NVO3 Workgroup                                           J. Rabadan, Ed.
Internet Draft                                                  M. Bocci
Intended status: Informational                                     Nokia

                                                              S. Boutros

                                                              A. Sajassi

Expires: March 15, April 25, 2019                               September 11,                                 October 22, 2018

                 Applicability of EVPN to NVO3 Networks


   In NVO3 networks, Network Virtualization Edge (NVE) devices sit at
   the edge of the underlay network and provide Layer-2 and Layer-3
   connectivity among Tenant Systems (TSes) of the same tenant. The NVEs
   need to build and maintain mapping tables so that they can deliver
   encapsulated packets to their intended destination NVE(s). While
   there are different options to create and disseminate the mapping
   table entries, NVEs may exchange that information directly among
   themselves via a control-plane protocol, such as EVPN. EVPN provides
   an efficient, flexible and unified control-plane option that can be
   used for Layer-2 and Layer-3 Virtual Network (VN) service
   connectivity. This document describes the applicability of EVPN to
   NVO3 networks and how EVPN solves the challenges in those networks.

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Table of Contents

   1. Introduction  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2. EVPN and NVO3 Terminology . . . . . . . . . . . . . . . . . . .  3
   3. Why Is EVPN Needed In NVO3 Networks?  . . . . . . . . . . . . .  6
   4. Applicability of EVPN to NVO3 Networks  . . . . . . . . . . . .  8
     4.1. EVPN Route Types used in NVO3 Networks  . . . . . . . . . .  8
     4.2. EVPN Basic Applicability For Layer-2 Services . . . . . . .  9
       4.2.1. Auto-Discovery and Auto-Provisioning of ES,
              Multi-Homing PEs and NVE services . . . . . . . . . . . 10
       4.2.2. Remote NVE Auto-Discovery . . . . . . . . . . . . . . . 11
       4.2.3. Distribution Of Tenant MAC and IP Information . . . . . 12
     4.3. EVPN Basic Applicability for Layer-3 Services . . . . . . . 13
     4.4. EVPN as a Control Plane for NVO3 Encapsulations and
          GENEVE  . . . . . . . . . . . . . . . . . . . . . . . . . . 15
     4.5. EVPN OAM and application to NVO3  . . . . . . . . . . . . . 15 16
     4.6. EVPN as the control plane for NVO3 security . . . . . . . . 16
     4.7. Advanced EVPN Features For NVO3 Networks  . . . . . . . . . 16
       4.7.1. Virtual Machine (VM) Mobility . . . . . . . . . . . . . 16
       4.7.2. MAC Protection, Duplication Detection and Loop
              Protection  . . . . . . . . . . . . . . . . . . . . . . 16 17
       4.7.3. Reduction/Optimization of BUM Traffic In Layer-2
              Services  . . . . . . . . . . . . . . . . . . . . . . . 17

       4.7.4. Ingress Replication (IR) Optimization For BUM Traffic . 18
       4.7.5. EVPN Multi-homing . . . . . . . . . . . . . . . . . . . 18 19
       4.7.6. EVPN Recursive Resolution for Inter-Subnet Unicast
              Forwarding  . . . . . . . . . . . . . . . . . . . . . . 19 20
       4.7.7. EVPN Optimized Inter-Subnet Multicast Forwarding  . . . 21
       4.7.8. Data Center Interconnect (DCI)  . . . . . . . . . . . . 21
   5. Conclusion  . . . . . . . . . . . . . . . . . . . . . . . . . . 22
   6. Conventions used in this document . . . . . . . . . . . . . . . 22
   7. Security Considerations . . . . . . . . . . . . . . . . . . . . 22
   8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 22
   9. References  . . . . . . . . . . . . . . . . . . . . . . . . . . 22
     9.1 Normative References . . . . . . . . . . . . . . . . . . . . 23
     9.2 Informative References . . . . . . . . . . . . . . . . . . . 23
   10. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 25
   11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 25
   12. Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 25

1. Introduction

   In NVO3 networks, Network Virtualization Edge (NVE) devices sit at
   the edge of the underlay network and provide Layer-2 and Layer-3
   connectivity among Tenant Systems (TSes) of the same tenant. The NVEs
   need to build and maintain mapping tables so that they can deliver
   encapsulated packets to their intended destination NVE(s). While
   there are different options to create and disseminate the mapping
   table entries, NVEs may exchange that information directly among
   themselves via a control-plane protocol, such as EVPN. EVPN provides
   an efficient, flexible and unified control-plane option that can be
   used for Layer-2 and Layer-3 Virtual Network (VN) service

   In this document, we assume that the EVPN control-plane module
   resides in the NVEs. The NVEs can be virtual switches in hypervisors,
   TOR/Leaf switches or Data Center Gateways. Note that Network
   Virtualization Authorities (NVAs) may be used to provide the
   forwarding information to the NVEs, and in that case, EVPN could be
   used to disseminate the information across multiple federated NVAs.
   The applicability of EVPN would then be similar to the one described
   in this document. However, for simplicity, the description assumes
   control-plane communication among NVE(s).

2. EVPN and NVO3 Terminology

   o EVPN: Ethernet Virtual Private Networks, as described in [RFC7432].

   o PE: Provider Edge router.

   o NVO3 or Overlay tunnels: Network Virtualization Over Layer-3
     tunnels. In this document, NVO3 tunnels or simply Overlay tunnels
     will be used interchangeably. Both terms refer to a way to
     encapsulate tenant frames or packets into IP packets whose IP
     Source Addresses (SA) or Destination Addresses (DA) belong to the
     underlay IP address space, and identify NVEs connected to the same
     underlay network. Examples of NVO3 tunnel encapsulations are VXLAN
     [RFC7348], [GENEVE] or MPLSoUDP [RFC7510].

   o VXLAN: Virtual eXtensible Local Area Network, an NVO3 encapsulation
     defined in [RFC7348].

   o GENEVE: Generic Network Virtualization Encapsulation, an NVO3
     encapsulation defined in [GENEVE].

   o CLOS: a multistage network topology described in [CLOS1953], where
     all the edge switches (or Leafs) are connected to all the core
     switches (or Spines). Typically used in Data Centers nowadays.

   o ECMP: Equal Cost Multi-Path.

   o NVE: Network Virtualization Edge is a network entity that sits at
     the edge of an underlay network and implements L2 and/or L3 network
     virtualization functions. The network-facing side of the NVE uses
     the underlying L3 network to tunnel tenant frames to and from other
     NVEs. The tenant-facing side of the NVE sends and receives Ethernet
     frames to and from individual Tenant Systems. In this document, an
     NVE could be implemented as a virtual switch within a hypervisor, a
     switch or a router, and runs EVPN in the control-plane.

   o EVI: or EVPN Instance. It is a Layer-2 Virtual Network that uses an
     EVPN control-plane to exchange reachability information among the
     member NVEs. It corresponds to a set of MAC-VRFs of the same
     tenant. See MAC-VRF in this section.

   o BD: or Broadcast Domain, it corresponds to a tenant IP subnet. If
     no suppression techniques are used, a BUM frame that is injected in
     a BD will reach all the NVEs that are attached to that BD. An EVI
     may contain one or multiple BDs depending on the service model
     [RFC7432]. This document will use the term BD to refer to a tenant

   o EVPN VLAN-based service model: it refers to one of the three
     service models defined in [RFC7432]. It is characterized as a BD
     that uses a single VLAN per physical access port to attach tenant
     traffic to the BD. In this service model, there is only one BD per

   o EVPN VLAN-bundle service model: similar to VLAN-based but uses a
     bundle of VLANs per physical port to attach tenant traffic to the
     BD. As in VLAN-based, in this model there is a single BD per EVI.

   o EVPN VLAN-aware bundle service model: similar to the VLAN-bundle
     model but each individual VLAN value is mapped to a different BD.
     In this model there are multiple BDs per EVI for a given tenant.
     Each BD is identified by an "Ethernet Tag", that is a control-plane
     value that identifies the routes for the BD within the EVI.

   o IP-VRF: an IP Virtual Routing and Forwarding table, as defined in
     [RFC4364]. It stores IP Prefixes that are part of the tenant's IP
     space, and are distributed among NVEs of the same tenant by EVPN.
     Route-Distinghisher (RD) and Route-Target(s) (RTs) are required
     properties of an IP-VRF. An IP-VRF is instantiated in an NVE for a
     given tenant, if the NVE is attached to multiple subnets of the
     tenant and local inter-subnet-forwarding is required across those

   o MAC-VRF: a MAC Virtual Routing and Forwarding table, as defined in
     [RFC7432]. The instantiation of an EVI (EVPN Instance) in an NVE.
     Route-distinghisher (RD) and Route-Target(s) (RTs) are required
     properties of a MAC-VRF and they are normally different than the
     ones defined in the associated IP-VRF (if the MAC-VRF has an IRB

   o BT: a Bridge Table, as defined in [RFC7432]. A BT is the
     instantiation of a BD in an NVE. When there is a single BD on a
     given EVI, the MAC-VRF is equivalent to the BT on that NVE.

   o AC: Attachment Circuit or logical interface associated to a given
     BT. To determine the AC on which a packet arrived, the NVE will
     examine the physical/logical port and/or VLAN tags (where the VLAN
     tags can be individual c-tags, s-tags or ranges of both).

   o IRB: Integrated Routing and Bridging interface. It refers to the
     logical interface that connects a BD instance (or a BT) to an IP-
     VRF and allows to forward packets with destination in a different

   o ES: Ethernet Segment. When a Tenant System (TS) is connected to one
     or more NVEs via a set of Ethernet links, then that set of links is
     referred to as an 'Ethernet segment'. Each ES is represented by a
     unique Ethernet Segment Identifier (ESI) in the NVO3 network and
     the ESI is used in EVPN routes that are specific to that ES.

   o DF and NDF: they refer to Designated Forwarder and Non-Designated
     Forwarder, which are the roles that a given PE can have in a given

   o VNI: Virtual Network Identifier. Irrespective of the NVO3
     encapsulation, the tunnel header always includes a VNI that is
     added at the ingress NVE (based on the mapping table lookup) and
     identifies the BT at the egress NVE. This VNI is called VNI in
     VXLAN or GENEVE, VSID in nvGRE or Label in MPLSoGRE or MPLSoUDP.
     This document will refer to VNI as a generic Virtual Network
     Identifier for any NVO3 encapsulation.

   o BUM: Broadcast, Unknown unicast and Multicast frames.

   o SA and DA: they refer to Source Address and Destination Address.
     They are used along with MAC or IP, e.g. IP SA or MAC DA.

   o RT and RD: they refer to Route Target and Route Distinguisher.

   o PTA: Provider Multicast Service Interface Tunnel Attribute.

   o RT-1, RT-2, RT-3, etc.: they refer to Route Type followed by the
     type number as defined in the IANA registry for EVPN route types.

   o TS: Tenant System.

   o ARP and ND: they refer to Address Resolution Protocol and Neighbor
     Discovery protocol.

3. Why Is EVPN Needed In NVO3 Networks?

   Data Centers have adopted NVO3 architectures mostly due to the issues
   discussed in [RFC7364]. The architecture of a Data Center is nowadays
   based on a CLOS design, where every Leaf is connected to a layer of
   Spines, and there is a number of ECMP paths between any two leaf
   nodes. All the links between Leaf and Spine nodes are routed links,
   forming what we also know as an underlay IP Fabric. The underlay IP
   Fabric does not have issues with loops or flooding (like old Spanning
   Tree Data Center designs did), convergence is fast and ECMP provides
   a fairly optimal bandwidth utilization on all the links.

   On this architecture and as discussed by [RFC7364] multi-tenant
   intra-subnet and inter-subnet connectivity services are provided by
   NVO3 tunnels, being VXLAN [RFC7348] or [GENEVE] two examples of such

   Why is a control-plane protocol along with NVO3 tunnels required?
   There are three main reasons:

   a) Auto-discovery of the remote NVEs that are attached to the same
      VPN instance (Layer-2 and/or Layer-3) as the ingress NVE is.

   b) Dissemination of the MAC/IP host information so that mapping
      tables can be populated on the remote NVEs.

   c) Advanced features such as MAC Mobility, MAC Protection, BUM and
      ARP/ND traffic reduction/suppression, Multi-homing, Prefix
      Independent Convergence (PIC) like functionality, Fast
      Convergence, etc.

   A possible approach to achieve points (a) and (b) above for
   multipoint Ethernet services, is "Flood and Learn". "Flood and Learn"
   refers to not using a specific control-plane on the NVEs, but rather
   "Flood" BUM traffic from the ingress NVE to all the egress NVEs
   attached to the same BD. The egress NVEs may then use data path MAC
   SA "Learning" on the frames received over the NVO3 tunnels. When the
   destination host replies back and the frames arrive at the NVE that
   initially flooded BUM frames, the NVE will also "Learn" the MAC SA of
   the frame encapsulated on the NVO3 tunnel. This approach has the
   following drawbacks:

   o In order to Flood a given BUM frame, the ingress NVE must know the
     IP addresses of the remote NVEs attached to the same BD. This may
     be done as follows:

     - The remote tunnel IP addresses can be statically provisioned on
       the ingress NVE. If the ingress NVE receives a BUM frame for the
       BD on an ingress AC, it will do ingress replication and will send
       the frame to all the configured egress NVE IP DAs in the BD.

     - All the NVEs attached to the same BD can subscribe to an underlay
       IP Multicast Group that is dedicated to that BD. When an ingress
       NVE receives a BUM frame on an ingress AC, it will send a single
       copy of the frame encapsulated into an NVO3 tunnel, using the
       multicast address as IP DA of the tunnel. This solution requires
       PIM in the underlay network and the association of individual BDs
       to underlay IP multicast groups.

   o "Flood and Learn" solves the issues of auto-discovery and learning
     of the MAC to VNI/tunnel IP mapping on the NVEs for a given BD.
     However, it does not provide a solution for advanced features and
     it does not scale well.

   EVPN provides a unified control-plane that solves the NVE auto-
   discovery, tenant MAP/IP dissemination and advanced features in a
   scalable way and keeping the independence of the underlay IP Fabric,
   i.e. there is no need to enable PIM in the underlay network and
   maintain multicast states for tenant BDs.

   Section 4 describes how to apply EVPN to meet the control-plane
   requirements in an NVO3 network.

4. Applicability of EVPN to NVO3 Networks

   This section discusses the applicability of EVPN to NVO3 networks.
   The intend is not to provide a comprehensive explanation of the
   protocol itself but give an introduction and point at the
   corresponding reference document, so that the reader can easily find
   more details if needed.

4.1. EVPN Route Types used in NVO3 Networks

   EVPN supports multiple Route Types and each type has a different
   function. For convenience, Table 1 shows a summary of all the
   existing EVPN route types and its usage. We will refer to these route
   types as RT-x throughout the rest of the document, where x is the
   type number included in the first column of Table 1.

   |Type|Description             |Usage                                |
   |1   |Ethernet Auto-Discovery |Multi-homing:                        |
   |    |                        |  Per-ES: Mass withdrawal            |
   |    |                        |  Per-EVI: aliasing/backup           |
   |2   |MAC/IP Advertisement    |Host MAC/IP dissemination            |
   |    |                        |Supports MAC mobility and protection |
   |3   |Inclusive Multicast     |NVE discovery and BUM flooding tree  |
   |    |Ethernet Tag            |setup                                |
   |4   |Ethernet Segment        |Multi-homing: ES auto-discovery and  |
   |    |                        |DF Election                          |
   |5   |IP Prefix               |IP Prefix dissemination              |
   |6   |Selective Multicast     |Indicate interest for a multicast    |
   |    |Ethernet Tag            |S,G or *,G                           |
   |7   |IGMP Join Synch         |Multi-homing: S,G or *,G state synch |
   |8   |IGMP Leave Synch        |Multi-homing: S,G or *,G leave synch |
   |9   |Per-Region I-PMSI A-D   |BUM tree creation across regions     |
   |10  |S-PMSI A-D              |Multicast tree for S,G or *,G states |
   |11  |Leaf A-D                |Used for responses to explicit       |
   |    |                        |tracking                             |

                      Table 1 EVPN route types

4.2. EVPN Basic Applicability For Layer-2 Services

   Although the applicability of EVPN to NVO3 networks spans multiple
   documents, EVPN's baseline specification is [RFC7432]. [RFC7432]
   allows multipoint layer-2 VPNs to be operated as [RFC4364] IP-VPNs,
   where MACs and the information to setup flooding trees are
   distributed by MP-BGP. Based on [RFC7432], [EVPN-OVERLAY] [RFC8365] describes how to
   use EVPN to deliver Layer-2 services specifically in NVO3 Networks.

   Figure 1 represents a Layer-2 service deployed with an EVPN BD in an
   NVO3 network.

                                 *        | Single-Active
                                 *        |   ESI-1
                               +----+  +----+
                               |BD1 |  |BD1 |
                 +-------------|    |--|    |-----------+
                 |             +----+  +----+           |
                 |              NVE2    NVE3          NVE4
                 |           EVPN NVO3 Network       +----+
            NVE1(IP-A)                               | BD1|=====+
           +-------------+      RT-2                 |    |     |
           | +-MAC-VRF1+ |    +-------+              +----+     |
           | | +----+  | |    |MAC1   |               NVE5     TS3
    TS1--------|BD1 |  | |    |IP1    |              +----+     |
    MAC1   | | +----+  | |    |Label L|--->          | BD1|=====+
    IP1    | +---------+ |    |NH IP-A|              |    | All-Active
           | Hypervisor  |    +-------+              +----+  ESI-2
           +-------------+                              |

          Figure 1 EVPN for L2 in an NVO3 Network - example

   In a simple NVO3 network, such as the example of Figure 1, these are
   the basic constructs that EVPN uses for Layer-2 services (or Layer-2
   Virtual Networks):

   o BD1 is an EVPN Broadcast Domain for a given tenant and TS1, TS2 and
     TS3 are connected to it. The five represented NVEs are attached to
     BD1 and are connected to the same underlay IP network. That is,
     each NVE learns the remote NVEs' loopback addresses via underlay
     routing protocol.

   o NVE1 is deployed as a virtual switch in a Hypervisor with IP-A as
     underlay loopback IP address. The rest of the NVEs in Figure 1 are
     physical switches and TS2/TS3 are multi-homed to them. TS1 is a
     virtual machine, identified by MAC1 and IP1.

4.2.1. Auto-Discovery and Auto-Provisioning of ES, Multi-Homing PEs and
     NVE services

   Auto-discovery is one of the basic capabilities of EVPN. The
   provisioning of EVPN components in NVEs is significantly automated,
   simplifying the deployment of services and minimizing manual
   operations that are prone to human error.

   These are some of the Auto-Discovery and Auto-Provisioning
   capabilities available in EVPN:

   o Automation on Ethernet Segments (ES): an ES is defined as a group
     of NVEs that are attached to the same TS or network. An ES is
     identified by an Ethernet Segment Identifier (ESI) in the control
     plane, but neither the ESI nor the NVEs that share the same ES are
     required to be manually provisioned in the local NVE:

     - If the multi-homed TS or network are running protocols such as
       LACP (Link Aggregation Control Protocol), MSTP (Multiple-instance
       Spanning Tree Protocol), G.8032, etc. and all the NVEs in the ES
       can listen to the protocol PDUs to uniquely identify the multi-
       homed TS/network, then the ESI can be "auto-sensed" or "auto-
       provisioned" following the guidelines in [RFC7432] section 5.

     - As described in [RFC7432], EVPN can also auto-derive the BGP
       parameters required to advertise the presence of a local ES in
       the control plane (RT and RD). Local ESes are advertised using
       RT-4s and the ESI-import Route-Target used by RT-4s can be auto-
       derived based on the procedures of [RFC7432], section 7.6.

     - By listening to other RT-4s that match the local ESI and import
       RT, an NVE can also auto-discover the other NVEs participating in
       the multi-homing for the ES.

     - Once the NVE has auto-discovered all the NVEs attached to the
       same ES, the NVE can automatically perform the DF Election
       algorithm (which determines the NVE that will forward traffic to
       the multi-homed TS/network). EVPN guarantees that all the NVEs in
       the ES have a consistent DF Election.

   o Auto-provisioning of services: when deploying a Layer-2 Service for
     a tenant in an NVO3 network, all the NVEs attached to the same
     subnet must be configured with a MAC-VRF and the BD for the subnet,
     as well as certain parameters for them. Note that, if the EVPN
     service model is VLAN-based or VLAN-bundle, implementations do not
     normally have a specific provisioning for the BD (since it is in
     that case the same construct as the MAC-VRF). EVPN allows auto-
     deriving as many MAC-VRF parameters as possible. As an example, the
     MAC-VRF's RT and RD for the EVPN routes may be auto-derived.
     Section in [EVPN-OVERLAY] [RFC8365] specifies how to auto-derive a
     MAC-VRF's MAC-
     VRF's RT as long as VLAN-based service model is implemented.
     [RFC7432] specifies how to auto-derive the RD.

4.2.2. Remote NVE Auto-Discovery

   Auto-discovery via MP-BGP is used to discover the remote NVEs
   attached to a given BD, NVEs participating in a given redundancy
   group, the tunnel encapsulation types supported by an NVE, etc.

   In particular, when a new MAC-VRF and BD are enabled, the NVE will
   advertise a new RT-3. Besides other fields, the RT-3 will encode the
   IP address of the advertising NVE, the Ethernet Tag (which is zero in
   case of VLAN-based and VLAN-bundle models) and also a PMSI Tunnel
   Attribute (PTA) that indicates the information about the intended way
   to deliver BUM traffic for the BD.

   In the example of Figure 1, when MAC-VRF1/BD1 are enabled, NVE1 will
   send an RT-3 including its own IP address, Ethernet-Tag for BD1 and
   the PTA. Assuming Ingress Replication (IR), the RT-3 will include an
   identification for IR in the PTA and the VNI the NVEs must use to
   send BUM traffic to the advertising NVE. The other NVEs in the BD,
   will import the RT-3 and will add NVE1's IP address to the flooding
   list for BD1. Note that the RT-3 is also sent with a BGP
   encapsulation attribute [TUNNEL-ENCAP] that indicates what NVO3
   encapsulation the remote NVEs should use when sending BUM traffic to

   Refer to [RFC7432] for more information about the RT-3 and forwarding
   of BUM traffic, and to [EVPN-OVERLAY] [RFC8365] for its considerations on NVO3

4.2.3. Distribution Of Tenant MAC and IP Information

   Tenant MAC/IP information is advertised to remote NVEs using RT-2s.
   Following the example of Figure 1:

   o In a given EVPN BD, TSes' MAC addresses are first learned at the
     NVE they are attached to, via data path or management plane
     learning. In Figure 1 we assume NVE1 learns MAC1/IP1 in the
     management plane (for instance, via Cloud Management System) since
     the NVE is a virtual switch. NVE2, NVE3, NVE4 and NVE4 are TOR/Leaf
     switches and they normally learn MAC addresses via data path.

   o Once NVE1's BD1 learns MAC1/IP1, NVE1 advertises that information
     along with a VNI and Next Hop IP-A in an RT-2. The EVPN routes are
     advertised using the RD/RTs of the MAC-VRF where the BD belongs.
     All the NVEs in BD1 learn local MAC/IP addresses and advertise them
     in RT-2 routes in a similar way.

   o The remote NVEs can then add MAC1 to their mapping table for BD1
     (BT). For instance, when TS3 sends frames to NVE4 with MAC DA =
     MAC1, NVE4 does a MAC lookup on the BT that yields IP-A and Label
     L. NVE4 can then encapsulate the frame into an NVO3 tunnel with IP-
     A as the tunnel IP DA and L as the Virtual Network Identifier. Note
     that the RT-2 may also contain the host's IP address (as in the
     example of Figure 1). While the MAC of the received RT-2 is
     installed in the BT, the IP address may be installed in the Proxy-
     ARP/ND table (if enabled) or in the ARP/IP-VRF tables if the BD has
     an IRB. See section 4.7.3. to see more information about Proxy-
     ARP/ND and section 4.3. for more details about IRB and Layer-3

   Refer to [RFC7432] and [EVPN-OVERLAY] [RFC8365] for more information about the RT-2
   and forwarding of known unicast traffic.

4.3. EVPN Basic Applicability for Layer-3 Services

   [IP-PREFIX] and [INTER-SUBNET] are the reference documents that
   describe how EVPN can be used for Layer-3 services. Inter Subnet
   Forwarding in EVPN networks is implemented via IRB interfaces between
   BDs and IP-VRFs. As discussed, an EVPN BD corresponds to an IP
   subnet. When IP packets generated in a BD are destined to a different
   subnet (different BD) of the same tenant, the packets are sent to the
   IRB attached to local BD in the source NVE. As discussed in [INTER-
   SUBNET], depending on how the IP packets are forwarded between the
   ingress NVE and the egress NVE, there are two forwarding models:
   Asymmetric and Symmetric.

   The Asymmetric model is illustrated in the example of Figure 2 and it
   requires the configuration of all the BDs of the tenant in all the
   NVEs attached to the same tenant. In that way, there is no need to
   advertise IP Prefixes between NVEs since all the NVEs are attached to
   all the subnets. It is called Asymmetric because the ingress and
   egress NVEs do not perform the same number of lookups in the data
   plane. In Figure 2, if TS1 and TS2 are in different subnets, and TS1
   sends IP packets to TS2, the following lookups are required in the
   data path: a MAC lookup (on BD1's table), an IP lookup (on the IP-
   VRF) and a MAC lookup (on BD2's table) at the ingress NVE1 and then
   only a MAC lookup at the egress NVE. The two IP-VRFs in Figure 2 are
   not connected by tunnels and all the connectivity between the NVEs is
   done based on tunnels between the BDs.

                  |             EVPN NVO3               |
                  |                                     |
                NVE1                                 NVE2
          +--------------------+            +--------------------+
          | +---+IRB +------+  |            |  +------+IRB +---+ |
    TS1-----|BD1|----|IP-VRF|  |            |  |IP-VRF|----|BD1| |
          | +---+    |      |  |            |  |      |    +---+ |
          | +---+    |      |  |            |  |      |    +---+ |
          | |BD2|----|      |  |            |  |      |----|BD2|----TS2
          | +---+IRB +------+  |            |  +------+IRB +---+ |
          +--------------------+            +--------------------+
                  |                                     |

        Figure 2 EVPN for L3 in an NVO3 Network - Asymmetric model

   In the Symmetric model, depicted in Figure 3, there are the same number of data
   path lookups is needed at the ingress and egress NVEs. For example,
   if TS1 sends IP packets to TS3, the following data path lookups are
   required: a MAC lookup at NVE1's BD1 table, an IP lookup at NVE1's
   IP-VRF and then IP lookup and MAC lookup at NVE2's IP-VRF and BD3
   respectively. In the Symmetric model, the Inter Subnet connectivity
   between NVEs is done based on tunnels between the IP-VRFs.

                  |             EVPN NVO3               |
                  |                                     |
                NVE1                                 NVE2
          +--------------------+            +--------------------+
          | +---+IRB +------+  |            |  +------+IRB +---+ |
    TS1-----|BD1|----|IP-VRF|  |            |  |IP-VRF|----|BD3|-----TS3
          | +---+    |      |  |            |  |      |    +---+ |
          | +---+IRB |      |  |            |  +------+          |
    TS2-----|BD2|----|      |  |            +--------------------+
          | +---+    +------+  |                        |
          +--------------------+                        |
                  |                                     |

        Figure 3 EVPN for L3 in an NVO3 Network - Symmetric model

   The Symmetric model scales better than the Asymmetric model because
   it does not require the NVEs to be attached to all the tenant's
   subnets. However, it requires the use of NVO3 tunnels on the IP-VRFs
   and the exchange of IP Prefixes between the NVEs in the control
   plane. EVPN uses RT-2 and RT-5 routes for the exchange of host IP
   routes (in the case of RT-2 and RT-5) and IP Prefixes (RT-5s) of any
   length. As an example, in Figure 3, NVE2 needs to advertise TS3's
   host route and/or TS3's subnet, so that the IP lookup on NVE1's IP-
   VRF succeeds.

   [INTER-SUBNET] specifies the use of RT-2s for the advertisement of
   host routes. Section 4.4.1 in [IP-PREFIX] specifies the use of RT-5s
   for the advertisement of IP Prefixes in an "Interface-less IP-VRF-to-
   IP-VRF Model". The Symmetric model for host routes can be implemented
   following either approach:

   a. [INTER-SUBNET] uses RT-2s to convey the information to populate
      L2, ARP/ND and L3 FIB tables in the remote NVE. For instance, in
      Figure 3, NVE2 would advertise a RT-2 with TS3's IP and MAC
      addresses, and including two labels/VNIs: a label-3/VNI-3 that
      identifies BD3 for MAC lookup (that would be used for L2 traffic
      in case NVE1 was attached to BD3 too) and a label-1/VNI-1 that
      identifies the IP-VRF for IP lookup (and will be used for L3
      traffic). NVE1 imports the RT-2 and installs TS3's IP in the IP-
      VRF route table with label-1/VNI-1. Traffic from e.g., TS2 to TS3,
      will be encapsulated with label-1/VNI-1 and forwarded to NVE2.

   b. [IP-PREFIX] uses RT-2s to convey the information to populate the
      L2 FIB and ARP/ND tables, and RT-5s to populate the IP-VRF L3 FIB
      table. For instance, in Figure 3, NVE2 would advertise a RT-2
      including TS3's MAC and IP addresses with a single label-3/VNI-3.
      In this example, this RT-2 wouldn't be imported by NVE1 because
      NVE1 is not attached to BD3. In addition, NVE2 would advertise a
      RT-5 with TS3's IP address and label-1/VNI-1. This RT-5 would be
      imported by NVE1's IP-VRF and the host route installed in the L3
      FIB associated to label-1/VNI-1. Traffic from TS2 to TS3 would be
      encapsulated with label-1/VNI-1.

4.4. EVPN as a Control Plane for NVO3 Encapsulations and GENEVE


   [RFC8365] describes how to use EVPN for NVO3 encapsulations, such us
   VXLAN, nvGRE or MPLSoGRE. The procedures can be easily applicable to
   any other NVO3 encapsulation, in particular GENEVE.

   The NVO3 working group has been working on different data plane
   encapsulations. The Generic Network Virtualization Encapsulation
   [GENEVE] has been recommended to be the proposed standard for NVO3
   Encapsulation. The EVPN control plane can signal the GENEVE
   encapsulation type in the BGP Tunnel Encapsulation Extended Community
   (see [TUNNEL-ENCAP]).

   The NVO3 encapsulation design team has made a recommendation in
   [NVO3-ENCAP] for a control plane to:

   1- Negotiate a subset of GENEVE option TLVs that can be carried on a
      GENEVE tunnel

   2- Enforce an order for GENEVE option TLVs and

   3- Limit the total number of options that could be carried on a
      GENEVE tunnel.

   The EVPN control plane can easily extend the BGP Tunnel Encapsulation
   Attribute sub-TLV [TUNNEL-ENCAP] to specify the GENEVE tunnel options
   that can be received or transmitted over a GENEVE tunnels by a given
   NVE. [EVPN-GENEVE] describes the EVPN control plane extensions to
   support GENEVE.

4.5. EVPN OAM and application to NVO3

   EVPN OAM (as in [EVPN-LSP-PING]) defines mechanisms to detect data
   plane failures in an EVPN deployment over an MPLS network. These
   mechanisms detect failures related to P2P and P2MP connectivity, for
   multi-tenant unicast and multicast L2 traffic, between multi-tenant
   access nodes connected to EVPN PE(s), and in a single-homed, single-
   active or all-active redundancy model.

   In general, EVPN OAM mechanisms defined for EVPN deployed in MPLS
   networks are equally applicable for EVPN in NVO3 networks.

4.6. EVPN as the control plane for NVO3 security

   EVPN can be used to signal the security protection capabilities of a
   sender NVE, as well as what portion of an NVO3 packet (taking a
   GENEVE packet as an example) can be protected by the sender NVE, to
   ensure the privacy and integrity of tenant traffic carried over the
   NVO3 tunnels.

4.7. Advanced EVPN Features For NVO3 Networks

   This section describes how EVPN can be used to deliver advanced
   capabilities in NVO3 networks.

4.7.1. Virtual Machine (VM) Mobility

   [RFC7432] replaces the traditional Ethernet Flood-and-Learn behavior
   among NVEs with BGP-based MAC learning, which in return provides more
   control over the location of MAC addresses in the BD and consequently
   advanced features, such as MAC Mobility. If we assume that VM
   Mobility means the VM's MAC and IP addresses move with the VM, EVPN's
   MAC Mobility is the required procedure that facilitates VM Mobility.
   According to [RFC7432] section 15, when a MAC is advertised for the
   first time in a BD, all the NVEs attached to the BD will store
   Sequence Number zero for that MAC. When the MAC "moves" within the
   same BD but to a remote NVE, the NVE that just learned locally the
   MAC, increases the Sequence Number in the RT-2's MAC Mobility
   extended community to indicate that it owns the MAC now. That makes
   all the NVE in the BD change their tables immediately with no need to
   wait for any aging timer. EVPN guarantees a fast MAC Mobility without
   flooding or black-holes in the BD.

4.7.2. MAC Protection, Duplication Detection and Loop Protection

   The advertisement of MACs in the control plane, allows advanced
   features such as MAC protection, Duplication Detection and Loop

   [RFC7432] MAC Protection refers to EVPN's ability to indicate - in an
   RT-2 - that a MAC must be protected by the NVE receiving the route.
   The Protection is indicated in the "Sticky bit" of the MAC Mobility
   extended community sent along the RT-2 for a MAC. NVEs' ACs that are
   connected to subject-to-be-protected servers or VMs may set the
   Sticky bit on the RT-2s sent for the MACs associated to the ACs. Also
   statically configured MAC addresses should be advertised as Protected
   MAC addresses, since they are not subject to MAC Mobility procedures.

   [RFC7432] MAC Duplication Detection refers to EVPN's ability to
   detect duplicate MAC addresses. A "MAC move" is a relearn event that
   happens at an access AC or through an RT-2 with a Sequence Number
   that is higher than the stored one for the MAC. When a MAC moves a
   number of times N within an M-second window between two NVEs, the MAC
   is declared as Duplicate and the detecting NVE does not re-advertise
   the MAC anymore.

   While [RFC7432] provides MAC Duplication Detection, it does not
   protect the BD against loops created by backdoor links between NVEs.
   However, the same principle (based on the Sequence Number) may be
   extended to protect the BD against loops. When a MAC is detected as
   duplicate, the NVE may install it as a black-hole MAC and drop
   received frames with MAC SA and MAC DA matching that duplicate MAC.
   Loop Protection is described in [LOOP].

4.7.3. Reduction/Optimization of BUM Traffic In Layer-2 Services
   In BDs with a significant amount of flooding due to Unknown unicast
   and Broadcast frames, EVPN may help reduce and sometimes even
   suppress the flooding.

   In BDs where most of the Broadcast traffic is caused by ARP (Address
   Resolution Protocol) and ND (Neighbor Discovery) protocols on the
   TSes, EVPN's Proxy-ARP and Proxy-ND capabilities may reduce the
   flooding drastically. The use of Proxy-ARP/ND is specified in [PROXY-

   Proxy-ARP/ND procedures along with the assumption that TSes always
   issue a GARP (Gratuitous ARP) or an unsolicited Neighbor
   Advertisement message when they come up in the BD, may drastically
   reduce the unknown unicast flooding in the BD.

   The flooding caused by TSes' IGMP/MLD or PIM messages in the BD may
   also be suppressed by the use of IGMP/MLD and PIM Proxy functions, as
   specified in [IGMP-MLD-PROXY] and [PIM-PROXY]. These two documents
   also specify how to forward IP multicast traffic efficiently within
   the same BD, translate soft state IGMP/MLD/PIM messages into hard
   state BGP routes and provide fast-convergence redundancy for IP
   Multicast on multi-homed Ethernet Segments (ESes).

4.7.4. Ingress Replication (IR) Optimization For BUM Traffic

   When an NVE attached to a given BD needs to send BUM traffic for the
   BD to the remote NVEs attached to the same BD, IR is a very common
   option in NVO3 networks, since it is completely independent of the
   multicast capabilities of the underlay network. Also, if the
   optimization procedures to reduce/suppress the flooding in the BD are
   enabled (section 4.7.3), in spite of creating multiple copies of the
   same frame at the ingress NVE, IR may be good enough. However, in BDs
   where Multicast (or Broadcast) traffic is significant, IR may be very
   inefficient and cause performance issues on virtual-switch-based

   [OPT-IR] specifies the use of AR (Assisted Replication) NVO3 tunnels
   in EVPN BDs. AR retains the independence of the underlay network
   while providing a way to forward Broadcast and Multicast traffic
   efficiently. AR uses AR-REPLICATORs that can replicate the
   Broadcast/Multicast traffic on behalf of the AR-LEAF NVEs. The AR-
   LEAF NVEs are typically virtual-switches or NVEs with limited
   replication capabilities. AR can work in a single-stage replication
   mode (Non-Selective Mode) or in a dual-stage replication mode
   (Selective Mode). Both modes are detailed in [OPT-IR].

   In addition, [OPT-IR] also describes a procedure to avoid sending
   Broadcast, Multicast or Unknown unicast to certain NVEs that don't
   need that type of traffic. This is done by enabling PFL (Pruned Flood
   Lists) on a given BD. For instance, an virtual-switch NVE that learns
   all its local MAC addresses for a BD via Cloud Management System,
   does not need to receive the BD's Unknown unicast traffic. PFLs help
   optimize the BUM flooding in the BD.

4.7.5. EVPN Multi-homing

   Another fundamental concept in EVPN is multi-homing. A given TS can
   be multi-homed to two or more NVEs for a given BD, and the set of
   links connected to the same TS is defined as Ethernet Segment (ES).
   EVPN supports single-active and all-active multi-homing. In single-
   active multi-homing only one link in the ES is active. In all-active
   multi-homing all the links in the ES are active for unicast traffic.
   Both modes support load-balancing:

     o Single-active multi-homing means per-service load-balancing
       to/from the TS, for example, in Figure 1, for BD1 only one of the
       NVEs can forward traffic from/to TS2. For a different BD, the
       other NVE may forward traffic.

     o All-active multi-homing means per-flow load-balanding for unicast
       frames to/from the TS. That is, in Figure 1 and for BD1, both
       NVE4 and NVE5 can forward known unicast traffic to/from TS3. For
       BUM traffic only one of the two NVEs can forward traffic to TS3,
       and both can forward traffic from TS3.

   There are two key aspects of EVPN multi-homing:

     o DF (Designated Forwarder) election: the DF is the NVE that
       forwards the traffic to the ES in single-active mode. In case of
       all-active, the DF is the NVE that forwards the BUM traffic to
       the ES.

     o Split-horizon function: prevents the TS from receiving echoed BUM
       frames that the TS itself sent to the ES. This is especially
       relevant in all-active ESes, where the TS may forward BUM frames
       to a non-DF NVE that can flood the BUM frames back to the DF NVE
       and then the TS. As an example, in Figure 1, assuming NVE4 is the
       DF for ES-2 in BD1, BUM frames sent from TS3 to NVE5 will be
       received at NVE4 and, since NVE4 is the DF for DB1, it will
       forward them back to TS3. Split-horizon allows NVE4 (and any
       multi-homed NVE for that matter) to identify if an EVPN BUM frame
       is coming from the same ES or different, and if the frame belongs
       to the same ES2, NVE4 will not forward the BUM frame to TS3, in
       spite of being the DF.

   While [RFC7432] describes the default algorithm for the DF Election,
   [HRW-DF], [PREF-DF]
   [DF] and [AC-DF] [PREF-DF] specify other algorithms and procedures that
   optimize the DF Election.

   The Split-horizon function is specified in [RFC7432] and it is
   carried out by using a special ESI-label that it identifies in the
   data path, all the BUM frames being originated from a given NVE and
   ES. Since the ESI-label is an MPLS label, it cannot be used in all
   the non-MPLS NVO3 encapsulations, therefore [EVPN-OVERLAY] [RFC8365] defines a
   modified Split-horizon procedure that is based on the IP SA of the
   NVO3 tunnel, known as "Local-Bias". It is worth noting that Local-
   Bias only works for all-active multi-homing, and not for single-
   active multi-homing.

4.7.6. EVPN Recursive Resolution for Inter-Subnet Unicast Forwarding

   Section 4.3. describes how EVPN can be used for Inter Subnet
   Forwarding among subnets of the same tenant. RT-2s and RT-5s allow
   the advertisement of host routes and IP Prefixes (RT-5) of any
   length. The procedures outlined by section 4.3. are similar to the
   ones in [RFC4364], only for NVO3 tunnels. However, [EVPN-PREFIX] also
   defines advanced Inter Subnet Forwarding procedures that allow the
   resolution of RT-5s to not only BGP next-hops but also "overlay
   indexes" that can be a MAC, a GW IP or an ESI, all of them in the
   tenant space.

   Figure 4 illustrates an example that uses Recursive Resolution to a
   GWIP as per [IP-PREFIX] section 4.4.2. In this example, IP-VRFs in
   NVE1 and NVE2 are connected by a SBD (Supplementary BD). An SBD is a
   BD that connects all the IP-VRFs of the same tenant, via IRB, and has
   no ACs. NVE1 advertises the host route TS2-IP/L (IP address and
   Prefix Length of TS2) in an RT-5 with overlay index GWIP=IP1. Also,
   IP1 is advertised in an RT-2 associated to M1, VNI-S and BGP next-hop
   NVE1. Upon importing the two routes, NVE2 installs TS2-IP/L in the
   IP-VRF with a next-hop that is the GWIP IP1. NVE2 also installs M1 in
   the SBD, with VNI-S and NVE1 as next-hop. If TS3 sends a packet with
   IP DA=TS2, NVE2 will perform a Recursive Resolution of the RT-5
   prefix information to the forwarding information of the correlated
   RT-2. The RT-5's Recursive Resolution has several advantages such as
   better convergence in scaled networks (since multiple RT-5s can be
   invalidated with a single withdrawal of the overlay index route) or
   the ability to advertise multiple RT-5s from an overlay index that
   can move or change dynamically. [EVPN-PREFIX] describes a few use-

                  |             EVPN NVO3               |
                  |                                     +
                NVE1                                 NVE2
          +--------------------+            +--------------------+
          | +---+IRB +------+  |            |  +------+IRB +---+ |
    TS1-----|BD1|----|IP-VRF|  |            |  |IP-VRF|----|BD3|-----TS3
          | +---+    |      |-(SBD)------(SBD)-|      |    +---+ |
          | +---+IRB |      |IRB(IP1/M1)    IRB+------+          |
    TS2-----|BD2|----|      |  |            +-----------+--------+
          | +---+    +------+  |                        |
          +--------------------+                        |
                  |   RT-2(M1,IP1,VNI-S,NVE1)-->        |
                  |     RT-5(TS2-IP/L,GWIP=IP1)-->      |

        Figure 4 EVPN for L3 - Recursive Resolution example

4.7.7. EVPN Optimized Inter-Subnet Multicast Forwarding

   The concept of the SBD described in section 4.7.6 is also used in
   [OISM] for the procedures related to Inter Subnet Multicast
   Forwarding across BDs of the same tenant. For instance, [OISM] allows
   the efficient forwarding of IP multicast traffic from any BD to any
   other BD (or even to the same BD where the Source resides). The
   [OISM] procedures are supported along with EVPN multi-homing, and for
   any tree allowed on NVO3 networks, including IR or AR. [OISM] also
   describes the interoperability between EVPN and other multicast
   technologies such as MVPN (Multicast VPN) and PIM for inter-subnet

   [EVPN-MVPN] describes another potential solution to support EVPN to
   MVPN interoperability.

4.7.8. Data Center Interconnect (DCI)

   Tenant Layer-2 and Layer-3 services deployed on NVO3 networks must be
   extended to remote NVO3 networks that are connected via non-NOV3 WAN
   networks (mostly MPLS based WAN networks). [EVPN-DCI] defines some
   architectural models that can be used to interconnect NVO3 networks
   via MPLS WAN networks.

   When NVO3 networks are connected by MPLS WAN networks, [EVPN-DCI]
   specifies how EVPN can be used end-to-end, in spite of using a
   different encapsulation in the WAN.

   Even if EVPN can also be used in the WAN for Layer-2 and Layer-3
   services, there may be a need to provide a Gateway function between
   EVPN for NVO3 encapsulations and IPVPN for MPLS tunnels. [EVPN-IPVPN]
   specifics the interworking function between EVPN and IPVPN for
   unicast Inter Subnet Forwarding. If Inter Subnet Multicast Forwarding
   is also needed across an IPVPN WAN, [OISM] describes the required
   interworking between EVPN and MVPN.

5. Conclusion

   EVPN provides a unified control-plane that solves the NVE auto-
   discovery, tenant MAP/IP dissemination and advanced features required
   by NVO3 networks, in a scalable way and keeping the independence of
   the underlay IP Fabric, i.e. there is no need to enable PIM in the
   underlay network and maintain multicast states for tenant BDs.

   This document justifies the use of EVPN for NVO3 networks, discusses
   its applicability to basic Layer-2 and Layer-3 connectivity
   requirements, as well as advanced features such as MAC-mobility, MAC
   Protection and Loop Protection, multi-homing, DCI and much more.

6. Conventions used in this document

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

7. Security Considerations

   This section will be added in future versions.

8. IANA Considerations


9. References
9.1 Normative References

   [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, <http://www.rfc-

   [RFC7365]  Lasserre, M., Balus, F., Morin, T., Bitar, N., and Y.
   Rekhter, "Framework for Data Center (DC) Network Virtualization",
   RFC 7365, DOI 10.17487/RFC7365, October 2014, <http://www.rfc-

   [RFC7364]  Narten, T., Ed., Gray, E., Ed., Black, D., Fang, L.,
   Kreeger, L., and M. Napierala, "Problem Statement: Overlays for
   Network Virtualization", RFC 7364, DOI 10.17487/RFC7364, October
   2014, <http://www.rfc-editor.org/info/rfc7364>.

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

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

9.2 Informative References

   [IP-PREFIX]  Rabadan et al., "IP Prefix Advertisement in EVPN",
   draft-ietf-bess-evpn-prefix-advertisement-11, work in progress, May,

   [INTER-SUBNET]  Sajassi et al., "IP Inter-Subnet Forwarding in EVPN",
   draft-ietf-bess-evpn-inter-subnet-forwarding-05, work in progress,
   July, 2018

   [EVPN-USAGE]  Rabadan et al., "Usage and applicability of BGP MPLS
   based Ethernet VPN", work in progress, draft-ietf-bess-evpn-usage-06,
   August 2017


   [RFC8365]  Sajassi-Drake et al., "A Network Virtualization Overlay
   Solution using EVPN", work in progress,  draft-ietf-bess-
   evpn-overlay-08, RFC 8365, March 2017 2017, <http://www.rfc-

   [GENEVE]  Gross et al., "Geneve: Generic Network Virtualization
   Encapsulation", draft-ietf-nvo3-geneve-05, draft-ietf-nvo3-geneve-08, work in progress,
   September 2017 October

   [NVO3-ENCAP]  Boutros et al., "NVO3 Encapsulation Considerations",
   draft-ietf-nvo3-encap-02, work in progress, October 2017 September 2018

   [TUNNEL-ENCAP]  Rosen et al., "The BGP Tunnel Encapsulation
   Attribute", draft-ietf-idr-tunnel-encaps-03, draft-ietf-idr-tunnel-encaps-10, work in progress, May
   31, 2016. August

   [EVPN-LSP-PING]  Jain et al., "LSP-Ping Mechanisms for EVPN and PBB-
   EVPN", draft-jain-bess-evpn-lsp-ping-05, draft-jain-bess-evpn-lsp-ping-07, work in progress, July 2017 June 2018

   [LOOP]  Rabadan et al., "Loop Protection in EVPN networks", draft-
   snr-bess-evpn-loop-protect-02, work in progress, July 2017 August 2018

   [PROXY-ARP-ND]  Rabadan et al., "Operational Aspects of Proxy-ARP/ND
   in EVPN Networks",  draft-ietf-bess-evpn-proxy-arp-nd-03,  draft-ietf-bess-evpn-proxy-arp-nd-05, work in
   progress, October 2017 2018

   [IGMP-MLD-PROXY]  Sajassi et al., "IGMP and MLD Proxy for EVPN",
   draft-ietf-bess-evpn-igmp-mld-proxy-02, work in progress, March 2017 June 2018

   [PIM-PROXY]  Rabadan et al., "PIM Proxy in EVPN Networks", draft-skr-
   bess-evpn-pim-proxy-01, work in progress, October 2017

   [OPT-IR]  Rabadan et al., "Optimized Ingress Replication solution for
   EVPN", draft-ietf-bess-evpn-optimized-ir-02, draft-ietf-bess-evpn-optimized-ir-06, work in progress, August

   [HRW-DF]  Mohanty
   October 2018

   [DF]  Rabadan-Mohanty et al., "A new "Framework for EVPN Designated
   Forwarder Election for
   the EVPN", draft-ietf-bess-evpn-df-election-03, Extensibility", draft-ietf-bess-evpn-df-election-
   04, work in progress, October 2017 2018

   [PREF-DF]  Rabadan et al., "Preference-based EVPN DF Election",
   draft-ietf-bess-evpn-pref-df-00, work in progress, June 2017

   [AC-DF]  Rabadan et al., "AC-Influenced Designated Forwarder Election
   for EVPN", draft-ietf-bess-evpn-ac-df-02,
   draft-ietf-bess-evpn-pref-df-02, work in progress, October
   2017 2018

   [OISM]  Lin at al., "EVPN Optimized Inter-Subnet Multicast (OISM)
   Forwarding", draft-lin-bess-evpn-irb-mcast-04, draft-ietf-bess-evpn-irb-mcast-01, work in progress,
   October 2017
   July 2018

   [EVPN-DCI]  Rabadan et al., "Interconnect Solution for EVPN Overlay
   networks", draft-ietf-bess-dci-evpn-overlay-10, work in progress,
   March 2018

   [BUM-UPDATE]  Zhang et al., "Updates on EVPN BUM Procedures", draft-
   ietf-bess-evpn-bum-procedure-updates-04, work in progress, September
   2017 June 2018

   [EVPN-IPVPN] Rabadan-Sajassi et al., "EVPN Interworking with IPVPN",
   draft-rabadan-sajassi-bess-evpn-ipvpn-interworking-01, work in
   progress, October 2017 July 2018

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

   [RFC7510]   Xu, X., Sheth, N., Yong, L., Callon, R., and D. Black,
   "Encapsulating MPLS in UDP", RFC 7510, DOI 10.17487/RFC7510, April
   2015, <http://www.rfc-editor.org/info/rfc7510>.

   [RFC4364]   Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
   Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February 2006,

   [CLOS1953] Clos, C., "A Study of Non-Blocking Switching Networks",
   The Bell System Technical Journal, Vol. 32(2), DOI 10.1002/j.1538-
   7305.1953.tb01433.x, March 1953.

   [EVPN-GENEVE]  Boutros et al., "EVPN control plane for Geneve",
   draft-boutros-bess-evpn-geneve-03, work in progress, February September 2018.

   [EVPN-MVPN]  Sajassi et al., "Seamless Multicast Interoperability
   between EVPN and MVPN PEs", draft-sajassi-bess-evpn-mvpn-seamless-
   interop-02, work in progress, July 2017. 2018.

10. Acknowledgments

   The authors want to thank Aldrin Isaac for his comments.

11. Contributors

12. Authors' Addresses

   Jorge Rabadan (Editor)
   777 E. Middlefield Road
   Mountain View, CA 94043 USA
   Email: jorge.rabadan@nokia.com

   Sami Boutros
   Email: sboutros@vmware.com

   Matthew Bocci
   Email: matthew.bocci@nokia.com

   Ali Sajassi
   Email: sajassi@cisco.com