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Versions: 00 01

Network Working Group                               R. Aggarwal (Editor)
Internet Draft                                          Juniper Networks
Category: Standards Track
Expiration Date: December 2010                                  A. Isaac
                                                               Bloomberg

                                                               J. Uttaro
                                                                    AT&T

                                                              R. Shekhar
                                                        Juniper Networks

                                                                F. Balus
                                                          Alcatel-Lucent

                                                           W. Henderickx
                                                          Alcatel-Lucent

                                                            June 2, 2010


                         BGP MPLS Based MAC VPN


                     draft-raggarwa-mac-vpn-01.txt

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
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Copyright and License Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors. All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   than English.


Abstract

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



















raggarwa                                                        [Page 2]


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Table of Contents

 1          Specification of requirements  .........................   4
 2          Contributors  ..........................................   4
 3          Introduction  ..........................................   4
 4          Terminology  ...........................................   5
 5          BGP MPLS Based MAC-VPN  ................................   6
 6          Ethernet Segment Identifier  ...........................   7
 7          BGP MAC-VPN NLRI  ......................................   8
 8          Auto-Discovery of Ethernet Tags on Ethernet Segments  ..   9
 9          Determining Reachability to Unicast MAC Addresses  .....  11
 9.1        Local Learning  ........................................  11
 9.2        Remote learning  .......................................  11
 9.2.1      BGP MAC-VPN MAC Address Advertisement  .................  12
10          Designated Forwarder Election  .........................  13
11          Handling of Broadcast, Multicast and Unknown Unicast Traffic  15
11.1        P-Tunnel Identification  ...............................  16
11.2        Ethernet Segment Identifier and Ethernet Tag  ..........  17
12          Processing of Unknown Unicast Packets  .................  17
12.1        Ingress Replication  ...................................  18
12.2        P2MP MPLS LSPs  ........................................  18
13          Forwarding Unicast Packets  ............................  19
13.1        Forwarding packets received from a CE  .................  19
13.2        Forwarding packets received from a remote MES  .........  20
13.2.1      Unknown Unicast Forwarding  ............................  20
13.2.2      Known Unicast Forwarding  ..............................  20
14          Split Horizon  .........................................  21
14.1        ESI MPLS Label: Ingress Replication  ...................  22
14.2        ESI MPLS Label: P2MP MPLS LSPs  ........................  23
15          Load Balancing of Unicast Packets  .....................  23
15.1        Load balancing of traffic from a MES to remote CEs  ....  23
15.2        Load balancing of traffic between a MES and a local CE  ....25
15.2.1      Data plane learning  ...................................  25
15.2.2      Control plane learning  ................................  25
16          MAC Moves  .............................................  25
17          Multicast  .............................................  26
17.1        Ingress Replication  ...................................  26
17.2        P2MP LSPs  .............................................  27
17.2.1      Inclusive Trees  .......................................  27
17.2.2      Selective Trees  .......................................  28
17.3        Explicit Tracking  .....................................  28
18          Convergence  ...........................................  29



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18.1        Transit Link and Node Failures between MESes  ..........  29
18.2        MES Failures  ..........................................  29
18.2.1      Local Repair  ..........................................  29
18.3        MES to CE Network Failures  ............................  29
19          Acknowledgements  ......................................  30
20          References  ............................................  30
21          Author's Address  ......................................  31






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
   Juniper Networks




3. Introduction

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

   There is a desire by Service Providers (SP) and data center providers
   to provide MPLS based bridged / LAN services or/and infrastructure
   such that they meet the requirements listed below. An example of such
   a service is a VPLS service offered by a SP. Another example is a
   MPLS based infrastructure in a data center. Here are the
   requirements:

   - Minimal or no configuration required. MPLS implementations have
   reduced the amount of configuration over the years. There is a need
   for greater auto-configuration.



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   - Support of multiple active points of attachment for CEs which may
   be hosts, switches or routers. Current MPLS technologies such as
   VPLS, currently do not support this. This allows load-balancing among
   multiple active paths. Regular Ethernet switching technologies, based
   on MAC learning  do not allow the same MAC to be learned from two
   different PEs and be active at the same time in the same switching
   instance

   - Ability to span a VLAN across multiple racks in different
   geographic locations, which may not be in the same data center.

   - Minimize or eliminate flooding of unknown unicast traffic.

   - Allow hosts and Virtual Machines (VMs) in a data center to relocate
   without requiring renumbering. For instnace VMs may be moved for load
   or failure reasons.

   - Ability to scale up to hundreds of thousands of hosts or more
   across multiple data centers, where connectivity is required between
   hosts in different data centers.

   - Support for virtualization. This includes the ability to separate
   hosts and VMs working together from other such groups, and the
   ability to have overlapping IP and MAC addresses/

   - Fast convergence

   This document proposes a MPLS based technology, referred to as MPLS-
   based MAC VPN (MAC-VPN) for meeting the requirements described in
   this section. MAC-VPN requires extensions to existing IP/MPLS
   protocols as described in section 5. In addition to these extensions
   MAC-VPN uses several building blocks from existing MPLS technologies.


4. Terminology

   MES: MPLS Edge Switch
   CE: Host or router or switch
   MVI: MAC VPN Instance
   ESI: Ethernet segment identifier











raggarwa                                                        [Page 5]


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5. BGP MPLS Based MAC-VPN

   This section describes the framework of MAC-VPN to meet the
   requirements described in section 3.

   An MAC-VPN comprises CEs that are connected to PEs or MPLS Edge
   Switches (MES) that comprise the edge of the MPLS infrastructure. A
   CE may be a host, a router or a switch. The MPLS Edge Switches
   provide layer 2 virtual bridge connectivity between the CEs. There
   may be multiple MAC VPNs in the provider's network. This document
   uses the terms MAC-VPN and MAC VPN inter-changeably. A MAC VPN
   routing and forwarding instance on a MES is referred to as a MAC VPN
   Instance (MVI).

   The MESes are connected by a MPLS LSP infrastructure which provides
   the benefits of MPLS such as fast-reroute, resiliency etc.

   In a MAC VPN, learning between MESes occurs not in the data plane (as
   happens with traditional bridging) but in the control plane. Control
   plane learning offers much greater control over the learning process,
   such as restricting who learns what, and the ability to apply
   policies.  Furthermore, the control plane chosen for this is BGP
   (very similar to IP VPNs (RFC 4364)), providing much greater scale,
   and the ability to "virtualize" or isolate groups of interacting
   agents (hosts, servers, Virtual Machines) from each other. In MAC
   VPNs MESes advertise the MAC addresses learned from the CEs that are
   connected to them, along with a MPLS label, to other MESes in the
   control plane. Control plane learning enables load balancing and
   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 and CEs is done by the method best
   suited to the CE: data plane learning, IEEE 802.1x, LLDP, 802.1aq or
   other protocols.

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

   The policy attributes of a MAC VPN are very similar to an IP VPN. A
   MAC-VPN instance requires a Route-Distinguisher (RD) and a MAC-VPN
   requires one or more Route-Targets (RTs). A CE attaches to a MAC-VPN
   on a MES in a particular MVI on a VLAN or simply an ethernet
   interface. When the point of attachment is a VLAN there may be one or
   more VLANs in a particular MAC-VPN. Some deployment scenarios



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   guarantee uniqueness of VLANs across MAC-VPNs: all points of
   attachment of a given MAC VPN use the same VLAN, and no other MAC VPN
   uses this VLAN. This document refers to this case as a "Default
   Single VLAN MAC-VPN" and describes simplified procedures to optimize
   for it.


6. Ethernet Segment Identifier

   If a CE is multi-homed to two or more MESes, the set of attachment
   circuits constitutes an "Ethernet 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).  A single-homed CE is considered to be attached to a 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 MAC VPNs are used to
   provide a VPLS service the ESI is fairly analogous to the VE ID used
   for the procedures in [BGP-VPLS] or the Multi-homing site ID in [BGP-
   VPLS-MH].

   2. If LACP is used, between the MESes and CEs that are hosts, then
   the ESI is determined by LACP. This is the 48 bit virtual MAC address
   of the host for the LACP link bundle. As far as the host is concerned
   it would treat the multiple MESes that it is homed to as the same
   switch.  This allows the host to aggregate links to different MESes
   in the same bundle.

   3. If LLDP is used, between the MESes 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 and a bridged LAN
   between the hosts and the MESes, the ESI is determined based on the
   Layer 2 bridge protocol as follows:

      If STP is used then the value of the ESI is derived by listening
   to BPDUs on the ethernet segment. The MES does not run STP. However
   it does learn the Switch ID, MSTP ID and Root Bridge ID by listening
   to BPDUs.  The ESI is as follows:

         {Switch ID (6 bits), MSTP ID (6 bits), Root Bridge ID (48
   bits)}






raggarwa                                                        [Page 7]


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7. BGP MAC-VPN NLRI

   This document defines a new BGP NLRI, called the MAC-VPN NLRI.

   Following is the format of the MAC-VPN NLRI:

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


   The Route Type field defines encoding of the rest of MAC-VPN NLRI
   (Route Type specific MAC-VPN NLRI).

   The Length field indicates the length in octets of the Route Type
   specific field of MAC-VPN NLRI.

   This document defines the following Route Types:

     + 1 - Ethernet Tag Auto-Discovery (A-D) route
     + 2 - MAC advertisement route
     + 3 - Inclusive Multicast Ethernet Tag Route
     + 4 - Ethernet Segment Route
     + 5 - Selective Multicast Auto-Discovery (A-D) Route
     + 6 - Leaf Auto-Discovery (A-D) Route

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

   The MAC-VPN NLRI is carried in BGP [RFC4271] using BGP Multiprotocol
   Extensions [RFC4760] with an AFI of TBD and an SAFI of MAC-VPN (To be
   assigned by IANA). The NLRI field in the
   MP_REACH_NLRI/MP_UNREACH_NLRI attribute contains the MAC-VPN NLRI
   (encoded as specified above).

   In order for two BGP speakers to exchange labeled MAC-VPN NLRI, they
   must use BGP Capabilities Advertisement to ensure that they both are
   capable 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 of MAC-VPN.







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8. Auto-Discovery of Ethernet Tags on Ethernet Segments

   If a CE is multi-homed to two or more MESes on a particular ethernet
   segment, each MES MUST advertise to other MSEs in the MAC VPN, the
   information about the Ethernet Tags (e.g., VLANs) on that ethernet
   segment.  If a CE is not multi-homed, then the MES that it is
   attached to MAY advertise the information about Ethernet Tags (e.g.,
   VLANs) on the ethernet segment connected to the CE.

   The information about an Ethernet Tag on a particular ethernet
   segment is advertised using a "Ethernet Tag Auto-Discovery route
   (Ethernet Tag A-D route)". This route is advertised using the MAC-VPN
   NLRI.

   MAC VPNs support both the non-qualified and qualified learning model.
   When non-qualified learning is used the Ethernet Tag Identifier
   specified in this section and in other places in this document MUST
   be set to a default value. When qualified learning is used the
   Ethernet Tag Identifier, when required, MUST be set to a MAC VPN
   provider assigned tag that maps locally on the advertising MES to an
   ethernet broadcast domain identifier such as a VLAN ID.

   The Ethernet Tag Auto-discovery information is used for Designated
   Forwarder (DF) election as described in section 10. It is also used
   to enable equal cost multi-path as described in section 15. Further,
   it can be used to optimize withdrawl of MAC addresses as described in
   section 18.

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

                +---------------------------------------+
                |      RD   (8 octets)                  |
                +---------------------------------------+
                | Ethernet Segment Identifier (8 octets)|
                +---------------------------------------+
                |  Ethernet Tag ID (4 octets)           |
                +---------------------------------------+
                |  MPLS Label (3 octets)                |
                +---------------------------------------+
                |   Originating Router's IP Addr        |
                +---------------------------------------+

   Route-Distinguisher (RD) MUST be set to the RD of the MAC-VPN
   instance that is advertising the NLRI. A RD MUST be assigned for a
   given MAC-VPN instance on a MES. This RD MUST be unique across all
   MAC-VPN instances on a MES. This can be accomplished by using a Type
   1 RD [RFC4364]. The value field comprises an IP address of the MES



raggarwa                                                        [Page 9]


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   (typically, the loopback address) followed by a number unique to the
   MES.  This number may be generated by the MES, or, in the Default
   Single VLAN MAC-VPN case, may be the 12 bit VLAN ID, with the
   remaining 4 bits set to 0.

   Ethernet Segment Identifier MUST be an 8 octet entity as described in
   section 6.

   The Ethernet Tag ID is the identifier of a Ethernet Tag on the
   ethernet segment. This value may be a two octet VLAN ID or it may be
   another Ethernet Tagused by the MAC VPN provider. It MAY be set to
   the default Ethernet Tag on the ethernet segment.

   The usage of the MPLS label is described in section 15.

   The Originating Router's IP address MUST be set to an IP address of
   the PE.  This address SHOULD be common for all the MVIs on the PE
   (e.,g., this address may be PE's loopback address).

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

   The Ethernet Tag A-D route MUST carry one or more Route Target (RT)
   attributes. RTs may be configured (as in IP VPNs), or may be derived
   automatically from the Ethernet Tag ID associated with the
   advertisement.

   The following is the procedure for deriving the RT attribute
   automatically from the Ethernet Tag ID associated with the
   advertisement:

     +      The Global Administrator field of the RT MUST
            be set to the Autonomous System (AS) number that the MES
       belongs to.

     +      The Local Administrator field of the RT contains a 4
            octets long number that encodes the Ethernet Tag-ID.

   The above auto-configuration of the RT implies that a different RT is
   used for every Ethernet Tag in a MAC-VPN, if the MAC-VPN contains
   multiple Ethernet Tags. For the "Default Single VLAN MAC-VPN" this
   results in auto-deriving the RT from the Ethernet Tag for that MAC-
   VPN.







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9. Determining Reachability to Unicast MAC Addresses

   MESes forward packets that they receive based on the destination MAC
   address. This implies that MESes 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 "remote learning":


9.1. Local Learning

   A particular MES must be able to learn the MAC addresses from the CEs
   that are connected to it. This is referred to as local learning.

   The MESes in a particular MAC-VPN MUST support local data plane
   learning using vanilla ethernet learning procedures. A MES must be
   capable of learning MAC addresses in the data plane when it receives
   packets such as the following from the CE network:

     - DHCP requests

     - gratuitous ARP request for its own MAC.

     - ARP request for a peer.

       Alternatively if a CE is a host then MESes MAY learn the MAC
       addresses of the host in the control plane.

       In the case where a CE is a host or a switched network connected
       on ESI X to hosts, the MAC address that is reachable via a given
       MES may move such that it becomes reachable via the same MES on
       another MES on ESI Y.  This is referred to as a "MAC Move"
       Procedures to support this are described in section 16.


9.2. Remote learning

   A particular MES must be able to determine how to send traffic to MAC
   addresses that belong to or are behind CEs connected to other MESes
   i.e. to remote CEs or hosts behind remote CEs. We call such MAC
   addresses as "remote" MAC addresses.

   This document requires a MES to learn remote MAC addresses in the
   control plane. In order to achieve this each MES advertises the MAC
   addresses it learns from its locally attached CEs in the control
   plane, to all the other MESes in the MAC-VPN, using BGP.




raggarwa                                                       [Page 11]


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9.2.1. BGP MAC-VPN MAC Address Advertisement

   BGP is extended to advertise these MAC addresses using the MAC
   advertisement route type in the MAC-VPN-NLRI.

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

                +---------------------------------------+
                |      RD   (8 octets)                  |
                +---------------------------------------+
                | Ethernet Segment Identifier (8 octets)|
                +---------------------------------------+
                |  Ethernet Tag ID (4 octets)           |
                +---------------------------------------+
                |  MAC Address (6 octets)               |
                +---------------------------------------+
                |  MPLS Label (3 octets)                |
                +---------------------------------------+
                |  Originating Router's IP Addr         |
                +---------------------------------------+

   The RD MUST be the RD of the MAC-VPN instance that is advertising the
   NLRI. The procedures for setting the RD for a given MAC VPN are
   described in section 8.

   The Ethernet Segment Identifier is set to the eight octet ESI
   identifier described in section 6.

   If qualified learning is used and the MAC address that is learned
   from the CE is associated with an Ethernet Tag, the Ethernet Tag ID
   MUST be the Ethernet Tag Identifier, assigned by the MAC VPN provider
   and mapped to the CE's ethernet tag. If non-qualified learning is
   used the Ethernet Tag identifier SHOULD be set to the default
   Ethernet Tag on the ethernet segment.

   The encoding of a MAC address is the 6-octet MAC address specified by
   IEEE 802 documents [802.1D-ORIG] [802.1D-REV].

   The MPLS label MUST be the downstream assigned MAC-VPN MPLS label
   that is used by the MES to forward MPLS encapsulated ethernet packets
   received from remote MESes, where the destination MAC address in the
   ethernet packet is the MAC address advertised in the above NLRI. The
   forwarding procedures are specified in section 13. A MES may
   advertise the same MAC-VPN label for all MAC addresses in a given
   MAC-VPN instance. This label assignment methodology is referred to as
   a per MVI label assigment. Or a MES may advertise a unique MAC-VPN
   label per <ESI, Ethernet Tag> combination.  This label methodology is



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   referred to as a per <ESI, Ethernet Tag> label assignment. Or a MES
   may advertise a unique MAC-VPN label per MAC address.  All of these
   methodologies have their tradeoffs.

   Per MVI label assignment requires the least number of MAC-VPN labels,
   but requires a MAC lookup in addition to a MPLS lookup on an egress
   MES for forwarding. On the other hand a unique label per <ESI,
   Ethernet Tag> or a 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 the MPLS labels and not having to do a MAC
   lookup.

   The Originating Router's IP address MUST be set to an IP address of
   the PE.  This address SHOULD be common for all the MVIs on the PE
   (e.,g., this address may be PE's loopback address).

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

   The BGP advertisement that advertises the MAC advertisement route
   MUST also carry one or more Route Target (RT) attributes. The
   assignemnt of RTs described in section 8 MUST be followed.

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


10. Designated Forwarder Election

   Consider a CE that is a host or a router that is multi-homed directly
   to more than one MES in a MAC-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, referred to as the Designated
   Forwarder (DF), is responsible for certain actions:

     -      Sending multicast and broadcast traffic, on a given Ethernet
       Tag
            on a particular ethernet segment, to the CE. Note that
            this behavior, which allows selecting a DF at the
            granularity of <ESI, Ethernet Tag> for multicast and
       broadcast
            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, S, G>.



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     -      Flooding unknown unicast traffic (i.e. traffic for
            which a 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 using a single link. 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 as a Link Aggregation
   Group (LAG).

   If a bridge network is multi-homed to more than one MES in a MAC-VPN
   via switches, then the support of active-active points of attachments
   as described in this specification requires the bridge network to be
   connected to two or more MESes 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 network does not connect to the MESes using LAG, then
   only one of the links between a CE that is a switch and the MESes
   must be the active link. Procedures for supporting active-active
   points of attachments, when a bridge network does not connect to the
   MESes 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. If the DF
   election is done at the ethernet segment granularity then a single
   MES MUST be elected as the DF on the ethernet segment.

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

   The MESes perform a designated forwarder (DF) election, for an
   ethernet segment, or ethernet segment, Ethernet Tag combination using
   the Ethernet Tag A-D BGP route described in section 8.

   The DF election for a particular ESI or a particular <ESI, Ethernet
   Tag> combination proceeds as follows. First a MES constructs a
   candidate list of MESes. This comprises all the Ethernet Tag A-D
   routes with that particular ESI or <ESI, Ethernet Tag> tuple that a
   MES imports in a MAC-VPN instance, including the Ethernet Tag A-D
   route 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



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   MESes that import the DF route.

   The default procedure for choosing the DF is the MES with the highest
   IP address, of all the MESes in the candidate list. This procedure
   MUST be implemented. It ensures that except during routing transients
   each MES chooses the same DF MES for a given ESI and Ethernet Tag
   combination.

   Other alternative procedures for performing DF election are possible
   and will be described in the future.




11. Handling of Broadcast, Multicast and Unknown Unicast Traffic

   Procedures are required for a given MES to send broadcast or
   multicast traffic, received from a CE encapsulated in a given
   Ethernet Tag in a MAC VPN, to all the other MESes that span that
   Ethernet Tag in the MAC VPN. In certain scenarios, described in
   section 12, a given MES may also need to flood unknown unicast
   traffic to other MESes.

   The MESes in a particular MAC-VPN may use ingress replication or P2MP
   LSPs to send unknown unicast, broadcast or multicast traffic to other
   MESes.

   Each MES MUST advertise an "Inclusive Multicast Ethernet Tag Route"
   to enable the above. This section provides the encoding and the
   overview of the Inclusive Multicast Ethernet Tag route. Subsequent
   sections describe in further detail its usage.

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

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


   The RD MUST be the RD of the MAC-VPN instance that is advertising the
   NLRI. The procedures for setting the RD for a given MAC VPN are



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   described in section 8.

   The Ethernet Segment Identifier MAY be set to the eight octet ESI
   identifier described in section 6. Or it MAY be set to 0. It MUST be
   set to 0 if the Ethernet Tag is set to 0.

   The Ethernet Tag ID is the identifier of the Ethernet Tag. It MAY be
   set to 0 in which case an egress MES MUST perform a MAC lookup to
   forward the packet.

   The Originating Router's IP address MUST be set to an IP address of
   the PE.  This address SHOULD be common for all the MVIs on the PE
   (e.,g., this address may be PE's loopback address).

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

   The BGP advertisement that advertises the Inclusive Multicast
   Ethernet Tag route MUST also carry one or more Route Target (RT)
   attributes. The assignemnt of RTs described in section 8 MUST be
   followed.


11.1. 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" specified in [BGP MVPN].

   Depending on the technology used for the P-tunnel for the MAC VPN on
   the PE, the PMSI Tunnel attribute of the Inclusive Multicast Ethernet
   Tag route is constructed as follows.

     + If the PE that originates the advertisement uses a P-Multicast
       tree for the P-tunnel for the MAC VPN, the PMSI Tunnel attribute
       MUST contain the identity of the tree (note that the PE could
       create the identity of the tree prior to the actual instantiation
       of the tree).

     + A PE that uses a P-Multicast tree for the P-tunnel MAY aggregate
       two or more Ethernet Tags in the same or different MAC VPNs
       present on the PE onto the same tree. In this case in addition to
       carrying the identity of the tree, the PMSI Tunnel attribute MUST
       carry an MPLS upstream assigned label which the PE has bound
       uniquely to the <ESI, Ethernet Tag> for MAC VPN associated with
       this update (as determined by its RTs).




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       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 label carried in that
       attribute.

     + If the PE that originates the advertisement uses ingress
       replication for the P-tunnel for the MAC VPN, the route MUST
       include the PMSI Tunnel attribute with the Tunnel Type set to
       Ingress Replication and Tunnel Identifier set to a routable
       address of the PE. The PMSI Tunnel attribute MUST carry a
       downstream assigned MPLS label. This label is used to demultiplex
       the broadcast, multicast or unknown unicast MAC VPN traffic
       received over a unicast tunnel by the PE.

     + The Leaf Information Required flag of the PMSI Tunnel attribute
       MUST be set to zero, and MUST be ignored on receipt.


11.2. Ethernet Segment Identifier and Ethernet Tag

   As described above the encoding rules allow setting the Ethernet
   Segment Identifier and Ethernet Tag to either valid values or to 0.
   If the Ethernet Tag is set to a valid value, then an egress MES can
   forward the packet to the set of egress ESIs in the Ethernet Tag, in
   the MAC VPN, by performing a MPLS lookup alone. Further if the ESI is
   also set to non zero then the egress MES does not need to replicate
   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 a
   MAC lookup in the MVI determined by the MPLS label, after the MPLS
   lookup, to forward the packet.

   If a MES advertises multiple Inclusive Ethernet Tag routes for a
   given MAC VPN then the PMSI Tunnel Attributes for these routes MUST
   be distinct.


12. Processing of Unknown Unicast Packets

   The procedures in this document do not require MESes to flood unknown
   unicast traffic to other MESes. If MESes learn CE MAC addresses via a
   control plane, the MESes 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 MES, the MES may have to flood the packet. Flooding must



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   take into account "split horizon forwarding" as follows. The
   principles behind the following procedures are borrowed from the
   split horizon forwarding rules in VPLS solutions [RFC 4761, RFC
   4762].  When a MES capable of flooding (say MESx) receives a
   broadcast Ethernet frame, or one with an unknown destination MAC
   address, it must flood the frame.  If the frame arrived from an
   attached CE, MESx must send a copy of the frame to every other
   attached CE, as well as to all other MESs participating in the MAC
   VPN. If, on the other hand, the frame arrived from another MES (say
   MESy), MESx must send a copy of the packet only 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
   multicast packets, as well as packets to an 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 MESes.

   The MESes in a particular MAC VPN may use ingress replication using
   RSVP-TE P2P LSPs or LDP MP2P LSPs for sending broadcast, multicast
   and unknown unicast traffic to other MESes. Or they may use RSVP-TE
   or LDP P2MP LSPs for sending such traffic to other MESes.


12.1. Ingress Replication

   If ingress replication is in use, the P-Tunnel attribute, carried in
   the Inclusive Multicast Ethernet Tag routes (section 11) for the MAC
   VPN, specifies the downstream label that the other MESes can use to
   send unknown unicast, multicast or broadcast traffic for the MAC VPN
   to this particular MES.

   The MES that receives a packet with this particular MPLS label MUST
   treat the packet as a broadcast, multicast or unknown unicast packet.
   Further if the MAC address is a unicast MAC address, the MES MUST
   treat the packet as an unknown unicast packet.


12.2. P2MP MPLS LSPs

   The procedures for using P2MP LSPs are very similar to VPLS
   procedures [VPLS-MCAST]. The P-Tunnel attribute used by a MES for
   sending unknown unicast, broadcast or multicast traffic for a
   particular ethernet segment, is advertised in the Inclusive Ethernet
   Tag Multicast route as described in section 11.

   The P-Tunnel attribute specifies the P2MP LSP identifier. This is the
   equivalent of an Inclusive tree in [VPLS-MCAST]. Note that multiple



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   Ethernet Tags, which may be in different MAC-VPNs, may use the same
   P2MP LSP, using upstream labels [VPLS-MCAST]. When P2MP LSPs are used
   for flooding unknown unicast traffic, packet re-ordering is possible.

   The MES that receives a packet on the P2MP LSP specified in the PMSI
   Tunnel Attribute MUST treat the packet as a broadcast, multicast or
   unknown unicast packet. Further if the MAC address is a unicast MAC
   address, the MES MUST treat the packet as an unknown unicast packet.


13. Forwarding Unicast Packets

13.1. Forwarding packets received from a CE

   When a MES receives a packet from a CE, on a given Ethernet Tag, it
   must first look up the source MAC address of the packet. In certain
   environments the source MAC address may be used to authenticate the
   CE and determine that traffic from the host can be allowed into the
   network.

   If the MES decides to forward the packet the destination MAC address
   of the packet must be looked up. If the MES has received MAC address
   advertisements for this destination MAC address from one or more
   other MESes or learned it from locally connected CEs, it is
   considered as a known MAC address. Else the MAC address is considered
   as an unknown MAC address.

   For known MAC addresses the MES forwards this packet to one of the
   remote MESes. The packet is encapsulated in the MAC-VPN MPLS label
   advertised by the remote MES, for that MAC address, and in the MPLS
   LSP label stack to reach the remote MES.

   If the MAC address is unknown then, if the administrative policy on
   the MES requires flooding of unknown unicast traffic:
       - The MES MUST flood the packet to other MESes. If the ESI over
   which the MES receives the packet is multi-homed, then the MES MUST
   first encapsulate the packet in the ESI MPLS label as described in
   section 14.  If ingress replication is used the packet MUST be
   replicated one or more times to each remote MES with the bottom label
   of the stack being a MPLS label determined as follows. This is the
   MPLS label advertised by the remote MES in a PMSI Tunnel Attribute in
   the Inclusive Multicast Ethernet Tag route for an <ESI, Ethernet Tag>
   combination. The Ethernet Tag in the route must be the same as the
   Ethernet Tag advertised by the ingress MES in its Ethernet Tag A-D
   route associated with the interface on which the ingress MES receives
   the packet. If P2MP LSPs are being used the packet MUST be sent on
   the P2MP LSP that the MES is the root of for the Ethernet Tag in the
   MAC-VPN. If the same P2MP LSP is used for all Ethernet Tags then all



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   the MESes in the MAC VPN MUST be the leaves of the P2MP LSP. If a
   distinct P2MP LSP is used for a given Ethernet Tag in the MAC VPN
   then only the MESes in the Ethernet Tag MUST be the leaves of the
   P2MP LSP. The packet MUST be encapsulated in the P2MP LSP label
   stack.

   If the MAC address is unknown then, if the admnistrative policy on
   the MES does not allow flooding of unknown unicast traffic:
       - The MES MUST drop the packet.


13.2. Forwarding packets received from a remote MES

13.2.1. Unknown Unicast Forwarding

   When a MES receives a 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 a MAC-VPN or the downstream label
   advertised in the P-Tunnel attribute and after performing the split
   horizon procedures described in section 14:

        - If the MES is the designated forwarder of unknown unicast,
   broadcast or multicast traffic, on a particular set of ESIs for the
   Ethernet Tag, the default behavior is for the MES to flood the packet
   on the ESIs. In other words the default behavior is for the MES to
   assume that the destination MAC address is unknown unicast, broadcast
   or multicast and it is not required to do a destination MAC address
   lookup, as long as the granularity of the MPLS label included the
   Ethernet Tag. As an option the MES may do a destination MAC lookup to
   flood the packet to only a subset of the CE interfaces in the
   Ethernet Tag. For instance the MES may decide to not flood an unknown
   unicast packet on certain ethernet segments even if it is the DF on
   the ethernet segment, based on administrative policy.

       - If the MES is not the designated forwarder on any of the ESIs
   for the Ethernet Tag, the default behavior is for it to drop the
   packet.


13.2.2. Known Unicast Forwarding

   If the top MPLS label ends up being a MAC-VPN label that was
   advertised in the unicast MAC advertisements, then the MES either
   forwards the packet based on CE next-hop forwarding information
   associated with the label or does a destination MAC address lookup to
   forward the packet to a CE.





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14. Split Horizon

   Consider a CE that is multi-homed to two or more MESes on an ethernet
   segment ES1. If the CE sends a multicast, broadcast or unknown
   unicast packet to a particular MES, say MES1, then MES1 will forward
   that packet to all or subset of the other MESes in the MAC VPN. In
   this case the MESes, other than MES1, that the CE is multi-homed to
   MUST drop the packet and not forward back to the CE. This is referred
   to as "split horizon" in this document.

   In order to accomplish this each MES distributes to other MESes that
   are connected to the ethernet segment an "Ethernet Segment Route".

   An Ethernet Segment route type specific MAC-VPN NLRI consists of the
   following:

                +---------------------------------------+
                |      RD   (8 octets)                  |
                +---------------------------------------+
                | Ethernet Segment Identifier (8 octets)|
                +---------------------------------------+
                |  MPLS Label (3 octets)                |
                +---------------------------------------+
                |   Originating Router's IP Addr        |
                +---------------------------------------+

   The RD MUST be the RD of the MAC-VPN instance that is advertising the
   NLRI. The procedures for setting the RD for a given MAC VPN are
   described in section 8.

   The Ethernet Segment Identifier MUST be set to the eight octet ESI
   identifier described in section 6.

   The MPLS label is referred to as an "ESI label". This label MUST be a
   downstream assigned MPLS label if the advertising MES is using
   ingress replication for sending multicast, broadcast or unknown
   unicast traffic, to other MESes. If the advertising MES is using P2MP
   MPLS LSPs for the same, then this label MUST be an upstream assigned
   MPLS label. The usage of this label is described below.

   The Originating Router's IP address MUST be set to an IP address of
   the PE.  This address SHOULD be common for all the MVIs on the PE
   (e.,g., this address may be PE's loopback address).

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




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   The BGP advertisement that advertises the MAC advertisement route
   MUST also carry one Route Target (RT) attribute. The construction of
   this RT will be specified in the next version.

   This route will be enhanced to carry LAG specific information such as
   LACP parameters in the future.


14.1. ESI MPLS Label: Ingress Replication

   An MES that is using ingress replication for sending broadcast,
   multicast or unknown unicast traffic, distributes to other MESes,
   that belong to the ethernet segment, a downstream assigned "ESI MPLS
   label" in the Ethernet Segment route. This label MUST be programmed
   in the platform label space by the advertising MES. Further the
   forwarding entry for this label must result in NOT forwarding packets
   received with this label onto the ethernet segment that the label was
   distributed for.

   Consider MES1 and MES2 that are multi-homed to CE1 on ES1. Further
   consider that MES1 is using P2P or MP2P LSPs to send packets to MES2.
   Consider that MES1 receives a a multicast, broadcast or unknown
   unicast packet from CE1 on VLAN1 on ESI1.

   First consider the case where MES2 distributes an unique Inclusive
   Multicast Ethernet Tag route for VLAN1, for each ethernet segment on
   MES2. In this case MES1 MUST NOT replicate the packet to MES2 for
   <ESI1, VLAN1>.

   Next consider the case where MES2 distributes a single Inclusive
   Multicast Ethernet Tag route for VLAN1 for all 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
   the MPLS label stack the ESI label that MES2 has distributed for
   ESI1. It MUST then push on the MPLS label distributed by MES2 in the
   Inclusive Ethernet Tag Multicast route for Ethernet Tag1. The
   resulting packet is further encapsulated in the P2P or MP2P LSP label
   stack required to transmit the packet to MES2.  When MES2 receives
   this packet it determines the set of ESIs to replicate the packet to
   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 MES2 then
   MES2 MUST NOT forward the packet onto ESI1.









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14.2. ESI MPLS Label: P2MP MPLS LSPs

   An MES that is using P2MP LSPs for sending broadcast, multicast or
   unknown unicast traffic, distributes to other MESes, that belong to
   the ethernet segment, an upstream assigned "ESI MPLS label" in the
   Ethernet Segment route. This label is upstream assigned by the MES
   that advertises the route. This label MUST be programmed by the other
   MESes, that are connected to the ESI advertised in the route, in the
   context label space for the advertising MES. Further the forwarding
   entry for this label must result in NOT forwarding packets received
   with this label onto the ethernet segment that the label was
   distributed for.

   Consider MES1 and MES2 that are multi-homed to CE1 on ES1. Further
   assume that MES1 is using P2MP MPLS LSPs to send broadcast, multicast
   or uknown unicast packets. When MES1 sends a multicast, broadcast or
   unknown unicast packet, that it receives from CE1, it MUST first push
   onto the MPLS label stack the ESI label that it has assigned for the
   ESI that the packet was received on. The resulting packet is further
   encapsulated in the P2MP MPLS label stack necessary to transmit the
   packet to the other MESes. Penultimate hop popping MUST be disabled
   on the P2MP LSPs used in the MPLS transport infrastructure for MAC
   VPN. When MES2 receives this packet it decapsulates the top MPLS
   label and forwards the packet using the context label space
   determined by the top label. If the next label is the ESI label
   assigned by MES1 then MES2 MUST NOT forward the packet onto ESI1.


15. Load Balancing of Unicast Packets

   This section specifies how load balancing is achieved to/from a CE
   that has more than one interface that is directly connected 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.


15.1. Load balancing of traffic from a MES to remote CEs

   Whenever a remote MES imports a MAC advertisement for a given <ESI,
   Ethernet Tag> in a MAC VPN instance, it MUST consider the MAC as
   reachahable via all the MESes from which it has imported Ethernet Tag
   A-D routes for that <ESI, Ethernet Tag>. Further the remote MES MUST
   use these MAC advertisement and Ethernet Tag A-D routes to constuct
   the set of next-hops that it can use to send the packet to the
   destination MAC. Each next-hop comprises a MPLS label, that is to be
   used by the egress MES to forward the packet. This label is
   determined as follows. If the next-hop is constructed as a result of
   a MAC route which has a valid MPLS label, then this label MUST be



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   used. However if the MAC route doesn't have a valid MPLS label or if
   the next-hop is constructed as a result of a Ethernet Tag A-D route
   then the MPLS label from the Ethernet Tag A-D route MUST be used.

   Consider a CE, CE1, that is dual homed to two MESes, MES1 and MES2 on
   a LAG interface, ES1, and is sending packets with MAC address MAC1 on
   VLAN1. Based on MAC-VPN extensions described in sections 8 and 9, a
   remote MES say MES3 is able to learn that a MAC1 is reachable via
   MES1 and MES2. Both MES1 and MES2 may advertise MAC1 in BGP if they
   receive packets with MAC1 from CE1. If this is not the case and if
   MAC1 is advertised only by MES1, MES3 still considers MAC1 as
   reachable via both MES1 and MES2 as both MES1 and MES2 advertise a
   Ethernet Tag A-D route for <ESI1, VLAN1>.

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

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

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

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

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

   When MES1 or MES2 receive the packet destined for CE1 from MES3, 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 or MES2
   must forward the packet to the CE. Which of MES1 or MES2 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.

   If the connectivity between the multi-homed CE and one of the MESes
   that it is multi-homed to fails, the MES MUST withdraw the MAC



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   address from BGP.  This enables the remote MESes to remove the MPLS
   next-hop to this particular MES from the set of MPLS next-hops that
   can be used to forward traffic to the CE. For further details and
   procedures on withdrawl of MAC VPN route types in the event of MES to
   CE failures please section 18.4.


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

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


15.2.1. Data plane learning

   Consider that the MESes perform data plane learning for local MAC
   addresses learned from local CEs. This enables the MES(s) to learn a
   particular MAC address and associate it with one or more interfaces.
   The MESes can now load balance traffic destined to that MAC address
   on the 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 MES(s) to learn
   the host's MAC address and associate it 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 the traffic it
   generates onto these interfaces and the MES that receives the traffic
   employs MAC-VPN forwarding procedures to forward the traffic.


16. MAC Moves

   In the case where a CE is a host or a switched network connected to
   hosts, the MAC address that is reachable via a given MES on a
   particular ESI may move such that it becomes reachable via another
   MES on another ESI.  This is referred to as a "MAC Move".

   Remote MESes must be able to distinguish a MAC move from the case
   where a MAC address on an ESI is reachable via two different MESes
   and load balancing is performed as described in section 15. This



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   distinction can be made as follows. If a MAC is learned by a
   particular MES from multiple MESes, then the MES performs load
   balancing only amongst the set of MESes that advertised the MAC with
   the same ESI. If this is not the case then the MES chooses only one
   of the advertising MESes to reach the MAC as per BGP path selection.

   There can be traffic loss during 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 the MAC in BGP. Until a remote
   MES, MES3, determines that the best path is via MES2, it will
   continue to send traffic destined for MAC1 to MES1. This will not
   occur deterministially until MES1 withdraws the advertisement for
   MAC1.

   One recommended optimization to reduce the traffic loss during MAC
   moves is the following option. When an MES sees a MAC update from a
   CE on an ESI, which is different from the ESI on 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 its own MAC-VPN MAC advertisement route and replace it
   with the update.

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


17. Multicast

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


17.1. Ingress Replication

   The MESes may use ingress replication for flooding unknown unicast,
   multicast or broadcast traffic as described in section 11. A given
   unknown unicast or broadcast packet must be sent to all the remote
   MESes. However a given multicast packet for a multicast flow may be
   sent to only a subset of the MESes. Specifically a given multicast
   flow may be sent to only those MESes that have receivers that are
   interested in the multicast flow. Determining which of the MESes have
   receivers for a given multicast flow is done using explicit tracking
   described below.








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17.2. P2MP LSPs

   A MES 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 tunnels (using MPLS or IP/GRE
   encapsulation) and P2MP LSPs are supported, and the supported P2MP
   LSP signaling protocols are RSVP-TE, and mLDP.


17.2.1. 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 MAC VPN
   instances on a given MES. A particular P-Multicast tree can be set up
   to carry the traffic originated by sites belonging to a single MAC
   VPN, or to carry the traffic originated by sites belonging to
   different MAC VPNs. The ability to carry the traffic of more than one
   MAC VPN on the same tree is termed 'Aggregation'. The tree needs to
   include every MES that is a member of any of the MAC VPNs that are
   using the tree. This implies that a MES 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 MAC VPN CEs that
   are connected to the MES 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 Tag A-D
   route as described in section 11.  Note that a MES can "aggregate"
   multiple inclusive trees for different MAC-VPNs 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
   MAC-VPN Inclusive Multicast Ethernet Tag A-D routes.









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17.2.2. Selective Trees

   A Selective P-Multicast tree is used by a MES to send IP multicast
   traffic for one or IP more specific multicast streams, originated by
   CEs connected to the MES, that belong to the same or different MAC
   VPNs, to a subset of the MESs that belong to those MAC VPNs. Each of
   the MESs 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 MAC
   VPNs is termed a MES 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 routers that have receivers in these streams. This
   avoids flooding other MES routers in the MAC VPN.

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

   The granularity of a selective tree is <RD, MES, 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 MAC-VPN MES advertises a selective tree using a MAC-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 MAC-VPN Selective A-D
   routes. The information elements of the MAC VPN selective
    A-D route are similar to those of the VPLS S-PMSI A-D route with the
   following differences. A MAC VPN Selective A-D route includes an
   optional Ethernet Tag field. Also a MAC VPN selective A-D route may
   encode a MAC address in the Group field. The encoding details of the
   MAC 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].


17.3. 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 MAC-VPN
   Leaf A-D routes.  These procedures allow a root MES to request
   multicast membership information for a given (S, G), from leaf MESs.
   Leaf MESs rely on IGMP snooping or PIM snooping between the MES and
   the CE to determine the multicast membership information. Note that



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   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.


18. Convergence

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


18.1. Transit Link and Node Failures between MESes

   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.


18.2. MES Failures

   Consider a host host1 that is dual homed to MES1 and MES2. If MES1
   fails, a remote MES, MES3, 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 can update
   its forwarding state to start sending all traffic for host1 to only
   MES2. 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 would have to rely on re-learning of MAC
   addresses via MES2.


18.2.1. Local Repair

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


18.3. MES to CE Network Failures

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

   The Ethernet Tag A-D routes should be used by an implementation to
   optimize the withdrawal of MAC advertisement routes. When a MES



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   receives a withdrawl of a particular Ethernet Tag A-D route it SHOULD
   consider all the MAC advertisement routes, that are learned from the
   same <ESI, Ethernet Tag> as in the Ethernet Tag A-D route, as having
   been withdrawn. This optimizes the network convergence times in the
   event of MES to CE failures.




19. Acknowledgements

   We would like to thank Yakov Rekhter, Kaushik Ghosh, Nischal Sheth
   and Amit Shukla for discussions that helped shape this document.  We
   would also like to thank Han Nguyen for his comments and support of
   this work.


20. References

   [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,









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21. Author's Address

   Rahul Aggarwal
   Juniper Networks
   1194 N. Mathilda Ave.
   Sunnyvale, CA  94089 US

   Email: rahul@juniper.net

   Aldrin Isaac
   Bloomberg
   Email: aisaac71@bloomberg.net

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

   Ravi Shekhar
   Juniper Networks
   1194 N. Mathilda Ave.
   Sunnyvale, CA  94089 US

   Wim Henderickx
   Alcatel-Lucent
   e-mail: wim.henderickx@alcatel-lucent.be

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



















raggarwa                                                       [Page 31]


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