Network Working Group                                        R. Aggarwal                                         A. Sajassi
INTERNET-DRAFT                                                    Arktan                                                     Cisco
Category: Standards Track
Expires: August 25, 2012                                      A. Sajassi
                                                                   Cisco

J. Uttaro                                                  W. Henderickx
AT&T                                                      Alcatel-Lucent

A. Isaac
                                                             R. Aggarwal
N. Bitar
Bloomberg                                                          Arktan
Verizon
                                                           W. Henderickx
S. Boutros                                                      F. Balus                                                      R. Shekhar
K. Patel                                                  Alcatel-Lucent
S. Salam
Cisco                                                       Aldrin Isaac
                                                               Bloomberg
J. Drake
R. Shekhar                                                     J. Uttaro
Juniper Networks
S. Boutros
K. Patel
Cisco                                                  February 24,                                                    AT&T

Expires: January 14, 2012                                  July 14, 2012

                      BGP MPLS Based Ethernet VPN
                        draft-ietf-l2vpn-evpn-00
                        draft-ietf-l2vpn-evpn-01

Status of this Memo

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   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors. All rights reserved.

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   described in the Simplified BSD License.

Abstract

   This document describes procedures for BGP MPLS based Ethernet VPNs
   (E-VPN).

Table of Contents

   1. Specification of requirements . . . . . . . . . . . . . . . . .  4  5
   2. Contributors  . . . . . . . . . . . . . . . . . . . . . . . . .  4  5
   3. Introduction  . . . . . . . . . . . . . . . . . . . . . . . . .  4  5
   4. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . .  4  5
   5. BGP MPLS Based E-VPN Overview . . . . . . . . . . . . . . . . .  4  6
   6. Ethernet Segment Identifier . .  . . . . . . . . . . . . . . . .  6
   7. BGP E-VPN NLRI  . . . . . . . . . .  7
   7. Ethernet Tag  . . . . . . . . . . . . . .  7
     7.1. Ethernet Auto-Discovery Route . . . . . . . . . . .  8
     7.1 VLAN Based Service Interface . . . .  8
     7.2.  MAC Advertisement Route . . . . . . . . . . . .  9
     7.2 VLAN Bundle Service Interface  . . . . .  8
     7.3. Inclusive Multicast Ethernet Tag Route . . . . . . . . . .  9
   8. ESI MPLS Label Extended Community .
       7.2.1 Port Based Service Interface . . . . . . . . . . . . . .  9
   9. Auto-Discovery  . . . .
     7.3 VLAN Aware Bundle Service Interface  . . . . . . . . . . . .  9
   8. BGP E-VPN NLRI  . . . . . . . .  9
   10. Auto-Discovery of Ethernet Tags on Ethernet Segments . . . . . 10
     10.1. Constructing the Ethernet A-D Route . . . . . . . . . . . 10
       10.1.1.
     8.1. Ethernet A-D Auto-Discovery Route per E-VPN . . . . . . . . . . . . . 11
         10.1.1.1. Ethernet A-D Route Targets . . 10
     8.2.  MAC Advertisement Route  . . . . . . . . . . 12
       10.1.2. Ethernet A-D Route per Ethernet Segment . . . . . . . 12
         10.1.2.1. 11
     8.3. Inclusive Multicast Ethernet A-D Tag Route Targets .  . . . . . . . . . . . 13
     10.2. Motivations for Ethernet A-D Route per 11
     8.4 Ethernet Segment Route . 13
       10.2.1. Multi-Homing . . . . . . . . . . . . . . . . . . 12
     8.5 ESI MPLS Label Extended Community  . . . 14
       10.2.2. Optimizing Control Plane Convergence . . . . . . . . . 14
       10.2.3. Reducing Number of Ethernet A-D Routes . 12
     8.6 ES-Import Extended Community . . . . . . . . . 14
   11. Determining Reachability to Unicast MAC Addresses . . . . . . 14
     11.1. Local Learning . 13
     8.7 MAC Mobility Extended Community  . . . . . . . . . . . . . . 13
   9. Multi-homing Functions  . . . . . . . 15
     11.2. Remote learning . . . . . . . . . . . . . 13
     9.1 Multi-homed Ethernet Segment Auto-Discovery  . . . . . . . . 15
       11.2.1. 13
       9.1.1 Constructing the BGP E-VPN MAC Address Advertisement Ethernet Segment Route  . 15
   12. Optimizing ARP . . . . . . . 14
     9.2 Fast Convergence . . . . . . . . . . . . . . . . . 17
   13. Designated Forwarder Election . . . . . 14
       9.2.1 Constructing the Ethernet A-D Route per Ethernet
             Segment  . . . . . . . . . . . 18
     13.1. DF Election Performed by All MESes . . . . . . . . . . . . 19
     13.2. DF Election Performed Only on Multi-Homed MESes . 15
         9.2.1.1. Ethernet A-D Route Targets  . . . . . 20
   14. Handling of Multi-Destination Traffic . . . . . . . 15
     9.3 Split Horizon  . . . . . 21
     14.1. Construction of the Inclusive Multicast Ethernet Tag
           Route . . . . . . . . . . . . . . . . . . 16
       9.3.1 ESI MPLS Label Assignment  . . . . . . . . 21
     14.2. P-Tunnel Identification . . . . . . . 16
         9.3.1.1 Ingress Replication  . . . . . . . . . . 22
     14.3. Ethernet Segment Identifier and Ethernet Tag . . . . . . 16
         9.3.1.2. P2MP MPLS LSPs  . 22
   15. Processing of Unknown Unicast Packets . . . . . . . . . . . . 23
     15.1. Ingress Replication . . . . . 17
         9.3.1.3. MP2MP LSPs  . . . . . . . . . . . . . . 24
     15.2. P2MP MPLS LSPs . . . . . . 18

     9.4 Aliasing . . . . . . . . . . . . . . . . 24
   16. Forwarding Unicast Packets . . . . . . . . . . 18
       9.4.1 Constructing the Ethernet A-D Route per EVI  . . . . . . 18
         9.4.1.1 Ethernet A-D Route Targets . . 24
     16.1. Forwarding packets received from a CE . . . . . . . . . . 24
     16.2. Forwarding packets received from a remote MES . 19
     9.5 Designated Forwarder Election  . . . . . 25
       16.2.1. Unknown Unicast Forwarding . . . . . . . . . . 20
       9.5.1 Default DF Election Procedure  . . . . 25
       16.2.2. Known Unicast Forwarding . . . . . . . . . 21
       9.5.2 DF Election with Service Carving . . . . . . 26
   17. Split Horizon . . . . . . 21
   10. Determining Reachability to Unicast MAC Addresses  . . . . . . 22
     10.1. Local Learning . . . . . . . . . . . . 26
     17.1. ESI MPLS Label: Ingress Replication . . . . . . . . . . 23
     10.2. Remote learning  . 26
     17.2. ESI MPLS Label: P2MP MPLS LSPs . . . . . . . . . . . . . . 27
     17.3. ESI MPLS Label: MP2MP LSPs . . . . . . 23
       10.2.1. Constructing the BGP E-VPN MAC Address Advertisement . 23
   11. ARP and ND . . . . . . . . . 28
   18. Load Balancing of Unicast Packets . . . . . . . . . . . . . . 28
     18.1. Load balancing of traffic from an MES to remote CEs . . . 28
     18.2. Load balancing 25
   12. Handling of traffic between an MES and a local CE Multi-Destination Traffic  . 30
       18.2.1. Data plane learning . . . . . . . . . . . 26
     12.1. Construction of the Inclusive Multicast Ethernet Tag
           Route  . . . . . . 31
       18.2.2. Control plane learning . . . . . . . . . . . . . . . . 31
   19. MAC Moves . . . . 26
     12.2. P-Tunnel Identification  . . . . . . . . . . . . . . . . . 27
   13. Processing of Unknown Unicast Packets  . . . . . 31
   20. Multicast . . . . . . . 28
     13.1. Ingress Replication  . . . . . . . . . . . . . . . . . . . 32
     20.1. Ingress Replication 28
     13.2. P2MP MPLS LSPs . . . . . . . . . . . . . . . . . . . 32
     20.2. P2MP LSPs . . . 29
   14. Forwarding Unicast Packets . . . . . . . . . . . . . . . . . . 29
     14.1. Forwarding packets received from a CE  . . . 32
     20.3. MP2MP LSPs . . . . . . . 29
     14.2. Forwarding packets received from a remote PE . . . . . . . 30
       14.2.1. Unknown Unicast Forwarding . . . . . . . . . . 32
       20.3.1. Inclusive Trees . . . . 30
       14.2.2. Known Unicast Forwarding . . . . . . . . . . . . . . . 33
       20.3.2. Selective Trees 31
   15. Load Balancing of Unicast Frames . . . . . . . . . . . . . . . 31
     15.1. Load balancing of traffic from an PE to remote CEs . . . . 33
     20.4. Explicit Tracking 31
       15.1.1 Active-Standby Redundancy Mode  . . . . . . . . . . . . 31
       15.1.2 All-Active Redundancy Mode  . . . . . . . . 34
   21. Convergence . . . . . . 32
     15.2. Load balancing of traffic between an PE and a local CE . . 33
       15.2.1. Data plane learning  . . . . . . . . . . . . . . . . . 34
     21.1. Transit Link and Node Failures between MESes
       15.2.2. Control plane learning . . . . . . . . . . . . . . . . 34
     21.2. MES Failures
   16. MAC Mobility . . . . . . . . . . . . . . . . . . . . . . . . . 34
       21.2.1. Local Repair
   17. Multicast  . . . . . . . . . . . . . . . . . . . . . 35
     21.3. MES to CE Network Failures . . . . . 36
     17.1. Ingress Replication  . . . . . . . . . . . 35
   22. LACP State Synchronization . . . . . . . . 36
     17.2. P2MP LSPs  . . . . . . . . . . . . . 35
   23. Acknowledgements . . . . . . . . . . . 36
     17.3. MP2MP LSPs . . . . . . . . . . . . . . . . . . . . . . . . 36
   24. References
       17.3.1. Inclusive Trees  . . . . . . . . . . . . . . . . . . . 36
       17.3.2. Selective Trees  . . . . . . . . . . . . . . . . . . . 37
   25. Author's Address
     17.4. Explicit Tracking  . . . . . . . . . . . . . . . . . . . . 38
   18. Convergence  . . . 37

1. Specification of requirements

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", . . . . . . . . . . . . . . . . . . . . . . 38
     18.1. Transit Link and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

2. Contributors

   In addition to the authors listed above, the following individuals
   also contributed to this document:
      Quaizar Vohra
      Kireeti Kompella
      Apurva Mehta
      Juniper Networks

      Samer Salam
      Cisco

3. Introduction

   This Node Failures between PEs . . . . . . . . 38
     18.2. PE Failures  . . . . . . . . . . . . . . . . . . . . . . . 38
       18.2.1. Local Repair . . . . . . . . . . . . . . . . . . . . . 38
     18.3. PE to CE Network Failures  . . . . . . . . . . . . . . . . 39
   19. LACP State Synchronization . . . . . . . . . . . . . . . . . . 39
   20. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 40
   21. References . . . . . . . . . . . . . . . . . . . . . . . . . . 40
   21. Author's Address . . . . . . . . . . . . . . . . . . . . . . . 41

1. Specification of requirements

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

2. Contributors

   In addition to the authors listed above, the following individuals
   also contributed to this document:

      Quaizar Vohra
      Kireeti Kompella
      Apurva Mehta
      Nadeem Mohammad
      Juniper Networks

      Clarence Filsfils
      Dennis Cai
      Cisco

3. Introduction

   This document describes procedures for BGP MPLS based Ethernet VPNs
   (E-VPN).  The procedures described here are intended to meet the
   requirements specified in [E-VPN-REQ].  Please refer to [E-VPN-REQ]
   for the detailed requirements and motivation.

   This document proposes an MPLS based technology, referred to as MPLS-
   based E-VPN (E-VPN). E-VPN requires
   extensions to existing IP/MPLS protocols as described in this
   document. In addition to these extensions E-VPN uses several building
   blocks from existing MPLS technologies.

4. Terminology

   CE: Customer Edge device e.g., host or router or switch
      MES: MPLS Edge Switch
      EVI:

   E-VPN Instance
      ESI: (EVI):  An E-VPN routing and forwarding instance on a
   PE.

   Ethernet segment identifier
      LACP: (ESI):  If a CE is multi-homed to two or
   more PEs, the set of Ethernet links that attaches the CE to the PEs
   is an 'Ethernet segment'.   Ethernet segments MUST have a unique non-
   zero identifier, the 'Ethernet Segment Identifier'.

   Ethernet Tag:  An Ethernet Tag identifies a particular broadcast
   domain, e.g., a VLAN.  An E-VPN instance consists of one or more
   broadcast domains. Ethernet tag(s) are assigned to the broadcast
   domains of a given E-VPN instance by the provider of that E-VPN, and
   each PE in that E-VPN instance performs a mapping between broadcast
   domain identifier(s) understood by each of its attached CEs and the
   corresponding Ethernet tag.

   Link Aggregation Control Protocol
      MP2MP: (LACP):

   Multipoint to Multipoint
      P2MP: (MP2MP):

   Point to Multipoint
      P2P: (P2MP):

   Point to Point (P2P):

5. BGP MPLS Based E-VPN Overview

   This section provides an overview of E-VPN.

   An E-VPN comprises CEs that are connected to PEs, or MPLS Edge
   Switches (MES), PEs that form the edge
   of the MPLS infrastructure. A CE may be a host, a router or a switch.
   The MPLS Edge Switches PEs provide
   layer 2 virtual bridge Layer 2 bridged connectivity between the CEs.
   There may be multiple E-VPNs in the provider's network. An E-VPN routing and
   forwarding instance on an MES is referred to as an E-VPN Instance
   (EVI).

   The MESes maybe PEs may be connected by an MPLS LSP infrastructure which provides
   the benefits of MPLS LSP technology such as fast-reroute, resiliency,
   etc.  The MESes PEs may also be connected by an IP infrastructure in which
   case IP/GRE tunneling is or other IP tunneling can be used between the
   MESes.
   PEs. The detailed procedures in this version of this document are
   specified only for MPLS LSPs as the tunneling technology. However
   these procedures are designed to be extensible to IP/GRE IP tunneling as the
   PSN tunneling technology.

   In an E-VPN, MAC learning between MESes PEs occurs not in the data plane
   (as happens with traditional bridging) but in the control plane.
   Control plane learning offers greater control over the MAC learning
   process, such as restricting who learns what, and the ability to
   apply policies.  Furthermore, the control plane chosen for
   advertising MAC reachability information is multi-protocol (MP) BGP
   (very similar
   (similar to IP VPNs (RFC 4364)), providing 4364)). This provides greater scale, scalability
   and the ability to preserve the "virtualization" or isolation of
   groups of interacting agents (hosts, servers, Virtual Machines) virtual machines) from
   each other. In E-VPNs MESes E-VPN, PEs advertise the MAC addresses learned from
   the CEs that are connected to them, along with an MPLS label, to
   other
   MESes PEs in the control plane using MP-BGP. Control plane learning
   enables load balancing of traffic to and from CEs that are multi-
   homed to multiple MESes. PEs. This is in addition to load balancing across
   the MPLS core via multiple LSPs betwen between the same pair of MESes. PEs.  In
   other words it allows CEs to connect to multiple active points of
   attachment. It also improves convergence times in the event of
   certain network failures.

   However, learning between MESes PEs and CEs is done by the method best
   suited to the CE: data plane learning, IEEE 802.1x, LLDP, 802.1aq,
   ARP, management plane or other protocols.

   It is a local decision as to whether the Layer 2 forwarding table on
   a MES
   an PE is populated with all the MAC destinations destination addresses known to
   the control
   plane plane, or whether the MES PE implements a cache based scheme.
   For instance the MAC forwarding table may be populated only with the
   MAC destinations of the active flows transiting a specific MES. PE.

   The policy attributes of an E-VPN are very similar to those of an IP
   VPN. IP-VPN.
   An E-VPN instance EVI requires a Route-Distinguisher (RD) and an E-
   VPN requires one or more Route-Targets Route-
   Targets (RTs). A CE attaches to an E-
   VPN E-VPN instance (EVI) on an MES, PE, on
   an Ethernet interface which may be configured for one or more
   Ethernet Tags, e.g., VLANs. Some deployment scenarios guarantee
   uniqueness of VLANs across E-VPNs: all points of attachment of a
   given E-VPN EVI use the same VLAN, and no other
   E-VPN EVI uses this VLAN.  This
   document refers to this case as a "Unique
   Single VLAN E-VPN" and describes
   simplified procedures to optimize for it.

6. Ethernet Segment Identifier

   If a CE is multi-homed to two or more MESes, PEs, the set of Ethernet links
   constitutes an "Ethernet segment". Segment". An Ethernet segment may appear to
   the CE as a Link Aggregation Group (LAG).  Ethernet segments have an
   identifier, called the "Ethernet Segment Identifier" (ESI) which is
   encoded as a ten octets integer.  A single-homed CE is considered to
   be attached to an Ethernet segment with ESI 0. Otherwise, an Ethernet
   segment MUST have a unique non-zero ESI.  The ESI can be assigned
   using various mechanisms:
      1. The ESI may be configured. For instance when E-VPNs are used to
      provide a VPLS service the ESI is fairly analogous to the Multi-
      homing site ID in [BGP-VPLS-MH].

      2. If IEEE 802.1AX LACP is used, used between the MESes PEs and CEs, then
      the ESI is determined from LACP by concatenating the following
      parameters:

        + CE LACP System Identifier comprised of two bytes octets of System
          Priority and six bytes octets of System MAC address, where the
          System Priority is encoded in the most significant two bytes. octets.
          The CE LACP identifier MUST be encoded in the high order eight bytes
          octets of the ESI.

        + CE LACP two byte octets Port Key. The CE LACP port key MUST be
          encoded in the low order two bytes octets of the ESI ESI.

      As far as the CE is concerned concerned, it would treat the multiple MESes PEs
      that it is connected to as the same switch. This allows the CE
      to aggregate links that are attached to different MESes PEs in the
      same bundle.

      3. If LLDP is used, used between the MESes PEs and CEs that are hosts, then
      the ESI is determined by LLDP. The ESI will be specified in a
      following version.

      4. In the case of indirectly connected hosts via a bridged LAN
      between the CEs and the MESes, PEs, the ESI is determined based on the
      Layer 2 bridge protocol as follows: If STP MST is used in the bridged
      LAN then the value of the ESI is derived by listening to BPDUs on
      the Ethernet segment. To achieve this the MES PE is not required to
      run STP. MST. However the MES PE must learn the Switch ID, MSTP ID and Root Bridge ID MAC address
      and Bridge Priority of the root of the Internal Spanning Tree
      (IST) by listening to STP the BPDUs. The ESI is constructed as
      follows:

      {Switch ID (6 bits), MSTP ID (6 bits),

      {Bridge Priority (16 bits) , Root Bridge ID MAC Address (48 bits)}

7. BGP E-VPN NLRI

   This document defines Ethernet Tag

   An Ethernet Tag identifies a new BGP NLRI, called the E-VPN NLRI.

   Following is the format of the E-VPN NLRI:

                   +-----------------------------------+
                   |    Route Type (1 octet)           |
                   +-----------------------------------+
                   |     Length (1 octet)              |
                   +-----------------------------------+
                   | Route Type specific (variable)    |
                   +-----------------------------------+

   The Route Type field defines encoding particular broadcast domain, e.g. a
   VLAN, in an EVI.  An EVI consists of one or more broadcast domains.
   Ethernet Tags are assigned to the rest broadcast domains of E-VPN NLRI
   (Route Type specific E-VPN NLRI).

   The Length field indicates a given EVI by
   the length in octets provider of the Route Type
   specific field of E-VPN NLRI.

   This document defines service. Each PE, in a given EVI, performs
   a mapping between the following Route Types:

        + 1 - Ethernet Auto-Discovery (A-D) route
        + 2 - MAC advertisement route
        + 3 - Inclusive Multicast Route
        + 5 - Selective Multicast Auto-Discovery (A-D) Route
        + 6 - Leaf Auto-Discovery (A-D) Route

   The detailed encoding Tag and procedures for these route types the corresponding broadcast
   domain identifier(s) understood by each of its attached CEs (e.g. CE
   VLAN Identifiers or CE-VIDs).

   If the broadcast domain identifiers(s) are
   described in subsequent sections.

   The E-VPN NLRI is carried in BGP [RFC4271] using BGP Multiprotocol
   Extensions [RFC4760] with an AFI understood consistently by
   all of TBD and the CEs in an SAFI of E-VPN (To EVI, the broadcast domain identifier(s) MAY be
   used as the corresponding Ethernet Tag(s). In other words, the
   Ethernet Tag ID assigned by IANA). The NLRI field in the
   MP_REACH_NLRI/MP_UNREACH_NLRI attribute contains the E-VPN NLRI
   (encoded as specified above).

   In order for two BGP speakers to exchange labeled E-VPN NLRI, they
   must use BGP Capabilities Advertisement provider is numerically equal to ensure that they both are
   capable the
   broadcast domain identifier (e.g., CE-VID = Ethernet Tag).

   Further, some deployment scenarios guarantee uniqueness of properly processing such NLRI. This is done as specified
   in [RFC4760], by using capability code 1 (multiprotocol BGP) with an
   AFI of TBD and an SAFI broadcast
   domain identifiers across all EVIs;  all points of E-VPN.

7.1. Ethernet Auto-Discovery Route

   A Ethernet A-D route type specific E-VPN NLRI consists attachment of a
   given EVI use the
   following:

                   +---------------------------------------+
                   |      RD   (8 octets)                  |
                   +---------------------------------------+
                   |Ethernet Segment Identifier (10 octets)|
                   +---------------------------------------+
                   |  Ethernet Tag ID (4 octets)           |
                   +---------------------------------------+
                   |  MPLS Label (3 octets)                |
                   +---------------------------------------+

   For procedures same broadcast domain identifier(s) and usage of this route please see no other
   EVI uses these broadcast domain identifier(s).  This allows the RT(s)
   for each EVI to be derived automatically, as described in section
   9.4.1.1.1 "Auto-Derivation from the sections on
   "Auto-Discovery of Ethernet Tags on Tag ID".

   The following subsections discuss the relationship between Ethernet Segments", "Designated
   Forwarder Election"
   Tags, EVIs and "Load Balancing".

7.2.  MAC Advertisement Route

   A MAC advertisement route type specific E-VPN NLRI consists broadcast domain identifiers as well as the setting of
   the
   following:

                   +---------------------------------------+
                   |      RD   (8 octets)                  |
                   +---------------------------------------+
                   |Ethernet Segment Identifier (10 octets)|
                   +---------------------------------------+
                   | Ethernet Tag ID (4 octets)           |
                   +---------------------------------------+
                   |  MAC Address Length (1 octet)         |
                   +---------------------------------------+
                   |  MAC Address (6 octets)               |
                   +---------------------------------------+
                   |  IP Address Length (1 octet)          |
                   +---------------------------------------+
                   |  IP Address (4 or 16 octets)          |
                   +---------------------------------------+
                   |  MPLS Label (n * 3 octets)            |
                   +---------------------------------------+

   For procedures and usage Identifier, in the various E-VPN BGP routes (defined
   in section 8), for the different types of service interfaces
   described in [EVPN-REQ].

7.1 VLAN Based Service Interface

   With this route please see service interface, there is a one-to-one mapping between
   the sections broadcast domain identifier understood by a CE on
   "Determining Reachability to Unicast MAC Addresses" a port (e.g.
   CE-VID) and "Load
   Balancing of Unicast Packets".

7.3. Inclusive Multicast Ethernet Tag Route

   An Inclusive Multicast Ethernet Tag route type specific E-VPN NLRI
   consists of the following:

                   +---------------------------------------+
                   |      RD   (8 octets)                  |
                   +---------------------------------------+
                   |Ethernet Segment Identifier (10 octets)|
                   +---------------------------------------+
                   |  Ethernet Tag ID (4 octets)           |
                   +---------------------------------------+
                   |   Originating Router's IP Addr        |
                   |          (4 or 16 octets)             |
                   +---------------------------------------+

   For procedures and usage of this route please see the sections on
   "Handling of Multi-Destination Traffic", "Unknown Unicast Traffic"
   and "Multicast".

8. ESI MPLS Label Extended Community

   This extended community an EVI. Furthermore, there is a new transitive extended community. It
   may be advertised along single bridge domain per
   PE for the EVI. Different CEs connected to different PE ports MAY use
   different broadcast domain identifiers (e.g. CE-VIDs) for the same
   EVI. If said identifiers are different, the frames SHOULD remain
   tagged with Ethernet Auto-Discovery routes. the originating CE's broadcast domain identifier (e.g.
   CE-VID). When
   used it carries properties associated with the ESI. Specifically it
   enables split horizon procedures for multi-homed sites. The
   procedures for using this Extended Community CE broadcast domain identifiers are described in
   following sections.

   Each ESI MPLS Label Extended Community is encoded as not consistent,
   a 8-octet value
   as follows:

        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | 0x44        |   Sub-Type    | Flags (One Octet)  |Reserved=0  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | Reserved = 0|          ESI MPLS label                         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The low order bit of the flags octet is defined as tag translation function MUST be supported in the "Active-
   Standby" bit data path and may
   MUST be set to 1. performed on the disposition PE. The other bits must Ethernet Tag Identifier
   in all E-VPN routes MUST be set to 0.

9. Auto-Discovery

   E-VPN requires

7.2 VLAN Bundle Service Interface

   With this service interface, there is a many-to-one mapping between
   the following types of auto-discovery procedures:
      + E-VPN Auto-Discovery, which allows broadcast domain identifier understood by a CE on a port (e.g.
   CE-VID) and an MES EVI. Furthermore, there is a single bridge domain per
   PE for the EVI. Different CEs connected to discover different PE ports MUST
   use the other
        MESes in same broadcast domain identifiers (e.g. CE-VIDs) for the E-VPN. Each MES advertises one or more "Inclusive
        Multicast Tag Routes". same
   EVI. The procedures for advertising these
        routes are described in MPLS encapsulated frames MUST remain tagged with the section on "Handling of Multi-
         Destination Traffic".

      + Auto-Discovery of Ethernet Tags on
   originating CE's broadcast domain identifier (e.g. CE-VID). Tag
   translation is NOT permitted. The Ethernet Segments, Tag Identifier in all E-
   VPN routes MUST be set to 0.

7.2.1 Port Based Service Interface

   This service interface is a
        particular E-VPN.  The procedures are described in section
        "Auto-Discovery special case of Ethernet Tags on Ethernet Segments".

      + Ethernet Segment Auto-Discovery used for auto-discovery the VLAN Bundle service
   interface, where all of MESes
        that the VLANs on the port are multi-homed part of the same
   service and map to the same Ethernet segment. bundle. The procedures are identical to
   those described in section "Auto-Discovery of Ethernet
        Tags on Ethernet Segments".

10. Auto-Discovery of Ethernet Tags on Ethernet Segments

   If a CE 7.2.

7.3 VLAN Aware Bundle Service Interface

   With this service interface, there is multi-homed to two or more MESes on a particular Ethernet
   segment, each MES MUST advertise, to other MESes in the E-VPN, the
   information about many-to-one mapping between
   the Ethernet Tags that are associated with that
   Ethernet segment. An Ethernet Tag identifies a particular broadcast
   domain. An example of an Ethernet Tag is a VLAN ID. The MES MAY
   advertise each Ethernet Tag associated with the Ethernet Segment, or
   it may advertise domain identifier understood by a wildcard to cover all the Ethernet Tags enabled CE on
   the segment.  If a CE is single-homed, then the MES that it is
   attached to MAY advertise port (e.g.
   CE-VID) and an EVI. Furthermore, there are multiple bridge domains
   per PE for the information about Ethernet Tags
   (e.g.,VLANs) on EVI: one broadcast domain per CE broadcast domain
   identifier. In the Ethernet segment connected to case where the CE.

   The information about an Ethernet Tag on CE broadcast domain identifiers are
   not consistent for different CEs, a particular Ethernet
   segment is advertised using an "Ethernet Auto-Discovery route
   (Ethernet A-D route)". This route is advertised using the E-VPN NLRI.

   The normalized Ethernet Tag Auto-discovery information SHOULD MUST be used to enable
   active-active load-balancing among MESes as described
   carried in section
   "Load Balancing of Unicast Packets". In the case of MPLS encapsulated frames and a multi-homed CE
   this route tag translation
   function MUST also carry the "ESI Label Extended Community" to
   enable split horizon as described be supported in section "Split Horizon".  Also, the route can data path. This translation MUST be used for Designated Forwarder (DF) election
   performed on both the imposition as
   described well as the disposition PEs. The
   Ethernet Tag Identifier in section "Designated Forwarder Election". Further,it MAY all E-VPN routes MUST be used set to optimize the withdrawal of MAC addresses upon failure as
   described in section "Convergence".

   This section describes procedures for advertising one or more
   Ethernet A-D routes per
   normalized Ethernet tag per E-VPN. We will call this as
   "Ethernet A-D route per E-VPN". Tag assigned by the E-VPN provider.

8. BGP E-VPN NLRI

   This section also describes
   procedures to advertise and withdraw document defines a single Ethernet A-D route per
   Ethernet Segment.  We will call this as "Ethernet A-D route per
   Segment".

10.1. Constructing new BGP NLRI, called the Ethernet A-D E-VPN NLRI.

   Following is the format of the E-VPN NLRI:

                   +-----------------------------------+
                   |    Route Type (1 octet)           |
                   +-----------------------------------+
                   |     Length (1 octet)              |
                   +-----------------------------------+
                   | Route Type specific (variable)    |
                   +-----------------------------------+

   The format Route Type field defines encoding of the Ethernet A-D rest of the E-VPN NLRI is specified
   (Route Type specific E-VPN NLRI).

   The Length field indicates the length in section "BGP E-
   VPN NLRI".

10.1.1. Ethernet A-D octets of the Route per Type
   specific field of E-VPN NLRI.

   This section describes procedures to construct document defines the following Route Types:

        + 1 - Ethernet A-D Auto-Discovery (A-D) route
   when one or more such routes
        + 2 - MAC advertisement route
        + 3 - Inclusive Multicast Route
        + 4 - Ethernet Segment Route

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

   The E-VPN NLRI is carried in BGP [RFC4271] using BGP Multiprotocol
   Extensions [RFC4760] with an MES for a given E-
   VPN instance.

   Route-Distinguisher (RD) MUST be set to the RD AFI of TBD and an SAFI of the E-VPN instance
   that is advertising the NLRI. A RD MUST (To be
   assigned for a given E-VPN
   instance on an MES. This RD MUST be unique across all E-VPN instances
   on an MES. It is RECOMMENDED to use the Type 1 RD [RFC4364]. by IANA). The
   value NLRI field comprises an IP address of in the MES (typically,
   MP_REACH_NLRI/MP_UNREACH_NLRI attribute contains the
   loopback address) followed by a number unique E-VPN NLRI
   (encoded as specified above).

   In order for two BGP speakers to the MES. exchange labeled E-VPN NLRI, they
   must use BGP Capabilities Advertisement to ensure that they both are
   capable of properly processing such NLRI. This
   number may be generated by the MES. Or is done as specified
   in the Unique Single VLAN E-
   VPN case, the low order 12 bits may be the 12 bit VLAN ID, [RFC4760], by using capability code 1 (multiprotocol BGP) with the
   remaining high order 4 bits set to 0. an
   AFI of TBD and an SAFI of E-VPN.

8.1. Ethernet Segment Identifier MAY be set to 0. When it is not zero the Auto-Discovery Route

   A Ethernet A-D route type specific E-VPN NLRI consists of the
   following:

                   +---------------------------------------+
                   |      RD   (8 octets)                  |
                   +---------------------------------------+
                   |Ethernet Segment Identifier MUST be a ten octet entity as described
   in (10 octets)|
                   +---------------------------------------+
                   |  Ethernet Tag ID (4 octets)           |
                   +---------------------------------------+
                   |  MPLS Label (3 octets)                |
                   +---------------------------------------+

   For procedures and usage of this route please see section "Ethernet 9.2 "Fast
   Convergence" and section 9.4 "Aliasing".

8.2.  MAC Advertisement Route

   A MAC advertisement route type specific E-VPN NLRI consists of the
   following:

                   +---------------------------------------+
                   |      RD   (8 octets)                  |
                   +---------------------------------------+
                   |Ethernet Segment Identifier".

   The Identifier (10 octets)|
                   +---------------------------------------+
                   |  Ethernet Tag ID is the identifier (4 octets)           |
                   +---------------------------------------+
                   |  MAC Address Length (1 octet)         |
                   +---------------------------------------+
                   |  MAC Address (6 octets)               |
                   +---------------------------------------+
                   |  IP Address Length (1 octet)          |
                   +---------------------------------------+
                   |  IP Address (4 or 16 octets)          |
                   +---------------------------------------+
                   |  MPLS Label (n * 3 octets)            |
                   +---------------------------------------+

   For procedures and usage of an this route please see section 10
   "Determining Reachability to Unicast MAC Addresses" and section 15
   "Load Balancing of Unicast Packets".

8.3. Inclusive Multicast Ethernet Tag on the Route

   An Inclusive Multicast Ethernet segment. This value may be a 12 bit VLAN ID, in which case
   the low order 12 bits are set to Tag route type specific E-VPN NLRI
   consists of the VLAN following:

                   +---------------------------------------+
                   |      RD   (8 octets)                  |
                   +---------------------------------------+
                   |  Ethernet Tag ID (4 octets)           |
                   +---------------------------------------+
                   |  IP Address Length (1 octet)          |
                   +---------------------------------------+
                   |   Originating Router's IP Addr        |
                   |          (4 or 16 octets)             |
                   +---------------------------------------+

   For procedures and usage of this route please see section 12
   "Handling of Multi-Destination Traffic", section 13 "Processing of
   Unknown Unicast Traffic" and the high order 20
   bits are set to 0. Or it may be another section 17 "Multicast".

8.4 Ethernet Tag used by the E-
   VPN.  It MAY be set to the default Segment Route

   The Ethernet Tag on Segment Route is encoded in the Ethernet
   segment or 0.

   Note that E-VPN NLRI using the above allows
   Route Type value of 4. The Route Type Specific field of the Ethernet A-D NLRI is
   formatted as follows:

                   +---------------------------------------+
                   |      RD   (8 octets)                  |
                   +---------------------------------------+
                   |Ethernet Segment Identifier (10 octets)|
                   +---------------------------------------+

   For procedures and usage of this route to please see section 9.5
   "Designated Forwarder Election".

8.5 ESI MPLS Label Extended Community

   This extended community is a new transitive extended community. It
   may be advertised along with one of the following granularities:

      + One Ethernet A-D route for a given <ESI, Ethernet Tag ID> tuple
        per E-VPN

      + One Ethernet A-D route Auto-Discovery routes and it
   enables split-horizon procedures for a given <Ethernet Tag ID> multi-homed sites as described
   in a given
        E-VPN, for all associated Ethernet segments, where the section 9.3 "Split Horizon".

   Each ESI MPLS Label Extended Community is
        set to 0.

      + One Ethernet A-D route for encoded as a 8-octet value
   as follows:

        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | 0x44        |   Sub-Type    | Flags (One Octet)  |Reserved=0  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | Reserved = 0|          ESI MPLS label                         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The low order bit of the E-VPN where both ESI flags octet is defined as the "Active-
   Standby" bit and Ethernet
        Tag ID are may be set to 1. The other bits must be set to 0.

   E-VPN supports both

8.6 ES-Import Extended Community

   This is a new transitive extended community carried with the non-qualified and qualified learning models. Ethernet
   Segment route. When non-qualified learning is used, it enables all the PEs connected to the
   same multi-homed site to import the Ethernet Tag Identifier
   specified Segment routes. The
   value is derived automatically from the ESI by encoding the 6-byte
   MAC address portion of the ESI in the ES-Import Extended Community.
   The format of this section extended community is as follows:

       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | 0x44        |   Sub-Type    |          ES-Import              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     ES-Import Cont'd                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   For procedures and in other places in usage of this document MUST attribute, please see section 9.1
   "Redundancy Group Discovery".

8.7 MAC Mobility Extended Community

   This extended community is a new transitive extended community. It
   may be set to the default Ethernet Tag, e.g., VLAN ID. When qualified
   learning advertised along with MAC Advertisement routes. The procedures
   for using this Extended Community are described in section 16 "MAC
   Mobility".

   The MAC Mobility Extended Community is used, and encoded as a 8-octet value as
   follows:

   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | 0x44          | Sub-Type      | Reserved=0                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Sequence Number                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

9. Multi-homing Functions

   This section discusses the Ethernet Tags between MESes functions, procedures and CEs associated BGP
   routes used to support multi-homing in the
   E-VPN are consistently assigned for a given broadcast domain, the E-VPN. This covers both multi-
   homed device (MHD) as well as multi-homed network (MHN) scenarios.

9.1 Multi-homed Ethernet Tag Identifier MUST be set Segment Auto-Discovery

   PEs connected to the same Ethernet Tag, e.g., VLAN
   ID for the concerned broadcast domain between the advertising MES and segment can automatically discover
   each other with minimal to no configuration through the CE.  When qualified learning is used, and exchange of
   the Ethernet Tags,
   e.g., VLAN IDs between MESes and CEs in Segment route.

9.1.1 Constructing the E-VPN are not
   consistently assigned for Ethernet Segment Route

   The Route-Distinguisher (RD) MUST be a given broadcast domain, Type 1 RD [RFC4364]. The value
   field comprises an IP address of the MES (typically, the loopback
   address) followed by 0's.

   The Ethernet Tag
   Identifier, e.g., VLAN ID Segment Identifier MUST be set to a common E-VPN provider
   assigned tag that maps locally on the advertising MES to an Ethernet
   broadcast domain ten octet ESI
   identifier such as a VLAN ID. The usage of the MPLS
   label is described in section on "Load Balancing of Unicast Packets". 6.

   The Next Hop field of the MP_REACH_NLRI attribute of BGP advertisement that advertises the Ethernet Segment route MUST
   also carry an ES-Import extended community attribute, as defined in
   section 8.6.

   The Ethernet Segment Route filtering MUST be set done such that the
   Ethernet Segment Route is imported only by the PEs that are multi-
   homed to the IPv4 or IPv6 address of same Ethernet Segment. To that end, each PE that is
   connected to a particular Ethernet segment constructs an import
   filtering rule to import a route that carries the ES-Import extended
   community, constructed from the ESI.

   Note that the new ES-Import extended community is not the same as the advertising MES.

10.1.1.1. Ethernet A-D
   Route Targets Target Extended Community. The Ethernet A-D Segment route MUST carry one or more Route Target (RT)
   attributes. RTs may be configured (as in IP VPNs), or may be derived
   automatically.

   If an MES uses Route Target Constrain [RT-CONSTRAIN], the MES SHOULD
   advertise all such RTs using Route Target Constrains. carries
   this new ES-Import extended community. The use of RT
   Constrains allows each PEs apply filtering on
   this new extended community. As a result the Ethernet A-D Segment route to reach
   is imported only those MESes by the PEs that are configured connected to import at least one RT from the set of RTs
   carried in the Ethernet A-D route.

10.1.1.1.1. Auto-Derivation from the same Ethernet Tag ID

   The following
   segment.

9.2 Fast Convergence

   In E-VPN, MAC address reachability is learnt via the procedure for deriving BGP control-
   plane over the RT attribute
   automatically from MPLS network. As such, in the Ethernet Tag ID associated with absence of any fast
   protection mechanism, the
   advertisement:

        +    The Global Administrator field network convergence time is a function of
   the RT MUST number of MAC Advertisement routes that must be set withdrawn by the
   PE encountering a failure. For highly scaled environments, this
   scheme yields slow convergence.

   To alleviate this, E-VPN defines a mechanism to efficiently and
   quickly signal, to remote PE nodes, the Autonomous System (AS) number that need to update their
   forwarding tables upon the MES
             belongs to.

        +    The Local Administrator field occurrence of the RT contains a 4
             octets long number failure in connectivity to
   an Ethernet segment. This is done by having each PE advertise an
   Ethernet A-D Route per Ethernet segment for each locally attached
   segment (refer to section 9.2.1 below for details on how this route
   is constructed). Upon a failure in connectivity to the attached
   segment, the PE withdraws the corresponding Ethernet A-D route. This
   triggers all PEs that encodes receive the withdrawal to update their next-hop
   adjacencies for all MAC addresses associated with the Ethernet Tag-ID.
   segment in question. If the no other PE had advertised an Ethernet Tag-ID is a two octet VLAN ID A-D
   route for the same segment, then it MUST be
             encoded in the lower two octets of PE that received the Local Administrator
             field and withdrawal
   simply invalidates the higher two octets MUST be set to zero.

   For MAC entries for that segment. Otherwise, the "Unique Single VLAN E-VPN" this results in auto-deriving
   PE updates the
   RT from next-hop adjacencies to point to the backup PE(s).

9.2.1 Constructing the Ethernet Tag, e.g., VLAN ID for that E-VPN.

10.1.2. Ethernet A-D Route per Ethernet Segment

   This section describes procedures to construct the Ethernet A-D route
   when a single such route is advertised by an MES PE for a given Ethernet
   Segment. This flavor of the Ethernet A-D route is used for fast
   convergence (as discussed above) as well as for advertising the ESI
   MPLS label used for split-horizon filtering (as discussed in section
   9.2). Support of this route flavor is MANDATORY.

   Route-Distinguisher (RD) MUST be a Type 1 RD [RFC4364]. The value
   field comprises an IP address of the MES PE (typically, the loopback
   address) followed by 0.  The reason for such encoding is that the RD
   cannot be that of a given E-VPN EVI since the ESI can span across one or
   more E-VPNs. EVIs.

   The Ethernet Segment Identifier MUST be a non-zero ten octet entity as
   described in section "Ethernet Segment". This document does not
   specify the use of the Ethernet A-D route when the Segment Identifier". Identifier
   is set to 0.

   The Ethernet Tag ID MUST be set to 0.

   If

   The MPLS label in the Ethernet Segment is connected NLRI MUST be set to more than one MES then the 0.

   The "ESI MPLS Label Extended Community" MUST be included in the
   route. If
   the Ethernet Segment is connected to more than one MES and active-
   active all-active multi-homing is desired desired, then the MPLS label "Active-
   Standby" bit in the flags of the ESI MPLS Label Extended Community
   MUST be set to 0 and the MPLS label in that extended community MUST
   be set to a valid MPLS label value. The MPLS label in this Extended
   Community is referred to as an "ESI label". This label MUST be a
   downstream assigned MPLS label if the advertising MES PE is using ingress
   replication for receiving multicast, broadcast or unknown unicast traffic,
   traffic from other MESes. PEs. If the advertising MES PE is using P2MP MPLS LSPs
   for sending multicast, broadcast or unknown unicast traffic, then
   this label MUST be an upstream assigned MPLS label. The usage of this
   label is described in section "Split Horizon". 9.2.

   If the Ethernet Segment is connected to more than one MES PE and active-
   standby multi-homing is desired desired, then the "Active-Standby" bit in the
   flags of the ESI MPLS Label Extended Community MUST be set to 1.

   If the per Ethernet Segment Ethernet A-D route is used in conjunction
   with the per {ESI, VLAN} Ethernet A-D route, for reasons described
   below, then the MPLS label in the NLRI ESI MPLS Label Extended Community MUST be set to 0.

10.1.2.1. 1.

9.2.1.1. Ethernet A-D Route Targets
   The Ethernet A-D route MUST carry one or more Route Target (RT)
   attributes. These RTs MUST be the set of RTs associated with all the
   E-VPN instances
   EVIs to which the Ethernet Segment, corresponding to the Ethernet A-D
   route, belongs.

10.2. Motivations for Ethernet A-D Route per Ethernet Segment

   This section describes various scenarios in which the Ethernet A-D
   route should be advertised per Ethernet Segment.

10.2.1. Multi-Homing

   The per Ethernet Segment Ethernet A-D route MUST be advertised when
   the Ethernet Segment is multi-homed. This allows Multi-Homed Ethernet
   Segment Auto-Discovery. It allows the set of MESes connected to the
   same customer site i.e., CE, to discover each other automatically
   with minimal to no configuration. It also allows other MESes

9.3 Split Horizon

   Consider a CE that
   have at least one E-VPN in common with the is multi-homed Ethernet
   Segment to discover the properties of the multi-homed two or more PEs on an Ethernet
   Segment.

   For active-active multi-homing this route is required for split
   horizon procedures as described in section "Split Horizon" and MUST
   carry
   segment ES1. If the ESI MPLS Label Extended Community with CE sends a valid ESI MPLS
   label. For active-standby multi-homing this route is required to
   indicate that active-standby multi-homing and not active-active
   multi-homing is desired.

   This route will be enhanced multicast, broadcast or unknown
   unicast packet to carry LAG specific information such as
   LACP parameters, which a particular PE, say PE1, then PE1 will be encoded as new BGP attributes or
   communities, in the future. Note forward
   that this information will be
   propagated packet to all MESes that have one or more sites in subset of the VLANs
   connected to other PEs in the Ethernet Segment. All EVI. In this
   case the MESes PEs, other than the ones PE1, that are connected the CE is multi-homed to MUST drop
   the packet and not forward back to the MESes will discard this information.

10.2.2. Optimizing Control Plane Convergence

   Ethernet A-D route per Ethernet Segment should be advertised when it CE. This is desired referred to as
   "split horizon" filtering in this document.

   In order to optimize the control plane convergence of the
   withdrawal of the Ethernet A-D routes. If achieve this split horizon function, every multicast,
   broadcast or unknown unicast packet is done then when encapsulated with an
   Ethernet segment fails, MPLS
   label that identifies the single Ethernet A-D route corresponding
   to segment of origin (i.e. the
   segment can be withdrawn first. from which the frame entered the E-VPN network). This allows all MESes that
   receive this withdrawal label
   is referred to invalidate the MAC routes learned from as the
   Ethernet segment.

   Note that ESI MPLS label, and is distributed using the Ethernet
   "Ethernet A-D route per Ethernet Segment, when used to
   optimize control plane convergence, MAY be advertised Segment" as per the procedures in addition
   section 9.1.1 above. This route is imported by the PEs connected to
   the Ethernet Tag A-D routes per E-VPN or MAY be advertised on its
   own.

10.2.3. Reducing Number of Ethernet A-D Routes

   In certain scenarios advertising Ethernet A-D routes per Ethernet
   segment, instead of per E-VPN, may reduce Segment and also by the number of Ethernet A-D
   routes PEs that have at least one EVI
   in common with the network. In these scenarios Ethernet A-D routes may be
   advertised per Ethernet segment instead of per E-VPN.

11. Determining Reachability to Unicast MAC Addresses
   MESes forward packets that they receive based on Segment in the destination MAC
   address. This implies that MESes must be able to learn how to reach route. As described in
   section 9.1.1, the route MUST carry an ESI MPLS Label Extended
   Community with a
   given destination unicast MAC address.

   There are two components to MAC address learning, "local learning"
   and "remote learning":

11.1. Local Learning

   A particular MES must be able to learn valid ESI MPLS label. The disposition PEs rely on
   the MAC addresses from value of the CEs
   that are connected ESI MPLS label to it. This determine whether or not a flooded
   frame is referred allowed to as local learning. egress a specific Ethernet segment.

9.3.1 ESI MPLS Label Assignment

   The MESes following subsections describe the assignment procedures for the
   ESI MPLS label, which differ depending on the type of tunnels being
   used to deliver multi-destination packets in a particular the E-VPN MUST support local data plane
   learning network.

9.3.1.1 Ingress Replication

   An PE that is using standard IEEE ingress replication for sending broadcast,
   multicast or unknown unicast traffic, distributes to other PEs, that
   belong to the Ethernet learning procedures. An MES
   must segment, a downstream assigned "ESI MPLS
   label" in the Ethernet A-D route. This label MUST be capable of learning MAC addresses programmed in
   the data plane when it
   receives packets such as platform label space by the following from advertising PE. Further the CE network:

        - DHCP requests

        - gratuitous ARP request for its own MAC.

        - ARP request
   forwarding entry for a peer.

   Alternatively MESes MAY learn the MAC addresses of the CEs this label must result in NOT forwarding packets
   received with this label onto the
   control plane or via management plane integration between Ethernet segment that the MESes label was
   distributed for.

   Consider PE1 and the CEs.

   There PE2 that are applications where a MAC address multi-homed to CE1 on ES1. Further
   consider that PE1 is reachable via using P2P or MP2P LSPs to send packets to PE2.

   Consider that PE1 receives a
   given MES multicast, broadcast or unknown unicast
   packet from CE1 on VLAN1 on ESI1. In this scenario, PE2 distributes
   an Inclusive Multicast Ethernet Tag route for VLAN1 in the associated
   EVI. So, when PE1 sends a locally attached Segment (e.g. with ESI X) may move
   such multicast, broadcast or unknown unicast
   packet, that it becomes reachable via receives from CE1, it MUST first push onto the MPLS
   label stack the same MES or another MES on
   another Segment (e.g. with ESI Y).  This label that PE2 has distributed for ESI1. It MUST
   then push on the MPLS label distributed by PE2 in the Inclusive
   Multicast Ethernet Tag route for VLAN1. The resulting packet is referred
   further encapsulated in the P2P or MP2P LSP label stack required to as a "MAC
   Move". Procedures
   transmit the packet to support PE2.  When PE2 receives this are described in section "MAC
   Moves".

11.2. Remote learning

   A particular MES must be able to determine how packet it
   determines the set of ESIs to send traffic replicate the packet to MAC
   addresses from the top
   MPLS label, after any P2P or MP2P LSP labels have been removed. If
   the next label is the ESI label assigned by PE2 for ESI1, then PE2
   MUST NOT forward the packet onto ESI1.

9.3.1.2. P2MP MPLS LSPs

   An PE that belong to is using P2MP LSPs for sending broadcast, multicast or are behind CEs connected
   unknown unicast traffic, distributes to other MESes
   i.e. PEs, that belong to remote CEs the
   Ethernet segment or hosts behind remote CEs. We call such MAC
   addresses as "remote" MAC addresses.

   This document requires have an MES to learn remote MAC addresses E-VPN in common with the
   control plane. In order to achieve this each MES Ethernet
   Segment, an upstream assigned "ESI MPLS label" in the Ethernet A-D
   route. This label is upstream assigned by the PE that advertises the MAC
   addresses it learns from its locally attached CEs in
   route. This label MUST be programmed by the control
   plane, other PEs, that are
   connected to all the other MESes ESI advertised in the E-VPN, using MP-BGP and route, in the MAC
   address advertisement route.

11.2.1. Constructing context label
   space for the BGP E-VPN MAC Address Advertisement
   BGP is extended to advertise these MAC addresses using advertising PE. Further the MAC
   advertisement route type forwarding entry for this
   label must result in NOT forwarding packets received with this label
   onto the E-VPN-NLRI.

   The RD Ethernet segment that the label was distributed for. This
   label MUST also be programmed by the RD of the E-VPN instance other PEs, that is advertising import the
   NLRI. The procedures route
   but are not connected to the ESI advertised in the route, in the
   context label space for setting the RD advertising PE. Further the forwarding
   entry for this label must be a given E-VPN POP with no other associated action.

   Consider PE1 and PE2 that are
   described multi-homed to CE1 on ES1. Also
   consider PE3 that is in section "Ethernet A-D Route per E-VPN".

   The Ethernet Segment Identifier the same EVI as one of the EVIs to which ES1
   belongs.  Further, assume that PE1 is set using P2MP MPLS LSPs to send
   broadcast, multicast or uknown unicast packets. When PE1 sends a
   multicast, broadcast or unknown unicast packet, that it receives from
   CE1, it MUST first push onto the MPLS label stack the ten octet ESI
   identifier described in section "Ethernet Segment Identifier". label that
   it has assigned for the ESI that the packet was received on. The Ethernet Tag ID may be zero or may represent a valid Ethernet Tag
   ID.  This field may be non-zero when there are multiple bridge
   domains
   resulting packet is further encapsulated in the E-VPN instance (e.g., P2MP MPLS label stack
   necessary to transmit the MES needs packet to perform
   qualified learning for the VLANs other PEs. Penultimate hop
   popping MUST be disabled on the P2MP LSPs used in that EVPN instance). the MPLS transport
   infrastructure for E-VPN. When PE2 receives this packet, it de-
   capsulates the top MPLS label and forwards the Ethernet Tag ID in packet using the NLRI
   context label space determined by the top label. If the next label is set
   the ESI label assigned by PE1 to a non-zero value,
   for a particular bridge domain, ESI1, then PE2 MUST NOT forward the
   packet onto ESI1. When PE3 receives this Ethernet Tag may either be packet, it de-capsulates the Ethernet tag value associated with
   top MPLS label and forwards the CE, e.g., VLAN ID, or it
   may be packet using the Ethernet Tag Identifier, e.g., VLAN ID assigned context label space
   determined by the E-
   VPN provider top label. If the next label is the ESI label
   assigned by PE1 to ESI1 and mapped PE3 is not connected to ESI1, then PE3
   MUST pop the CE's Ethernet tag. label and flood the packet over all local ESIs in the
   EVI.

9.3.1.3. MP2MP LSPs

   The latter would procedures for ESI MPLS Label assignment and usage for MP2MP LSPs
   will be described in a future version.

9.4 Aliasing

   In the case if the where a CE Ethernet tags, e.g., VLAN ID, for is multi-homed to multiple PE nodes, using a particular
   bridge domain are different on different CEs.

   The MAC address length field
   LAG with all-active redundancy, it is typically possible that only a single PE
   learns a set to 48. However this
   specification enables specifying of the MAC address as addresses associated with traffic transmitted
   by the CE. This leads to a situation where remote PE nodes receive
   MAC advertisement routes, for these addresses, from a single PE even
   though multiple PEs are connected to the multi-homed segment. As a prefix in which
   case
   result, the MAC address length field is set remote PEs are not able to effectively load-balance
   traffic among the length of PE nodes connected to the prefix. multi-homed Ethernet
   segment. This provides could be the ability to aggregate MAC addresses if case, for e.g. when the
   deployment environment supports that.  The encoding of a MAC address
   MUST be PEs perform data-
   path learning on the 6-octet MAC address specified by IEEE 802 documents
   [802.1D-ORIG] [802.1D-REV]. If access, and the load-balancing function on the
   CE hashes traffic from a given source MAC address is advertised as to a
   prefix then single PE.
   Another scenario where this occurs is when the trailing bits of PEs rely on control
   plane learning on the prefix MUST access (e.g. using ARP), since ARP traffic will
   be set to 0 to
   ensure that the entire prefix is encoded as 6 octets.

   The MPLS Label Length field value is set hashed to the number of octets a single link in the MPLS Label field. The MPLS label field carries one or more labels
   (that corresponds to LAG.

   To alleviate this issue, E-VPN introduces the stack concept of labels [MPLS-ENCAPS]).  Each label
   is encoded as 3 octets, where the high-order 20 bits contain the
   label value, and 'Aliasing'.
   Aliasing refers to the low order bit contains "Bottom ability of Stack" (as
   defined in [MPLS-ENCAPS]).

   The MPLS label stack MUST be the downstream assigned E-VPN MPLS label
   stack an PE to signal that is used by the MES it has
   reachability to forward MPLS encapsulated a given locally attached Ethernet
   packets received segment, even when
   it has learnt no MAC addresses from remote MESes, where that segment. The Ethernet A-D
   route per EVI is used to that end. Remote PEs which receive MAC
   advertisement routes with non-zero ESI SHOULD consider the destination advertised
   MAC address
   in as reachable via all PEs which have advertised
   reachability to the relevant Segment using Ethernet packet is A-D routes with
   the MAC address advertised in same ESI (and Ethernet Tag if applicable).

9.4.1 Constructing the above
   NLRI. The forwarding procedures are specified in Ethernet A-D Route per EVI

   This section "Forwarding
   Unicast Packets" and "Load Balancing of Unicast Packets".

   An MES may advertise describes procedures to construct the same single E-VPN label Ethernet A-D route
   when one or more such routes are advertised by an PE for all MAC
   addresses in a given E-VPN instance. EVI.
   This label assignment
   methodology flavor of the Ethernet A-D route is referred used for aliasing, and
   support of this route flavor is OPTIONAL.

   Route-Distinguisher (RD) MUST be set to as the RD of the EVI that is
   advertising the NLRI. An RD MUST be assigned for a per given EVI label assigment.
   Alternatively on an MES may advertise a unique E-VPN label per <ESI,
   Ethernet Tag> combination.
   PE. This label assignment methodology RD MUST be unique across all EVIs on an PE. It is
   referred
   RECOMMENDED to as a per <ESI, Ethernet Tag> label assignment. Or use the Type 1 RD [RFC4364]. The value field comprises
   an MES
   may advertise a unique E-VPN label per MAC address. All IP address of these
   methodologies have their tradeoffs.

   Per EVI label assignment requires the least number of E-VPN labels,
   but requires a MAC lookup in addition to an MPLS lookup on an egress
   MES for forwarding. On PE (typically, the other hand a unique label per <ESI,
   Ethernet Tag> or loopback address) followed by
   a number unique label per MAC allows an egress MES to
   forward a packet that it receives from another MES, to the connected
   CE, after looking up only PE.  This number may be generated by the PE.
   Or in the MPLS labels and not having Unique VLAN E-VPN case, the low order 12 bits may be the 12
   bit VLAN ID, with the remaining high order 4 bits set to do 0.

   The Ethernet Segment Identifier MUST be a MAC
   lookup.

   As well ten octet entity as to insert
   described in section "Ethernet Segment Identifier". This document
   does not specify the appropriate VLAN use of the Ethernet A-D route when the Segment
   Identifier is set to 0.

   The Ethernet Tag ID is the identifier of an Ethernet Tag on egress to the CE A
   MES
   Ethernet segment. This value may also advertise more than one label for be a given MAC address.
   For instance an MES may advertise two labels, one of 12 bit VLAN ID, in which is for case
   the
   ESI corresponding low order 12 bits are set to the MAC address VLAN ID and the second is for high order 20
   bits are set to 0. Or it may be another Ethernet Tag used by the E-
   VPN.  It MAY be set to the default Ethernet Tag on the ESI Ethernet
   segment or to the value 0.

   Note that the MAC address is learnt on.

   The IP Address field above allows the Ethernet A-D route to be advertised
   with one of the following granularities:

      + One Ethernet A-D route for a given <ESI, Ethernet Tag ID> tuple
        per EVI. This is optional. By default applicable when the IP Address length PE uses MPLS-based
        disposition.

      + One Ethernet A-D route per <ESI, EVI> (where the Ethernet
        Tag ID is set to 0 and the IP address 0). This is excluded. When a valid IP address applicable when the PE uses
        MAC-based disposition, or when the PE uses MPLS-based
        disposition when no VLAN translation is
   included it required.

   The usage of the MPLS label is encoded as specified described in the section "Optimizing ARP". on "Load
   Balancing of Unicast Packets".

   The Next Hop field of the MP_REACH_NLRI attribute of the route MUST
   be set to the IPv4 or IPv6 address of the advertising MES. PE.

9.4.1.1 Ethernet A-D Route Targets

   The BGP advertisement that advertises the MAC advertisement Ethernet A-D route MUST also carry one or more Route Target (RT)
   attributes. RTs may be configured (as in IP VPNs), or may be derived automatically from
   automatically.

   If an PE uses Route Target Constrain [RT-CONSTRAIN], the PE SHOULD
   advertise all such RTs using Route Target Constrains. The use of RT
   Constrains allows each Ethernet Tag ID, in the Unique Single VLAN case as described in
   section "Ethernet A-D Route per E-VPN".

   It is route to be noted reach only those PEs
   that this document does not require MESes to create
   forwarding state for remote MACs when they are learnt in the control
   plane. When this forwarding state is actually created is a local
   implementation matter.

12. Optimizing ARP

   The IP address field in the MAC advertisement route may optionally
   carry one of the IP addresses associated with the MAC address. This
   provides an option which can be used configured to minimize import at least one RT from the flooding set of ARP
   messages to MAC VPN CEs and to MESes. This option also minimizes ARP
   message processing on MAC VPN CEs. A MES may learn the IP address
   associated with a MAC address RTs
   carried in the control or management plane
   between the CE and the MES. Or it may learn this binding by snooping
   certain messages to or Ethernet A-D route.

9.4.1.1.1 Auto-Derivation from a CE. When a MES learns the IP address
   associated with a MAC address, of a locally connected CE, it may
   advertise it to other MESes by including it in the MAC route
   advertisement. Ethernet Tag ID
   The IP Address may be an IPv4, encoded using four
   octets or an IPv6 address encoded using sixteen octets. following is the procedure for deriving the RT attribute
   automatically from the Ethernet Tag ID associated with the
   advertisement:

        +    The IP
   Address length Global Administrator field of the RT MUST
             be set to 32 for an IPv4 address and 128
   for an IPv6 address. the Autonomous System (AS) number that the PE
             belongs to.

        +    The Local Administrator field of the RT contains a 4
             octets long number that encodes the Ethernet Tag-ID. If there are multiple IP addresses associated with the
             Ethernet Tag-ID is a MAC address two octet VLAN ID then
   multiple MAC advertisement routes it MUST be generated, one for each IP
   address. For instance this may be the case when there is both an IPv4
   and an IPv6 address associated with the MAC address. When
             encoded in the IP
   address is dis-associated with lower two octets of the MAC address then Local Administrator
             field and the MAC
   advertisement route with that particular IP address higher two octets MUST be
   withdrawn.

   When an MES receives an ARP request for an IP address from a CE, and
   if set to zero.

   For the MES has "Unique VLAN E-VPN" this results in auto-deriving the MAC address binding RT from
   the Ethernet Tag, e.g., VLAN ID for that IP address, the MES
   should perform ARP proxy and respond to the ARP request.

   Further detailed procedures will be specified in a later version.

13. E-VPN.

9.5 Designated Forwarder Election

   Consider a CE that is a host or a router that is multi-homed directly
   to more than one MES PE in an E-VPN on a given Ethernet segment. One or
   more Ethernet Tags may be configured on the Ethernet segment. In this
   scenario only one of the MESes, PEs, referred to as the Designated Forwarder
   (DF), is responsible for certain actions:

        -   Sending multicast and broadcast traffic,   Sending multicast and broadcast traffic, on a given Ethernet
            Tag on a particular Ethernet segment, to the CE.

        -   Flooding unknown unicast traffic (i.e. traffic for
            which an PE does not know the destination MAC address),
            on a given Ethernet Tag on a particular Ethernet segment, segment
            to the CE. CE, if the environment requires flooding of
            unknown unicast traffic.
   Note that this behavior, which allows selecting a DF at the
   granularity of <ESI, Ethernet Tag> EVI> for multicast and multicast, broadcast traffic and unknown
   unicast traffic, is the default behavior in this specification.
   Optional mechanisms, which will be specified in the future, will
   allow selecting a DF at the granularity of <ESI, Ethernet Tag, EVI, S, G>.

        -   Flooding unknown unicast traffic (i.e. traffic for
            which an MES does not know the destination MAC address),
            on a given Ethernet Tag on a particular Ethernet segment
            to the CE, if the environment requires flooding of
            unknown unicast traffic.

   Note that a CE always sends packets belonging to a specific flow
   using a single link towards an MES. PE. For instance, if the CE is a host
   then, as mentioned earlier, the host treats the multiple links that
   it uses to reach the MESes PEs as a Link Aggregation Group (LAG). The CE
   employs a local hashing function to map traffic flows onto links in
   the LAG.

   If a bridge bridged network is multi-homed to more than one MES PE in an E-VPN
   via switches, then the support of active-active all-active points of attachments attachments,
   as described in this specification specification, requires the bridge network to be
   connected to two or more MESes PEs using a LAG. In this case the reasons
   for doing DF election are the same as those described above when a CE
   is a host or a router.

   If a bridge bridged network does not connect to the MESes PEs using LAG, then only
   one of the links between the switched bridged network and the
   MESes PEs
   must be the active link. link for a given Ethernet Tag. In this case case, the per
   Ethernet Segment A-D route per Ethernet Tag routes segment MUST be advertised with the
   "Active-Standby" flag set to one. Procedures for supporting active-active all-
   active points of attachments, when a bridge network does not connect connects to the MESes
   PEs using LAG, are for further study.

   The granularity of the DF election MUST be at least the Ethernet
   segment via which the CE is multi-homed to the MESes. PEs. If the DF
   election is done at the Ethernet segment granularity then a single
   MES PE
   MUST be elected as the DF on the Ethernet segment.

   If there are one or more EVIs enabled on the Ethernet Tags (e.g., VLANs) segment, then
   the granularity of the DF election SHOULD be the combination of the
   Ethernet segment and EVI on that Ethernet segment. In this case a
   single PE MUST be elected as the DF for a particular EVI on that
   Ethernet segment.

   The detailed procedures for DF election are described next.

9.5.1 Default DF Election Procedure

   As a PE discovers the other PEs that are connected to the same
   Ethernet Segment, using the Ethernet Segment routes, it starts
   building an ordered list based on the originating PE IP addresses.
   This list is used to select a DF and a backup DF (BDF) on a per
   Ethernet Segment basis. By default, the PE with the numerically
   highest IP address is considered the DF for that Ethernet Segment and
   the next PE in the list is considered the BDF.

   If the Ethernet
   segment Segment is a multi-homed device, then the granularity of the elected DF election SHOULD be the
   combination of
   is the Ethernet segment and Ethernet Tag on only PE that Ethernet must forward flooded multi-destination packets
   towards the segment. All other PE nodes must not permit multi-
   destination packets to egress to the segment. In this the case a single MES MUST be elected as where the
   DF for fails, the BDF takes over its functionality.

   This procedure enables the election of a
   particular single DF per Ethernet Tag
   Segment, for all EVIs enabled on that Ethernet the segment.

   There are two specified mechanisms for performing DF election.

13.1. DF Election Performed It is possible to
   achieve more granular load-balancing of traffic among the PE nodes by All MESes

   The MESes perform a designated forwarder (DF) election, for an
   Ethernet segment, or <ESI, Ethernet Tag> combination using
   employing Service Carving, as discussed in the next section.

9.5.2 DF Election with Service Carving
   With service carving, it is possible to elect multiple DFs per
   Ethernet Tag A-D BGP route described Segment (one per EVI) in section "Auto-Discovery order to perform load-balancing of
   Ethernet Tags on Ethernet Segments".
   multi-destination traffic destined to a given Segment. The load-
   balancing procedures carve up the EVI space among the PE nodes
   evenly, in such a way that every PE is the DF election for a particular ESI or a particular <ESI, Ethernet
   Tag> combination proceeds disjoint set of
   EVIs. The procedure for service carving is as follows. First an MES constructs follows:

   1. When a
   candidate list of MESes. This comprises all PE discovers the Ethernet A-D routes
   with that particular ESI or <ESI, Ethernet Tag> tuple that an MES
   imports in an E-VPN instance, including of the attached Ethernet A-D route(s)
   generated by the MES itself, if any.  The DF MES is chosen from this
   candidate list. Note that DF election is carried out by all the MESes
   that import Segment, it
   advertises an Ethernet Segment route with the DF route. associated ES-Import
   extended community attribute.

   2. The default procedure for choosing PE then starts a timer to allow the DF is reception of Ethernet
   Segment routes from other PE nodes connected to the MES with same Ethernet
   Segment.

   3. When the timer expires, each PE builds an ordered list of the highest IP address,
   addresses of all the MESes PE nodes connected to the Ethernet Segment
   (including itself), in increasing numeric value. Every PE is then
   given an ordinal indicating its position in the candidate list. This procedure
   MUST be implemented. It ensures that, except during routing
   transients each MES chooses ordered list,
   starting with 0 as the same DF MES ordinal for a given ESI and
   Ethernet Tag combination.

   Other alternative procedures for performing DF election the PE with the numerically lowest
   IP address. The ordinals are possible
   and used to determine which PE node will be described in
   the future.

13.2. DF Election Performed Only for a given EVI on Multi-Homed MESes

   As an MES discovers other MESs that are members of the same multi-
   homed segment, using per Ethernet Segment Ethernet A-D Routes, it
   starts building an ordered list based on using the originating MES IP
   addresses. This list is used to select a DF and a backup DF (BDF) on following
   rule: Assuming a per redundancy group of Ethernet Tag basis. For example, N PE nodes, the MES PE with the
   numerically highest IP address ordinal
   i is considered the DF for a given group
   of VLANs for that Ethernet segment and the next MES EVI V when (V mod N) = i.

   The above procedure results in the list is
   considered entire EVI range being divided up
   among the BDF. To that end, PEs in the range RG, regardless of Ethernet Tags
   associated with whether a given EVI is
   configured/enabled on the CE must be partitioned into disjoint sets. associated Ethernet Segment or not.

   4. The
   size of each set PE that is elected as a function of the total number of CE Ethernet
   Tags and the total number of MESs DF for a given EVI will unblock
   traffic for that EVI only if the Ethernet segment EVI is multi-
   homed to. The DF can employ any distribution function that achieves
   an even distribution of Ethernet Tags across configured/enabled on the MESes
   Segment. Note that are
   multi-homed to the Ethernet segment. The DF takes over PE unblocks multi-destination traffic in
   the Ethernet
   Tag set of any MES encountering either a node failure or a
   link/Ethernet segment failure causing that MES egress direction towards the Segment. All non-DF PEs continue to be isolated from
   drop multi-destination traffic (for the multi-homed segment. associated EVIs) in the
   egress direction towards the Segment.

   In the case of a failure that is affecting the
   DF, then link or port failure, the BDF takes over affected PE withdraws its
   Ethernet Segment route. This will re-trigger the DF VLAN set.

   It should be noted that once service carving
   procedures on all the MESs participating PEs in an
   Ethernet segment have the same ordered list for that site, then
   Ethernet Tag groups can be assigned RG. For PE node failure, or upon PE
   commissioning or decommissioning, the PEs re-trigger the service
   carving. When a service moves from one PE in the RG to each member another PE as
   a result of that list
   deterministically without any need to explicitly distribute Ethernet
   Tags among re-carving, the member MESs of that list. In other words, PE, which ends up being the elected DF
   election
   for the service, must trigger a group of MAC address flush notification
   towards the associated Ethernet Tags is a local matter and Segment. This can be
   done deterministically. As an example, consider, done, for e.g.
   using IEEE 802.1ak MVRP 'new' declaration.

10. Determining Reachability to Unicast MAC Addresses
   PEs forward packets that they receive based on the ordered
   list consists of m MESes: (MES1, MES2,., MESm),  and there are n
   Ethernet Tags for destination MAC
   address. This implies that site (V0, V1, V2, ., Vn-1). Then MES1 PEs must be able to learn how to reach a
   given destination unicast MAC address.

   There are two components to MAC address learning, "local learning"
   and MES2
   can "remote learning":

10.1. Local Learning

   A particular PE must be able to learn the DF and the BDF respectively for all MAC addresses from the Ethernet Tags
   corresponding CEs
   that are connected to (i mod m) for i:0 it. This is referred to n-1. MES2 and MES3 can as local learning.

   The PEs in a particular E-VPN MUST support local data plane learning
   using standard IEEE Ethernet learning procedures. An PE must be
   capable of learning MAC addresses in the
   DF and data plane when it receives
   packets such as the BDF respectively following from the CE network:

        - DHCP requests

        - ARP request for all its own MAC.

        - ARP request for a peer.

   Alternatively PEs MAY learn the Ethernet Tags corresponding
   to (i mod m) + 1 and so on till MAC addresses of the last MES CEs in the order list is
   reached. As a result MESm and MES1 is
   control plane or via management plane integration between the DF PEs and
   the BDF respectively
   for the all CEs.

   There are applications where a MAC address that is reachable via a
   given PE on a locally attached Segment (e.g. with ESI X) may move
   such that it becomes reachable via the VLANs corresponding same PE or another PE on
   another Segment (e.g. with ESI Y).  This is referred to (i mod m) + m-1.

14. Handling of Multi-Destination Traffic as a "MAC
   Mobility". Procedures to support this are required for a given MES described in section "MAC
   Mobility".

10.2. Remote learning

   A particular PE must be able to determine how to send broadcast traffic to MAC
   addresses that belong to or
   multicast traffic, received from a CE encapsulated in a given
   Ethernet Tag in are behind CEs connected to other PEs
   i.e. to remote CEs or hosts behind remote CEs. We call such MAC
   addresses as "remote" MAC addresses.

   This document requires an E-VPN, PE to all the other MESes that span that
   Ethernet Tag learn remote MAC addresses in the E-VPN.
   control plane. In certain scenarios, described in section
   "Processing of Unknown Unicast Packets", a given MES may also need order to
   flood unknown unicast traffic achieve this, each PE advertises the MAC
   addresses it learns from its locally attached CEs in the control
   plane, to all the other MESes.

   The MESes PEs in a particular the EVI, using MP-BGP and specifically
   the MAC Advertisement route.

10.2.1. Constructing the BGP E-VPN may use ingress replication or P2MP
   LSPs or MP2MP LSPs to send unknown unicast, broadcast or multicast
   traffic MAC Address Advertisement
   BGP is extended to other MESes.

   Each MES MUST advertise an "Inclusive Multicast Ethernet Tag Route"
   to enable the above. Next section provides procedures to construct these MAC addresses using the Inclusive Multicast Ethernet Tag route. Subsequent sections
   describe MAC
   Advertisement route type in further detail its usage.

14.1. Construction of the Inclusive Multicast Ethernet Tag Route E-VPN NLRI.

   The RD MUST be the RD of the E-VPN instance EVI that is advertising the NLRI. The
   procedures for setting the RD for a given E-VPN EVI are described in
   section "Ethernet A-D Route per E-VPN". 9.4.1.

   The Ethernet Segment Identifier MAY be is set to the ten octet ESI
   identifier described
   in section "Ethernet Segment Identifier". Or it
   MAY Segment".

   The Ethernet Tag ID may be set to 0.  It MUST zero or may represent a valid Ethernet Tag
   ID.  This field may be set non-zero when there are multiple bridge
   domains in the EVI (e.g., the PE needs to 0 if perform qualified learning
   for the VLANs in that EVI).

   When the the Ethernet Tag ID in the NLRI is set to
   0.

   The a non-zero value,
   for a particular bridge domain, then this Ethernet Tag may either be
   the Ethernet tag value associated with the CE, e.g., VLAN ID, or it
   may be the Ethernet Tag Identifier, e.g., VLAN ID is assigned by the identifier of E-
   VPN provider and mapped to the CE's Ethernet Tag. It MAY tag. The latter would be
   set to 0 in which
   the case an egress MES MUST perform a MAC lookup to
   forward if the packet. CE Ethernet tags, e.g., VLAN ID, for a particular
   bridge domain are different on different CEs.

   The Originating Router's IP MAC address MUST be length field is typically set to an IP address of 48. However this
   specification enables specifying the PE.  This MAC address SHOULD be common for all the EVIs on as a prefix; in
   which case, the PE
   (e.,g., this MAC address may be PE's loopback address).

   The Next Hop length field of the MP_REACH_NLRI attribute of the route MUST
   be is set to the same IP address as length of the one carried in
   prefix. This provides the Originating
   Router's IP Address field.

   The BGP advertisement that advertises ability to aggregate MAC addresses if the Inclusive Multicast
   Ethernet Tag route MUST also carry one or more Route Target (RT)
   attributes.
   deployment environment supports that.  The assignment encoding of RTs described in the section on
   "Constructing the BGP E-VPN a MAC Address Advertisement" address
   MUST be
   followed.

14.2. P-Tunnel Identification

   In order to identify the P-Tunnel used for sending broadcast, unknown
   unicast or multicast traffic, the Inclusive Multicast Ethernet Tag
   route MUST carry a "PMSI Tunnel Attribute" 6-octet MAC address specified in [BGP MVPN].

   Depending on by [802.1D-ORIG] [802.1D-
   REV]. If the technology used for MAC address is advertised as a prefix then the P-tunnel for trailing
   bits of the E-VPN on prefix MUST be set to 0 to ensure that the PE, entire prefix
   is encoded as 6 octets.

   The IP Address Length field value is set to the PMSI Tunnel attribute number of octets in
   the Inclusive Multicast Ethernet
   Tag route IP Address field.

   The IP Address field is constructed as follows.

        + If optional. By default, the PE that originates IP Address Length
   field is set to 0 and the advertisement uses a P-Multicast
          tree for IP address field is omitted from the P-tunnel for route.
   When a valid IP address is included, it is encoded as specified in
   section 12.

   The MPLS label field carries one or more labels (that corresponds to
   the E-VPN, stack of labels [MPLS-ENCAPS]).  Each label is encoded as 3
   octets, where the PMSI Tunnel attribute
          MUST high-order 20 bits contain the identity label value, and the
   low order bit contains "Bottom of Stack" (as defined in [MPLS-
   ENCAPS]). The MPLS label stack MUST be the tree (note downstream assigned E-VPN
   MPLS label stack that is used by the PE could
          create to forward MPLS-encapsulated
   Ethernet frames received from remote PEs, where the identity of destination MAC
   address in the tree prior to Ethernet frame is the actual
          instantiation MAC address advertised in the
   above NLRI. The forwarding procedures are specified in section
   "Forwarding Unicast Packets" and "Load Balancing of Unicast Packets".

   An PE may advertise the tree).

        + A same single E-VPN label for all MAC addresses
   in a given EVI. This label assignment methodology is referred to as a
   per EVI label assignment. Alternatively, an PE that uses may advertise a P-Multicast tree for the P-tunnel MAY
          aggregate two or more unique
   E-VPN label per <ESI, Ethernet Tags in the same or different
          E-VPNs present on the Tag> combination. This label
   assignment methodology is referred to as a per <ESI, Ethernet Tag>
   label assignment. As a third option, an PE onto may advertise a unique E-
   VPN label per MAC address. All of these methodologies have their
   tradeoffs.

   Per EVI label assignment requires the same tree. In this case least number of E-VPN labels,
   but requires a MAC lookup in addition to carrying the identity of the tree, the PMSI Tunnel
          attribute MUST carry an MPLS upstream assigned label which
          the lookup on an egress
   PE has bound uniquely to for forwarding. On the other hand, a unique label per <ESI,
   Ethernet Tag> for
          E-VPN associated with this update (as determined by its RTs).

          If the PE has already advertised Inclusive Multicast Ethernet
          Tag routes for two or more Ethernet Tags that it now desires
          to aggregate, then the PE MUST re-advertise those routes.
          The re-advertised routes MUST be the same as the original
          ones, except for the PMSI Tunnel attribute and the a unique label
          carried in that attribute.

        + If the per MAC allows an egress PE that originates the advertisement uses ingress
          replication for the P-tunnel for the E-VPN, the route MUST
          include the PMSI Tunnel attribute with the Tunnel Type set to
          Ingress Replication and Tunnel Identifier set to
   forward a routable
          address of packet that it receives from another PE, to the connected
   CE, after looking up only the PE. The PMSI Tunnel attribute MUST carry a
          downstream assigned MPLS label. This label is used labels without having to
          demultiplex the broadcast, multicast or unknown unicast E-VPN
          traffic received over perform a unicast tunnel by
   MAC lookup. This includes the PE.

        + The Leaf Information Required flag capability to perform appropriate VLAN
   ID translation on egress to the CE.

   The Next Hop field of the PMSI Tunnel MP_REACH_NLRI attribute of the route MUST
   be set to zero, and the IPv4 or IPv6 address of the advertising PE.

   The BGP advertisement for the MAC advertisement route MUST also carry
   one or more Route Target (RT) attributes.  RTs may be ignored on receipt.

14.3. Ethernet Segment Identifier and Ethernet Tag

   As described above the encoding rules allow setting configured (as
   in IP VPNs), or may be derived automatically from the Ethernet
   Segment Identifier and Ethernet Tag
   ID, in the Unique VLAN case, as described in section "Ethernet A-D
   Route per E-VPN".

   It is to either non-zero valid values
   or be noted that this document does not require PEs to 0. If create
   forwarding state for remote MACs when they are learnt in the Ethernet Tag control
   plane. When this forwarding state is actually created is set to a non-zero valid value, then local
   implementation matter.

11. ARP and ND

   The IP address field in the MAC advertisement route may optionally
   carry one of the IP addresses associated with the MAC address. This
   provides an egress MES option which can forward the packet be used to minimize the set flooding of egress ESIs in the
   Ethernet Tag, in ARP
   or Neighbor Discovery (ND) messages over the E-VPN, by performing an MPLS lookup only.
   Further if the ESI is network and to
   remote CEs. This option also set minimizes ARP (or ND) message processing
   on end-stations/hosts connected to non zero then the egress MES does
   not need to replicate E-VPN network. An PE may learn
   the packet as it is destined for a given
   Ethernet segment. If both Ethernet Tag and ESI are set to 0 then an
   egress MES MUST perform IP address associated with a MAC lookup address in the EVI determined by control or
   management plane between the
   MPLS label, after CE and the MPLS lookup, PE. Or, it may learn this
   binding by snooping certain messages to forward the packet.

   If an MES advertises multiple Inclusive Ethernet Tag routes for or from a
   given E-VPN then CE. When an PE
   learns the PMSI Tunnel Attributes for these routes MUST be
   distinct.

15. Processing IP address associated with a MAC address, of Unknown Unicast Packets

   The procedures in a locally
   connected CE, it may advertise this document do not require MESes to flood unknown
   unicast traffic address to other MESes. If MESes learn CE MAC addresses via a
   control plane, PEs by including
   it in the MESes can then distribute MAC addresses via BGP,
   and all unicast MAC addresses will Advertisement route. The IP Address may be learnt prior an IPv4
   address encoded using four octets, or an IPv6 address encoded using
   sixteen octets. The IP Address length field MUST be set to traffic 32 for an
   IPv4 address or to
   those destinations.

   However, if 128 for an IPv6 address.

   If there are multiple IP addresses associated with a destination MAC address of a received packet is not
   known by the MES, the MES address,
   then multiple MAC advertisement routes MUST be generated, one for
   each IP address. For instance, this may have to flood the packet. Flooding must
   take into account "split horizon forwarding" as follows. The
   principles behind be the following procedures case when there are borrowed from the
   split horizon forwarding rules in VPLS solutions [RFC 4761, RFC
   4762].  When
   both an MES capable of flooding (say MESx) receives a
   broadcast Ethernet frame, or one IPv4 and an IPv6 address associated with an unknown destination the MAC
   address, it must flood address.
   When the frame.  If IP address is dissociated with the frame arrived from MAC address, then the MAC
   advertisement route with that particular IP address MUST be
   withdrawn.

   When an
   attached CE, MESx must send PE receives an ARP request for an IP address from a copy of the frame to every other
   attached CE, on a different ESI than the one it received and
   if the frame
   on, as well as to all other MESs participating in PE has the E-VPN. If, on MAC address binding for that IP address, the other hand, PE
   SHOULD perform ARP proxy and respond to the frame arrived from another MES (say MESy), MESx
   must send ARP request.

   Further detailed procedures will be specified in a copy later version.

12. Handling of the packet only Multi-Destination Traffic

   Procedures are required for a given PE to attached CEs. MESx MUST NOT send the frame to other MESs, since MESy would have already done so.
   Split horizon forwarding rules apply to broadcast and or multicast
   packets, as well as packets to
   traffic, received from a CE encapsulated in a given Ethernet Tag in
   an unknown MAC address.

   Whether or not EVI, to flood packets to unknown destination MAC addresses
   should be an administrative choice, depending on how learning happens
   between CEs and MESes.

   The MESes all the other PEs that span that Ethernet Tag in the EVI.
   In certain scenarios, described in section "Processing of Unknown
   Unicast Packets", a particular E-VPN given PE may use ingress replication using
   RSVP-TE P2P LSPs or LDP MP2P LSPs for sending broadcast, multicast
   and also need to flood unknown unicast
   traffic to other MESes. Or they PEs.

   The PEs in a particular E-VPN may use RSVP-TE
   P2MP or LDP ingress replication, P2MP LSPs
   or LDP MP2MP LSPs for sending such to send unknown unicast, broadcast or multicast traffic
   to other
   MESes.

15.1. Ingress Replication

   If ingress replication is in use, PEs.

   Each PE MUST advertise an "Inclusive Multicast Ethernet Tag Route" to
   enable the P-Tunnel attribute, carried above. The following subsection provides the procedures to
   construct the Inclusive Multicast Ethernet Tag route. Subsequent
   subsections describe in further detail its usage.

12.1. Construction of the Inclusive Multicast Ethernet Tag routes for Route

   The RD MUST be the E-VPN, specifies RD of the downstream label EVI that is advertising the other MESes can use to send unknown
   unicast, multicast or broadcast traffic NLRI. The
   procedures for setting the RD for a given E-VPN to this
   particular MES. are described in
   section 9.4.1.

   The MES that receives Ethernet Tag ID is the identifier of the Ethernet Tag. It MAY be
   set to 0 or to a packet with this particular MPLS label valid Ethernet Tag value.

   The Originating Router's IP address MUST
   treat be set to an IP address of
   the packet as a broadcast, multicast or unknown unicast packet.
   Further if PE.  This address SHOULD be common for all the MAC EVIs on the PE
   (e.,g., this address is a unicast MAC address, may be PE's loopback address).

   The Next Hop field of the MES MP_REACH_NLRI attribute of the route MUST
   treat
   be set to the packet same IP address as an unknown unicast packet.

15.2. P2MP MPLS LSPs the one carried in the Originating
   Router's IP Address field.

   The procedures BGP advertisement for using P2MP LSPs are very similar the Inclusive Multicast Ethernet Tag route
   MUST also carry one or more Route Target (RT) attributes. The
   assignment of RTs described in the section on "Constructing the BGP
   E-VPN MAC Address Advertisement" MUST be followed.

12.2. P-Tunnel Identification

   In order to VPLS
   procedures [VPLS-MCAST]. The identify the P-Tunnel attribute used by an MES for sending broadcast, unknown unicast, broadcast
   unicast or multicast traffic for a
   particular Ethernet segment, is advertised in traffic, the Inclusive Multicast Ethernet Tag Multicast
   route MUST carry a "PMSI Tunnel Attribute" as described in section "Handling of Multi-
   Destination Traffic".

   The P-Tunnel attribute specifies the P2MP LSP identifier. This is the
   equivalent of an Inclusive tree in [VPLS-MCAST]. Note that multiple
   Ethernet Tags, which may be specified in different E-VPNs, may use [BGP
   MVPN].

   Depending on the same
   P2MP LSP, using upstream labels [VPLS-MCAST]. When P2MP LSPs are technology used for flooding unknown unicast traffic, packet re-ordering is possible.

   The MES that receives a packet the P-tunnel for the E-VPN on
   the P2MP LSP specified in PE, the PMSI Tunnel Attribute MUST treat the packet as a broadcast, multicast or
   unknown unicast packet. Further if attribute of the MAC address Inclusive Multicast Ethernet
   Tag route is a unicast MAC
   address, constructed as follows.

        + If the MES MUST treat PE that originates the packet as an unknown unicast packet.

16. Forwarding Unicast Packets

16.1. Forwarding packets received from a CE

   When an MES receives a packet from a CE, on advertisement uses a given Ethernet Tag, it
   must first look up
          P-Multicast tree for the source MAC address of P-tunnel for E-VPN, the packet. In certain
   environments PMSI
          Tunnel attribute MUST contain the source MAC address MAY be used to authenticate identity of the
   CE and determine tree
          (note that traffic from the host can be allowed into the
   network. Source MAC lookup MAY also used for local MAC address
   learning.

   If the MES decides to forward the packet PE could create the destination MAC address identity of the packet must be looked up. If
          tree prior to the MES has received MAC address
   advertisements actual instantiation of the tree).

        + An PE that uses a P-Multicast tree for this destination MAC address from one the P-tunnel MAY
          aggregate two or more
   other MESes Ethernet Tags in the same or learned it from locally connected CEs, it is
   considered as a known MAC address. Else different
          EVIs present on the MAC address is considered
   as an unknown MAC address.

   For known MAC addresses PE onto the MES forwards same tree. In this packet case, in
          addition to one of carrying the
   remote MESes or to a locally attached CEs. When forwarding to remote
   MESes, identity of the packet is encapsulated in tree, the E-VPN PMSI Tunnel
          attribute MUST carry an MPLS upstream assigned label advertised
   by the remote MES, for that MAC address, and in which
          the MPLS LSP label
   stack PE has bound uniquely to reach the remote MES.

   If Ethernet Tag for the MAC address is unknown then, if EVI
          associated with this update (as determined by its RTs).

          If the administrative policy on PE has already advertised Inclusive Multicast
          Ethernet Tag routes for two or more Ethernet Tags that it
          now desires to aggregate, then the MES requires flooding of unknown unicast traffic:

          - PE MUST re-advertise
          those routes. The MES re-advertised routes MUST flood the packet to other MESes. If the ESI
           over which the MES receives be the packet is multi-homed, then same
          as the MES MUST first encapsulate original ones, except for the packet in PMSI Tunnel attribute
          and the ESI MPLS label as described carried in section "Split Horizon". that attribute.

        + If the PE that originates the advertisement uses ingress
          replication is used for the packet P-tunnel for E-VPN, the route MUST be replicated
           one or more times to each remote MES
          include the PMSI Tunnel attribute with the bottom label Tunnel Type set to
          Ingress Replication and Tunnel Identifier set to a routable
          address of the stack being an PE. The PMSI Tunnel attribute MUST carry a
          downstream assigned MPLS label determined as follows. label. This label is used to
          demultiplex the MPLS label advertised broadcast, multicast or unknown unicast E-VPN
          traffic received over a MP2P tunnel by the remote MES in a PE.

        + The Leaf Information Required flag of the PMSI Tunnel Attribute in the Inclusive Multicast Ethernet Tag
           route for an <ESI, Ethernet Tag> combination.
          attribute MUST be set to zero, and MUST be ignored on receipt.

13. Processing of Unknown Unicast Packets

   The Ethernet
           Tag procedures in this document do not require the route must PEs to flood
   unknown unicast traffic to other PEs. If PEs learn CE MAC addresses
   via a control plane protocol, the PEs can then distribute MAC
   addresses via BGP, and all unicast MAC addresses will be learnt prior
   to traffic to those destinations.

   However, if a destination MAC address of a received packet is not
   known by the same PE, the PE may have to flood the packet. Flooding must
   take into account "split horizon forwarding" as follows: The
   principles behind the Ethernet Tag
           advertised by following procedures are borrowed from the ingress MES
   split horizon forwarding rules in its VPLS solutions [RFC 4761, RFC
   4762].  When an PE capable of flooding (say PEx) receives a broadcast
   or multicast Ethernet Tag A-D route
           associated frame, or one with an unknown destination MAC
   address, it must flood the interface on which frame.  If the ingress MES
           receives frame arrived from an
   attached CE, PEx must send a copy of the packet. If P2MP LSPs are being used frame to every other
   attached CE participating in the packet
           MUST be sent EVI, on a different ESI than the P2MP LSP that one
   it received the MES frame on, as long as the PE is the root of DF for the Ethernet Tag in egress
   ESI. In addition, the E-VPN. If PE must flood the same P2MP LSP is used
           for all Ethernet Tags then frame to all the MESes other PEs
   participating in the E-VPN MUST
           be EVI. If, on the leaves of other hand, the P2MP LSP. If a distinct P2MP LSP is
           used for frame arrived
   from another PE (say PEy), PEx must send a given Ethernet Tag in the E-VPN then only the
           MESes in the Ethernet Tag MUST be the leaves copy of the P2MP
           LSP. The packet MUST be encapsulated in the P2MP LSP label
           stack.

   If the MAC address only to
   attached CEs as long as it is unknown then, if the admnistrative policy on DF for the MES does not allow flooding of unknown unicast traffic:

          - The MES egress ESI. PEx MUST drop NOT
   send the packet.

16.2. Forwarding frame to other PEs, since PEy would have already done so.
   Split horizon forwarding rules apply to broadcast and multicast
   packets, as well as packets received from a remote MES
16.2.1. Unknown Unicast Forwarding

   When an MES receives to an MPLS packet from a remote MES then, after
   processing the MPLS label stack, if the top MPLS label ends up being
   a P2MP LSP label associated with unknown MAC address.

   Whether or not to flood packets to unknown destination MAC addresses
   should be an administrative choice, depending on how learning happens
   between CEs and PEs.

   The PEs in a particular E-VPN may use ingress replication using RSVP-
   TE P2P LSPs or the downstream label
   advertised in the P-Tunnel attribute LDP MP2P LSPs for sending broadcast, multicast and after performing the split
   horizon procedures described in section "Split Horizon":

   - If the MES is the designated forwarder of
   unknown unicast,
   broadcast unicast traffic to other PEs. Or they may use RSVP-TE P2MP or multicast traffic, on a particular set of ESIs
   LDP P2MP or LDP MP2MP LSPs for sending such traffic to other PEs.

13.1. Ingress Replication

   If ingress replication is in use, the
   Ethernet Tag, P-Tunnel attribute, carried in
   the default behavior is Inclusive Multicast Ethernet Tag routes for the MES to flood EVI, specifies
   the packet
   on downstream label that the ESIs. In other words the default behavior is for the MES PEs can use to
   assume that the destination MAC address is send unknown
   unicast, broadcast
   or multicast and it is not required or broadcast traffic for the EVI to do this
   particular PE.

   The PE that receives a destination MAC address
   lookup, as long as the granularity of the packet with this particular MPLS label included the
   Ethernet Tag. As an option the MES may do a destination MAC lookup to
   flood MUST
   treat the packet to only as a subset of broadcast, multicast or unknown unicast packet.
   Further if the CE interfaces in MAC address is a unicast MAC address, the
   Ethernet Tag. For instance PE MUST
   treat the MES may decide packet as an unknown unicast packet.

13.2. P2MP MPLS LSPs

   The procedures for using P2MP LSPs are very similar to not flood VPLS
   procedures [VPLS-MCAST]. The P-Tunnel attribute used by an PE for
   sending unknown
   unicast packet on certain Ethernet segments even if it unicast, broadcast or multicast traffic for a
   particular EVI is advertised in the DF on
   the Inclusive Ethernet segment, based on administrative policy.

   - If Tag Multicast
   route as described in section "Handling of Multi-Destination
   Traffic".

   The P-Tunnel attribute specifies the MES P2MP LSP identifier. This is not the designated forwarder on any
   equivalent of the ESIs for
   the an Inclusive tree in [VPLS-MCAST]. Note that multiple
   Ethernet Tag, Tags, which may be in different EVIs, may use the default behavior same P2MP
   LSP, using upstream labels [VPLS-MCAST]. This is for it to drop the packet.

16.2.2. Known Unicast Forwarding

   If the top MPLS label ends up being equivalent of an E-VPN label that was
   advertised
   Aggregate Inclusive tree in the [VPLS-MCAST]. When P2MP LSPs are used for
   flooding unknown unicast MAC advertisements, then the MES either
   forwards the traffic, packet re-ordering is possible.

   The PE that receives a packet based on CE next-hop forwarding information
   associated with the label or does P2MP LSP specified in the PMSI
   Tunnel Attribute MUST treat the packet as a destination broadcast, multicast or
   unknown unicast packet. Further if the MAC address lookup to
   forward is a unicast MAC
   address, the PE MUST treat the packet to a CE.

17. Split Horizon

   Consider as an unknown unicast packet.

14. Forwarding Unicast Packets

14.1. Forwarding packets received from a CE that is multi-homed to two or more MESes on

   When an Ethernet
   segment ES1. If the CE sends PE receives a multicast, broadcast or unknown
   unicast packet to from a particular MES, say MES1, then MES1 will forward
   that packet to all or subset of CE, on a given Ethernet Tag, it
   must first look up the other MESes in source MAC address of the E-VPN. packet. In this
   case certain
   environments the MESes, other than MES1, that source MAC address MAY be used to authenticate the
   CE is multi-homed and determine that traffic from the host can be allowed into the
   network. Source MAC lookup MAY also be used for local MAC address
   learning.

   If the PE decides to MUST
   drop forward the packet, the destination MAC address
   of the packet and not forward back to must be looked up. If the CE. This is referred to
   as "split horizon" in this document.

   In order to accomplish PE has received MAC address
   advertisements for this each MES distributes to destination MAC address from one or more
   other MESes the
   "per Ethernet Segment Ethernet A-D route" PEs or learned it from locally connected CEs, it is considered
   as per the procedures in a known MAC address. Otherwise, the section "Ethernet A-D Route per Ethernet Segment". This route MAC address is
   imported by considered as
   an unknown MAC address.

   For known MAC addresses the MESes connected PE forwards this packet to the Ethernet Segment and also by
   the MESes that have at least one E-VPN in common with the Ethernet
   Segment in the route. As described in the section "Ethernet A-D Route
   per Ethernet Segment", of the route MUST carry an ESI MPLS Label
   Extended Community with a valid ESI MPLS label.

17.1. ESI MPLS Label: Ingress Replication

   An MES that is using ingress replication for sending broadcast,
   multicast
   remote PEs or unknown unicast traffic, distributes to other MESes,
   that belong to the Ethernet segment, a downstream assigned "ESI MPLS
   label" in the Ethernet A-D route. This label MUST be programmed locally attached CE. When forwarding to a remote
   PE, the packet is encapsulated in the platform E-VPN MPLS label space advertised by
   the advertising MES. Further the
   forwarding entry remote PE, for this label must result that MAC address, and in NOT forwarding packets
   received with this the MPLS LSP label onto stack
   to reach the Ethernet segment that remote PE.

   If the label was
   distributed for.

   Consider MES1 MAC address is unknown and MES2 that are multi-homed to CE1 if the administrative policy on ES1. Further
   consider that MES1 is using P2P or MP2P LSPs to send packets to MES2.
   Consider that MES1 receives a multicast, broadcast or the
   PE requires flooding of unknown unicast
   packet from CE1 on VLAN1 on ESI1.

   First consider traffic then:

          - The PE MUST flood the case where MES2 distributes an unique Inclusive
   Multicast Ethernet Tag route for VLAN1, for each Ethernet segment on
   MES2. In this case MES1 packet to other PEs. The
           PE MUST NOT replicate first encapsulate the packet in the ESI MPLS
           label as described in section 9.3.
           If ingress replication is used, the packet MUST be replicated
           one or more times to MES2 for
   <ESI1, VLAN1>.

   Next consider each remote PE with the case where MES2 distributes outermost
           label being an MPLS label determined as follows: This
           is the MPLS label advertised by the remote PE in a single PMSI
           Tunnel Attribute in the Inclusive Multicast Ethernet Tag
           route for VLAN1 for all an <EVI, Ethernet segments on
   MES2. In this case when MES1 sends a multicast, broadcast or unknown
   unicast packet, that it receives from CE1, it MUST first push onto Tag> combination. The Ethernet
           Tag in the MPLS label stack route must be the ESI label that MES2 has distributed for
   ESI1. It MUST then push same as the Ethernet Tag
           associated with the interface on which the ingress PE
           receives the MPLS label distributed by MES2 in packet. If P2MP LSPs are being used the
   Inclusive Ethernet Tag Multicast route for Ethernet Tag1. The
   resulting packet is further encapsulated in
           MUST be sent on the P2P or MP2P P2MP LSP label
   stack required to transmit that the packet to MES2.  When MES2 receives
   this packet it determines PE is the set root of ESIs to replicate for
           the packet to
   from Ethernet Tag in the top MPLS label, after any P2P or MP2P LSP labels have been
   removed. EVI. If the next label same P2MP LSP is the ESI label assigned by MES2 used
           for all Ethernet Tags, then
   MES2 all the PEs in the EVI MUST NOT forward
           be the leaves of the packet onto ESI1.

17.2. ESI MPLS Label: P2MP MPLS LSPs

   An MES that is using LSP. If a distinct P2MP LSPs LSP is
           used for sending broadcast, multicast or
   unknown unicast traffic, distributes to other MESes, that belong to
   the a given Ethernet segment or have an E-VPN Tag in common with the Ethernet
   Segment, an upstream assigned "ESI MPLS label" EVI, then only the
           PEs in the Ethernet A-D
   route. This label is upstream assigned by Tag MUST be the MES that advertises leaves of the
   route. This label P2MP
           LSP. The packet MUST be programmed by encapsulated in the other MESes, that are
   connected to P2MP LSP label
           stack.

   If the ESI advertised in MAC address is unknown then, if the route, in administrative policy on
   the context label
   space for PE does not allow flooding of unknown unicast traffic:

          - The PE MUST drop the advertising MES. Further packet.

14.2. Forwarding packets received from a remote PE
14.2.1. Unknown Unicast Forwarding

   When an PE receives an MPLS packet from a remote PE then, after
   processing the forwarding entry for this
   label must result in NOT forwarding packets received with this MPLS label
   onto the Ethernet segment that stack, if the top MPLS label was distributed for. This ends up being
   a P2MP LSP label MUST also be programmed by the other MESes, that import the
   route but are not connected to associated with an EVI or the ESI downstream label
   advertised in the route, P-Tunnel attribute, and after performing the split
   horizon procedures described in section "Split Horizon":

   - If the context label space PE is the designated forwarder of unknown unicast, broadcast
   or multicast traffic, on a particular set of ESIs for the advertising MES. Further Ethernet
   Tag, the
   forwarding entry default behavior is for this label must be a POP with no other
   associated action.

   Consider MES1 and MES2 that are multi-homed the PE to CE1 flood the packet on ES1. Also
   consider MES3 that is in these
   ESIs. In other words, the same E-VPN as one of default behavior is for the E-VPNs PE to which
   ES1 belongs.  Further assume
   that MES1 the destination MAC address is using P2MP MPLS LSPs to
   send broadcast, multicast or uknown unicast packets. When MES1 sends
   a multicast, unknown unicast, broadcast or unknown unicast packet, that it receives
   from CE1,
   multicast and it MUST first push onto is not required to perform a destination MAC address
   lookup. As an option, the MPLS label stack PE may perform a destination MAC lookup to
   flood the ESI label
   that it has assigned for packet to only a subset of the ESI that CE interfaces in the
   Ethernet Tag. For instance the PE may decide to not flood an unknown
   unicast packet was received on. The
   resulting packet on certain Ethernet segments even if it is further encapsulated in the P2MP MPLS label stack
   necessary to transmit DF on
   the packet to Ethernet segment, based on administrative policy.

   - If the other MESes. Penultimate hop
   popping MUST be disabled PE is not the designated forwarder on any of the P2MP LSPs used in ESIs for
   the MPLS transport
   infrastructure Ethernet Tag, the default behavior is for E-VPN. When MES2 receives this packet it
   decapsulates to drop the packet.

14.2.2. Known Unicast Forwarding

   If the top MPLS label and forwards the packet using the
   context label space determined by the top label. If the next ends up being an E-VPN label is that was
   advertised in the ESI label assigned by MES1 unicast MAC advertisements, then MES2 MUST NOT forward the packet
   onto ESI1. When MES3 receives this packet it decapsulates the top
   MPLS label and PE either
   forwards the packet using the context label space
   determined by the top label. If the next label is based on CE next-hop forwarding information
   associated with the ESI label
   assigned by MES1 then MES3 MUST pop or does a destination MAC address lookup to
   forward the label.

17.3. ESI MPLS Label: MP2MP LSPs

   The procedures for ESI MPLS Label assignment and usage for MP2MP LSPs
   will be described in packet to a future version.

18. CE.

15. Load Balancing of Unicast Packets Frames

   This section specifies how the load balancing is achieved to/from a CE
   that has more than one interface that is directly connected procedures for sending
   known unicast frames to one or
   more MESes. The CE may be a host or a router or it may be a switched
   network that is connected via LAG to the MESes.

18.1. multi-homed CE.

15.1. Load balancing of traffic from an MES PE to remote CEs

   Whenever a remote MES PE imports a MAC advertisement for a given <ESI,
   Ethernet Tag> in an E-VPN instance, it MUST consider the MAC as
   reachahable via all the MESes from which
   Ethernet Tag> in an EVI, it has MUST examine all imported Ethernet A-D
   routes for that <ESI, Ethernet Tag>. Let us call this ESI in order to determine the initial
   Ethernet A-D route set for load-balancing
   characteristics of the given ESI. Ethernet segment.

15.1.1 Active-Standby Redundancy Mode

   For the a given ESI ESI, if the remote MES PE has imported a an Ethernet A-D route
   per Ethernet Segment
   Ethernet A-D route, from at least one MES, PE, where the "Active-Standby"
   flag in the ESI MPLS Label Extended Community is set, then the remote
   MES
   PE MUST first use deduce that the procedures Ethernet segment is operating in Active-
   Standby redundancy mode. As such, the section "Designated
   Forwarder Election" MAC address will be reachable
   only via the PE announcing the associated MAC Advertisement route -
   this is referred to pick a Designated Forwarder. as the primary PE. The eligible set of other PE nodes
   advertising Ethernet A-D routes used per Ethernet Segment for the same ESI
   serve as backup paths, in case the procedures below must comprise
   this active PE encounters a failure.
   These are referred to as the backup PEs.

   If the primary PE encounters a failure, it MAY withdraw its Ethernet
   A-D route for the affected segment prior to withdrawing the entire
   set of MAC Advertisement routes. In the case where only a single
   other backup PE in the network had advertised an Ethernet A-D route from
   for the DF. same ESI, the remote PE can then use the Ethernet A-D route
   withdrawal as a trigger to update its forwarding entries, for the
   associated MAC addresses, to point towards the backup PE. As the
   backup PE starts learning the MAC addresses over its attached
   Ethernet segment, it will start sending MAC Advertisement routes
   while the failed PE withdraws its own. This mechanism minimizes the
   flooding of traffic during fail-over events.

15.1.2 All-Active Redundancy Mode

   If for the given ESI ESI, none of the  Ethernet A-D routes per Ethernet
   Segment Ethernet A-D
   routse, imported by the remote MES, PE have the "Active-Standby" flag set
   in the ESI MPLS Label Extended Community, then the eligble set remote PE MUST
   treat the Ethernet segment as operating in all-active redundancy
   mode. The remote PE would then treat the MAC address as reachable via
   all of the PE nodes from which it has received both an Ethernet A-D
   route per Ethernet A-D routes is set to the initial Segment as well as an Ethernet A-D route set. per EVI
   for the ESI in question. The remote MES PE MUST use the MAC advertisement
   and eligible Ethernet A-D routes to constuct construct the set of next-hops
   that it can use to send the packet to the destination MAC. Each next-hop next-
   hop comprises an MPLS label stack, stack that is to be used by the egress MES PE
   to forward the packet. This label stack is determined as follows. If follows:

   -If the next-hop is constructed as a result of a MAC route which has a valid MPLS label
   stack, then this
   label stack MUST be used. However However, if the MAC route doesn't exist or if it doesn't have a valid MPLS label stack exist,
   then the next-hop and MPLS label stack is constructed as a result of one or
   more corresponding
   the Ethernet A-D routes as follows. routes. Note that the following description applies
   to determining the label stack for a particular next-hop to reach a
   given MES, PE, from which the remote MES PE has received and imported one or more Ethernet
   A-D routes that have the matching ESI and Ethernet Tag as the one
   present in the MAC advertisement. The Ethernet A-D routes mentioned
   in the following description refer to the ones imported from this
   given MES.

   If there is a corresponding Ethernet A-D route for that <ESI,
   Ethernet Tag> then that label stack MUST be used. If such PE.

   -If an Ethernet
   Tag A-D route doesn't exist but Ethernet A-D routes exist for <ESI,
   Ethernet Tag = 0> and <ESI = 0, Ethernet Tag> then the label stack
   must be constructed by using the labels from these two routes. If
   this is not the case but an per Ethernet A-D route exists Segment for <ESI,
   Ethernet Tag = 0> then the label from that route must be used.
   Finally if this is also not the case but ESI exists,
   together with an Ethernet A-D route exists
   for <ESI = 0, Ethernet Tag = 0> per EVI, then the label from that
   latter route must be used.

   The following example explains the above when Ethernet A-D routes are
   advertised per <ESI, Ethernet Tag>. above.

   Consider a CE, CE1, CE (CE1) that is dual homed dual-homed to two MESes, MES1 PEs (PE1 and MES2 PE2) on a
   LAG interface, ES1, interface (ES1), and is sending packets with MAC address MAC1 on
   VLAN1. Based on E-VPN extensions described in sections "Determining
   Reachability of Unicast Addresses" and "Auto-Discovery of Ethernet
   Tags on Ethernet Segments", a A remote MES PE, say MES3 PE3, is able to learn that a MAC1 is reachable
   via MES1 PE1 and MES2. PE2. Both MES1 PE1 and MES2 PE2 may advertise MAC1 in BGP if they
   receive packets with MAC1 from CE1. If this is not the case case, and if
   MAC1 is advertised only by MES1, MES3 PE1, PE3 still considers MAC1 as reachable
   via both MES1 PE1 and MES2 PE2 as both MES1 PE1 and MES2 PE2 advertise a Ethernet A-D
   route per ESI for ESI1 as well as an Ethernet A-D route per EVI for
   <ESI1, VLAN1>.

   The MPLS label stack to send the packets to MES1 PE1 is the MPLS LSP stack
   to get to MES1 PE1 and the E-VPN label advertised by MES1 PE1 for CE1's MAC.

   The MPLS label stack to send packets to MES2 PE2 is the MPLS LSP stack to
   get to MES2 PE2 and the MPLS label in the Ethernet A-D route advertised by MES2
   PE2 for <ES1, VLAN1>, if MES2 PE2 has not advertised MAC1 in BGP.

   We will refer to these label stacks as MPLS next-hops.

   The remote MES, MES3, PE (PE3) can now load balance the traffic it receives from
   its CEs, destined for CE1, between MES1 PE1 and MES2.  MES3 PE2.  PE3 may use
   the IP N-Tuple
   flow information for it to hash traffic into one of the MPLS next-hops for
   load balancing for of IP traffic. Or MES3 Alternatively PE3 may rely on the
   source and
   destination MAC addresses for load balancing.

   Note that once MES3 PE3 decides to send a particular packet to MES1 PE1 or
   MES2 PE2
   it can pick from more than path one out of multiple possible paths to reach the
   particular remote
   MES PE using regular MPLS procedures. For instance instance, if
   the tunneling technology is based on RSVP-TE LSPs, and MES3 PE3 decides to
   send a particular packet to MES1 PE1, then MES3 PE3 can choose from multiple
   RSVP-TE LSPs that have MES1 PE1 as their destination.

   When MES1 PE1 or MES2 PE2 receive the packet destined for CE1 from MES3, PE3, if the
   packet is a unicast MAC packet it is forwarded to CE1.  If it is a
   multicast or broadcast MAC packet then only one of MES1 PE1 or MES2 PE2 must
   forward the packet to the CE. Which of MES1 PE1 or MES2 PE2 forward this packet
   to the CE is determined by default based on which of the two
   is the DF. An alternate procedure to load balance multicast packets
   will be described in the future. two is the DF.

   If the connectivity between the multi-homed CE and one of the MESes PEs
   that it is multi-homed attached to fails, the MES MUST withdraw the MAC
   address from BGP.  In addition the MES PE MUST withdraw the Ethernet Tag
   A-D routes, that had been previously advertised, for the Ethernet
   Segment to the CE. When the MAC entry on the PE ages out, the PE MUST
   withdraw the MAC address from BGP. Note that to aid convergence convergence, the
   Ethernet Tag A-D routes MAY be withdrawn before the MAC routes. This
   enables the remote MESes PEs to remove the MPLS next-hop to this particular MES
   PE from the set of MPLS next-hops that can be used to forward traffic
   to the CE. For further details and procedures on withdrawal of E-VPN
   route types in the event of MES PE to CE failures please section "MES "PE to
   CE Network  Failures".

18.2.

15.2. Load balancing of traffic between an MES PE and a local CE

   A CE may be configured with more than one interface connected to
   different MESes PEs or the same MES PE for load balancing, using a technology
   such as LAG. The MES(s) PE(s) and the CE can load balance traffic onto these
   interfaces using one of the following mechanisms.

18.2.1.

15.2.1. Data plane learning

   Consider that the MESes PEs perform data plane learning for local MAC
   addresses learned from local CEs. This enables the MES(s) PE(s) to learn a
   particular MAC address and associate it with one or more interfaces,
   if the technology between the MES PE and the CE supports multi-pathing.
   The MESes PEs can now load balance traffic destined to that MAC address on
   the multiple interfaces.

   Whether multiple interfaces.

   Whether the CE can load balance traffic that it generates on the
   multiple interfaces is dependent on the CE implementation.

15.2.2. Control plane learning

   The CE can be a host that advertises the same MAC address using a
   control protocol on both interfaces. This enables the PE(s) to learn
   the host's MAC address and associate it with one or more interfaces.
   The PEs can now load balance traffic destined to the host on the
   multiple interfaces. The host can also load balance the traffic it
   generates onto these interfaces and the PE that receives the traffic
   employs E-VPN forwarding procedures to forward the traffic.

16. MAC Mobility

   It is possible for a given host or end-station (as defined by its MAC
   address) to move from one Ethernet segment to another;  this is
   referred to as 'MAC Mobility' or 'MAC move' and it is different from
   the multi-homing situation in which a given MAC address is reachable
   via multiple PEs for the same Ethernet segment.  In a MAC move, there
   would be two sets of MAC Advertisement routes, one set with the new
   Ethernet segment and one set with the previous Ethernet segment, and
   the MAC address would appear to be reachable via each of these
   segments.

   In order to allow all of the PEs in the E-VPN to correctly determine
   the current location of the CE can load balance traffic that MAC address, all advertisements of it generates on
   being reachable via the
   multiple interfaces is dependent on previous Ethernet segment MUST be withdrawn
   by the CE implementation.

18.2.2. Control plane PEs, for the previous Ethernet segment, that had advertised
   it.

   If local learning

   The CE can is performed using the data plane, these PEs will
   not be a host able to detect that advertises the same MAC address using a
   control protocol on both interfaces. This enables the MES(s) has moved to learn another
   Ethernet segment and the host's receipt of MAC address and associate it Advertisement routes, with one or more interfaces.
   The MESes can now load balance traffic destined to the host on
   the
   multiple interfaces. The host can also load balance MAC Mobility extended community attribute, from other PEs serves
   as the traffic it
   generates onto trigger for these interfaces and PEs to withdraw their advertisements.  If
   local learning is performed using the MES that receives control or management planes,
   these interactions serve as the traffic
   employs E-VPN forwarding procedures trigger for these PEs to forward the traffic.

19. MAC Moves withdraw
   their advertisements.

   In the case where a CE is a host or a switched network connected to
   hosts, the MAC address that is reachable via situation where there are multiple moves of a given MES on a
   particular ESI MAC,
   possibly between the same two Ethernet segments, there may move such be
   multiple withdrawals and re-advertisements.  In order to ensure that
   all PEs in the E-VPN receive all of these correctly through the
   intervening BGP infrastructure, it becomes reachable via another
   MES on another ESI.  This is referred necessary to as introduce a "MAC Move".

   Remote MESes
   sequence number into the MAC Mobility extended community attribute.

   Since the sequence number is an unsigned 32 bit integer, all sequence
   number comparisons must be able performed modulo 2**32. This unsigned
   arithmetic preserves the relationship of sequence numbers as they
   cycle from 2**32 - 1 to distinguish 0.

   Every MAC mobility event for a given MAC move from address will contain a
   sequence number that is set using the case
   where following rules:

   - A PE advertising a MAC address on an ESI is reachable via two for the first time advertises it
   with no MAC Mobility extended community attribute.

   - A PE detecting a locally attached MAC address for which it had
   previously received a MAC Advertisement route with a different MESes
   and load balancing is performed as described
   Ethernet segment identifier advertises the MAC address in section "Load
   Balancing of Unicast Packets".  This distinction can be made as
   follows. If a MAC is learned by
   Advertisement route tagged with a particular MES from multiple MESes,
   then MAC Mobility extended community
   attribute with a sequence number one greater than the MES performs load balancing only amongst sequence number
   in the set MAC mobility attribute of MESes
   that advertised the received MAC with the same ESI. If this is not Advertisement
   route. In the case
   then the MES chooses only one of the advertising MESes to reach first mobility event for a given MAC
   address, where the received MAC as per BGP path selection.

   There can be traffic loss during Advertisement route does not carry a
   MAC move. Consider MAC1 that is
   advertised by MES1 and learned from CE1 on ESI1. If MAC1 now moves
   behind MES2, on ESI2, MES2 advertises Mobility attribute, the MAC value of the sequence number in BGP. Until a remote
   MES, MES3, determines that the best path
   received route is via MES2, it will
   continue assumed to send traffic destined be 0 for MAC1 to MES1. This will purpose of this processing.

   - A PE detecting a locally attached MAC address for which it had
   previously received a MAC Advertisement route with the same Ethernet
   segment identifier advertises it with:
      i.  no MAC Mobility extended community attribute, if the received
      route did not
   occur deterministially until MES1 withdraws carry said attribute.

      ii. a MAC Mobility extended community attribute with the advertisement for
   MAC1.

   One recommended optimization sequence
      number equal to reduce the traffic loss during sequence number in the received MAC
   moves is
      Advertisement route, if the following option. When an MES sees received route is tagged with a MAC update from
      Mobility extended community attribute.

   A PE receiving a MAC Advertisement route for a MAC address with a
   locally attached CE on an ESI, which is
   different from the ESI on Ethernet segment identifier and a higher sequence number
   than that which the MES has currently learned the MAC, the corresponding entry
   in the local bridge forwarding table SHOULD be immediately purged
   causing the MES to withdraw it had previously advertised, withdraws its own E-VPN MAC advertisement
   Advertisement route. If two (or more) PEs advertise the same MAC
   address with same sequence number but different Ethernet segment
   identifiers, a PE that receives these routes selects the route and
   replace it
   advertised by the PE with lowest IP address as the update.

   A future version of this specification will describe other optimized
   procedures to minimize traffic loss during MAC moves.

20. best route.

17. Multicast

   The MESes PEs in a particular E-VPN may use ingress replication or P2MP
   LSPs to send multicast traffic to other MESes.

20.1. PEs.

17.1. Ingress Replication

   The MESes PEs may use ingress replication for flooding unknown unicast,
   multicast or broadcast traffic as described in section "Handling of
   Multi-Destination Traffic". A given unknown unicast or broadcast
   packet must be sent to all the remote MESes. PEs. However a given multicast
   packet for a multicast flow may be sent to only a subset of the MESes. PEs.
   Specifically a given multicast flow may be sent to only those MESes PEs
   that have receivers that are interested in the multicast flow.
   Determining which of the MESes PEs have receivers for a given multicast
   flow is done using explicit tracking described below.

20.2.

17.2. P2MP LSPs

   A MES

   An PE may use an "Inclusive" tree for sending an unknown unicast,
   broadcast or multicast packet or a "Selective" tree. This terminology
   is borrowed from [VPLS-MCAST].

   A variety of transport technologies may be used in the SP network.
   For inclusive P-Multicast trees, these transport technologies include
   point-to-multipoint LSPs created by RSVP-TE or mLDP. For selective P-
   Multicast trees, only unicast MES-MES PE-PE tunnels (using MPLS or IP/GRE
   encapsulation) and P2MP LSPs are supported, and the supported P2MP
   LSP signaling protocols are RSVP-TE, and mLDP.

20.3.

17.3. MP2MP LSPs

   The root of the MP2MP LDP LSP advertises the Inclusive Multicast Tag
   route with the PMSI Tunnel attribute set to the MP2MP Tunnel
   identifier.  This advertisement is then sent to all MESes PEs in the E-
   VPN. E-VPN.
    Upon receiving the Inclusive Multicast Tag routes with a PMSI Tunnel
   attribute that contains the MP2MP Tunnel identifier, the receiving MESes
   PEs initiate the setup of the MP2MP tunnel towards the root using the
   procedures in [MLDP].

20.3.1.

17.3.1. Inclusive Trees

   An Inclusive Tree allows the use of a single multicast distribution
   tree, referred to as an Inclusive P-Multicast tree, in the SP network
   to carry all the multicast traffic from a specified set of E-VPN
   instances EVIs on a
   given MES. PE. A particular P-Multicast tree can be set up to carry the
   traffic originated by sites belonging to a single E-VPN, or to carry
   the traffic originated by sites belonging to different E-
   VPNs. E-VPNs. The
   ability to carry the traffic of more than one E-VPN on the same tree
   is termed 'Aggregation'. The tree needs to include every
   MES PE that is a
   member of any of the E-VPNs that are using the tree. This implies
   that an MES PE may receive multicast traffic for a multicast stream even
   if it doesn't have any receivers that are interested in receiving
   traffic for that stream.

   An Inclusive P-Multicast tree as defined in this document is a P2MP
   tree.  A P2MP tree is used to carry traffic only for E-VPN CEs that
   are connected to the MES PE that is the root of the tree.

   The procedures for signaling an Inclusive Tree are the same as those
   in [VPLS-MCAST] with the VPLS-AD route replaced with the Inclusive
   Multicast Ethernet Tag route. The P-Tunnel attribute [VPLS-MCAST] for
   an Inclusive tree is advertised in the Inclusive Ethernet A-D Multicast route as
   described in section "Handling of Multi-Destination Traffic". Note
   that an MES PE can "aggregate" multiple inclusive trees for different E-
   VPNs
   EVIs on the same P2MP LSP using upstream labels. The procedures for
   aggregation are the same as those described in [VPLS-MCAST], with
   VPLS A-D routes replaced by E-VPN Inclusive Multicast Ethernet A-D routes.

20.3.2.

17.3.2. Selective Trees

   A Selective P-Multicast tree is used by an MES PE to send IP multicast
   traffic for one or more specific IP multicast streams, originated by
   CEs connected to the MES, PE, that belong to the same or different E-
   VPNs, E-VPNs,
   to a subset of the MESs PEs that belong to those E-VPNs. Each of the MESs PEs
   in the subset should be on the path to a receiver of one or more
   multicast streams that are mapped onto the tree. The ability to use
   the same tree for multicast streams that belong to different E-
   VPNs E-VPNs
   is termed an MES PE the ability to create separate SP multicast trees for
   specific multicast streams, e.g. high bandwidth multicast streams.
   This allows traffic for these multicast streams to reach only those MES
   PE routers that have receivers in these streams. This avoids flooding
   other MES PE routers in the E-VPN.

   A

   An SP can use both Inclusive P-Multicast trees and Selective P-
   Multicast trees or either of them for a given E-VPN on an MES, PE, based
   on local configuration.

   The granularity of a selective tree is <RD, MES, PE, S, G> where S is an
   IP multicast source address and G is an IP multicast group address or
   G is a multicast MAC address. Wildcard sources and wildcard groups
   are supported. Selective trees require explicit tracking as described
   below.

   A E-VPN MES PE advertises a selective tree using a E-VPN selective A-D
   route. The procedures are the same as those in [VPLS-MCAST] with S-
   PMSI A-D routes in [VPLS-MCAST] replaced by E-VPN Selective A-D
   routes. The information elements of the E-VPN selective  A-D route
   are similar to those of the VPLS S-PMSI A-D route with the following
   differences. A E-VPN Selective A-D route includes an optional
   Ethernet Tag field. Also an E-VPN selective A-D route may encode a
   MAC address in the Group field. The encoding details of the E-VPN
   selective A-D route will be described in the next revision.

   Selective trees can also be aggregated on the same P2MP LSP using
   aggregation as described in [VPLS-MCAST].

20.4.

17.4. Explicit Tracking

   [VPLS-MCAST] describes procedures for explicit tracking that rely on
   Leaf A-D routes. The same procedures are used for explicit tracking
   in this specification with VPLS Leaf A-D routes replaced with E-VPN
   Leaf A-D routes.  These procedures allow a root MES PE to request
   multicast membership information for a given (S, G), from leaf MESs. PEs.
   Leaf MESs PEs rely on IGMP snooping or PIM snooping between the MES PE and the
   CE to determine the multicast membership information. Note that the
   procedures in [VPLS-MCAST] do not describe how explicit tracking is
   performed if the CEs are enabled with join suppression. The
   procedures for this case will be described in a future version.

21.

18. Convergence

   This section describes failure recovery from different types of
   network failures.

21.1.

18.1. Transit Link and Node Failures between MESes PEs

   The use of existing MPLS Fast-Reroute mechanisms can provide failure
   recovery in the order of 50ms, in the event of transit link and node
   failures in the infrastructure that connects the MESes.

21.2. MES PEs.

18.2. PE Failures

   Consider a host host1 that is dual homed to MES1 PE1 and MES2. PE2. If MES1 PE1
   fails, a remote MES, MES3, PE, PE3, can discover this based on the failure of
   the BGP session.  This failure detection can be in the sub-second
   range if BFD is used to detect BGP session failure. MES3 PE3 can update
   its forwarding state to start sending all traffic for host1 to only
   MES2.
   PE2. It is to be noted that this failure recovery is potentially
   faster than what would be possible if data plane learning were to be
   used. As in that case MES3 PE3 would have to rely on re-learning of MAC
   addresses via MES2.

21.2.1. PE2.

18.2.1. Local Repair
   It is possible to perform local repair in the case of MES PE failures.
   Details will be specified in the future.

21.3. MES

18.3. PE to CE Network Failures

   When an Ethernet segment connected to an MES PE fails or when a Ethernet
   Tag is deconfigured decommissioned on an Ethernet segment, then the MES PE MUST
   withdraw the Ethernet A-D route(s) announced for the <ESI, Ethernet
   Tags> that are impacted by the failure or de-configuration. decommissioning. In
   addition
   addition, the MES PE MUST also withdraw the MAC advertisement routes that
   are impacted by the failure or de-configuration. decommissioning.

   The Ethernet A-D routes should be used by an implementation to
   optimize the withdrawal of MAC advertisement routes. When an MES PE
   receives a withdrawal of a particular Ethernet A-D route from an MES PE
   it SHOULD consider all the MAC advertisement routes, that are learned
   from the same <ESI, Ethernet Tag> as in the Ethernet A-D route, from
   the advertising MES, PE, as having been withdrawn. This optimizes the
   network convergence times in the event of MES PE to CE failures.

22.

19. LACP State Synchronization

   This section requires review and discussion amongst the authors and
   will be revised in the next version.

   To support CE multi-homing with multi-chassis Ethernet bundles, the
   MESes
   PEs connected to a given CE should synchronize [802.1AX] LACP state
   amongst each other. This ensures that the MESes PEs can present a single
   LACP bundle to the CE. This is required for initial system bring-up
   and upon any configuration change.

   This includes at least the following LACP specific configuration
   parameters:

      - System Identifier (MAC Address): uniquely identifies a LACP
        speaker.
      - System Priority: determines which LACP speaker's port
        priorities are used in the Selection logic.
      - Aggregator Identifier: uniquely identifies a bundle within
        a LACP speaker.
      - Aggregator MAC Address: identifies the MAC address of the
        bundle.
      - Aggregator Key: used to determine which ports can join an
        Aggregator.
      - Port Number: uniquely identifies an interface within a LACP
        speaker.
      - Port Key: determines the set of ports that can be bundled.
      - Port Priority: determines a port's precedence level to join
        a bundle in case the number of eligible ports exceeds the
        maximum number of links allowed in a bundle.

   Furthermore, the MESes PEs should also synchronize operational (run-time)
   data, in order for the LACP Selection logic state-machines to
   execute. This operational data includes the following LACP
   operational parameters, on a per port basis:

      - Partner System Identifier: this is the CE System MAC address.
      - Partner System Priority: the CE LACP System Priority
      - Partner Port Number: CE's AC port number.
      - Partner Port Priority: CE's AC Port Priority.
      - Partner Key: CE's key for this AC.
      - Partner State: CE's LACP State for the AC.
      - Actor State: PE's LACP State for the AC.
      - Port State: PE's AC port status.

   The above state needs to be communicated between MESes PEs forming a
   multi-chassis multi-
   chassis bundle during LACP initial bringup, upon any configuration
   change and upon the occurrence of a failure.

   It should be noted that the above configuration and operational state
   is localized in scope and is only relevant to MESes PEs which connect to
   the same multi-homed CE over a given Ethernet bundle.

   Furthermore, the communication of state changes, upon failures, must
   occur with minimal latency, in order to minimize the switchover time
   and consequent service disruption. The protocol details for
   synchronizing the LACP state will be described in the following
   version.

23.

20. Acknowledgements

   We would like to thank Yakov Rekhter, Pedro Marques, Kaushik Ghosh,
   Nischal Sheth, Robert Raszuk and Raszuk, Amit Shukla and Nadeem Mohammed for
   discussions that helped shape this document. We would also like to
   thank Han Nguyen for his comments and support of this work. We would
   also like to thank Steve Kensil for his review.

24.

21. References
   [E-VPN-REQ] A. Sajassi, R. Aggarwal et. al., "Requirements for
              Ethernet VPN", draft-sajassi-raggarwa-l2vpn-evpn-req-
              00.txt

   [RFC4364] "BGP/MPLS IP VPNs", Rosen, Rekhter, et. al., February 2006

   [VPLS-MCAST] "Multicast in VPLS". R. Aggarwal et.al., draft-ietf-
              l2vpn-vpls-mcast-04.txt

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

   [RFC4762] Lasserre, M. and V. Kompella, "Virtual Private LAN Service
              (VPLS) Using Label Distribution Protocol (LDP) Signaling",
              RFC 4762, January 2007.

   [VPLS-MULTIHOMING] "BGP based Multi-homing in Virtual Private LAN
              Service", K. Kompella et. al., draft-ietf-l2vpn-vpls-
              multihoming-00.txt

   [PIM-SNOOPING] "PIM Snooping over VPLS", V. Hemige et. al., draft-
              ietf-l2vpn-vpls-pim-snooping-01

   [IGMP-SNOOPING] "Considerations for Internet Group Management
              Protocol (IGMP) and Multicast Listener Discovery (MLD)
              Snooping Switches", M. Christensen et. al., RFC4541,

   [RT-CONSTRAIN] P. Marques et. al., "Constrained Route Distribution
              for Border Gateway Protocol/MultiProtocol Label Switching
              (BGP/MPLS) Internet Protocol (IP) Virtual Private Networks
              (VPNs)", RFC 4684, November 2006

25.

   [EVPN-SEGMENT-ROUTE] A. Sajassi et. al., "E-VPN Ethernet Segment
              Route", draft-sajassi-l2vpn-evpn-segment-route-00.txt,
              work in progress.

21. Author's Address

      Rahul Aggarwal
      Email: raggarwa_1@yahoo.com

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

      Wim Henderickx
      Alcatel-Lucent
      e-mail: wim.henderickx@alcatel-lucent.com
      Aldrin Isaac
      Bloomberg
      Email: aisaac71@bloomberg.net

      James Uttaro
      AT&T
      200 S. Laurel Avenue
      Middletown, NJ  07748
      USA
      Email: uttaro@att.com

      Nabil Bitar
      Verizon Communications
      Email : nabil.n.bitar@verizon.com

      Ravi Shekhar
      Juniper Networks
      1194 N. Mathilda Ave.
      Sunnyvale, CA  94089 US
      Email: rshekhar@juniper.net

      John Drake
      Juniper Networks
      1194 N. Mathilda Ave.
      Sunnyvale, CA 94089 US
      Email: jdrake@juniper.net

      Florin Balus
      Alcatel-Lucent
      e-mail: Florin.Balus@alcatel-lucent.com

      Keyur Patel
      Cisco
      170 West Tasman Drive
      San Jose, CA  95134, US
      Email: keyupate@cisco.com

      Sami Boutros
      Cisco
      170 West Tasman Drive
      San Jose, CA  95134, US
      Email: sboutros@cisco.com

      Samer Salam
      Cisco
      595 Burrard Street, Suite 2123
      Vancouver, BC V7X 1J1, Canada
      Email: ssalam@cisco.com