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Versions: 00 01

BESS Working Group                                            A. Sajassi
Internet Draft                                                 S. Thoria
Category: Standard Track                                           Cisco
                                                                A. Gupta
                                                            Avi Networks

Expires: October 26, 2018                                 April 26, 2018


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

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 to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

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

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."



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   described in the Simplified BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Requirements Language  . . . . . . . . . . . . . . . . . . . .  5
   3.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  5
   4.  Requirements . . . . . . . . . . . . . . . . . . . . . . . . .  6
     4.1. Optimum Forwarding  . . . . . . . . . . . . . . . . . . . .  6
     4.2. Optimum Replication . . . . . . . . . . . . . . . . . . . .  6
     4.3. All-Active and Single-Active Multi-Homing . . . . . . . . .  7
     4.4. Inter-AS Tree Stitching . . . . . . . . . . . . . . . . . .  7
     4.5. EVPN Service Interfaces . . . . . . . . . . . . . . . . . .  7
     4.6. Distributed Anycast Gateway . . . . . . . . . . . . . . . .  7
     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 . . .  8
   5. IRB Unicast versus IRB Multicast  . . . . . . . . . . . . . . .  8
     5.1. Emulated Virtual LAN Service  . . . . . . . . . . . . . . .  9
   6.  Solution Overview  . . . . . . . . . . . . . . . . . . . . . .  9
     6.1.  Operational Model for EVPN IRB PEs . . . . . . . . . . . .  9
     6.2.  Unicast Route Advertisements for IP multicast Source . . . 12
     6.3.  Multi-homing of IP Multicast Source and Receivers  . . . . 13
       6.3.1.  Single-Active Multi-Homing . . . . . . . . . . . . . . 13
       6.3.2.  All-Active Multi-Homing  . . . . . . . . . . . . . . . 14
     6.4.  Mobility for Tenant's Sources and Receivers  . . . . . . . 16



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     6.5.  Intra-Subnet BUM Traffic Handling  . . . . . . . . . . . . 17
   7.  Control Plane Operation  . . . . . . . . . . . . . . . . . . . 17
     7.1. Intra-subnet/Intra-ES IP multicast tunnel . . . . . . . . . 17
     7.2. Intra-subnet BUM tunnel . . . . . . . . . . . . . . . . . . 18
     7.3. Inter-subnet IP Multicast tunnel  . . . . . . . . . . . . . 18
     7.4.  IGMP Hosts as TSes . . . . . . . . . . . . . . . . . . . . 19
     7.5.  TS PIM Routers . . . . . . . . . . . . . . . . . . . . . . 20
   8  Data Plane Operation  . . . . . . . . . . . . . . . . . . . . . 20
     8.1 Intra-Subnet L2 Switching  . . . . . . . . . . . . . . . . . 21
     8.2 Inter-Subnet L3 Routing  . . . . . . . . . . . . . . . . . . 21
   9.  DCs with only EVPN PEs . . . . . . . . . . . . . . . . . . . . 22
     9.1. Setup of overlay multicast delivery . . . . . . . . . . . . 22
     9.2. Handling of different encapsulations  . . . . . . . . . . . 24
       9.2.1.  MPLS Encapsulation . . . . . . . . . . . . . . . . . . 24
       9.2.2  VxLAN Encapsulation . . . . . . . . . . . . . . . . . . 24
       9.2.3.  Other Encapsulation  . . . . . . . . . . . . . . . . . 24
   10.  DCI with MPLS in WAN and VxLAN in DCs . . . . . . . . . . . . 24
     10.1. Control plane inter-connect  . . . . . . . . . . . . . . . 25
     10.2. Data plane inter-connect . . . . . . . . . . . . . . . . . 26
   11.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27
   12.  Security Considerations . . . . . . . . . . . . . . . . . . . 27
   13.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . 27
   14.  References  . . . . . . . . . . . . . . . . . . . . . . . . . 27
     14.1.  Normative References  . . . . . . . . . . . . . . . . . . 27
     14.2.  Informative References  . . . . . . . . . . . . . . . . . 27
   15.  Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . 28
   Appendix A.  Use Cases . . . . . . . . . . . . . . . . . . . . . . 29
     A.1.  DCs with only IGMP/MLD hosts w/o tenant router . . . . . . 29
     A.2.  DCs with mixed of IGMP/MLD hosts & multicast routers
           running PIM-SSM  . . . . . . . . . . . . . . . . . . . . . 30
     A.3.  DCs with mixed of IGMP/MLD hosts & multicast routers
           running PIM-ASM  . . . . . . . . . . . . . . . . . . . . . 30
     A.4.  DCs with mixed of IGMP/MLD hosts & multicast routers
           running PIM-Bidir  . . . . . . . . . . . . . . . . . . . . 30

















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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 can
   be used as a routed multicast solution in data centers with only EVPN



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   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: 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: 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

   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



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   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



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



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   single multicast tunnel among EVPN and MVPN PEs for IP multicast
   traffic. 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.

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]:

   - VLAN-based service interface
   - VLAN-bundle service interface
   - 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.



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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.

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.


5. IRB Unicast versus IRB Multicast

   [EVPN-IRB] describes the operation for EVPN PEs in IRB mode for
   unicast traffic. The same IRB model for a PE described in [EVPN-IRB],
   where an IP-VRF is attached to one or more bridge tables (BTs) via
   virtual IRB interfaces, is also applicable here. However, there are
   some noticeable differences between the IRB operation for unicast
   traffic described in [EVPN-IRB] 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



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   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.

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 [EVPN-IGMP-PROXY] and [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 can get 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 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



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   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
   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 [RFC 6513]. 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.

















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

                         Figure-1: EVPN & MVPN PEs Seamless Interop


   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.

















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

        1) Unicast route advertisements for IP multicast source
        2) Multi-homing of IP multicast sources and receivers
        3) Mobility for Tenant's sources and receivers
        4) 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 (or 5) and IPVPN unicast route along
   with VRF Route Import extended community. EVPN route type 2 (or 5) is
   advertised with the Route Targets corresponding to both IP-VRF and



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   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 (or 5) and IPVPN unicast route along
   with VRF Route Import extended community. EVPN route type 2 (or 5) 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.


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.



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   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
   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
   PE.

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 an intra-subnet overlay tunnel. There will be a dedicated
   intra-subnet tunnel for this purpose which is different from inter-
   subnet overlay tunnel setup by MVPN procedures.

   When the multi-homing EVPN PEs receive the IP multicast flow via this



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    intra-subnet 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-subnet 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 will serve well. For a
   given ES, since multicast traffic that is locally received by one
   multi-homing PE is sent to other multi-homing PEs via this intra-
   subnet 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-subnet tunnel to other multi-homing PEs (only one
   other in case of dual-homing) for a given ES, is sent regardless of
   whether there is a receiver on these multi-homing PEs.

   By feeding IP multicast flow received on one of the EVPN multi-homing
   PEs to the rest of the EVPN PEs in the multi-homing group, we have
   essentially enabled all the 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-subnet
   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 type can selective or aggregate
   selective or inclusive tree. This gives the network operator the
   maximum flexibility of choosing any overlay tree type that is



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   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-subnet tunnel or MVPN inter-subnet tunnel. Furthermore, if it
   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-
   subnet 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



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   to that receiver only till the new PE for that receiver discovers the
   source and joins the overlay tree for that flow.

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 [RF7432]
   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
   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 5.1.1 for data
   plane operation).



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-subnet/Intra-ES IP multicast tunnel

   2) Intra-subnet BUM tunnel

   3) Inter-subnet IP multicast tunnel


7.1. Intra-subnet/Intra-ES 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 EVPN PEs for that ES to carry multicast flow received by
   one of the multi-homing PEs to the other PEs in that ES. 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-subnet/intra-ES
   tunnel is only needed for All-Active multi-homing and it is not
   required for Single-Active multi-homing.



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   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], [EVPN-
   DF-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 multicast
   enabled for it, then each PE sets up an intra-subnet/intra-ES tunnel
   to forward IP multicast traffic received locally on that BD to other
   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-subnet/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
   versus a source behind a remote PE, the PE always chooses its local
   AC.

   When ingress replication is used for intra-subnet/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 b)
   each PE already knows what MPLS label to use for multicast traffic to
   every other PE for that ES via EVPN IMET route. Both EVPN ES and IMET
   routes are composed and advertised per [RFC7432].


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-subnet/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-subnet/intra-ES
   tunnel carries only user IP multicast traffic; whereas, intra-subnet
   tunnel carries link-local IP multicast traffic and BUM traffic (w/
   non-IP multicast).

7.3. Inter-subnet IP Multicast tunnel



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   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.

      Intra-AS I-PMSI A-D route is used to form 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 to form 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 [IGMP-PROXY]. IGMP states are built in the corresponding
   BDs of the multi-homing EVPN PEs. In [IGMP-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



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   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 SPT-
   only 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.

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



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   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-
   subnet/intra-ES tunnel. 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 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



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   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
   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. Based on past experiences with MVPN over last
   dozen years for supported IP multicast applications, layer-3
   forwarding of intra-subnet multicast traffic should be fine. However,
   if there are applications that require intra-subnet multicast traffic
   to be L2 forwarded (e.g., without decrementing TTL value), then
   [EVPN-IRB-MCAST] proposes a solution to accommodate such
   applications.


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 via the EVPN unicast
   routes instead. 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



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         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.

   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 core VRF 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
   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



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   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 [TUNNEL-ENCAP] 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
   [TUNNEL-ENCAP] 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 [TUNNEL-ENCAP], then the MPLS label
   in the PMSI Tunnel Attribute MUST be the VNI associated with the
   customer MVPN. Same as 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



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   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 [INTERCON-EVPN] are not applicable here. Some
   aspects of the multi-homing between VxLAN DC networks and MPLS WAN is
   in common with [INTERCON-EVPN].

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 [INTERCON-EVPN]. 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:





















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        - 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).

        - 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
                * 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

        - Source Active A-D Route: same as joins

        - 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.



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   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.



11.  IANA Considerations

   There is no additional IANA considerations for PBB-EVPN beyond what
   is already described in [RFC7432].


12.  Security Considerations

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


13.  Acknowledgements

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


14.  References

14.1.  Normative References

   [RFC7432]  A. Sajassi, et al., "BGP MPLS Based Ethernet VPN", RFC
              7432 , February 2015.

   [RFC8365]  A. Sajassi, et al., "A Network Virtualization Overlay
              Solution using EVPN", RFC 8365, February 2018.

   [RFC6513] E. Rosen, et al., "Multicast in MPLS/BGP IP VPNs", RFC6513,
              February 2012.

   [RFC6514] R. Aggarwal, et al., "BGP Encodings and Procedures for
              Multicast in MPLS/BGP IP VPNs", RFC6514, February 2012.


14.2.  Informative References



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   [RFC7080]  A. Sajassi, et al., "Virtual Private LAN Service (VPLS)
              Interoperability with Provider Backbone Bridges", RFC
              7080, December 2013.

   [RFC7209]  D. Thaler, et al., "Requirements for Ethernet VPN (EVPN)",
              RFC 7209, May 2014.

   [RFC4389]  A. Sajassi, et al., "Neighbor Discovery Proxies (ND
              Proxy)", RFC 4389, April 2006.

   [RFC4761]  K. Kompella, et al., "Virtual Private LAN Service (VPLS)
              Using BGP for Auto-Discovery and Signaling", RFC 4761,
              Jauary 2007.

   [INTERCON-EVPN] J. Rabadan, et al., "Interconnect Solution for EVPN
              Overlay networks", https://tools.ietf.org/html/draft-ietf-
              bess-dci-evpn-overlay-04, September 2016

   [TUNNEL-ENCAPS] E. Rosen, et al. "The BGP Tunnel Encapsulation
              Attribute", https://tools.ietf.org/html/draft-ietf-idr-
              tunnel-encaps-06, work in progress, June 2017.

   [EVPN-IGMP-PROXY] A. Sajassi, et. al., "IGMP and MLD Proxy for EVPN",
              https://tools.ietf.org/html/draft-ietf-bess-evpn-igmp-mld-
              proxy-01, work in progress, March 2018.

   [EVPN-PIM-PROXY] J. Rabadan, et. al., "PIM Proxy in EVPN Networks",
              https://tools.ietf.org/html/draft-skr-bess-evpn-pim-proxy-
              00, work in progress, July 3, 2017.

15.  Authors' Addresses

              Ali Sajassi
              Cisco
              170 West Tasman Drive
              San Jose, CA  95134, US
              Email: sajassi@cisco.com


              Samir Thoria
              Cisco
              170 West Tasman Drive
              San Jose, CA  95134, US
              Email: sthoria@cisco.com


              Ashutosh Gupta
              Avi Networks



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              Email: ashutosh@avinetworks.com



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
              RFC 6514 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 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 RFC-6514 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.



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              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.

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 RFC 6513 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 RFC 6513 and RFC 6514 apply
              when PIM-Bidir is used.









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