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Versions: (draft-sajassi-bess-evpn-igmp-mld-proxy) 00 01 02 03

BESS Working Group                                           Ali Sajassi
Internet-Draft                                              Samir Thoria
Intended Status: Standards Track                                   Cisco
                                                             Keyur Patel
                                                             Derek Yeung
                                                                  Arrcus
                                                              John Drake
                                                                 Wen Lin
                                                                 Juniper

Expires: December 12, 2019                                 June 10, 2019


                      IGMP and MLD Proxy for EVPN
                draft-ietf-bess-evpn-igmp-mld-proxy-03


Abstract

   Ethernet Virtual Private Network (EVPN) solution [RFC 7432] is
   becoming pervasive in data center (DC) applications for Network
   Virtualization Overlay (NVO) and DC interconnect (DCI) services, and
   in service provider (SP) applications for next generation virtual
   private LAN services.

   This draft describes how to support efficiently endpoints running
   IGMP for the above services over an EVPN network by incorporating
   IGMP proxy procedures on EVPN PEs.


Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as
   Internet-Drafts.

   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."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/1id-abstracts.html




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   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html


Copyright and License Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors. All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document. Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document. Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.



Table of Contents

   1  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1  Terminology . . . . . . . . . . . . . . . . . . . . . . . .  5
   2  IGMP Proxy  . . . . . . . . . . . . . . . . . . . . . . . . . .  6
     2.1  Proxy Reporting . . . . . . . . . . . . . . . . . . . . . .  6
       2.1.1  IGMP Membership Report Advertisement in BGP . . . . . .  7
       2.1.1  IGMP Leave Group Advertisement in BGP . . . . . . . . .  8
     2.2  Proxy Querier . . . . . . . . . . . . . . . . . . . . . . .  9
   3 Operation  . . . . . . . . . . . . . . . . . . . . . . . . . . .  9
     3.1 PE with only attached hosts/VMs for a given subnet . . . . . 10
     3.2 PE with mixed of attached hosts/VMs and multicast source . . 11
     3.3 PE with mixed of attached hosts/VMs, multicast source and
         router . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
   4 All-Active Multi-Homing  . . . . . . . . . . . . . . . . . . . . 11
     4.1 Local IGMP Join Synchronization  . . . . . . . . . . . . . . 11
     4.2 Local IGMP Leave Group Synchronization . . . . . . . . . . . 12
       4.2.1 Remote Leave Group Synchronization . . . . . . . . . . . 13
       4.2.2 Common Leave Group Synchronization . . . . . . . . . . . 13
     4.3 Mass Withdraw of Multicast join Sync route in case of
         failure  . . . . . . . . . . . . . . . . . . . . . . . . . . 14
   5 Single-Active Multi-Homing . . . . . . . . . . . . . . . . . . . 14
   6 Selective Multicast Procedures for IR tunnels  . . . . . . . . . 14
   7 BGP Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . 15
     7.1 Selective Multicast Ethernet Tag Route . . . . . . . . . . . 15
       7.1.1 Constructing the Selective Multicast Ethernet Tag
             route  . . . . . . . . . . . . . . . . . . . . . . . . . 17



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       7.1.2 Default Selective Multicast Route  . . . . . . . . . . . 18
     7.2  Multicast Join Synch Route  . . . . . . . . . . . . . . . . 19
       7.2.1  Constructing the Multicast Join Synch Route . . . . . . 21
     7.3 Multicast Leave Synch Route  . . . . . . . . . . . . . . . . 22
       7.3.1  Constructing the Multicas Leave Synch Route . . . . . . 24
     7.4 Multicast Flags Extended Community . . . . . . . . . . . . . 25
     7.5 EVI-RT Extended Community  . . . . . . . . . . . . . . . . . 26
     7.6 Rewriting of RT ECs and EVI-RT ECs by ASBRs  . . . . . . . . 28
   8  IGMP/MLD Immediate leave  . . . . . . . . . . . . . . . . . . . 28
   9 IGMP Version 1 membership request  . . . . . . . . . . . . . . . 29
   10  Security Considerations  . . . . . . . . . . . . . . . . . . . 29
   11  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 29
   12  References . . . . . . . . . . . . . . . . . . . . . . . . . . 30
     12.1  Normative References . . . . . . . . . . . . . . . . . . . 30
     12.2  Informative References . . . . . . . . . . . . . . . . . . 30
   13  Acknowledgement  . . . . . . . . . . . . . . . . . . . . . . . 30
   14 Contributors  . . . . . . . . . . . . . . . . . . . . . . . . . 30
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 30

































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1  Introduction

   Ethernet Virtual Private Network (EVPN) solution [RFC 7432] is
   becoming pervasive in data center (DC) applications for Network
   Virtualization Overlay (NVO) and DC interconnect (DCI) services, and
   in service provider (SP) applications for next generation virtual
   private LAN services.

   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 way of
   standard inter-POD communication for both intra-DC and inter-DC. A
   subnet can span across multiple PODs and DCs. EVPN provides robust
   multi-tenant solution with extensive multi-homing capabilities to
   stretch a subnet (e.g., VLAN) across multiple PODs and DCs. There can
   be many hosts/VMs (e.g., several hundreds) attached to a subnet that
   is stretched across several PODs and DCs.

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

   1) Reduce flooding of IGMP messages: just like 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 flood of IGMP
   messages (both Queries and Reports) in EVPN.

   2) Distributed anycast multicast proxy: it is desired 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.

   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) - i.e., multicast traffic will not
   be forwarded to the PEs that have no receivers attached to them for
   that multicast group. This draft 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 [bum-procedure-updates]

   The first two objectives are achieved by using IGMP/MLD proxy on the



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   PE and the third objective is achieved by setting up a multicast
   tunnel (e.g., ingress replication) 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.


1.1  Terminology

   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.

   POD: Point of Delivery

   ToR: Top of Rack

   NV: Network Virtualization

   NVO: Network Virtualization Overlay

   VNI:  Virtual Network Identifier (for VXLAN)

   EVPN: Ethernet Virtual Private Network

   IGMP: Internet Group Management Protocol

   MLD: Multicast Listener Discovery

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

   MAC-VRF: A Virtual Routing and Forwarding table for Media Access
   Control (MAC) addresses on a PE

   Ethernet Segment (ES): When a customer site (device or network) is
   connected to one or more PEs via a set of Ethernet links, then that
   set of links is referred to as an 'Ethernet segment'.

   Ethernet Segment Identifier (ESI): A unique non-zero identifier that
   identifies an Ethernet segment is called an 'Ethernet Segment
   Identifier'.

   PE: Provider Edge device.

   BD: Broadcast Domain. As per [RFC7432], an EVI consists of a single



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   or multiple BDs. In case of VLAN-bundle and VLAN-based service models
   VLAN-aware bundle service model, an EVI contains multiple BDs. Also,
   in this document, BD and subnet are equivalent terms.

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

   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.

   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.

   This document also assumes familiarity with the terminology of
   [RFC7432]. Though most of the place this document uses term IGMP
   membership request (Joins), it MUST be considered true for MLD
   membership request too. IGMPv2 corresponds to MLDv1 & IGMPv3
   corresponds to MLDv2.


2  IGMP Proxy

   IGMP Proxy mechanism is used to reduce the flooding of IGMP messages
   over EVPN network similar to ARP proxy used in reducing the flooding
   of ARP messages over EVPN. It also provides triggering mechanism for
   the PEs to setup their underlay multicast tunnels. IGMP Proxy
   mechanism consist of two components: a) Proxy for IGMP Reports and b)
   Proxy for IGMP Queries.

2.1  Proxy Reporting

   When IGMP protocol is used between host/VMs and its 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
   it in BGP to other PEs that are interested in the information. This
   is done by terminating IGMP Reports in the first hop PE, 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, EVPN Selective Multicast Ethernet Tag
   route, along with its procedures to help exchange and register IGMP
   multicast groups [section 5].



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2.1.1  IGMP Membership Report Advertisement in BGP

   When a PE wants to advertise an IGMP membership report (Join) using
   the BGP EVPN route, it follows the following rules:

   1) When the first hop PE receives several IGMP membership reports
   (Joins) , belonging to the same IGMP version, from different attached
   hosts/VMs for the same (*,G) or (S,G), it only sends a single BGP
   message corresponding to the very first IGMP Join. This is because
   BGP is a statefull protocol and no further transmission of the same
   report is needed. If the IGMP Join is for (*,G), then multicast group
   address along with the corresponding version flag (v2 or v3) are set.
   In case of IGMPv3, exclude flag also needs to be set to indicate that
   no source IP address to be excluded (e.g., include all sources "*").
   If the IGMP Join is for (S,G), then besides setting multicast group
   address along with the version flag v3, the source IP address and the
   include/exclude flag must be set. It should be noted that when
   advertising the EVPN route for (S,G), the only valid version flag is
   v3 (i.e., v1 and v2 flags must be set to zero).


   2) When the first hop PE receives an IGMPv3 Join for (S,G) on a given
   BD, it advertises 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 Join first for
   (*,G) and then later it receives an IGMP version-Y Join for the same
   (*,G), then it will 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 does 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 Join first for
   (*,G) and then later it receives an IGMPv3 Join for the same
   multicast group address but for a specific source address S, then the
   PE will advertise a new EVPN SMET route with v3 flag set (and v1 and
   v2 reset). Include/exclude flag also need to be set accordingly.
   Since source IP address is used as part of BGP route key processing,
   it is considered as a new BGP route advertisement.


   5) 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 flag field. With multiple version
   flags set, there MUST not be source IP address in the receive EVPN
   route. If there is, then an error SHOULD be logged. If v3 flag is set



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   (in addition to v2), then the include/exclude flag MUST indicate
   "exclude". If not, then an error SHOULD be logged. The PE MUST
   generate an IGMP membership report (Join) for that (*,G) and each
   IGMP version in the version flag.


   6) 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.

   7) Upon receiving EVPN SMET route(s) and before generating the
   corresponding IGMP Join(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 check by listening for PIM hellos on that AC (i.e, <ES,BD>). If
   it has router's ACs, then the generated IGMP Join(s) are sent to
   those ACs. If it doesn't have any router's AC, then no IGMP Join(s)
   needs to be generated because sending IGMP Joins to other hosts can
   result in unintentionally preventing a host from joining a specific
   multicast group for IGMPv2 - i.e., if the PE does not receive a join
   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. In other words, an IGMPv2 Join
   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.

2.1.1  IGMP Leave Group Advertisement in BGP

   When a PE wants to withdraw an EVPN SMET route corresponding to an
   IGMPv2 Leave Group (Leave) or IGMPv3 "Leave" equivalent message, it
   follows the following rules:

   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 who is interested in this multicast group by
   sending a query for the multicast group. If the host was indeed the
   last one, then the PE 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 withdraws the EVPN route for that
   (*,G).

   2) When a PE receives an EVPN SMET route for a given (*,G), it



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   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 generates 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 should 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. If the PE receives an EVPN SMET route withdraw, then it must
   remove the remote PE from the OIF list associated with that multicast
   group.

   3) 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 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.


2.2  Proxy Querier

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

   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/VMs in that subnet.

   2) To enable suppression of IGMP membership reports and queries over
   MPLS/IP core.

3 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). Lets consider that this EVPN instance consist of a
   single bridge domain (single subnet) with all the hosts, sources and
   the multicast router shown in this figure connected to this subnet.
   PE1 only has hosts connected to it. PE2 has a mix of hosts and
   multicast source. PE3 has a mix of hosts, multicast source, and
   multicast router. Further more, lets 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:

        - only hosts/VMs



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        - mix of hosts/VMs and multicast source
        - mix of hosts/VMs, multicast source, and multicast router





                           +--------------+
                           |              |
                           |              |
                    +----+ |              | +----+
     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:

3.1 PE with only attached hosts/VMs for a given subnet

   When PE1 receives an IGMPv2 Join Report from H1, it does not forward
   this join to any of its other ports (for this subnet) because all
   these local ports are associated with the hosts/VMs. PE1 sends an
   EVPN Multicast Group route corresponding to this join for (*,G1) and
   setting v2 flag. This EVPN route is received by PE2 and PE3 that are
   the member 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 IGMPv2 Join 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
   Join Report for (*,G1) to only R1. Furthermore, PE2 although receives
   the EVPN BGP route, it does not send it to any of its port for that
   subnet - namely ports associated with H6 and H7.

   When PE1 receives the second IGMPv2 Join 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 Join from H3 for



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   the same (*,G1), besides adding the corresponding port to its OIF
   list, it re-advertises the previously sent EVPN SMET route with the
   version-3 & exclude flag set.

   Finally when PE1 receives the IMGMPv3 Join from H4 for (S2,G2), it
   advertises a new EVPN SMET route corresponding to it.


3.2 PE with mixed of attached hosts/VMs and multicast source

   The main difference in here is that when PE2 receives IGMPv3 Join
   from H7 for (S2,G2), it does advertises 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 v2 Join
   described in previous section.

3.3 PE with mixed of attached hosts/VMs, multicast source and router

   The main difference in here relative to the previous two sections is
   that Join messages received locally needs to be sent to the port
   associated with router R1. Furthermore, the Joins received via BGP
   need to be passed to the R1 port but filtered for all other ports.


4 All-Active Multi-Homing

   Because a CE's LAG flow hashing algorithm is unknown, 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 Join 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 received
   the Join messages.  Therefore, all PEs attached to a given ES must
   coordinate IGMP Join and Leave Group (x, G) state, where x may be
   either '*' or a particular source S, for each BD on that ES. 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 synch
   procedures described in this section if they want to perform IGMP
   proxy for hosts connects to that ES.

4.1 Local IGMP Join 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



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   for (x, G), it determines the BD to which the IGMP Membership Report
   belongs. If the PE doesn't already have local IGMP Join (x, G) state
   for that BD on that ES, it instantiates local IGMP Join (x, G) state
   and advertises a BGP IGMP Join Synch route for that [ES, BD]. Local
   IGMP Join (x, G) state refers to IGMP Join (x, G) state that is
   created as the result of processing an IGMP Membership Report for (x,
   G).

   The IGMP Join Synch route carries the ES-Import RT for the ES on
   which the IGMP Membership Report was received.  Thus it may only go
   to the PEs attached to that ES (and not any other PEs).

   When a PE, either DF or non-DF, receives an IGMP Join Synch route it
   installs that route and if it doesn't already have IGMP Join (x, G)
   state for that [ES, BD], it instantiates that IGMP Join (x,G) state -
   i.e., IGMP Join (x, G) state is the union of local IGMP Join (x, G)
   state and installed IGMP Join Synch route. If the DF is not currently
   advertising (originating) a SMET route for that (x, G) group in that
   BD, it does so now.

   When a PE, either DF or non-DF, deletes its local IGMP Join (x, G)
   state for that [ES, BD], it withdraws its BGP IGMP Join Synch route
   for that [ES, BD].

   When a PE, either DF or non-DF, receives the withdrawal of an IGMP
   Join Synch route from another PE it removes that route.  When a PE
   has no local IGMP Join (x, G) state and it has no installed IGMP Join
   Synch routes, it removes IGMP Join (x, G) state for that [ES, BD].
   If the DF no longer has IGMP Join (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.

   I.e., A PE advertises an SMET route for that (x, G) group in that BD
   when it has IGMP Join (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 Join (x, G) state in that BD on any ES for which it is DF.

4.2 Local IGMP 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 Join
   (x, G) state for that [ES, BD], it initiates the (x, G) leave group
   synchronization procedure, which consists of the following steps:

   1) It computes the Maximum Response Time, which is the duration of
   (x, G) leave group synchronization procedure.  This is the product of



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   two locally configured values, Last Member Query Count and Last
   Member Query Interval (described in Section 3 of [RFC2236]), plus
   delta, 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 and the Leave Group Synchronization Procedure
   Sequence number. The latter identifies the specific (x, G) leave
   group synchronization procedure initiated by the advertising PE,
   which increments the value whenever it initiates a procedure.

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


4.2.1 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.

4.2.2 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 Join Synch route for that [ES, BD]. If it
   doesn't already have local IGMP Join (x, G) state for that [ES, BD],
   it instantiates local IGMP Join (x, G) state. If the DF is not
   currently advertising (originating) a SMET route for that (x, G)



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   group in that BD, it does so now.

   If a PE attached to the multihomed ES receives an IGMP Join Synch
   route for (x, G) before the Maximum Response Time timer expires, it
   installs that route and if it doesn't already have IGMP Join (x, G)
   state for that BD on that ES, it instantiates that IGMP Join (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.

   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 Join (x, G) state and no installed IGMP Join Synch routes,
   it removes IGMP Join (x, G) state for that [ES, BD].  If the DF no
   longer has IGMP Join (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.

4.3 Mass Withdraw of Multicast join Sync route in case of failure

   A PE which has received IGMP join, would have synced IGMP join by
   procedure section(4.1). If PE with local join state goes down or PE
   to CE link goes down, it would lead to mass withdraw of multicast
   routes. Remote PE (PE where these routes were remote IGMP join)
   SHOULD not remove the state immediately where as General Query SHOULD
   be generated to refresh the states. Some of the way (But not limited
   to) to detect failure at peer could be IGP next hop tracking or ES
   route withdraw.

5 Single-Active Multi-Homing

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


6 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
   Proxy.  This set consists of any PE that has advertised an Inclusive
   Multicast Tag route for the BD without the "IGMP Proxy Support" flag.

   2)  It sends (x, G) traffic to the set of PEs supporting IGMP Proxy



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   and having listeners for that (x, G) group in that BD. This set
   consists of any PE that has advertised an Inclusive Multicast Tag
   route for the BD with the "IGMP Proxy Support" flag and that has
   advertised an SMET route for that (x, G) group in that BD.

   If an ingress PE's Selective P-Tunnel for a given BD uses P2MP and
   all of the PEs in the BD support that tunnel type and IGMP, then for
   a given (x, G) group in a given BD it sends (x, G) traffic using the
   Selective P-Tunnel for that (x, G) group in that BD.  This tunnel
   will include those PEs that have advertised an SMET route for that
   (x, G) group on that BD (for Selective P-tunnel) but it may include
   other PEs as well (for Aggregate Selective P-tunnel).


7 BGP Encoding

   This document defines three new BGP EVPN routes to carry IGMP
   membership reports. This route type is known as:


           + 6 - Selective Multicast Ethernet Tag Route
           + 7 - Multicast Join Synch Route
           + 8 - Multicast Leave Synch Route

   The detailed encoding and procedures for this route type is described
   in subsequent section.


7.1 Selective Multicast Ethernet Tag Route

   An 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 octets) (optional)          |
                   +---------------------------------------+


   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 optional flag field (if included). The Flags fields are defined
   as follows:

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

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

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

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

   The forth 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.

   This EVPN route type is used to carry tenant IGMP multicast group
   information. The flag field assists in distributing IGMP membership
   interest of a given host/VM for a given multicast route. The version



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   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.


7.1.1 Constructing the Selective Multicast Ethernet Tag route

   This section describes the procedures used to construct the Selective
   Multicast Ethernet Tag (SMET) route. Support for this route type is
   optional.

   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 follows:

   EVI is VLAN-Based or VLAN Bundle service - set to 0
   EVI is VLAN-Aware Bundle service without translation - set to
   the customer VID for that BD
   EVI is VLAN-Aware Bundle service with translation - set to the
   normalized Ethernet Tag ID - e.g., normalized VID


   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) Join, 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) Join, 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.



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   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. It should be noted that using the "Originating Router's
   IP address" field is needed for local-bias procedures and may be
   needed for building inter-AS multicast underlay tunnels where BGP
   next hop can get over written.

   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.

   IGMP protocol is used to receive group membership information from
   hosts/VMs by TORs. Upon receiving the hosts/VMs expression of
   interest of a particular group membership, this information is then
   forwarded using Ethernet Multicast Source Group Route NLRI. 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.

7.1.2 Default Selective Multicast Route

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






















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


   Figure 2:

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


7.2  Multicast Join Synch Route

   This EVPN route type is used to coordinate IGMP Join (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)            |
             +--------------------------------------------------+
             |  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|
                       +--+--+--+--+--+--+--+--+


   The least significant bit, bit 7 indicates support for IGMP version
   1.  The second least significant bit, bit 6 indicates support for
   IGMP version 2.     The third least significant bit, bit 5 indicates
   support for IGMP version 3.  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.

   The Flags field assists in distributing IGMP membership interest of a
   given host/VM 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



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   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.

7.2.1  Constructing the Multicast Join Synch Route

   This section describes the procedures used to construct the IGMP Join
   Synch route.  Support for this route type 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 Join Synch route MUST carry exactly one ES-Import Route
   Target extended community, the one that corresponds to the ES on
   which the IGMP Join was received.  It MUST also carry exactly one
   EVI-RT EC, the one that corresponds to the EVI on which the IGMP Join
   was received.  See Section 7.5 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 follows:

   EVI is VLAN-Based or VLAN Bundle service - set to 0
   EVI is VLAN-Aware Bundle service without translation - set to
   the customer VID for the BD
   EVI is VLAN-Aware Bundle service with translation - set to the
   normalized Ethernet Tag ID - e.g., normalized VID

   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) Join, the Multicast Source Length is set to 0.

   The Multicast Source is the Source IP address of the IGMP membership



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   report.  In case of a (*, G) Join, 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.


7.3 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)            |
             +--------------------------------------------------+
             |  Leave Group Synchronization  # (4 octets)       |
             +--------------------------------------------------+
             |  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
   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|
                       +--+--+--+--+--+--+--+--+


   The least significant bit, bit 7 indicates support for IGMP version
   1.  The second least significant bit, bit 6 indicates support for
   IGMP version 2.     The third least significant bit, bit 5 indicates
   support for IGMP version 3.  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.




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   The Flags field assists in distributing IGMP membership interest of a
   given host/VM 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.


7.3.1  Constructing the Multicas Leave Synch Route

   This section describes the procedures used to construct the IGMP
   Leave Synch route.  Support for this route type 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 7.5 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 follows:

   EVI is VLAN-Based or VLAN Bundle service - set to 0
   EVI is VLAN-Aware Bundle service without translation - set to
   the customer VID for the BD
   EVI is VLAN-Aware Bundle service with translation - set to the
   normalized Ethernet Tag ID - e.g., normalized VID


   The Multicast Source length MUST be set to length of multicast source
   address in bits. If the Multicast Source field contains an IPv4



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   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) Join, 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) Join, 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.



7.4 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 proxy on a given BD MUST attach this extended
   community to the  Inclusive Multicast Ethernet Tag (IMET) route it
   advertises for that BD and it Must set the IGMP Proxy Support flag 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 IGMP 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



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   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:


                         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=TBD |       Flags (2 Octets)        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                           Reserved=0                        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   The low-order bit of the Flags is defined as the "IGMP Proxy Support"
   bit.  A value of 1 means that the PE supports IGMP Proxy as defined
   in this document, and a value of 0 means that the PE does not support
   IGMP proxy. The absence of this extended community also means that
   the PE does not support IGMP proxy.


7.5 EVI-RT Extended Community

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

   - 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.

   - 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 Join 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 Join 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



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   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 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".

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

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

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

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

   Each IGMP Join 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 Join or an IGMP Leave message from a particular BD.
   We will say that the route is 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 Join Synch or Leave Synch route is associated
   with a given BD, say BD1, and suppose that the corresponding RT for
   BD1 is RT1. Then:

   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.

   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.

   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.

   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 Join Synch or Leave Synch route MUST carry exactly one  EVI-
   RT EC.

   Suppose a PE receives a particular IGMP Join Synch or IGMP Leave



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   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.


7.6 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
   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.

8  IGMP/MLD Immediate leave

   IGMP MAY be configured with immediate leave option. This allows the
   device to remove the group entry from the multicast routing table
   immediately upon receiving a IGMP leave message for (x,G). In case of
   all active multi-homing while synchronizing IGMP leave state to
   redundancy peers, Maximum Response Time MAY be filled as Zero.
   Implementation SHOULD make sure to have identical configuration
   across multi home peer. In case IGMP leave Synch route is received



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   with Maximum Response Time Zero, irrespective of local IGMP
   configuration it MAY be processed as immediate leave.

9 IGMP Version 1 membership request

   This document does not provide any detail about IGMPv1 processing.
   Multicast working group are in process of absoluting uses of IGMPv1
   so implementation are RECOMENDED to use IGMPv2 / MLDv1 and above
   only.

10  Security Considerations

   Same security considerations as [RFC7432].

11  IANA Considerations

   IANA has allocated the following codepoints from the EVPN Extended
   Community sub-types registry.

       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]

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

        6 - Selective Multicast Ethernet Tag Route
        7 - IGMP Join Synch Route
        8 - IGMP Leave Synch Route

   IANA is requested to create a registry, "Multicast Flags Extended
   Community Flags", in the BGP registry.

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

   The registry should be initialized as follows:

        0    : IGMP Proxy Support                      [this document]
        1-15 : unassigned

   The registration policy should be "Standards Action".



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12  References

12.1  Normative References

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



   [RFC4360] S. Sangli et al, ""BGP Extended Communities Attribute",
              February, 2006.

   [RFC7432] Sajassi et al., "BGP MPLS Based Ethernet VPN", February,
              2015.

12.2  Informative References

   [RFC7387] Key, et al., ""A Framework for Ethernet Tree (E-Tree)
   Service over a Multiprotocol Label Switching (MPLS) Network", October
   2014.

   [RFC7623] Sajassi, et al., ""Provider Backbone Bridging Combined with
   Ethernet VPN (PBB-EVPN)", September 2015.

   [FC4541] Christensen, M., Kimball, K., and F. Solensky,
   "Considerations for IGMP and MLD snooping PEs", 2006.

   [RFC3376] Cain, et. al., "Internet Group Management Protocol, Version
   3", October 2002.

   [RFC3810] Vida & Costa , "Multicast Listener Discovery Version 2
   (MLDv2) for IPv6", June 2004


13  Acknowledgement

14 Contributors

   Mankamana Mishra
   Cisco systems
   Email: mankamis@cisco.com

Authors' Addresses


   Ali Sajassi



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   Cisco
   Email: sajassi@cisco.com


   Samir Thoria
   Cisco
   Email: sthoria@cisco.com


   Keyur Patel
   Arrcus
   Email: keyur@arrcus.com


   Derek Yeung
   Arrcus
   Email: derek@arrcus.com


   John Drake
   Juniper
   Email: jdrake@juniper.net


   Wen Lin
   Juniper
   Email: wlin@juniper.net
























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