--+--+--+--+--+--+--+

   o  The least significant bit, bit 7 indicates support for IGMP
      version 1.  Since IGMP V1 is being deprecated sender MUST set it
      as 0 for IGMP and receiver MUST ignore it.

   o  The second least significant bit, bit 6 indicates support for IGMP
      version 2.

   o  The third least significant bit, bit 5 indicates support for IGMP
      version 3.

   o  The fourth least significant bit, bit 4 indicates whether the
      (S,G) information carried within the route-type is of an Include
      Group type (bit value 0) or an Exclude Group type (bit value 1).
      The Exclude Group type bit MUST be ignored if bit 5 is not set.

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   o  This EVPN route type is used to carry tenant IGMP multicast group
      information.  The flag field assists in distributing IGMP
      Membership Report of a given host for a given multicast route.
      The version bits help associate IGMP version of receivers
      participating within the EVPN domain.

   o  The include/exclude (IE) bit helps in creating filters for a given
      multicast route.

   o  If route is used for IPv6 (MLD) then bit 7 indicates support for
      MLD version 1.  The second least significant bit, bit 6 indicates
      support for MLD version 2.  Since there is no MLD version 3, in
      case of IPv6 route third least significant bit MUST be 0.  In case
      of IPv6 routes, the fourth least significant bit MUST be ignored
      if bit 6 is not set.

   o  Reserved bits MUST be set to 0 by sender.  And receiver MUST
      ignore the Reserved bits.

9.1.1.  Constructing the Selective Multicast Ethernet Tag route

   This section describes the procedures used to construct the Selective
   Multicast Ethernet Tag (SMET) route.

   The Route Distinguisher (RD) SHOULD be a Type 1 RD [RFC4364].  The
   value field comprises an IP address of the PE (typically, the
   loopback address) followed by a number unique to the PE.

   The Ethernet Tag ID MUST be set as procedure defined in [RFC7432].

   The Multicast Source Length MUST be set to length of the multicast
   Source address in bits.  If the Multicast Source Address field
   contains an IPv4 address, then the value of the Multicast Source
   Length field is 32.  If the Multicast Source Address field contains
   an IPv6 address, then the value of the Multicast Source Length field
   is 128.  In case of a (*,G) Membership Report, the Multicast Source
   Length is set to 0.

   The Multicast Source Address is the source IP address from the IGMP
   Membership Report.  In case of a (*,G), this field is not used.

   The Multicast Group Length MUST be set to length of multicast group
   address in bits.  If the Multicast Group Address field contains an
   IPv4 address, then the value of the Multicast Group Length field is
   32.  If the Multicast Group Address field contains an IPv6 address,
   then the value of the Multicast Group Length field is 128.

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   The Multicast Group Address is the Group address from the IGMP or MLD
   Membership Report.

   The Originator Router Length is the length of the Originator Router
   Address in bits.

   The Originator Router Address is the IP address of router originating
   this route.  The SMET Originator Router IP address MUST match that of
   the IMET (or S-PMSI AD) route originated for the same EVI by the same
   downstream PE.

   The Flags field indicates the version of IGMP protocol from which the
   Membership Report was received.  It also indicates whether the
   multicast group had the INCLUDE or EXCLUDE bit set.

   Reserved bits MUST be set to 0.  They can be defined in future by
   other document.

   IGMP is used to receive group membership information from hosts by
   TORs.  Upon receiving the hosts expression of interest of a
   particular group membership, this information is then forwarded using
   SMET route.  The NLRI also keeps track of receiver's IGMP protocol
   version and any source filtering for a given group membership.  All
   EVPN SMET routes are announced with per- EVI Route Target extended
   communities.

9.1.2.  Reconstructing IGMP / MLD Membership Reports from Selective
        Multicast Route

   This section describes the procedures used to reconstruct IGMP / MLD
   Membership Reports from SMET route.

   o  If multicast group length is 32, route would be translated to IGMP
      membership request.  If multicast group length is 128, route would
      be translated to MLD membership request.

   o  Multicast group address field would be translated to IGMP / MLD
      group address.

   o  If Multicast source length is set to zero it would be translated
      to any source (*).  If multicast source length is non zero,
      Multicast source address field would be translated to IGMP / MLD
      source address.

   o  If flag bit 7 is set, it translates Membership report to be IGMP
      V1 or MLD V1.

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   o  If flag bit 6 is set, it translates Membership report to be IGMP
      V2 or MLD V2.

   o  Flag bit 5 is only valid for IGMP Membership report and if it is
      set, it translates to IGMP V3 report.

   o  If IE flag is set, it translate to IGMP / MLD Exclude mode
      membership report.  If IE flag is not set (zero), it translates to
      Include mode membership report.

9.1.3.  Default Selective Multicast Route

   If there is multicast router connected behind the EVPN domain, the PE
   MAY originate a default SMET (*,*) to get all multicast traffic in
   domain.

                              +--------------+
                              |              |
                              |              |
                              |              | +----+
                              |              | |    |---- H1(*,G1)v2
                              |   IP/MPLS    | | PE1|---- H2(S2,G2)v3
                              |   Network    | |    |---- S2
                              |              | |    |
                              |              | +----+
                              |              |
                       +----+ |              |
       +----+          |    | |              |
       |    |    S1 ---| PE2| |              |
       |PIM |----R1 ---|    | |              |
       |ASM |          +----+ |              |
       |    |                 |              |
       +----+                 +--------------+

      Figure 2: Multicast Router behind EVPN domain

   Consider the EVPN network of Figure-2, where there is an EVPN
   instance configured across the PEs.  Let's consider that PE2 is
   connected to multicast router R1 and there is a network running PIM
   ASM behind R1.  If there are receivers behind the PIM ASM network the
   PIM Join would be forwarded to the PIM RP (Rendezvous Point).  If
   receivers behind PIM ASM network are interested in a multicast flow
   originated by multicast source S2 (behind PE1), it is necessary for
   PE2 to receive multicast traffic.  In this case PE2 MUST originate a
   (*,*) SMET route to receive all of the multicast traffic in the EVPN

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   domain.  To generate Wildcards (*,*) routes, the procedure from
   [RFC6625] MUST be used.

9.2.  Multicast Membership Report Synch Route

   This EVPN route type is used to coordinate IGMP Membership Report
   (x,G) state for a given BD between the PEs attached to a given ES
   operating in All- Active (or Single-Active) redundancy mode and it
   consists of following:

                +--------------------------------------------------+
                |  RD (8 octets)                                   |
                +--------------------------------------------------+
                | Ethernet Segment Identifier (10 octets)          |
                +--------------------------------------------------+
                |  Ethernet Tag ID  (4 octets)                     |
                +--------------------------------------------------+
                |  Multicast Source Length (1 octet)               |
                +--------------------------------------------------+
                |  Multicast Source Address (variable)             |
                +--------------------------------------------------+
                |  Multicast Group Length (1 octet)                |
                +--------------------------------------------------+
                |  Multicast Group Address (Variable)              |
                +--------------------------------------------------+
                |  Originator Router Length (1 octet)              |
                +--------------------------------------------------+
                |  Originator Router Address (variable)            |
                +--------------------------------------------------+
                |  Flags (1 octet)                                 |
                +--------------------------------------------------+

   For the purpose of BGP route key processing, all the fields are
   considered to be part of the prefix in the NLRI except for the one-
   octet Flags field, whose fields are defined as follows:

                            0  1  2  3  4  5  6  7
                          +--+--+--+--+--+--+--+--+
                          | reserved  |IE|v3|v2|v1|
                          +--+--+--+--+--+--+--+--+

   o  The least significant bit, bit 7 indicates support for IGMP
      version 1.

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   o  The second least significant bit, bit 6 indicates support for IGMP
      version 2.

   o  The third least significant bit, bit 5 indicates support for IGMP
      version 3.

   o  The fourth least significant bit, bit 4 indicates whether the (S,
      G) information carried within the route-type is of Include Group
      type (bit value 0) or an Exclude Group type (bit value 1).  The
      Exclude Group type bit MUST be ignored if bit 5 is not set.

   o  Reserved bits MUST be set to 0.

   The Flags field assists in distributing IGMP Membership Report of a
   given host for a given multicast route.  The version bits help
   associate IGMP version of receivers participating within the EVPN
   domain.  The include/exclude bit helps in creating filters for a
   given multicast route.

   If route is being prepared for IPv6 (MLD) then bit 7 indicates
   support for MLD version 1.  The second least significant bit, bit 6
   indicates support for MLD version 2.  Since there is no MLD version
   3, in case of IPv6 route third least significant bit MUST be 0.  In
   case of IPv6 route, the fourth least significant bit MUST be ignored
   if bit 6 is not set.

9.2.1.  Constructing the Multicast Membership Report Synch Route

   This section describes the procedures used to construct the IGMP
   Membership Report Synch route.  Support for these route types is
   optional.  If a PE does not support this route, then it MUST NOT
   indicate that it supports 'IGMP proxy' in the Multicast Flag extended
   community for the EVIs corresponding to its multi-homed Ethernet
   Segments (ESs).

   An IGMP Membership Report Synch route MUST carry exactly one ES-
   Import Route Target extended community, the one that corresponds to
   the ES on which the IGMP Membership Report was received.  It MUST
   also carry exactly one EVI-RT EC, the one that corresponds to the EVI
   on which the IGMP Membership Report was received.  See Section 9.5
   for details on how to encode and construct the EVI-RT EC.

   The Route Distinguisher (RD) SHOULD be a Type 1 RD [RFC4364].  The
   value field comprises an IP address of the PE (typically, the
   loopback address) followed by a number unique to the PE.

   The Ethernet Segment Identifier (ESI) MUST be set to the 10-octet
   value defined for the ES.

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   The Ethernet Tag ID MUST be set as per procedure defined in
   [RFC7432].

   The Multicast Source length MUST be set to length of Multicast Source
   address in bits.  If the Multicast Source field contains an IPv4
   address, then the value of the Multicast Source Length field is 32.
   If the Multicast Source field contains an IPv6 address, then the
   value of the Multicast Source Length field is 128.  In case of a
   (*,G) Membership Report, the Multicast Source Length is set to 0.

   The Multicast Source is the Source IP address of the IGMP Membership
   Report.  In case of a (*,G) Membership Report, this field does not
   exist.

   The Multicast Group length MUST be set to length of multicast group
   address in bits.  If the Multicast Group field contains an IPv4
   address, then the value of the Multicast Group Length field is 32.
   If the Multicast Group field contains an IPv6 address, then the value
   of the Multicast Group Length field is 128.

   The Multicast Group is the Group address of the IGMP Membership
   Report.

   The Originator Router Length is the length of the Originator Router
   address in bits.

   The Originator Router Address is the IP address of Router Originating
   the prefix.

   The Flags field indicates the version of IGMP protocol from which the
   Membership Report was received.  It also indicates whether the
   multicast group had INCLUDE or EXCLUDE bit set.

   Reserved bits MUST be set to 0.

9.2.2.  Reconstructing IGMP / MLD Membership Reports from Multicast
        Membership Report Sync Route

   This section describes the procedures used to reconstruct IGMP / MLD
   Membership Reports from Multicast Membership Report Sync route.

   o  If multicast group length is 32, route would be translated to IGMP
      membership request.  If multicast group length is 128, route would
      be translated to MLD membership request.

   o  Multicast group address field would be translated to IGMP / MLD
      group address.

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   o  If Multicast source length is set to zero it would be translated
      to any source (*).  If multicast source length is non zero,
      Multicast source address field would be translated to IGMP / MLD
      source address.

   o  If flag bit 7 is set, it translates Membership report to be IGMP
      V1 or MLD V1.

   o  If flag bit 6 is set, it translates Membership report to be IGMP
      V2 or MLD V2.

   o  Flag bit 5 is only valid for IGMP Membership report and if it is
      set, it translates to IGMP V3 report.

   o  If IE flag is set, it translate to IGMP / MLD Exclude mode
      membership report.  If IE flag is not set (zero), it translates to
      Include mode membership report.

9.3.  Multicast Leave Synch Route

   This EVPN route type is used to coordinate IGMP Leave Group (x,G)
   state for a given BD between the PEs attached to a given ES operating
   in All-Active (or Single-Active) redundancy mode and it consists of
   following:

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                +--------------------------------------------------+
                |  RD (8 octets)                                   |
                +--------------------------------------------------+
                | Ethernet Segment Identifier (10 octets)          |
                +--------------------------------------------------+
                |  Ethernet Tag ID  (4 octets)                     |
                +--------------------------------------------------+
                |  Multicast Source Length (1 octet)               |
                +--------------------------------------------------+
                |  Multicast Source Address (variable)             |
                +--------------------------------------------------+
                |  Multicast Group Length (1 octet)                |
                +--------------------------------------------------+
                |  Multicast Group Address (Variable)              |
                +--------------------------------------------------+
                |  Originator Router Length (1 octet)              |
                +--------------------------------------------------+
                |  Originator Router Address (variable)            |
                +--------------------------------------------------+
                |  Reserved (4 octet)                              |
                +--------------------------------------------------+
                |  Maximum Response Time (1 octet)                 |
                +--------------------------------------------------+
                |  Flags (1 octet)                                 |
                +--------------------------------------------------+

   For the purpose of BGP route key processing, all the fields are
   considered to be part of the prefix in the NLRI except for the
   Reserved, Maximum Response Time and the one-octet Flags field, whose
   fields are defined as follows:

                            0  1  2  3  4  5  6  7
                          +--+--+--+--+--+--+--+--+
                          | reserved  |IE|v3|v2|v1|
                          +--+--+--+--+--+--+--+--+

   o  The least significant bit, bit 7 indicates support for IGMP
      version 1.

   o  The second least significant bit, bit 6 indicates support for IGMP
      version 2.

   o  The third least significant bit, bit 5 indicates support for IGMP
      version 3.

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   o  The fourth least significant bit, bit 4 indicates whether the (S,
      G) information carried within the route-type is of Include Group
      type (bit value 0) or an Exclude Group type (bit value 1).  The
      Exclude Group type bit MUST be ignored if bit 5 is not set.

   o  Reserved bits MUST be set to 0.  They can be defined in future by
      other document.

   The Flags field assists in distributing IGMP Membership Report of a
   given host for a given multicast route.  The version bits help
   associate IGMP version of receivers participating within the EVPN
   domain.  The include/exclude bit helps in creating filters for a
   given multicast route.

   If route is being prepared for IPv6 (MLD) then bit 7 indicates
   support for MLD version 1.  The second least significant bit, bit 6
   indicates support for MLD version 2.  Since there is no MLD version
   3, in case of IPv6 route third least significant bit MUST be 0.  In
   case of IPv6 route, the fourth least significant bit MUST be ignored
   if bit 6 is not set.

   Reserved bits in flag MUST be set to 0.  They can be defined in
   future by other document.

9.3.1.  Constructing the Multicast Leave Synch Route

   This section describes the procedures used to construct the IGMP
   Leave Synch route.  Support for these route types is optional.  If a
   PE does not support this route, then it MUST NOT indicate that it
   supports 'IGMP proxy' in Multicast Flag extended community for the
   EVIs corresponding to its multi-homed Ethernet Segments.

   An IGMP Leave Synch route MUST carry exactly one ES-Import Route
   Target extended community, the one that corresponds to the ES on
   which the IGMP Leave was received.  It MUST also carry exactly one
   EVI-RT EC, the one that corresponds to the EVI on which the IGMP
   Leave was received.  See Section 9.5 for details on how to form the
   EVI-RT EC.

   The Route Distinguisher (RD) SHOULD be a Type 1 RD [RFC4364].  The
   value field comprises an IP address of the PE (typically, the
   loopback address) followed by a number unique to the PE.

   The Ethernet Segment Identifier (ESI) MUST be set to the 10-octet
   value defined for the ES.

   The Ethernet Tag ID MUST be set as per procedure defined in
   [RFC7432].

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   The Multicast Source length MUST be set to length of multicast source
   address in bits.  If the Multicast Source field contains an IPv4
   address, then the value of the Multicast Source Length field is 32.
   If the Multicast Source field contains an IPv6 address, then the
   value of the Multicast Source Length field is 128.  In case of a
   (*,G) Membership Report, the Multicast Source Length is set to 0.

   The Multicast Source is the Source IP address of the IGMP Membership
   Report.  In case of a (*,G) Membership Report, this field does not
   exist.

   The Multicast Group length MUST be set to length of multicast group
   address in bits.  If the Multicast Group field contains an IPv4
   address, then the value of the Multicast Group Length field is 32.
   If the Multicast Group field contains an IPv6 address, then the value
   of the Multicast Group Length field is 128.

   The Multicast Group is the Group address of the IGMP Membership
   Report.

   The Originator Router Length is the length of the Originator Router
   address in bits.

   The Originator Router Address is the IP address of Router Originating
   the prefix.

   Reserved field is not part of the route key.  The originator MUST set
   the reserved field to Zero , the receiver SHOULD ignore it and if it
   needs to be propagated, it MUST propagate it unchanged

   Maximum Response Time is value to be used while sending query as
   defined in [RFC2236]

   The Flags field indicates the version of IGMP protocol from which the
   Membership Report was received.  It also indicates whether the
   multicast group had INCLUDE or EXCLUDE bit set.

9.3.2.  Reconstructing IGMP / MLD Leave from Multicast Leave Sync Route

   This section describes the procedures used to reconstruct IGMP / MLD
   Leave from Multicast Leave Sync route.

   o  If multicast group length is 32, route would be translated to IGMP
      Leave.  If multicast group length is 128, route would be
      translated to MLD Leave.

   o  Multicast group address field would be translated to IGMP / MLD
      group address.

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   o  If Multicast source length is set to zero it would be translated
      to any source (*).  If multicast source length is non zero,
      Multicast source address field would be translated to IGMP / MLD
      source address.

   o  If flag bit 7 is set, it translates Membership report to be IGMP
      V1 or MLD V1.

   o  If flag bit 6 is set, it translates Membership report to be IGMP
      V2 or MLD V2.

   o  Flag bit 5 is only valid for IGMP Membership report and if it is
      set, it translates to IGMP V3 report.

   o  If IE flag is set, it translate to IGMP / MLD Exclude mode Leave.
      If IE flag is not set (zero), it translates to Include mode Leave.

   o

9.4.  Multicast Flags Extended Community

   The 'Multicast Flags' extended community is a new EVPN extended
   community.  EVPN extended communities are transitive extended
   communities with a Type field value of 6.  IANA will assign a Sub-
   Type from the 'EVPN Extended Community Sub-Types' registry.

   A PE that supports IGMP and/or MLD Proxy on a given BD MUST attach
   this extended community to the IMET route it advertises advertises
   for that BD and it MUST set the IGMP and/or MLD Proxy Support flags
   to 1.  Note that an [RFC7432] compliant PE will not advertise this
   extended community so its absence indicates that the advertising PE
   does not support either IGMP or MLD Proxy.

   The advertisement of this extended community enables more efficient
   multicast tunnel setup from the source PE specially for ingress
   replication - i.e., if an egress PE supports IGMP proxy but doesn't
   have any interest in a given (x,G), it advertises its IGMP proxy
   capability using this extended community but it does not advertise
   any SMET route for that (x,G).  When the source PE (ingress PE)
   receives such advertisements from the egress PE, it does not
   replicate the multicast traffic to that egress PE; however, it does
   replicate the multicast traffic to the egress PEs that don't
   advertise such capability even if they don't have any interests in
   that (x,G).

   A Multicast Flags extended community is encoded as an 8-octet value,
   as follows:

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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=0x06     |Sub-Type=0x09  |     Flags (2 Octets)      |M|I|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                           Reserved=0                          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The low-order (lease significant) two bits are defined as the "IGMP
   Proxy Support and MLD Proxy Support" bit.  The absence of this
   extended community also means that the PE does not support IGMP
   proxy. where:

   o  Type is 0x06 as registered with IANA for EVPN Extended
      Communities.

   o  Sub-Type : 0x09

   o  Flags are two Octets value.

      *  Bit 15 (shown as I) defines IGMP Proxy Support.  Value of 1 for
         bit 15 means that PE supports IGMP Proxy.  Value of 0 for bit
         15 means that PE does not supports IGMP Proxy.

      *  Bit 14 (shown as M) defines MLD Proxy Support.  Value of 1 for
         bit 14 means that PE supports MLD Proxy.  Value of 0 for bit 14
         means that PE does not support MLD proxy.

      *  Bit 0 to 13 are reserved for future.  Sender MUST set it 0 and
         receiver MUST ignore it.

   o  Reserved bits are set to 0.  Sender MUST set it to 0 and receiver
      MUST ignore it.

   If a router does not support this specification, it MUST NOT add
   Multicast Flags Extended Community in BGP route.  A router receiving
   BGP update, if M and I both flag are zero (0), the router MUST treat
   this Update as malformed.  Receiver of such update MUST ignore the
   extended community.

9.5.  EVI-RT Extended Community

   In EVPN, every EVI is associated with one or more Route Targets
   (RTs).  These Route Targets serve two functions:

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   1.  Distribution control: RTs control the distribution of the routes.
       If a route carries the RT associated with a particular EVI, it
       will be distributed to all the PEs on which that EVI exists.

   2.  EVI identification: Once a route has been received by a
       particular PE, the RT is used to identify the EVI to which it
       applies.

   An IGMP Membership Report Synch or IGMP Leave Synch route is
   associated with a particular combination of ES and EVI.  These routes
   need to be distributed only to PEs that are attached to the
   associated ES.  Therefore these routes carry the ES-Import RT for
   that ES.

   Since an IGMP Membership Report Synch or IGMP Leave Synch route does
   not need to be distributed to all the PEs on which the associated EVI
   exists, these routes cannot carry the RT associated with that EVI.
   Therefore, when such a route arrives at a particular PE, the route's
   RTs cannot be used to identify the EVI to which the route applies.
   Some other means of associating the route with an EVI must be used.

   This document specifies four new Extended Communities (EC) that can
   be used to identify the EVI with which a route is associated, but
   which do not have any effect on the distribution of the route.  These
   new ECs are known as the "Type 0 EVI-RT EC", the "Type 1 EVI-RT EC",
   the "Type 2 EVI-RT EC", and the "Type 3 EVI-RT EC".

   1.  A Type 0 EVI-RT EC is an EVPN EC (type 6) of sub-type 0xA.

   2.  A Type 1 EVI-RT EC is an EVPN EC (type 6) of sub-type 0xB.

   3.  A Type 2 EVI-RT EC is an EVPN EC (type 6) of sub-type 0xC.

   4.  A Type 3 EVI-RT EC is an EVPN EC (type 6) of sub-type 0xD

   Each IGMP Membership Report Synch or IGMP Leave Synch route MUST
   carry exactly one EVI-RT EC.  The EVI-RT EC carried by a particular
   route is constructed as follows.  Each such route is the result of
   having received an IGMP Membership Report or an IGMP Leave message
   from a particular BD.  The route is said to be associated with that
   BD.  For each BD, there is a corresponding RT that is used to ensure
   that routes "about" that BD are distributed to all PEs attached to
   that BD.  So suppose a given IGMP Membership Report Synch or Leave
   Synch route is associated with a given BD, say BD1, and suppose that
   the corresponding RT for BD1 is RT1.  Then:

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   o  0.  If RT1 is a Transitive Two-Octet AS-specific EC, then the EVI-
      RT EC carried by the route is a Type 0 EVI-RT EC.  The value field
      of the Type 0 EVI-RT EC is identical to the value field of RT1.

   o  1.  If RT1 is a Transitive IPv4-Address-specific EC, then the EVI-
      RT EC carried by the route is a Type 1 EVI-RT EC.  The value field
      of the Type 1 EVI-RT EC is identical to the value field of RT1.

   o  2.  If RT1 is a Transitive Four-Octet-specific EC, then the EVI-RT
      EC carried by the route is a Type 2 EVI-RT EC.  The value field of
      the Type 2 EVI-RT EC is identical to the value field of RT1.

   o  3.  If RT1 is a Transitive IPv6-Address-specific EC, then the EVI-
      RT EC carried by the route is a Type 3 EVI-RT EC.  The value field
      of the Type 3 EVI-RT EC is identical to the value field of RT1.

   An IGMP Membership Report Synch or Leave Synch route MUST carry
   exactly one EVI-RT EC.

   Suppose a PE receives a particular IGMP Membership Report Synch or
   IGMP Leave Synch route, say R1, and suppose that R1 carries an ES-
   Import RT that is one of the PE's Import RTs.  If R1 has no EVI-RT
   EC, or has more than one EVI-RT EC, the PE MUST apply the "treat-as-
   withdraw" procedure of [RFC7606].

   Note that an EVI-RT EC is not a Route Target Extended Community, is
   not visible to the RT Constrain mechanism [RFC4684], and is not
   intended to influence the propagation of routes by BGP.

                             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=0x06     |  Sub-Type=n   |       RT associated with EVI  |
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         |             RT associated with the EVI  (cont.)               |
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Where the value of 'n' is 0x0A, 0x0B, 0x0C, or 0x0D corresponding to
   EVI-RT type 0, 1, 2, or 3 respectively.

9.6.  Rewriting of RT ECs and EVI-RT ECs by ASBRs

   There are certain situations in which an ES is attached to a set of
   PEs that are not all in the same AS, or not all operated by the same
   provider.  In some such situations, the RT that corresponds to a
   particular EVI may be different in each AS.  If a route is propagated

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   from AS1 to AS2, an ASBR at the AS1/AS2 border may be provisioned
   with a policy that removes the RTs that are meaningful in AS1 and
   replaces them with the corresponding (i.e., RTs corresponding to the
   same EVIs) RTs that are meaningful in AS2.  This is known as RT-
   rewriting.

   Note that if a given route's RTs are rewritten, and the route carries
   an EVI-RT EC, the EVI-RT EC needs to be rewritten as well.

9.7.  BGP Error Handling

   If a received BGP update contains Flags not in accordance with IGMP/
   MLD version-X expectation, the PE MUST apply the "treat-as-withdraw"
   procedure as per [RFC7606]

   If a received BGP update is malformed such that BGP route keys cannot
   be extracted, then BGP update MUST be considered as invalid.
   Receiving PE MUST apply the "Session reset" procedure of [RFC7606].

10.  IGMP Version 1 Membership Report

   This document does not provide any detail about IGMPv1 processing.
   Implementations are expected to only use IGMPv2 and above for IPv4
   and MLDv1 and above for IPv6.  IGMPv1 routes are considered invalid
   and the PE MUST apply the "treat-as-withdraw" procedure as per
   [RFC7606].

11.  Security Considerations

   This document describes a means to efficiently operate IGMP and MLD
   on a subnet constructed across multiple PODs or DCs via an EVPN
   solution.  The security considerations for the operation of the
   underlying EVPN and BGP substrate are described in [RFC7432], and
   specific multicast considerations are outlined in [RFC6513] and
   [RFC6514].  The EVPN and associated IGMP proxy provides a single
   broadcast domain so the same security considerations of IGMPv2
   [RFC2236], [RFC3376], MLD [RFC2710], or MLDv2 [RFC3810] apply.

12.  IANA Considerations

12.1.  EVPN Extended Community Sub-Types Registrations

   IANA has allocated the following codepoints from the EVPN Extended
   Community Sub-Types sub-registry of the BGP Extended Communities
   registry.

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            0x09    Multicast Flags Extended Community   [this document]
            0x0A    EVI-RT Type 0                        [this document]
            0x0B    EVI-RT Type 1                        [this document]
            0x0C    EVI-RT Type 2                        [this document]

   IANA is requested to allocate a new codepoint from the EVPN Extended
   Community sub-types registry for the following.

            0x0D    EVI-RT Type 3                        [this document]

12.2.  EVPN Route Type Registration

   IANA has allocated the following EVPN route types from the EVPN Route
   Type registry.

                   6 - Selective Multicast Ethernet Tag Route
                   7 - Multicast Membership Report Synch Route
                   8 - Multicast Leave Synch Route

12.3.  Multicast Flags Extended Community Registry

   The Multicast Flags Extended Community contains a 16-bit Flags field.
   The bits are numbered 0-15, from high-order to low-order.

               The registry should be initialized as follows:

       Bit         Name                             Reference            Change Controller
       ----        --------------                   -------------        ------------------
       0 - 13       Unassigned
       14           MLD Proxy Support                This document.           IETF
       15           IGMP Proxy Support               This document            IETF

       The registration policy should be "First Come First Served".

13.  Acknowledgement

   The authors would like to thank Stephane Litkowski, Jorge Rabadan,
   Anoop Ghanwani, Jeffrey Haas, Krishna Muddenahally Ananthamurthy,
   Swadesh Agrawal for reviewing and providing valuable comment.

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14.  Contributors

   Derek Yeung

   Arrcus

   Email: derek@arrcus.com

15.  References

15.1.  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>.

   [RFC2236]  Fenner, W., "Internet Group Management Protocol, Version
              2", RFC 2236, DOI 10.17487/RFC2236, November 1997,
              <https://www.rfc-editor.org/info/rfc2236>.

   [RFC2710]  Deering, S., Fenner, W., and B. Haberman, "Multicast
              Listener Discovery (MLD) for IPv6", RFC 2710,
              DOI 10.17487/RFC2710, October 1999,
              <https://www.rfc-editor.org/info/rfc2710>.

   [RFC3376]  Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A.
              Thyagarajan, "Internet Group Management Protocol, Version
              3", RFC 3376, DOI 10.17487/RFC3376, October 2002,
              <https://www.rfc-editor.org/info/rfc3376>.

   [RFC3810]  Vida, R., Ed. and L. Costa, Ed., "Multicast Listener
              Discovery Version 2 (MLDv2) for IPv6", RFC 3810,
              DOI 10.17487/RFC3810, June 2004,
              <https://www.rfc-editor.org/info/rfc3810>.

   [RFC4364]  Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
              Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February
              2006, <https://www.rfc-editor.org/info/rfc4364>.

   [RFC4684]  Marques, P., Bonica, R., Fang, L., Martini, L., Raszuk,
              R., Patel, K., and J. Guichard, "Constrained Route
              Distribution for Border Gateway Protocol/MultiProtocol
              Label Switching (BGP/MPLS) Internet Protocol (IP) Virtual
              Private Networks (VPNs)", RFC 4684, DOI 10.17487/RFC4684,
              November 2006, <https://www.rfc-editor.org/info/rfc4684>.

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   [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>.

   [RFC7606]  Chen, E., Ed., Scudder, J., Ed., Mohapatra, P., and K.
              Patel, "Revised Error Handling for BGP UPDATE Messages",
              RFC 7606, DOI 10.17487/RFC7606, August 2015,
              <https://www.rfc-editor.org/info/rfc7606>.

   [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>.

15.2.  Informative References

   [I-D.ietf-bess-evpn-bum-procedure-updates]
              Zhang, Z., Lin, W., Rabadan, J., Patel, K., and A.
              Sajassi, "Updates on EVPN BUM Procedures", draft-ietf-
              bess-evpn-bum-procedure-updates-14 (work in progress),
              November 2021.

   [RFC4541]  Christensen, M., Kimball, K., and F. Solensky,
              "Considerations for Internet Group Management Protocol
              (IGMP) and Multicast Listener Discovery (MLD) Snooping
              Switches", RFC 4541, DOI 10.17487/RFC4541, May 2006,
              <https://www.rfc-editor.org/info/rfc4541>.

Authors' Addresses

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   Ali Sajassi
   Cisco Systems
   821 Alder Drive,
   MILPITAS, CALIFORNIA 95035
   UNITED STATES

   Email: sajassi@cisco.com

   Samir Thoria
   Cisco Systems
   821 Alder Drive,
   MILPITAS, CALIFORNIA 95035
   UNITED STATES

   Email: sthoria@cisco.com

   Mankamana Mishra
   Cisco Systems
   821 Alder Drive,
   MILPITAS, CALIFORNIA 95035
   UNITED STATES

   Email: mankamis@cisco.com

   Keyur PAtel
   Arrcus
   UNITED STATES

   Email: keyur@arrcus.com

   John Drake
   Juniper Networks

   Email: jdrake@juniper.net

   Wen Lin
   Juniper Networks

   Email: wlin@juniper.net

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