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Versions: (draft-sajassi-bess-evpn-mvpn-seamless-interop) 00 01

BESS WorkGroup                                                A. Sajassi
Internet-Draft                                       K. Thiruvenkatasamy
Intended status: Standards Track                               S. Thoria
Expires: January 11, 2021                                          Cisco
                                                                A. Gupta
                                                                  VMware
                                                                L. Jalil
                                                                 Verizon
                                                           July 10, 2020


     Seamless Multicast Interoperability between EVPN and MVPN PEs
             draft-ietf-bess-evpn-mvpn-seamless-interop-01

Abstract

   Ethernet Virtual Private Network (EVPN) solution is becoming
   pervasive for Network Virtualization Overlay (NVO) services in data
   center (DC) networks and as the next generation VPN services in
   service provider (SP) networks.

   As service providers transform their networks in their COs toward
   next generation data center with Software Defined Networking (SDN)
   based fabric and Network Function Virtualization (NFV), they want to
   be able to maintain their offered services including Multicast VPN
   (MVPN) service between their existing network and their new Service
   Provider Data Center (SPDC) network seamlessly without the use of
   gateway devices.  They want to have such seamless interoperability
   between their new SPDCs and their existing networks for a) reducing
   cost, b) having optimum forwarding, and c) reducing provisioning.
   This document describes a unified solution based on RFCs 6513 & 6514
   for seamless interoperability of Multicast VPN between EVPN and MVPN
   PEs.  Furthermore, it describes how the proposed solution can be used
   as a routed multicast solution in data centers with only EVPN 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




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   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 January 11, 2021.

Copyright Notice

   Copyright (c) 2020 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
   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
   2.  Requirements Language . . . . . . . . . . . . . . . . . . . .   5
   3.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   5
   4.  Requirements  . . . . . . . . . . . . . . . . . . . . . . . .   7
     4.1.  Optimum Forwarding  . . . . . . . . . . . . . . . . . . .   7
     4.2.  Optimum Replication . . . . . . . . . . . . . . . . . . .   7
     4.3.  All-Active and Single-Active Multi-Homing . . . . . . . .   7
     4.4.  Inter-AS Tree Stitching . . . . . . . . . . . . . . . . .   8
     4.5.  EVPN Service Interfaces . . . . . . . . . . . . . . . . .   8
     4.6.  Distributed Anycast Gateway . . . . . . . . . . . . . . .   8
     4.7.  Selective &  Aggregate Selective Tunnels  . . . . . . . .   8
     4.8.  Tenants' (S,G) or (*,G) states  . . . . . . . . . . . . .   8
     4.9.  Zero Disruption upon BD/Subnet Addition . . . . . . . . .   8
     4.10. No Changes to Existing EVPN Service Interface Models  . .   9
     4.11. External source and receivers . . . . . . . . . . . . . .   9
     4.12. Tenant RP placement . . . . . . . . . . . . . . . . . . .   9
   5.  IRB Unicast versus IRB Multicast  . . . . . . . . . . . . . .   9
     5.1.  Emulated Virtual LAN Service  . . . . . . . . . . . . . .  10
   6.  Solution Overview . . . . . . . . . . . . . . . . . . . . . .  10
     6.1.  Operational Model for EVPN IRB PEs  . . . . . . . . . . .  10
     6.2.  Unicast Route Advertisements for IP multicast Source  . .  13
     6.3.  Multi-homing of IP Multicast Source and Receivers . . . .  14
       6.3.1.  Single-Active Multi-Homing  . . . . . . . . . . . . .  14
       6.3.2.  All-Active Multi-Homing . . . . . . . . . . . . . . .  15
     6.4.  Mobility for Tenant's Sources and Receivers . . . . . . .  17
     6.5.  Intra-Subnet BUM Traffic Handling . . . . . . . . . . . .  18



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     6.6.  EVPN and MVPN interworking with gateway model . . . . . .  18
   7.  Control Plane Operation . . . . . . . . . . . . . . . . . . .  19
     7.1.  Intra-ES/Intra-Subnet IP Multicast Tunnel . . . . . . . .  19
     7.2.  Intra-Subnet BUM Tunnel . . . . . . . . . . . . . . . . .  20
     7.3.  Inter-Subnet IP Multicast Tunnel  . . . . . . . . . . . .  20
     7.4.  IGMP Hosts as TSes  . . . . . . . . . . . . . . . . . . .  21
     7.5.  TS PIM Routers  . . . . . . . . . . . . . . . . . . . . .  22
   8.  Data Plane Operation  . . . . . . . . . . . . . . . . . . . .  22
     8.1.  Intra-Subnet L2 Switching . . . . . . . . . . . . . . . .  23
     8.2.  Inter-Subnet L3 Routing . . . . . . . . . . . . . . . . .  23
   9.  DCs with only EVPN PEs  . . . . . . . . . . . . . . . . . . .  23
     9.1.  Setup of overlay multicast delivery . . . . . . . . . . .  24
     9.2.  Handling of different encapsulations  . . . . . . . . . .  26
       9.2.1.  MPLS Encapsulation  . . . . . . . . . . . . . . . . .  26
       9.2.2.  VxLAN Encapsulation . . . . . . . . . . . . . . . . .  26
       9.2.3.  Other Encapsulation . . . . . . . . . . . . . . . . .  26
   10. DCI with MPLS in WAN and VxLAN in DCs . . . . . . . . . . . .  27
     10.1.  Control plane inter-connect  . . . . . . . . . . . . . .  27
     10.2.  Data plane inter-connect . . . . . . . . . . . . . . . .  28
   11. Supporting application with TTL value 1 . . . . . . . . . . .  29
     11.1.  Policy based model . . . . . . . . . . . . . . . . . . .  29
     11.2.  Exercising BUM procedure for VLAN/BD . . . . . . . . . .  29
     11.3.  Intra-subnet bridging  . . . . . . . . . . . . . . . . .  29
   12. Interop with L2 EVPN PEs  . . . . . . . . . . . . . . . . . .  31
   13. Connecting external Multicast networks or PIM routers.  . . .  33
   14. RP handling . . . . . . . . . . . . . . . . . . . . . . . . .  33
     14.1.  Various RP deployment options  . . . . . . . . . . . . .  33
       14.1.1.  RP-less mode . . . . . . . . . . . . . . . . . . . .  33
       14.1.2.  Fabric anycast RP  . . . . . . . . . . . . . . . . .  33
       14.1.3.  Static RP  . . . . . . . . . . . . . . . . . . . . .  34
       14.1.4.  Co-existence of Fabric anycast RP and external RP  .  34
     14.2.  RP configuration options . . . . . . . . . . . . . . . .  34
   15. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  34
   16. Security Considerations . . . . . . . . . . . . . . . . . . .  34
   17. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  35
   18. References  . . . . . . . . . . . . . . . . . . . . . . . . .  35
     18.1.  Normative References . . . . . . . . . . . . . . . . . .  35
     18.2.  Informative References . . . . . . . . . . . . . . . . .  36
   Appendix A.  Use Cases  . . . . . . . . . . . . . . . . . . . . .  36
     A.1.  DCs with only IGMP/MLD hosts w/o tenant router  . . . . .  36
     A.2.  DCs with mixed of IGMP/MLD hosts & multicast routers
           running PIM-SSM . . . . . . . . . . . . . . . . . . . . .  37
     A.3.  DCs with mixed of IGMP/MLD hosts & multicast routers
           running PIM-ASM . . . . . . . . . . . . . . . . . . . . .  38
     A.4.  DCs with mixed of IGMP/MLD hosts & multicast routers
           running PIM-Bidir . . . . . . . . . . . . . . . . . . . .  38
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  38




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1.  Introduction

   Ethernet Virtual Private Network (EVPN) solution is becoming
   pervasive for Network Virtualization Overlay (NVO) services in data
   center (DC) networks and as the next generation VPN services in
   service provider (SP) networks.

   As service providers transform their networks in their COs toward
   next generation data center with Software Defined Networking (SDN)
   based fabric and Network Function Virtualization (NFV), they want to
   be able to maintain their offered services including Multicast VPN
   (MVPN) service between their existing network and their new SPDC
   network seamlessly without the use of gateway devices.  There are
   several reasons for having such seamless interoperability between
   their new DCs and their existing networks:

   - Lower Cost: gateway devices need to have very high scalability to
   handle VPN services for their DCs and as such need to handle large
   number of VPN instances (in tens or hundreds of thousands) and very
   large number of routes (e.g., in tens of millions).  For the same
   speed and feed, these high scale gateway boxes are relatively much
   more expensive than the edge devices (e.g., PEs and TORs) that
   support much lower number of routes and VPN instances.

   - Optimum Forwarding: in a given CO, both EVPN PEs and MVPN PEs can
   be connected to the same fabric/network (e.g., same IGP domain).  In
   such scenarios, the service providers want to have optimum forwarding
   among these PE devices without the use of gateway devices.  Because
   if gateway devices are used, then the IP multicast traffic between an
   EVPN and MVPN PEs can no longer be optimum and in some case, it may
   even get tromboned.  Furthermore, when an SPDC network spans across
   multiple LATA (multiple geographic areas) and gateways are used
   between EVPN and MVPN PEs, then with respect to IP multicast traffic,
   only one GW can be designated forwarder (DF) between EVPN and MVPN
   PEs.  Such scenarios not only results in non-optimum forwarding but
   also it can result in tromboing of IP multicast traffic between the
   two LATAs when both source and destination PEs are in the same LATA
   and the DF gateway is elected to be in a different LATA.

   - Less Provisioning: If gateways are used, then the operator need to
   configure per-tenant info on the gateways.  In other words, for each
   tenant that is configured, one (or maybe two) additional touch points
   are needed.

   This document describes a unified solution based on [RFC6513] and
   [RFC6514] for seamless interoperability of multicast VPN between EVPN
   and MVPN PEs.  Furthermore, it describes how the proposed solution




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   can be used as a routed multicast solution in data centers with only
   EVPN PEs (e.g., routed multicast VPN only among EVPN PEs).

2.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" are to
   be interpreted as described in [RFC2119] only when they appear in all
   upper case.  They may also appear in lower or mixed case as English
   words, without any normative meaning.

3.  Terminology

   Most of the terminology used in this documents comes from [RFC8365]

   Broadcast Domain (BD): In a bridged network, the broadcast domain
   corresponds to a Virtual LAN (VLAN), where a VLAN is typically
   represented by a single VLAN ID (VID) but can be represented by
   several VIDs where Shared VLAN Learning (SVL) is used per [802.1Q].

   Bridge Table (BT): An instantiation of a broadcast domain on a MAC-
   VRF.

   VXLAN: Virtual Extensible LAN

   POD: Point of Delivery

   NV: Network Virtualization

   NVO: Network Virtualization Overlay

   NVE: Network Virtualization Endpoint

   VNI: Virtual Network Identifier (for VXLAN)

   EVPN: Ethernet VPN

   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

   IP-VRF: A Virtual Routing and Forwarding table for Internet Protocol
   (IP) addresses on a PE






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   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'.

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

   PE: Provider Edge device.

   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.

   PIM-SM: Protocol Independent Multicast - Sparse-Mode

   PIM-SSM: Protocol Independent Multicast - Source Specific Multicast

   Bidir PIM: Bidirectional PIM

   FHR: First Hop Router

   LHR: Last Hop Router

   CO: Central Office of a service provider

   SPDC: Service Provider Data Center

   LATA: Local Access and Transport Area

   Border Leafs: A set of EVPN-PE acting as exit point for EVPN fabric.

   L3VNI: A VNI in the tenant VRF, which is associated with the core
   facing interface.







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4.  Requirements

   This section describes the requirements specific in providing
   seamless multicast VPN service between MVPN and EVPN capable
   networks.

4.1.  Optimum Forwarding

   The solution SHALL support optimum multicast forwarding between EVPN
   and MVPN PEs within a network.  The network can be confined to a CO
   or it can span across multiple LATAs.  The solution SHALL support
   optimum multicast forwarding with both ingress replication tunnels
   and P2MP tunnels.

4.2.  Optimum Replication

   For EVPN PEs with IRB capability, the solution SHALL use only a
   single multicast tunnel among EVPN and MVPN PEs for IP multicast
   traffic, when both PEs use the same tunnel type.  Multicast tunnels
   can be either ingress replication tunnels or P2MP tunnels.  The
   solution MUST support optimum replication for both Intra-subnet and
   Inter-subnet IP multicast traffic:

   - Non-IP traffic SHALL be forwarded per EVPN baseline [RFC7432] or
   [RFC8365]

   - If a Multicast VPN spans across both Intra and Inter subnets, then
   for Ingress replication regardless of whether the traffic is Intra or
   Inter subnet, only a single copy of IP multicast traffic SHALL be
   sent from the source PE to the destination PE.

   - If a Multicast VPN spans across both Intra and Inter subnets, then
   for P2MP tunnels regardless of whether the traffic is Intra or Inter
   subnet, only a single copy of multicast data SHALL be transmitted by
   the source PE.  Source PE can be either EVPN or MVPN PE and receiving
   PEs can be a mix of EVPN and MVPN PEs - i.e., a multicast VPN can be
   spread across both EVPN and MVPN PEs.

4.3.  All-Active and Single-Active Multi-Homing

   The solution MUST support multi-homing of source devices and
   receivers that are sitting in the same subnet (e.g., VLAN) and are
   multi-homed to EVPN PEs.  The solution SHALL allow for both Single-
   Active and All-Active multi-homing.  The solution MUST prevent loop
   during steady and transient states just like EVPN baseline solution
   [RFC7432] and [RFC8365] for all multi-homing types.





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4.4.  Inter-AS Tree Stitching

   The solution SHALL support multicast tree stitching when the tree
   spans across multiple Autonomous Systems.

4.5.  EVPN Service Interfaces

   The solution MUST support all EVPN service interfaces listed in
   section 6 of [RFC7432]:

   o  VLAN-based service interface

   o  VLAN-bundle service interface

   o  VLAN-aware bundle service interface.

4.6.  Distributed Anycast Gateway

   The solution SHALL support distributed anycast gateways for tenant
   workloads on NVE devices operating in EVPN-IRB mode..

4.7.  Selective & Aggregate Selective Tunnels

   The solution SHALL support selective and aggregate selective P-
   tunnels as well as inclusive and aggregate inclusive P-tunnels.  When
   selective tunnels are used, then multicast traffic SHOULD only be
   forwarded to the remote PE which have receivers - i.e., if there are
   no receivers at a remote PE, the multicast traffic SHOULD NOT be
   forwarded to that PE and if there are no receivers on any remote PEs,
   then the multicast traffic SHOULD NOT be forwarded to the core.

4.8.  Tenants' (S,G) or (*,G) states

   The solution SHOULD store (C-S,C-G) and (C-*,C-G) states only on PE
   devices that have interest in such states hence reducing memory and
   processing requirements - i.e., PE devices that have sources and/or
   receivers interested in such multicast groups.

4.9.  Zero Disruption upon BD/Subnet Addition

   In DC environments, various Bridge Domains are provisioned and
   removed on regular basis due to host mobility, policy and tenant
   changes.  Such change in BD configuration should not affect existing
   flows within the same BD or any other BD in the network.







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4.10.  No Changes to Existing EVPN Service Interface Models

   VLAN-aware bundle service as defined in [RFC7432] typically does not
   require any VLAN ID translation from one tenant site to another -
   i.e., the same set of VLAN IDs are configured consistently on all
   tenant segments.  In such scenarios, EVPN-IRB multicast service MUST
   maintain the same mode of operation and SHALL NOT require any VLAN ID
   translation.

4.11.  External source and receivers

   The solution SHALL support sources and receivers external to the
   tenant domain. i.e., multicast source inside the tenant domain can
   have receiver outside the tenant domain and vice versa.

4.12.  Tenant RP placement

   The solution SHALL support a tenant to have RP anywhere in the
   network.  RP can be placed inside the EVPN network or MVPN network or
   external domain.

5.  IRB Unicast versus IRB Multicast

   [I-D.ietf-bess-evpn-inter-subnet-forwarding] describes the operation
   for EVPN PEs in IRB mode for unicast traffic.  The same IRB model
   used for unicast traffic in
   [I-D.ietf-bess-evpn-inter-subnet-forwarding] , where an IP-VRF in an
   EVPN PE is attached to one or more bridge tables (BTs) via virtual
   IRB interfaces, is also applicable for multicast traffic.  However,
   there are some noticeable differences between the IRB operation for
   unicast traffic described in
   [I-D.ietf-bess-evpn-inter-subnet-forwarding] versus for multicast
   traffic described in this document.  For unicast traffic, the intra-
   subnet traffic, is bridged within the MAC-VRF associated with that
   subnet (i.e., a lookup based on MAC-DA is performed); whereas, the
   inter-subnet traffic is routed in the corresponding IP-VRF (ie, a
   lookup based on IP-DA is performed).  A given tenant can have one or
   more IP-VRFs; however, without loss of generality, this document
   assumes one IP-VRF per tenant.  In context of a given tenant's
   multicast traffic, the intra-subnet traffic is bridged for non-IP
   traffic and it is Layer-2 switched for IP traffic.  Whereas, the
   tenants's inter-subnet multicast traffic is always routed in the
   corresponding IP-VRF.  The difference between bridging and
   L2-switching for multicast traffic is that the former uses MAC-DA
   lookup for forwarding the multicast traffic; whereas, the latter uses
   IP-DA lookup for such forwarding where the forwarding states are
   built in the MAC-VRF using IGMP/MLD or PIM snooping.




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5.1.  Emulated Virtual LAN Service

   EVPN does not provide a Virtual LAN (VLAN) service per [IEEE802.1Q]
   but rather an emulated VLAN service.  This VLAN service emulation is
   not only done for unicast traffic but also is extended for intra-
   subnet multicast traffic described in
   [I-D.ietf-bess-evpn-igmp-mld-proxy] and
   [I-D.skr-bess-evpn-pim-proxy].  For intra-subnet multicast, an EVPN
   PE builds multicast forwarding states in its bridge table (BT) based
   on snooping of IGMP/MLD and/or PIM messages and the forwarding is
   performed based on destination IP multicast address of the Ethernet
   frame rather than destination MAC address as noted above.  In order
   to enable seamless integration of EVPN and MVPN PEs, this document
   extends the concept of an emulated VLAN service for multicast IRB
   applications such that the intra-subnet IP multicast traffic can get
   treated same as inter- subnet IP multicast traffic which means intra-
   subnet IP multicast traffic destined to remote PEs gets routed
   instead of being L2- switched - i.e., TTL value gets decremented and
   the Ethernet header of the L2 frame is de-capsulated an encapsulated
   at both ingress and egress PEs.  It should be noted that the non-IP
   multicast or L2 broadcast traffic still gets bridged and frames get
   forwarded based on their destination MAC addresses.

6.  Solution Overview

   This section describes a multicast VPN solution based on [RFC6513]
   and [RFC6514] for EVPN PEs operating in IRB mode that want to perform
   seamless interoperability with their counterparts MVPN PEs.

6.1.  Operational Model for EVPN IRB PEs

   Without the loss of generality, this section assumes that all EVPN
   PEs have IRB capability and operating in IRB mode for both unicast
   and multicast traffic (e.g., all EVPN PEs are homogenous in terms of
   their capabilities and operational modes).  As it will be seen later,
   an EVPN network can consist of a mix of PEs where some are capable of
   multicast IRB and some are not and the multicast operation of such
   heterogeneous EVPN network will be an extension of an EVPN homogenous
   network.  Therefore, we start with the multicast IRB solution
   description for the EVPN homogenous network.

   The EVPN PEs terminate IGMP/MLD messages from tenant host devices or
   PIM messages from tenant routers on their IRB interfaces, thus avoid
   sending these messages over MPLS/IP core.  A tenant virtual/physical
   router (e.g., CE) attached to an EVPN PE becomes a multicast routing
   adjacency of that PE.  Furthermore, the PE uses MVPN BGP protocol and
   procedures per [RFC6513] and [RFC6514].  With respect to multicast
   routing protocol between tenant's virtual/physical router and the PE



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   that it is attached to, any of the following PIM protocols is
   supported per [RFC6513]: PIM-SM with Any Source Multicast (ASM) mode,
   PIM-SM with Source Specific Multicast (SSM) mode, and PIM
   Bidirectional (BIDIR) mode.  Support of PIM-DM (Dense Mode) is
   excluded in this document per [RFC6513].

   The EVPN PEs use MVPN BGP routes defined in [RFC6514] to convey
   tenant (S,G) or (*,G) states to other MVPN or EVPN PEs and to set up
   overlay trees (inclusive or selective) for a given MVPN instance.
   The root or a leaf of such an overlay tree is terminated on an EVPN
   or MVPN PE.  Furthermore, this inclusive or selective overlay tree is
   terminated on a single IP-VRF of the EVPN or MVPN PE.  In case of
   EVPN PE, these overlay trees never get terminated on MAC-VRFs of that
   PE.

   Overlay trees are instantiated by underlay provider tunnels (P-
   tunnels) - e.g., P2MP, MP2MP, or unicast tunnels per [RFC6513].  When
   there are several overlay trees mapped to a single underlay P-tunnel,
   the tunnel is referred to as an aggregate tunnel.

   Figure-1 below depicts a scenario where a tenant's MVPN spans across
   both EVPN and MVPN PEs; where all EVPN PEs have multicast IRB
   capability.  An EVPN PE (with multicast IRB capability) can be
   modeled as a MVPN PE where the virtual IRB interface of an EVPN PE
   (virtual interface between a BT and IP-VRF) can be considered a
   routed interface for the MVPN PE.

                        EVPN PE1
                     +------------+
           Src1 +----|(MAC-VRF1)  |                   MVPN PE3
          Rcvr1 +----|      \     |    +---------+   +--------+
                     |    (IP-VRF)|----|         |---|(IP-VRF)|--- Rcvr5
                     |      /     |    |         |   +--------+
           Rcvr2 +---|(MAC-VRF2)  |    |         |
                     +------------+    |         |
                                       |  MPLS/  |
                        EVPN PE2       |  IP     |
                     +------------+    |         |
           Rcvr3 +---|(MAC-VRF1)  |    |         |    MVPN PE4
                     |       \    |    |         |   +--------+
                     |    (IP-VRF)|----|         |---|(IP-VRF)|--- Rcvr6
                     |       /    |    +---------+   +--------+
           Rcvr4 +---|(MAC-VRF3)  |
                     +------------+

                           Figure-1: EVPN & MVPN PEs Seamless Interop





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   Figure 2 depicts the modeling of EVPN PEs based on MVPN PEs where an
   EVPN PE can be modeled as a PE that consists of a MVPN PE whose
   routed interfaces (e.g., attachment circuits) are replaced with IRB
   interfaces connecting each IP-VRF of the MVPN PE to a set of BTs.
   Similar to a MVPN PE where an attachment circuit serves as a routed
   multicast interface for an IP-VRF associated with a MVPN instance, an
   IRB interface serves as a routed multicast interface for the IP-VRF
   associated with the MVPN instance.  Since EVPN PEs run MVPN protocols
   (e.g., [RFC6513] and [RFC6514] ), for all practical purposes, they
   look just like MVPN PEs to other PE devices.  Such modeling of EVPN
   PEs, transforms the multicast VPN operation of EVPN PEs to that of
   MVPN and thus simplifies the interoperability between EVPN and MVPN
   PEs to that of running a single unified solution based on MVPN.


                        EVPN PE1
                     +------------+
           Src1 +----|(MAC-VRF1)  |
                     |     \      |
          Rcvr1 +----|  +--------+|    +---------+   +--------+
                     |  |MVPN PE1||----|         |---|MVPN PE3|--- Rcvr5
                     |  +--------+|    |         |   +--------+
                     |      /     |    |         |
           Rcvr2 +---|(MAC-VRF2)  |    |         |
                     +------------+    |         |
                                       |  MPLS/  |
                        EVPN PE2       |  IP     |
                     +------------+    |         |
           Rcvr3 +---|(MAC-VRF1)  |    |         |
                     |       \    |    |         |
                     |  +--------+|    |         |   +--------+
                     |  |MVPN PE2||----|         |---|MVPN PE4|--- Rcvr6
                     |  +--------+|    |         |   +--------+
                     |       /    |    +---------+
           Rcvr4 +---|(MAC-VRF3)  |
                     +------------+

                           Figure-2: Modeling EVPN PEs as MVPN PEs

   Although modeling an EVPN PE as a MVPN PE, conceptually simplifies
   the operation to that of a solution based on MVPN, the following
   operational aspects of EVPN need to be factored in when considering
   seamless integration between EVPN and MVPN PEs.

   o  Unicast route advertisements for IP multicast source

   o  Multi-homing of IP multicast sources and receivers




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   o  Mobility for Tenant's sources and receivers

   o  non-IP multicast traffic handling

6.2.  Unicast Route Advertisements for IP multicast Source

   When an IP multicast source is attached to an EVPN PE, the unicast
   route for that IP multicast source needs to be advertised.  When the
   source is attached to a Single-Active multi-homed ES, then the EVPN
   DF PE is the PE that advertises a unicast route corresponding to the
   source IP address with VRF Route Import extended community which in
   turn is used as the Route Target for Join (S,G) messages sent toward
   the source PE by the remote PEs.  The EVPN PE advertises this unicast
   route using EVPN route type 2 and IPVPN unicast route along with VRF
   Route Import extended community.  EVPN route type 2 is advertised
   with the Route Targets corresponding to both IP-VRF and MAC-VRF/BT;
   whereas, IPVPN unicast route is advertised with RT corresponding to
   the IP-VRF.  When unicast routes are advertised by MVPN PEs, they are
   advertised using IPVPN unicast route along with VRF Route Import
   extended community per [RFC6514].

   When the source is attached to an All-Active multi-homed ES, then the
   PE that learns the source advertises the unicast route for that
   source using EVPN route type 2 and IPVPN unicast route along with VRF
   Route Import extended community.  EVPN route type 2 is advertised
   with the Route Targets corresponding to both IP-VRF and MAC-VRF/BT;
   whereas, IPVPN unicast route is advertised with RT corresponding to
   the IP-VRF.  When the other multi-homing EVPN PEs for that ES receive
   this unicast EVPN route, they import the route and check to see if
   they have learned the route locally for that ES, if they have, then
   they do nothing.  But if they have not, then they add the IP and MAC
   addresses to their IP-VRF and MAC-VRF/BT tables respectively with the
   local interface corresponding to that ES as the corresponding route
   adjacency.  Furthermore, these PEs advertise an IPVPN unicast route
   along with VRF Route Import extended community and Route Target
   corresponding to IP-VRF to other remote PEs for that MVPN.
   Therefore, the remote PEs learn the unicast route corresponding to
   the source from all multi-homing PEs associated with that All- Active
   Ethernet Segment even though one of the multi-homing PEs may only
   have directly learned the IP address of the source.

   EVPN-PEs advertise unicast routes as host routes using EVPN route
   type 2 for sources that are directly attached to a tenant BD that has
   been extended in the EVPN fabric.  EVPN-PE may summarize sources (IP
   networks) behind a router that are attached to EVPN-PE or sources
   that are connected to a BD, which is not extended across EVPN fabric
   and advertises those routes with EVPN route type 5.  EVPN host-routes




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   are advertised as IPVPN host-routes to MVPN-PEs only incase of
   seamless interop mode.

   Section 6.6 discusses connecting EVPN and MVPN networks with gateway
   model.  Section 9 extends seamless interop procedures to EVPN only
   fabrics as an IRB solution for multicast.

   EVPN-PEs only need to advertise unicast routes using EVPN route-type
   2 or route-type 5 and don't need to advertise IPVPN routes within
   EVPN only fabric.  No L3VPN provisioning is needed between EVPN-PEs.

   In gateway model, EVPN-PE advertises unicast routes as IPVPN routes
   along with VRI extended community for all multicast sources attached
   behind EVPN-PEs.  All IPVPN routes SHOULD be summarized while
   adverting to MVPN-PEs.

6.3.  Multi-homing of IP Multicast Source and Receivers

   EVPN [RFC7432] has extensive multi-homing capabilities that allows
   TSes to be multi-homed to two or more EVPN PEs in Single-Active or
   All-Active mode.  In Single-Active mode, only one of the multi-homing
   EVPN PEs can receive/transmit traffic for a given subnet (a given BD)
   for that multi-homed Ethernet Segment (ES).  In All-Active mode, any
   of the multi-homing EVPN PEs can receive/transmit unicast traffic but
   only one of them (the DF PE) can send BUM traffic to the multi-homed
   ES for a given subnet.

   The multi-homing mode (Single-Active versus All-Active) of a TS
   source can impact the MVPN procedures as described below.

6.3.1.  Single-Active Multi-Homing

   When a TS source reside on an ES that is multi-homed to two or more
   EVPN PEs operating in Single-Active mode, only one of the EVPN PEs
   can be active for the source subnet on that ES.  Therefore, only one
   of the multi-homing PE learns the unicast route of the TS source and
   advertises that using EVPN and IPVPN to other PEs as described
   previously.

   A downstream PE that receives a Join/Prune message from a TS host/
   router, selects a Upstream Multicast Hop (UMH) which is the upstream
   PE that receives the IP multicast flow in case of Singe- Active
   multi-homing.  An IP multicast flow belongs to either a source-
   specific tree (S,G) or to a shared tree (*,G).  We use the notation
   (X,G) to refer to either (S,G) or (*,G); where X refers to S in case
   of (S,G) and X refers to the Rendezvous Point (RP) for G in case of
   (*,G).  Since the active PE (which is also the UMH PE) has advertised
   unicast route for X along with the VRF Route Import EC, the



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   downstream PEs selects the UMH without any ambiguity based on MVPN
   procedures described in section 5.1 of [RFC6513].  Any of the three
   algorithms described in that section works fine.

   The multi-homing PE that receives the IP multicast flow on its local
   AC, performs the following tasks:

   - L2 switches the multicast traffic in its BT associated with the
   local AC over which it received the flow if there are any interested
   receivers for that subnet.

   - L3 routes the multicast traffic to other BTs for other subnets if
   there are any interested receivers for those subnets.

   - L3 routes the multicast traffic to other PEs per MVPN procedures.

   The multicast traffic can be sent on Inclusive, Selective, or
   Aggregate-Selective tree.  Regardless what type of tree is used, only
   a single copy of the multicast traffic is received by the downstream
   PEs and the multicast traffic is forwarded optimally from the
   upstream PE to the downstream PEs.

6.3.2.  All-Active Multi-Homing

   When a TS source reside on an ES that is multi-homed to two or more
   EVPN PEs operating in All-Active mode, then any of the multi-homing
   PEs can learn the TS source's unicast route; however, that PE may not
   be the same PE that receives the IP multicast flow.  Therefore, the
   procedures for Single-Active Multi-homing need to be augmented for
   All-Active scenario as below.

   The multi-homing EVPN PE that receives the IP multicast flow on its
   local AC, needs to do the following task in additions to the ones
   listed in the previous section for Single-Active multi-homing: L2
   switch the multicast traffic to other multi-homing EVPN PEs for that
   ES via a multicast tunnel which it is called intra-ES tunnel.  There
   will be a dedicated tunnel for this purpose which is different from
   inter-subnet overlay tree/tunnel setup by MVPN procedures.

   When the multi-homing EVPN PEs receive the IP multicast flow via this
   tunnel, they treat it as if they receive the flow via their local ACs
   and thus perform the tasks mentioned in the previous section for
   Single-Active multi-homing.  The tunnel type for this intra-ES tunnel
   can be any of the supported tunnel types such as ingress-replication,
   P2MP tunnel, BIER, and Assisted Replication; however, given that vast
   majority of multi-homing ESes are just dual-homing, a simple ingress
   replication tunnel can serve well.  For a given ES, since multicast
   traffic that is locally received by one multi-homing PE is sent to



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   other multi-homing PEs via this intra-ES tunnel, there is no need for
   sending the multicast tunnel via MVPN tunnel to these multi-homing
   PEs - i.e., MVPN multicast tunnels are used only for remote EVPN and
   MVPN PEs.  Multicast traffic sent over this intra-ES tunnel to other
   multi-homing PEs (only one other in case of dual-homing) for a given
   ES can be either fixed or on demand basis.  If on-demand basis, then
   one of the other multi-homing PEs that is selected as a UMH upon
   receiving a join message from a downstream PE, sends a request to
   receive this multicast flow from the source multi-homing PE over the
   special intra-ES tunnel.

   By feeding IP multicast flow received on one of the EVPN multi-homing
   PEs to the interested EVPN PEs in the same multi-homing group, we
   have essentially enabled all the EVPN PEs in the multi-homing group
   to serve as UMH for that IP multicast flow.  Each of these UMH PEs
   advertises unicast route for X in (X,G) along with the VRF Route
   Import EC to all PEs for that MVPN instance.  The downstream PEs
   build a candidate UMH set based on procedures described in section
   5.1 of [RFC6513] and pick a UMH from the set.  It should be noted
   that both the default UMH selection procedure based on highest UMH PE
   IP address and the UMH selection algorithm based on hash function
   specified in section 5.1.3 of [RFC6513] (which is also a MUST
   implement algorithm) result in the same UMH PE be selected by all
   downstream PEs running the same algorithm.  However, in order to
   allow a form of "equal cost load balancing", the hash algorithm is
   recommended to be used among all EVPN and MVPN PEs.  This hash
   algorithm distributes UMH selection for different IP multicast flows
   among the multi-homing PEs for a given ES.

   Since all downstream PEs (EVPN and MVPN) use the same hash-based
   algorithm for UMH determination, they all choose the same upstream PE
   as their UMH for a given (X,G) flow and thus they all send their
   (X,G) join message via BGP to the same upstream PE.  This results in
   one of the multi-homing PEs to receive the join message and thus send
   the IP multicast flow for (X,G) over its associated overlay tree even
   though all of the multi-homing PEs in the All-Active redundancy group
   have received the IP multicast flow (one of them directly via its
   local AC and the rest indirectly via the associated intra-ES tunnel).
   Therefore, only a single copy of routed IP multicast flow is sent
   over the network regardless of overlay tree type supported by the PEs
   - i.e., the overlay tree can be of type selective or aggregate
   selective or inclusive tree.  This gives the network operator the
   maximum flexibility for choosing any overlay tree type that is
   suitable for its network operation and still be able to deliver only
   a single copy of the IP multicast flows to the egress PEs.  In other
   words, an egress PE only receives a single copy of the IP multicast
   flow over the network, because it either receives it via the EVPN
   intra-ES tunnel or MVPN inter-subnet tunnel.  Furthermore, if it



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   receives it via MVPN inter-subnet tunnel, then only one of the multi-
   homing PEs associated with the source ES, sends the IP multicast
   traffic.

   Since the network of interest for seamless interoperability between
   EVPN and MVPN PEs is MPLS, the EVPN handling of BUM traffic for MPLS
   network needs to be considered.  EVPN [RFC7432] uses ESI MPLS label
   for split-horizon filtering of Broadcast/Unknown unicast/multicast
   (BUM) traffic from an All-Active multi-homing Ethernet Segment to
   ensure that BUM traffic doesn't get loop back to the same Ethernet
   Segment that it came from.  This split-horizon filtering mechanism
   applies as-is for multicast IRB scenario because of using the intra-
   ES tunnel among multi-homing PEs.  Since the multicast traffic
   received from a TS source on an All-Active ES by a multi-homing PE is
   bridged to all other multi-homing PEs in that group, the standard
   EVPN split-horizon filtering described in [RFC7432] applies as-is.
   Split-horizon filtering for non-MPLS encapsulations such as VxLAN is
   described in section 9.2.2 that deals with a DC network that consists
   of only EVPN PEs.

6.4.  Mobility for Tenant's Sources and Receivers

   When a tenant system (TS), source or receiver, is multi-homed behind
   a group of multi-homing EVPN PEs, then TS mobility SHALL be supported
   among EVPN PEs.  Furthermore, such TS mobility SHALL only cause an
   temporary disruption to the related multicast service among EVPN and
   MVPN PEs.  If a source is moved from one EVPN PE to another one, then
   the EVPN mobility procedure SHALL discover this move and a new
   unicast route advertisement (using both EVPN and IP-VPN routes) is
   made by the EVPN PE where the source has moved to per section 6.3
   above and unicast route withdraw (for both EVPN and IP-VPN routes) is
   performed by the EVPN PE where the source has moved from.

   The move of a source results in disruption of the IP multicast flow
   for the corresponding (S,G) flow till the new unicast route
   associated with the source is advertised by the new PE along with the
   VRF Route Import EC, the join messages sent by the egress PEs are
   received by the new PE, the multicast state for that flow is
   installed in the new PE and a new overlay tree is built for that
   source from the new PE to the egress PEs that are interested in
   receiving that IP multicast flow.

   The move of a receiver results in disruption of the IP multicast flow
   to that receiver only till the new PE for that receiver discovers the
   source and joins the overlay tree for that flow.






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6.5.  Intra-Subnet BUM Traffic Handling

   Link local IP multicast traffic consists IPv4 traffic with a
   destination address prefix of 224/8 and IPv6 traffic with a
   destination address prefix of FF02/16.  Such IP multicast traffic as
   well as non-IP multicast/broadcast traffic are sent per EVPN
   [RFC7432] BUM procedures and does not get routed via IP-VRF for
   multicast addresses.  So, such BUM traffic will be limited to a given
   EVI/VLAN (e.g., a give subnet); whereas, IP multicast traffic, will
   be locally L2 switched for local interfaces attached on the same
   subnet and will be routed for local interfaces attached on a
   different subnet or for forwarding traffic to other EVPN PEs (refer
   to section 8 for data plane operation).

6.6.  EVPN and MVPN interworking with gateway model

   The procedures specified in this document offers optimal multicast
   forwarding within a data center and also enables seamless
   interoperability of multicast traffic between EVPN and MVPN networks,
   when same tunnel types are used in the data plane.

   There are few other use cases in connecting MVPN networks in the EVPN
   fabric other than seamless interop model, where gateway model is used
   to interconnect both networks.


       Case1: All EVPN-PEs in the fabric can be made as MVPN exit points
       Case2: MVPN network can be attached behind a EVPN PE or subset of
              EVPN-PEs
       Case3: MVPN network (MVPN-PEs) which uses different tunnel model
              can be directly attached to EVPN fabric.

   In gateway model, MVPN routes from one domain are terminated at the
   gateway PE and re-originated for another domain.

   With use case 1 & 2, All PEs connected to an EVPN fabric can use one
   data plane to send & receive traffic within the fabric/data center.
   Also, IPVPN routes need not be advertised inside the fabric.
   Instead, PE where MVPN is terminated should advertise IPVPN as EVPN
   routes.

   With use case 3, Fabric will get two copies per multicast flow, if
   receivers exist both MVPN and EVPN networks.  (Two different data
   planes are used to send the traffic in the fabric; one for EVPN
   network and one for MVPN network).






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7.  Control Plane Operation

   In seamless interop between EVPN and MVPN PEs, the control plane may
   need to setup the following three types of multicast tunnels.  The
   first two are among EVPN PEs only but the third one is among EVPN and
   MVPN PEs.

   1) Intra-ES IP multicast tunnel

   2) Intra-subnet BUM tunnel

   3) Inter-subnet IP multicast tunnel

7.1.  Intra-ES/Intra-Subnet IP Multicast Tunnel

   As described in section 6.3.2, when a multicast source is sitting
   behind an All-Active ES, then an intra-subnet multicast tunnel is
   needed among the multi-homing EVPN PEs for that ES to carry multicast
   flow received by one of the multi-homing PEs to the other PEs in that
   ES.  We refer to this multicast tunnel as Intra-ES/Intra-Subnet
   tunnel.  Vast majority of All-Active multi-homing for TOR devices in
   DC networks are just dual-homing which means the multicast flow
   received by one of the dual-homing PE only needs to be sent to the
   other dual-homing PE.  Therefore, a simple ingress replication tunnel
   is all that is needed.  In case of multi-homing to three or more EVPN
   PEs, then other tunnel types such as P2MP, MP2MP, BIER, and Assisted
   Replication can be considered.  It should be noted that this intra-ES
   tunnel is only needed for All-Active multi-homing and it is not
   required for Single- Active multi-homing.

   The EVPN PEs belonging to a given All-Active ES discover each other
   using EVPN Ethernet Segment route per procedures described in
   [RFC7432].  These EVPN PEs perform DF election per [RFC7432],
   [I-D.ietf-bess-evpn-df-election-framework], or other DF election
   algorithms to decide who is a DF for a given BD.  If the BD belongs
   to a tenant that has IRB IP multicast enabled for it, then for fixed-
   mode, each PE sets up an intra-ES tunnel to forward IP multicast
   traffic received locally on that BD to other multi-homing PE(s) for
   that ES.  Therefore, IP multicast traffic received via a local
   attachment circuit is sent on this tunnel and on the associated IRB
   interface for that BT and other local attachment circuits if there
   are interested receivers for them.  The other multi-homing EVPN PEs
   treat this intra-ES tunnel just like their local ACs - i.e., the
   multicast traffic received over this tunnel is treated as if it is
   received via its local AC.  Thus, the multi-homing PEs cannot receive
   the same IP multicast flow from an MVPN tunnel (e.g., over an IRB
   interface for that BD) because between a source behind a local AC




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   versus a source behind a remote PE, the PE always chooses its local
   AC.

   When ingress replication is used for intra-ES tunnel, every PE in the
   All-Active multi-homing ES has all the information to setup these
   tunnels - i.e., a) each PE knows what are the other multi-homing PEs
   for that ES via EVPN Ethernet Segment route and can use this
   information to setup intra-ES/Intra-Subnet IP multicast tunnel among
   themselves.

   If a source exists behind inter-subnet tunnel, it is possible that
   more than one multihomed PEs send MVPN join towards remote PE based
   on incoming join on their local interfaces.  When the traffic is
   received on the inter-subnet tunnel, it is sent towards locally
   attached receivers.  Only DF sends traffic towards multihomed
   ethernet segment.  Traffic received on the inter-subnet tunnel,
   should not be sent towards intra-ES tunnel.

7.2.  Intra-Subnet BUM Tunnel

   As the name implies, this tunnel is setup to carry BUM traffic for a
   given subnet/BD among EVNP PEs.  In [RFC7432] , this overlay tunnel
   is used for transmission of all BUM traffic including user IP
   multicast traffic.  However, for multicast traffic handling in EVPN-
   IRB PEs, this tunnel is used for all broadcast, unknown-unicast, non-
   IP multicast traffic, and link-local IP multicast traffic - i.e., it
   is used for all BUM traffic except user IP multicast traffic.  This
   tunnel is setup using IMET route for a given EVI/BD.  The composition
   and advertisement of IMET routes are exactly per [RFC7432] . It
   should be noted that when an EVPN All-Active multi-homing PE uses
   both this tunnel as well as intra-ES tunnel, there SHALL be no
   duplication of multicast traffic over the network because they carry
   different types of multicast traffic - i.e., intra-ES tunnel among
   multi-homing PEs carries only user IP multicast traffic; whereas,
   intra-subnet BUM tunnel carries link-local IP multicast traffic and
   BUM traffic (w/ non-IP multicast).

7.3.  Inter-Subnet IP Multicast Tunnel

   As its name implies, this tunnel is setup to carry IP-only multicast
   traffic for a given tenant across all its subnets (BDs) among EVPN
   and MVPN PEs.

   The following NLRIs from [RFC6514] is used for setting up this inter-
   subnet tunnel in the network.






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       Intra-AS I-PMSI A-D route is used for the setup of default
       underlay tunnel (also called inclusive tunnel) for a tenant IP-
       VRF.  The tunnel attributes are indicated using PMSI attribute
       with this route.

       S-PMSI A-D route is used for the setup of Customer flow specific
       underlay tunnels.  This enables selective delivery of data to PEs
       having active receivers and optimizes fabric bandwidth
       utilization.  The tunnel attributes are indicated using PMSI
       attribute with this route.

   Each EVPN PE supporting a specific MVPN instance discovers the set of
   other PEs in its AS that are attached to sites of that MVPN using
   Intra-AS I-PMSI A-D route (route type 1) per [RFC6514].  It can also
   discover the set of other ASes that have PEs attached to sites of
   that MVPN using Inter-AS I-PMSI A-D route (route type 2) per
   [RFC6514].  After the discovery of PEs that are attached to sites of
   the MVPN, an inclusive overlay tree (I-PMSI) can be setup for
   carrying tenant multicast flows for that MVPN; however, this is not a
   requirement per [RFC6514] and it is possible to adopt a policy in
   which all tenant flows are carried on S-PMSIs.

   An EVPN-IRB PE sends a user IP multicast flow to other EVPN and MVPN
   PEs over this inter-subnet tunnel that is instantiated using MVPN I-
   PMSI or S-PMSI.  This tunnel can be considered as being originated
   and terminated from/to among IP-VRFs of EVPN/MVPN PEs; whereas,
   intra- subnet tunnel is originated/terminated among MAC-VRFs of EVPN
   PEs.

7.4.  IGMP Hosts as TSes

   If a tenant system which is an IGMP host is multi-homed to two or
   more EVPN PEs using All-Active multi-homing, then IGMP join and leave
   messages are synchronized between these EVPN PEs using EVPN IGMP Join
   Synch route (route type 7) and EVPN IGMP Leave Synch route (route
   type 8) per [I-D.ietf-bess-evpn-igmp-mld-proxy].  IGMP states are
   built in the corresponding BDs of the multi-homing EVPN PEs.  In
   [I-D.ietf-bess-evpn-igmp-mld-proxy] the DF PE for that BD originates
   an EVPN Selective Multicast Tag route (SMET route) route to other
   EVPN PEs.  However, in here there is no need to use SMET because the
   IGMP messages are terminated by the EVPN-IRB PE and tenant (*,G) or
   (S,G) join messages are sent via MVPN Shared Tree Join route (route
   type 6) or Source Tree Join route (route type 7) respectively of
   MCAST-VPN NLRI per [RFC6514].  In case of a network with only IGMP
   hosts, the preferred mode of operation is that of Shortest Path
   Tree(SPT) per section 14 of [RFC6514].  This mode is only supported
   for PIM-SM and avoids the RP configuration overhead.  Such mode is
   chosen by provisioning/ configuration.



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7.5.  TS PIM Routers

   Just like a MVPN PE, an EVPN PE runs a separate tenant multicast
   routing instance (VPN-specific) per MVPN instance and the following
   tenant multicast routing instances are supported:

        - PIM Sparse Mode (PIM-SM) with the ASM service model
        - PIM Sparse Mode with the SSM service model
        - PIM Bidirectional Mode (BIDIR-PIM), which uses bidirectional
          tenant-trees to support the ASM service model

   A given tenant's PIM join messages for (*,G) or (S, G) are processed
   by the corresponding tenant multicast routing protocol and they are
   advertised over MPLS/IP network using Shared Tree Join route (route
   type 6) and Source Tree Join route (route type 7) respectively of
   MCAST-VPN NLRI per [RFC6514].

8.  Data Plane Operation

   When an EVPN-IRB PE receives an IGMP/MLD join message over one of its
   Attachment Circuits (ACs), it adds that AC to its Layer-2 (L2) OIF
   list.  This L2 OIF list is associated with the MAC-VRF/BT
   corresponding to the subnet of the tenant device that sent the IGMP/
   MLD join.  Therefore, tenant (S,G) or (*,G) forwarding entries are
   created/updated for the corresponding MAC-VRF/BT based on these
   source and group IP addresses.  Furthermore, the IGMP/MLD join
   message is propagated over the corresponding IRB interface and it is
   processed by the tenant multicast routing instance which creates the
   corresponding tenant (S,G) or (*,G) Layer-3 (L3) forwarding entries.
   It adds this IRB interface to the L3 OIF list.  An IRB is removed as
   a L3 OIF when all L2 tenant (S,G) or (*,G) forwarding states is
   removed for the MAC-VRF/BT associated with that IRB.  Furthermore,
   tenant (S,G) or (*,G) L3 forwarding state is removed when all of its
   L3 OIFs are removed - i.e., all the IRB and L3 interfaces associated
   with that tenant (S,G) or (*,G) are removed.

   When an EVPN PE receives IP multicast traffic from one of its AC, if
   it has any attached receivers for that subnet, it performs L2
   switching of the intra-subnet traffic within the BT attached to that
   AC.  If the multicast flow is received over an AC that belongs to an
   All-Active ES, then the multicast flow is also sent over the intra-
   ES/Intra-Subnet tunnel among multi-homing PEs.  The EVPN PE then
   sends the multicast traffic over the corresponding IRB interface.
   The multicast traffic then gets routed in the corresponding IP-VRF
   and it gets forwarded to interfaces in the L3 OIF list which can
   include other IRB interfaces, other L3 interfaces directly connected
   to TSes, and the MVPN Inter-Subnet tunnel which is instantiated by an
   I-PMSI or S-PMSI tunnel.  When the multicast packet is routed within



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   the IP- VRF of the EVPN PE, its Ethernet header is stripped and its
   TTL gets decremented as the result of this IP routing.  When the
   multicast traffic is received on an IRB interface by the BT
   corresponding to that interface, it gets L2 switched and sent over
   ACs that belong to the L2 OIF list.

8.1.  Intra-Subnet L2 Switching

   Rcvr1 in Figure 1 is connected to PE1 in MAC-VRF1 (same as Src1) and
   sends IGMP join for (C-S, C-G), IGMP snooping will record this state
   in local bridging entry.  A routing entry will be formed as well
   which will point to MAC-VRF1 as RPF for Src1.  We assume that Src1 is
   known via ARP or similar procedures.  Rcvr1 will get a locally
   bridged copy of multicast traffic from Src1.  Rcvr3 is also connected
   in MAC-VRF1 but to PE2 and hence would send IGMP join which will be
   recorded at PE2.  PE2 will also form routing entry and RPF will be
   assumed as Tenant Tunnel "Tenant1" formed beforehand using MVPN
   procedures.  Also this would cause multicast control plane to
   initiate a BGP MCAST-VPN type 7 route which would include VRI for PE1
   and hence be accepted on PE1.  PE1 will include Tenant1 tunnel as
   Outgoing Interface (OIF) in the routing entry.  Now, since it has
   knowledge of remote receivers via MVPN control plane it will
   encapsulate original multicast traffic in Tenant1 tunnel towards
   core.

8.2.  Inter-Subnet L3 Routing

   Rcvr2 in Figure 1 is connected to PE1 in MAC-VRF2 and hence PE1 will
   record its membership in MAC-VRF2.  Since MAC-VRF2 is enabled with
   IRB, it gets added as another OIF to routing entry formed for (C-S,
   C-G).  Rcvr2 and Rcvr4 are also in different MAC-VRFs than multicast
   speaker Src1 and hence need Inter-subnet forwarding.  PE2 will form
   local bridging entry in MAC-VRF2 due to IGMP joins received from
   Rcvr3 and Rcvr4 respectively.  PE2 now adds another OIF 'MAC-VRF2' to
   its existing routing entry.  But there is no change in control plane
   states since its already sent MVPN route and no further signaling is
   required.  Also since Src1 is not part of MAC-VRF2 subnet, it is
   treated as routing OIF and hence MAC header gets modified as per
   normal procedures for routing.  PE3 forms routing entry very similar
   to PE2.  It is to be noted that PE3 does not have MAC-VRF1 configured
   locally but still can receive the multicast data traffic over Tenant1
   tunnel formed due to MVPN procedures

9.  DCs with only EVPN PEs

   As mentioned earlier, the proposed solution can be used as a routed
   multicast solution in data center networks with only EVPN PEs (e.g.,
   routed multicast VPN only among EVPN PEs).  It should be noted that



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   the scope of intra-subnet forwarding for the solution described in
   this document, is limited to a single EVPN PE for Single-Active
   multi-homing and to multi-homing PEs for All-Active multi-homing.  In
   other words, the IP multicast traffic that needs to be forwarded from
   the source PE to remote PEs is routed to remote PEs regardless of
   whether the traffic is intra-subnet or inter-subnet.  As the result,
   the TTL value for intra-subnet traffic that spans across two or more
   PEs get decremented.

   However, if there are applications that require intra-subnet
   multicast traffic to be L2 forwarded, Section 11 discusses some
   options to support applications having TTL value 1.  The procedure
   discussed in Section 11 may be used to support applications that
   require intra-subnet multicast traffic to be L2 forwarded.

9.1.  Setup of overlay multicast delivery

   It must be emphasized that this solution poses no restriction on the
   setup of the tenant BDs and that neither the source PE, nor the
   receiver PEs do not need to know/learn about the BD configuration on
   other PEs in the MVPN.  The Reverse Path Forwarder (RPF) is selected
   per the tenant multicast source and the IP-VRF in compliance with the
   procedures in [RFC6514], using the incoming EVPN route type 2 or 5
   NLRI per [RFC7432].

   The VRF Route Import (VRI) extended community that is carried with
   the IP-VPN routes in [RFC6514] MUST be carried with the EVPN unicast
   routes when these routes are used.  The construction and processing
   of the VRI are consistent with [RFC6514].  The VRI MUST uniquely
   identify the PE which is advertising a multicast source and the IP-
   VRF it resides in.

   VRI is constructed as following:

       - The 4-octet Global Administrator field MUST be set to an IP
         address of the PE.  This address SHOULD be common for all the
         IP-VRFs on the PE (e.g., this address may be the PE's loopback
         address or VTEP address).

       - The 2-octet Local Administrator field associated with a given
         IP-VRF contains a number that uniquely identifies that IP-VRF
         within the PE that contains the IP-VRF.

   EVPN PE MUST have Route Target Extended Community to import/export
   MVPN routes.  In data center environment, it is desirable to have
   this RT configured using auto-generated method than static
   configuration.




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   The following is one recommended model to auto-generate MVPN RT:

      - The Global Administrator field of the MVPN RT MAY be set
        to BGP AS Number.

      - The Local Administrator field of the MVPN RT MAY be set to
        the VNI associated with the tenant VRF.

   Every PE which detects a local receiver via a local IGMP join or a
   local PIM join for a specific source (overlay SSM mode) MUST
   terminate the IGMP/PIM signaling at the IP-VRF and generate a (C-S,C-
   G) via the BGP MCAST-VPN route type 7 per [RFC6514] if and only if
   the RPF for the source points to the fabric.  If the RPF points to a
   local multicast source on the same MAC-VRF or a different MAC-VRF on
   that PE, the MCAST-VPN MUST NOT be advertised and data traffic will
   be locally routed/bridged to the receiver as detailed in section 6.2.

   The VRI received with EVPN route type 2 or 5 NLRI from source PE will
   be appended as an export route-target extended community.  More
   details about handling of various types of local receivers are in
   section 10.  The PE which has advertised the unicast route with VRI,
   will import the incoming MCAST-VPN NLRI in the IP-VRF with the same
   import route-target extended-community and other PEs SHOULD ignore
   it.  Following such procedure the source PE learns about the
   existence of at least one remote receiver in the tenant overlay and
   programs data plane accordingly so that a single copy of multicast
   data is forwarded into the fabric using tenant VRF tunnel.

   If the multicast source is unknown (overlay ASM mode), the MCAST-VPN
   route type 6 (C-*,C-G) join SHOULD be targeted towards the designated
   overlay Rendezvous Point (RP) by appending the received RP VRI as an
   export route-target extended community.  Every PE which detects a
   local source, registers with its RP PE.  That is how the RP learns
   about the tenant source(s) and group(s) within the MVPN.  Once the
   overlay RP PE receives either the first remote (C-RP,C-G) join or a
   local IGMP/PIM join, it will trigger an MCAST-VPN route type 7 (C-
   S,C-G) towards the actual source PE for which it has received PIM
   register message in full compliance with regular PIM procedures.
   This involves the source PE to advertise the MCAST-VPN Source Active
   A-D route (MCAST-VPN route-type 5) towards all PEs.  The Source
   Active A- D route is used to inform all PEs in a given MVPN about the
   active multicast source for switching from RPT to SPT when MVPNs use
   tenant RP-shared trees (i.e., rooted at tenant's RP) per section 13
   of [RFC6514].  This is done in order to choose a single forwarder PE
   and to suppress receiving duplicate traffic.  In such scenarios, the
   active multicast source is used by the receiver PEs to join the SPT
   if they have not received tenant (S,G) joins and by the RPT PEs to
   prune off the tenant (S,G) state from the RPT.  The Source Active A-D



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   route is also used for MVPN scenarios without tenant RP-shared trees.
   In such scenarios, the receiver PEs with tenant (*,G) states use the
   Source Active A-D route to know which upstream PEs with sources
   behind them to join per section 14 of [RFC6514] - i.e., to suppress
   joining Overlay shared tree.

9.2.  Handling of different encapsulations

   Just as in [RFC6514] the MVPN I-PMSI and S-PMSI A-D routes are used
   to form the overlay multicast tunnels and signal the tunnel type
   using the P-Multicast Service Interface Tunnel (PMSI Tunnel)
   attribute.

9.2.1.  MPLS Encapsulation

   The [RFC6514] assumes MPLS/IP core and there is no modification to
   the signaling procedures and encoding for PMSI tunnel formation
   therein.  Also, there is no need for a gateway to inter-operate with
   non-EVPN PEs supporting [RFC6514] based MVPN over IP/MPLS.

9.2.2.  VxLAN Encapsulation

   In order to signal VXLAN, the corresponding BGP encapsulation
   extended community [I-D.ietf-idr-tunnel-encaps] SHOULD be appended to
   the MVPN I- PMSI and S-PMSI A-D routes.  The MPLS label in the PMSI
   Tunnel Attribute MUST be the Virtual Network Identifier (VNI)
   associated with the customer MVPN.  The supported PMSI tunnel types
   with VXLAN encapsulation are: PIM-SSM Tree, PIM-SM Tree, BIDIR-PIM
   Tree, Ingress Replication [RFC6514].  Further details are in
   [RFC8365].

   In this case, a gateway is needed for inter-operation between the
   EVPN PEs and non-EVPN MVPN PEs.  The gateway should re-originate the
   control plane signaling with the relevant tunnel encapsulation on
   either side.  In the data plane, the gateway terminates the tunnels
   formed on either side and performs the relevant stitching/re-
   encapsulation on data packets.

9.2.3.  Other Encapsulation

   In order to signal a different tunneling encapsulation such as NVGRE,
   GPE, or GENEVE the corresponding BGP encapsulation extended community
   [I-D.ietf-idr-tunnel-encaps] SHOULD be appended to the MVPN I-PMSI
   and S-PMSI A-D routes.  If the Tunnel Type field in the encapsulation
   extended- community is set to a type which requires Virtual Network
   Identifier (VNI), e.g., VXLAN-GPE or NVGRE
   [I-D.ietf-idr-tunnel-encaps], then the MPLS label in the PMSI Tunnel
   Attribute MUST be the VNI associated with the customer MVPN.  Same as



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   in VXLAN case, a gateway is needed for inter- operation between the
   EVPN-IRB PEs and non-EVPN MVPN PEs.

10.  DCI with MPLS in WAN and VxLAN in DCs

   This section describers the inter-operation between MVPN PEs in WAN
   using MPLS encapsulation with EVPN PEs in a DC network using VxLAN
   encapsulation.  Since the tunnel encapsulation between these networks
   are different, we must have at least one gateway in between.
   Usually, two or more are required for redundancy and load balancing
   purpose.  In such scenarios, a DC network can be represented as a
   customer network that is multi-homed to two or more MVPN PEs via L3
   interfaces and thus standard MVPN multi-homing procedures are
   applicable here.  It should be noted that a MVPN overlay tunnel over
   the DC network is terminated on the IP-VRF of the gateway and not the
   MAC-VRF/BTs.  Therefore, the considerations for loop prevention and
   split-horizon filtering described in [I-D.ietf-bess-dci-evpn-overlay]
   are not applicable here.  Some aspects of the multi-homing between
   VxLAN DC networks and MPLS WAN is in common with
   [I-D.ietf-bess-dci-evpn-overlay] .

10.1.  Control plane inter-connect

   The gateway(s) MUST be setup with the inclusive set of all the IP-
   VRFs that span across the two domains.  On each gateway, there will
   be at least two BGP sessions: one towards the DC side and the other
   towards the WAN side.  Usually for redundancy purpose, more sessions
   are setup on each side.  The unicast route propagation follows the
   exact same procedures in [I-D.ietf-bess-dci-evpn-overlay].  Hence, a
   multicast host located in either domain, is advertised with the
   gateway IP address as the next-hop to the other domain.  As a result,
   PEs view the hosts in the other domain as directly attached to the
   gateway and all inter-domain multicast signaling is directed towards
   the gateway(s).  Received MVPN routes type 1-7 from either side of
   the gateway(s), MUST NOT be reflected back to the same side but
   processed locally and re-advertised (if needed) to the other side:

   o  Intra-AS I-PMSI A-D Route: these are distributed within each
      domain to form the overlay tunnels which terminate at gateway(s).
      They are not passed to the other side of the gateway(s).

   o  C-Multicast Route: joins are imported into the corresponding IP-
      VRF on each gateway and advertised as a new route to the other
      side with the following modifications (the rest of NLRI fields and
      path attributes remain on-touched):

      *  Route-Distinguisher is set to that of the IP-VRF




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      *  Route-target is set to the exported route-target list on IP-VRF

      *  The PMSI tunnel attribute and BGP Encapsulation extended
         community will be modified according to section 8

      *  Next-hop will be set to the IP address which represents the
         gateway on either domain

   o  Source Active A-D Route: same as joins

   o  S-PMSI A-D Route: these are passed to the other side to form
      selective PMSI tunnels per every (C-S,C-G) from the gateway to the
      PEs in the other domain provided it contains receivers for the
      given (C-S, C-G).  Similar modifications made to joins are made to
      the newly originated S-PMSI.

   In addition, the Originating Router's IP address is set to GW's IP
   address.  Multicast signaling from/to hosts on local ACs on the
   gateway(s) are generated and propagated in both domains (if needed)
   per the procedures in section 7 in this document and in [RFC6514]
   with no change.  It must be noted that for a locally attached source,
   the gateway will program an OIF per every domain from which it
   receives a remote join in its forwarding plane and different
   encapsulation will be used on the data packets.

10.2.  Data plane inter-connect

   Traffic forwarding procedures on gateways are same as those described
   for PEs in section 5 and 6 except that, unlike a non-border leaf PE,
   the gateway will not only route the incoming traffic from one side to
   its local receivers, but will also send it to the remote receivers in
   the the other domain after de-capsulation and appending the right
   encapsulation.  The OIF and IIF are programmed in FIB based on the
   received joins from either side and the RPF calculation to the source
   or RP.  The de-capsulation and encapsulation actions are programmed
   based on the received I-PMSI or S-PMSI A-D routes from either sides.
   If there are more than one gateway between two domains, the multi-
   homing procedures described in the following section must be
   considered so that incoming traffic from one side is not looped back
   to the other gateway.

   The multicast traffic from local sources on each gateway flows to the
   other gateway with the preferred WAN encapsulation.








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11.  Supporting application with TTL value 1

   It is possible that some deployments may have a host on the tenant
   domain that sends multicast traffic with TTL value 1.  The interested
   receiver for that traffic flow may be attached to different PEs on
   the same subnet.  The procedures specified in section 6 always routes
   the traffic between PEs for both intra and inter subnet traffic.
   Hence traffic with TTL value 1 is dropped due to the nature of
   routing.

   This section discusses few possible ways to support traffic having
   TTL value 1.  Implementation MAY support any of the following model.

11.1.  Policy based model

   Policies may be used to enforce EVPN BUM procedure for traffic flows
   with TTL value 1.  Traffic flow that matches the policy is excluded
   from seamless interop procedure specified in this document, hence TTL
   decrement issue will not apply.

11.2.  Exercising BUM procedure for VLAN/BD

   Servers/hosts sending the traffic with TTL value 1 may be attached to
   a separate VLAN/BD, where multicast routing is disabled.  When
   multicast routing is disabled, EVPN BUM procedure may be applied to
   all traffic ingressing on that VLAN/BD.  On the Egress PE, the RPF
   for such traffic may be set to BD interface, where the source is
   attached.

11.3.  Intra-subnet bridging

   The procedure specified in the section enables a PE to detect an
   attached subnet source (i.e., source that is directly attached in the
   tenant BD/VLAN).  By applying the following procedure for the
   attached source, Traffic flows having TTL value 1 can be supported.

       - On the ingress PE, do the bridging on the interface towards the
         core interface
       - On the egress side, make a decision whether to bridge or route
         at the outgoing interface (OIF) based on whether the source is
         attached to the OIF's BD/VLAN or not.

   Recent ASIC supports single lookup forwarding for brigading and
   routing (L2+L3).  The procedure mentioned here leverages this ASIC
   capability.






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                       PE1
                      +------------+
              S11 +---+(BD1)       |  +---------+
                      |  \         |  |         |
                      |(IP-VRF)-(CORE)|         |
                      |  /         |  |         |
              R12 +---+(BD2)       |  |         |
                      +------------+  |         |
                                      |         |
                       PE2            | VXLAN.  |
                      +------------+  |         |
              R21 +---+(BD1)       |  |         |
                      |  \         |  |         |
                      |(IP-VRF)-(CORE)|         |
                      |  /         |  |         |
              R22+----+(BD3)       |  +---------+
                      +------------+


                            Figure 3 Intra-subnet bridging


   Consider the above picture.  In the picture

        - PE1 and PE2 are seamless interop capable PEs
        - S11 is a multicast host directly attached to PE1 in BD1
        - Source S11 sends traffic to Group G11
        - R21, R22 are IGMP receivers for group G11
        - R21 and R22 are attached to BD1 and BD3 respectively at PE2.

   When source S11 starts sending the traffic, PE1 learns the source and
   announces the source using MVPN procedures to the remote PEs.

   At PE2, IGMP joins from R21, R22 result the creation of (*,G11) entry
   with outgoing OIF as IRB interface of BD1 and BD3.  When PE2 learns
   the source information from PE1, it installs the route (S11, G11) at
   the tenant VRF with RPF as CORE interface.

   PE2 inherits (*, G11) OIFs to (S11, G11) entry.  While inheriting
   OIF, PE2 checks whether source is attached to OIF's subnet.  OIF
   matching source subnet is added with flag indicating bridge only
   interface.  In case of (S11, G11) entry, BD1 is added as the bridge
   only OIF, while BD3 is added as normal OIF(L3 OIF).  PEs (PE2) sends
   MVPN join (S11, G11) towards PE1, since it has local receivers.

   At Ingress PE(PE1), CORE interface is added to (S11, G11) entry as an
   OIF (outgoing interface) with a flag indicating that bridge only
   interface.  With this procedure, ingress PE(PE1) bridges the traffic



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   on CORE interface.  (PE1 retains the TTL and source-MAC).  The
   traffic is encapsulated with VNI associated with CORE
   interface(L3VNI).  PE1 also routes the traffic for R12 which is
   attached to BD2 on the same device.

   PE2 decapsulates the traffic from PE1 and does inner lookup on the
   tenant VRF associated with incoming VNI.  Traffic lookup on the
   tenant VRF yields (S11, G11) entry as the matching entry.  Traffic
   gets bridged on BD1 (PE2 retains the TTL and source-MAC) since the
   OIF is marked as bridge only interface.  Traffic gets routed on BD2.

12.  Interop with L2 EVPN PEs

   A gateway device is needed to do interop between EVPN PEs that
   support seamless interop procedure specified in this document and
   L2EVPN-PEs.  A tenant domain can be provisioned with one or more such
   gateway devices known as "Seamless interop EVPN Multicast Gateway
   (SEMG)".  PE that is configured as SEMG must be provisioned with all
   BDs that are available in the tenant domain.

   When advertising IMET route for a BD, PE configured as SEMG
   advertises EVPN Multicast Flags Extended Community with SEMG flag
   set.  Given set of eligible PEs, one PE is selected as the SEMG
   designated forwarder (SEMG-DF).  PE should use procedure specified in
   [I-D.ietf-bess-evpn-df-election-framework] for the SEMG DF election.

   L2EVPN PE may or may not have support for
   [I-D.ietf-bess-evpn-igmp-mld-proxy].  Procedure specified in the
   section supports both such PEs.

   [I-D.ietf-bess-evpn-igmp-mld-proxy] support is recommended for
   seamless interop capable PE.  The following section describes interop
   procedure assuming that seamless interop capable PE supports
   [I-D.ietf-bess-evpn-igmp-mld-proxy].

   SEMG-DF has the following special responsibilities on a BD for which
   it is the DF

   o  Process IGMP control packets from remote L2 EVPN PEs that doesn't
      support [I-D.ietf-bess-evpn-igmp-mld-proxy].

   o  Process EVPN SMET routes from remote L2 EVPN PE that support
      [I-D.ietf-bess-evpn-igmp-mld-proxy] and creates L2 multicast
      state.  (Remote IGMP join and SMET route in-turn triggers creation
      of L3 multicast state similar to IGMP join received on local AC)

   o  Originate SMET(*,*) route towards L2EVPN PEs.  This is to attract
      traffic from L2EPN PEs that support



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      [I-D.ietf-bess-evpn-igmp-mld-proxy]. ( L2EVPN PEs that doesn't
      support [I-D.ietf-bess-evpn-igmp-mld-proxy] will drop this route )

   o  Forward the incoming traffic (S,G) from MVPN side (including non
      DF SEMG) to

      *  Locally attached receivers on all BDs

      *  Send the traffic via L2 BUM tunnels, if it has L2 forwarding
         state due to

         +  incoming SMET route from remote L2EVPN PEs or

         +  due to incoming IGMP control packets

         (SEMG-DF could send the traffic on multiple BDs, if the PE ends
         up being DF for more than one customer BDs and if remote
         receivers exist on those BD)

   o  When it receives traffic from L2 EVPN PE on the intra-subnet
      tunnel on BD-X

      *  Performs FHR functionality

      *  Should advertise host route with L3 label and VRF Route-Import
         corresponds to PE's tenant domain

      *  Send the traffic towards local attached receivers

      *  Send the traffic towards MVPN tunnel for the remote L3
         receivers

      *  Send the traffic towards L2EVPN receiver on BDs other than
         incoming BD

   All seamless interop capable PEs other than SEMG should discard SMET
   routes that is coming from L2EVPN PEs and must discard all IGMP
   control packets, if any received on the intra-subnet tunnel.  SEMG
   should discard incoming SMET routes and IGMP joins from L2EVPN PEs,
   if it is not the DF for the incoming BD.

   If [I-D.ietf-bess-evpn-igmp-mld-proxy] support is not available SEMG-
   DF, It should get all multicast traffic from L2EVPN PEs.  This may be
   achieved by sending IGMP query or PIM hello on the intra-subnet
   tunnel.  The exact of procedure is outside the scope of this
   document.





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   When [I-D.ietf-bess-evpn-igmp-mld-proxy] is supported both at
   seamless interop capable PE and L2EVPN PE, selective forwarding is
   done based on receiver interest at the egress-PE, when overlay tunnel
   type is Ingress-replication or selective tunnel.

13.  Connecting external Multicast networks or PIM routers.

   External multicast networks or PIM routers can be attached to any
   seamless interop capable EVPN-PEs or set of EVPN-PEs.  Multicast
   network or PIM router can also be attached to any IRB enabled BDI
   interface or L3 enabled interface or set of interfaces.  The fabric
   can be used as a Transit network.  All PIM signaling is terminated at
   EVPN-PEs.

   No additional procedures are required while connecting external
   multicast networks.

14.  RP handling

   This section describes various RP models for a tenant VRF.  The RP
   model SHOULD be consistent across all EVPN-PEs for given group/group
   range in the tenant VRF.

14.1.  Various RP deployment options

14.1.1.  RP-less mode

   EVPN fabric without having any external multicast network/attached
   MVPN network, doesn't need RP configuration.  A configuration option
   SHALL be provided to the end user to operate the fabric in RP less
   mode.  When an EVPN-PE is operating in RP-less mode, EVPN-PE MUST
   advertise all attached sources to remote EVPN PEs using procedure
   specified in [RFC6514].

   In RP less mode, (C-*,C-G) RPF may be set to NULL or may be set to
   wild card interface( Any interface on the tenant VRF).  In RP-less
   mode, traffic is always forwarded based on (C-S,C-G) state.

14.1.2.  Fabric anycast RP

   In this model, anycast GW IP address is configured as RP in all EVPN-
   PE.  When an EVPN-PE is operating in Fabric anycast-RP mode, an EVPN-
   PE MUST advertise all sources behind that PE to other EVPN PEs using
   procedure specified in [RFC6514].  In this model, Sources may be
   directly attached to tenant BDs or sources may be attached behind a
   PIM router (In that case EVPN-PE learns source information due to PIM
   register terminating at RP interface at the tenant VRF side)




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   In RP-less mode and Fabric anycast RP mode, EVPN-PE operates SPT-only
   mode as per section 14 of [RFC6514].

14.1.3.  Static RP

   The procedure specified in this document supports configuring EVPN
   fabric with static RP.  RP can be configured in the EVPN-PE itself in
   the tenant VRF or in the external multicast networks connected behind
   an EVPN PE or in the MVPN network.  When RPF is not local to EVPN-PE,
   EVPN-PE operates in rpt-spt mode as PER procedures specified in
   section 13 of [RFC6514].

14.1.4.  Co-existence of Fabric anycast RP and external RP

   External multicast network using its own RP may be connected to EVPN
   fabric operating with Fabric anycast RP mode.  In this case, subset
   of EVPN-PEs may be designated as border leafs.  Anycast RP may be
   configured between border leafs and external RP.  Border leafs
   originates SA-AD routes for external sources towards fabric PEs.
   Border leaf acts as FHR for the sources inside the fabric.
   Configuration option may be provided to define the PE role as BL.

14.2.  RP configuration options

   PIM Bidir and PIM-SM ASM mode require Rendezvous point (RP)
   configuration, which acts as a shared root for a multicast shared
   tree.  RP can be configured using static configuration or by using
   BSR or Auto-RP procedures on the tenant VRF.  This document only
   discusses static RP configuration.  The use of BSR or Auto-RP
   procedure in the EVPN fabric is beyond the scope of this document.

15.  IANA Considerations

   IANA is requested to assign new flags in the "Multicast Flags
   Extended Community Flags" registry for the following.

   o  Seamless interop capable PE

   o  SEMG

16.  Security Considerations

   All the security considerations in [RFC7432] apply directly to this
   document because this document leverages [RFC7432] control plane and
   their associated procedures.






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17.  Acknowledgements

   The authors would like to thank Niloofar Fazlollahi, Aamod
   Vyavaharkar, Raunak Banthia, and Swadesh Agrawal for their
   discussions and contributions.

18.  References

18.1.  Normative References

   [I-D.ietf-bess-dci-evpn-overlay]
              Rabadan, J., Sathappan, S., Henderickx, W., Sajassi, A.,
              and J. Drake, "Interconnect Solution for EVPN Overlay
              networks", draft-ietf-bess-dci-evpn-overlay-10 (work in
              progress), March 2018.

   [I-D.ietf-bess-evpn-df-election-framework]
              Rabadan, J., satyamoh@cisco.com, s., Sajassi, A., Drake,
              J., Nagaraj, K., and S. Sathappan, "Framework for EVPN
              Designated Forwarder Election Extensibility", draft-ietf-
              bess-evpn-df-election-framework-09 (work in progress),
              January 2019.

   [I-D.ietf-bess-evpn-igmp-mld-proxy]
              Sajassi, A., Thoria, S., Patel, K., Drake, J., and W. Lin,
              "IGMP and MLD Proxy for EVPN", draft-ietf-bess-evpn-igmp-
              mld-proxy-05 (work in progress), April 2020.

   [I-D.ietf-bess-evpn-inter-subnet-forwarding]
              Sajassi, A., Salam, S., Thoria, S., Drake, J., and J.
              Rabadan, "Integrated Routing and Bridging in EVPN", draft-
              ietf-bess-evpn-inter-subnet-forwarding-09 (work in
              progress), June 2020.

   [I-D.ietf-idr-tunnel-encaps]
              Patel, K., Velde, G., and S. Ramachandra, "The BGP Tunnel
              Encapsulation Attribute", draft-ietf-idr-tunnel-encaps-15
              (work in progress), December 2019.

   [I-D.skr-bess-evpn-pim-proxy]
              Rabadan, J., Kotalwar, J., Sathappan, S., Zhang, Z., and
              A. Sajassi, "PIM Proxy in EVPN Networks", draft-skr-bess-
              evpn-pim-proxy-01 (work in progress), October 2017.

   [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>.




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   [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>.

   [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>.

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

18.2.  Informative References

   [RFC4389]  Thaler, D., Talwar, M., and C. Patel, "Neighbor Discovery
              Proxies (ND Proxy)", RFC 4389, DOI 10.17487/RFC4389, April
              2006, <https://www.rfc-editor.org/info/rfc4389>.

   [RFC4761]  Kompella, K., Ed. and Y. Rekhter, Ed., "Virtual Private
              LAN Service (VPLS) Using BGP for Auto-Discovery and
              Signaling", RFC 4761, DOI 10.17487/RFC4761, January 2007,
              <https://www.rfc-editor.org/info/rfc4761>.

   [RFC7080]  Sajassi, A., Salam, S., Bitar, N., and F. Balus, "Virtual
              Private LAN Service (VPLS) Interoperability with Provider
              Backbone Bridges", RFC 7080, DOI 10.17487/RFC7080,
              December 2013, <https://www.rfc-editor.org/info/rfc7080>.

   [RFC7209]  Sajassi, A., Aggarwal, R., Uttaro, J., Bitar, N.,
              Henderickx, W., and A. Isaac, "Requirements for Ethernet
              VPN (EVPN)", RFC 7209, DOI 10.17487/RFC7209, May 2014,
              <https://www.rfc-editor.org/info/rfc7209>.

Appendix A.  Use Cases

A.1.  DCs with only IGMP/MLD hosts w/o tenant router

   In a EVPN network consisting of only IGMP/MLD hosts, PE's will
   receive IGMP (*, G) or (S, G) joins from their locally attached host
   and would originate MVPN C-Multicast Route Type 6 and 7 NLRI's
   respectively.  As described in [RFC6514] these NLRI's are directed
   towards RP-PE for Type 6 or Source-PE for Type 7.  In case of (*, G)
   join a Shared-Path Tree will be built in the core from RP-PE towards
   all Receiver-PE's.  Once a Source starts to send Multicast data to



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   specified multicast-group, the PE directly connected to Source will
   do PIM-registration with RP.  Since there are existing receivers for
   the Group, RP will originate a PIM (S, G) join towards Source.  This
   will be converted to MVPN Type 7 NLRI by RP-PE.  Please note that the
   router RP-PE would be the PE configured as RP (e.g., using static
   configuration or by using BSR or Auto- RP procedures).  The detailed
   working of such protocols is beyond the scope of this document.  Upon
   receiving Type 7 NLRI, Source-PE will include MVPN Tunnel in its
   Outgoing Interface List.  Furthermore, Source-PE will follow the
   procedures in [RFC6514] to originate MVPN SA-AD route (RT 5) to avoid
   duplicate traffic and allow all Receiver-PE's to shift from Share-
   Tree to Shortest-Path-Tree rooted at Source-PE.  Section 13 of
   [RFC6514] describes it.

   However a network operator can chose to have only Shortest-Path-Tree
   built in MVPN core as described in section 14 of [RFC6514].  One way
   to achieve this, is for all PE's act as RP for its locally connected
   hosts and thus avoid sending any Shared-Tree Join (MVPN Type 6) into
   the core.  In this scenario, there will be no PIM registration needed
   since all PE's are first-hop router as well as acting RP.  Once a
   source starts to send multicast data, the PE directly connected to it
   originates Source- Active AD (RT 5) to all other PE's in network.
   Upon Receiving Source-Active AD route a PE must cache it in its local
   database and also look for any matching interest for (*, G) where G
   is the multicast group described in received Source-Active AD route.
   If it finds any such matching entry, it must originate a C-Multicast
   route (RT 7) in order to start receiving traffic from Source-PE.
   This procedure must be repeated on reception of any further Source-
   Active AD routes.

A.2.  DCs with mixed of IGMP/MLD hosts & multicast routers running PIM-
      SSM

   This scenario has multicast routers which can send PIM SSM (S, G)
   joins.  Upon receiving these joins and if source described in join is
   learnt to be behind a MVPN peer PE, local PE will originate
   C-Multicast Join (RT 7) towards Source-PE.  It is expected that PIM
   SSM group ranges are kept separate from ASM range for which IGMP
   hosts can send (*, G) joins.  Hence both ASM and SSM groups shall
   operate without any overlap.  There is no RP needed for SSM range
   groups and Shortest Path tree rooted at Source is built once a
   receiver interest is known.









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A.3.  DCs with mixed of IGMP/MLD hosts & multicast routers running PIM-
      ASM

   This scenario includes reception of PIM (*, G) joins on PE's local
   AC.  These joins are handled similar to IGMP (*, G) join as explained
   in sections above.  Another interesting case can arise here is when
   one of the tenant routers can act as RP for some of the ASM Groups.
   In such scenario, a Upstream Multicast Hop (UMH) will be elected by
   other PE's in order to send C-Multicast Routes (RT 6).  All
   procedures described in [RFC6513] with respect to UMH should be used
   to avoid traffic duplication due to incoherent selection of RP-PE by
   different Receiver-PE's.

A.4.  DCs with mixed of IGMP/MLD hosts & multicast routers running PIM-
      Bidir

   Creating Bidirectional (*, G) trees is useful when a customer wants
   least amount of control state in network.  But on downside all
   receivers for a particular multicast group receive traffic from all
   sources sending to that group.  However for the purpose of this
   document, all procedures as described in [RFC6513] and [RFC6514]
   apply when PIM-Bidir is used.

Authors' Addresses

   Ali Sajassi
   Cisco
   170 West Tasman Drive
   San Jose, CA  95134, US

   Email: sajassi@cisco.com


   Kesavan Thiruvenkatasamy
   Cisco
   170 West Tasman Drive
   San Jose, CA  95134, US

   Email: kethiruv@cisco.com


   Samir Thoria
   Cisco
   170 West Tasman Drive
   San Jose, CA  95134, US

   Email: sthoria@cisco.com




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   Ashutosh Gupta
   VMware
   3401 Hillview Ave, Palo Alto, CA 94304

   Email: ashutoshgupta@vmware.com


   Luay Jalil
   Verizon

   Email: luay.jalil@verizon.com








































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