[Docs] [txt|pdf] [Tracker] [Email] [Nits] [IPR]

Versions: 00 01

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

                                                               J. Uttaro
                                                                    AT&T

                                                              R. Shekhar
                                                        Juniper Networks




                                                          March 26, 2010


                         BGP MPLS Based MAC VPN


                     draft-raggarwa-mac-vpn-00.txt

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

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

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

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.






raggarwa                                                        [Page 1]


Internet Draft        draft-raggarwa-mac-vpn-00.txt           March 2010


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
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008. The person(s) controlling the copyright in some of this
   material may not have granted the IETF Trust the right to allow
   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.



Abstract

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


















raggarwa                                                        [Page 2]


Internet Draft        draft-raggarwa-mac-vpn-00.txt           March 2010


Table of Contents

 1          Specification of requirements  .........................   4
 2          Contributors  ..........................................   4
 3          Introduction  ..........................................   4
 4          BGP MPLS Based MAC-VPN  ................................   5
 5          Ethernet Segment Identifier  ...........................   6
 6          Determining Reachability to Unicast MAC Addresses  .....   7
 6.1        Local Learning  ........................................   7
 6.2        Remote learning  .......................................   8
 6.2.1      BGP MAC-VPN MAC Address Advertisement  .................   8
 7          Designated Forwarder Election  .........................  10
 8          Forwarding Unicast Packets  ............................  12
 8.1        Processing of Unknown Unicast Packets  .................  12
 8.2        Forwarding packets received from a CE  .................  13
 8.3        Forwarding packets received from a remote MES  .........  14
 9          Split Horizon  .........................................  15
10          Load Balancing of Unicast Packets  .....................  15
10.1        Load balancing of traffic from a MES to remote CEs  ....  16
10.2        Load balancing of traffic between a MES and a local CE  ....17
10.2.1      Data plane learning  ...................................  17
10.2.2      Control plane learning  ................................  17
11          MAC Moves  .............................................  18
12          Multicast  .............................................  18
12.1        Ingress Replication  ...................................  18
12.2        P2MP LSPs  .............................................  19
12.2.1      Inclusive Trees  .......................................  19
12.2.2      Selective Trees  .......................................  20
12.3        Explicit Tracking  .....................................  20
13          Convergence  ...........................................  21
13.1        Transit Link and Node Failures between MESes  ..........  21
13.2        MES Failures  ..........................................  21
13.2.1      Local Repair  ..........................................  21
13.3        MES to CE Network Failures  ............................  21
14          Acknowledgements  ......................................  22
15          References  ............................................  22
16          Author's Address  ......................................  22






raggarwa                                                        [Page 3]


Internet Draft        draft-raggarwa-mac-vpn-00.txt           March 2010


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 Virtual Bridged Network 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.

   - 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 paths active. MPLS technologies such as VPLS currently do
   not allow the same MAC to be learned from two different PEs and be
   active at the same time.

   - Ability to span a VLAN across multiple racks in different
   geographic locations.

   - Minimize or eliminate flooding of unknown unicast traffic.




raggarwa                                                        [Page 4]


Internet Draft        draft-raggarwa-mac-vpn-00.txt           March 2010


   - 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 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 the next section. In addition to these
   extensions MAC-VPN uses several building blocks from existing MPLS
   technologies.


4. BGP MPLS Based MAC-VPN

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

   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, MAC VPN inter-changeably. The instance of a
   MAC VPN on an 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



raggarwa                                                        [Page 5]


Internet Draft        draft-raggarwa-mac-vpn-00.txt           March 2010


   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, 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
   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 "Single VLAN
   MAC-VPN" and describes simplified procedures to optimize for it.

   The next section discusses how layer 2 connectivity is achieved
   between the CEs.

   Section 8 describes how load balancing and link bonding is achieved
   for MAC-VPN. Section 10 describes procedures for handling MAC moves.


5. 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.  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].




raggarwa                                                        [Page 6]


Internet Draft        draft-raggarwa-mac-vpn-00.txt           March 2010


   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)}



6. 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":


6.1. 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:







raggarwa                                                        [Page 7]


Internet Draft        draft-raggarwa-mac-vpn-00.txt           March 2010


     - 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 using extensions to
       protocols such as LLDP that run between the MES and the hosts.

       In the case where a CE is a host or a switched network connected
       to hosts, the MAC address is reachable via a given MES may move
       such that it becomes reachable via another MES. This is referred
       to as a "MAC Move". Procedures to support this are described in
       section 10.


6.2. 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.


6.2.1. BGP MAC-VPN MAC Address Advertisement

   BGP is extended to advertise these MAC addresses using a new NLRI
   called the MAC-VPN-NLRI, with AFI (TBD) and a new SAFI of MAC-VPN
   (TBD).

   The MAC-VPN-NLRI encodes the following elements when it is used for
   advertising MAC addresses:

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




raggarwa                                                        [Page 8]


Internet Draft        draft-raggarwa-mac-vpn-00.txt           March 2010


   b) VLAN ID if the MAC address is learned over a VLAN from the CE,
   else this field is set to 0.

   c) The Ethernet Segment Identifier described in the previous section.

   d) The MAC address.

   e) The advertisement may optionally carry one of the IP addresses
   associated with the MAC address. If used, this aids the implemntation
   of proxy ARP on MESes thereby reducing the flooding of broadcast
   packets.

   f) A MAC-VPN MPLS label that is used by the MES to forward packets
   received from remote MESes. The forwarding procedures are specified
   in section 8.  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 MAC address. Both 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 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 BGP advertisement also carries the following attributes:

   a) One or more Route Target (RT) attributes MUST be carried.

   RTs may be configured (as in IP VPNs), or may be derived
   automatically from the VLAN ID associated with the advertisement.

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

     +      The Global Administrator field of the RT MUST
            be set to an IP address of the MES. This address SHOULD be
            common for all the MAC-VPN instances on the MES (e.,g., this
            address may be the MES's loopback address).

     +      The Local Administrator field of the RT contains a 2
            octets long number that encodes the VLAN-ID.

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



raggarwa                                                        [Page 9]


Internet Draft        draft-raggarwa-mac-vpn-00.txt           March 2010


   b) The advertisement may optionally carry the IP addresses associated
   with the MAC address, if the number of IP addresses is more than one
   and cannot be encoded in the NLRI. This aids the implemntation of
   proxy ARP on MESes thereby reducing the flooding of broadcast
   packets.

   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.


7. Designated Forwarder Election

   If a CE that is a host or a router is multi-homed directly to more
   than one MES in a MAC-VPN, only one of the MESes is responsible for
   certain actions:

     -      Sending multicast and broadcast traffic to the CE. Note
            that this is the default behavior. Optional mechanisms,
            which will be specified later, will allow load balancing
            of multicast and broadcast traffic from MESes to CEs on
            multiple active points of attachment

     -      Flooding unknown unicast traffic (i.e. traffic for which a
            MES does not know the destination MAC address) 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 LAG or a bundle.

   If a bridge network is multi-homed to more than one MES in a MAC-VPN
   via switches, only one of the MESes is responsible for certain
   actions:

     +    - Forwarding packets to other MESes, out of the bridged LAN
            which is multi-homed to more than one MES. This is the
            case when the MAC-VPN cloud is inter-connecting bridged
            LAN islands. There are certain cases where this may not
            be the case. For instance this is not required if the
            topology is loop free.







raggarwa                                                       [Page 10]


Internet Draft        draft-raggarwa-mac-vpn-00.txt           March 2010


     +    - Sending multicast and broadcast traffic to the bridge
            network. Note that this is the default behavior.
            Optional mechanisms, which will be specified later,
            will allow load balancing of multicast and broadcast
            traffic from MESes on CEs on multiple active points
            of attachment

     +    - Flooding unknown unicast traffic (i.e. traffic for which
            a MES does not know the destination MAC address) to the
            bridge network.

   This particular MES is referred to as the designated forwarder (DF)
   MES, for the ethernet segment over which the host is multi-homed to
   two or more MESes. This ethernet segment may be a link bundle if the
   host or router is directly connected to the MESes. Or this ethernet
   segment may be a bridged LAN network, if the CEs are switches. The
   bridged LAN network may be running a protocol such as STP. The
   granularity of the DF election MUST be at least this ethernet
   segment. In this case the same MES MUST be elected as the DF for all
   CEs on the ethernet segment. The granularity of the DF election MAY
   be the combination of the ethernet segment and VLAN on that ethernet
   segment. In this case the same MES MUST be elected as the DF for all
   hosts on a VLAN on that ethernet segment.

   The MESes perform a designated forwarder (DF) election, for an
   ethernet segment, or ethernet segment, vlan combination using BGP.
   The Ethernet Segment Identifier is assigned as described in section
   4.

   In order to perform DF election each MES advertises in BGP, a DF
   election route, using the MAC-VPN-NLRI, for each ethernet segment in
   a MAC-VPN. This route contains the following information elements

   a) Route-Distinguisher of the MAC-VPN instance that is advertising
   the NLRI. This RD is the same as the one used in section 5.2.1.

   b) Ethernet Segment Identifier

   c) Optional VLAN ID which may be set to 0.

   d) An upstream assigned MPLS label referred to as the "ESI label".
   The usage of this label is described in section 8.

   This route also carries the following BGP attributes:

     - P-Tunnel attribute which is specified in [VPLS-MCAST]. The usage
   of this attribute is described in section 11.




raggarwa                                                       [Page 11]


Internet Draft        draft-raggarwa-mac-vpn-00.txt           March 2010


    - One or more Route Target (RT) attributes. These RTs are assigned
   using the same procedure as the one described in section 5.

   The DF election for a particular ESI and VLAN combination proceeds as
   follows. First a MES constructs a candidate list of MESes.  This
   comprises all the DF routes with that particular {ESI, VLAN} tuple
   that a MES imports in a MAC-VPN instance, including the DF 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 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 VLAN
   combination.

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



8. Forwarding Unicast Packets

8.1. 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
   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.  f 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.




raggarwa                                                       [Page 12]


Internet Draft        draft-raggarwa-mac-vpn-00.txt           March 2010


   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.

   If ingress replication is in use, the P-Tunnel attribute, carried in
   the DF routes 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. Note that
   if a MES has multiple ethernet segments for the same MAC-VPN instance
   and ingress replication is in use, then the MES SHOULD advertise the
   same P-Tunnel attribute for each DF route for that MAC-VPN instance.

   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 DF route as
   described in section 6. Note that if a MES has multiple ethernet
   segments for the same MAC-VPN instance then it SHOULD advertise the
   same P-Tunnel attribute for each DF route for that MAC-VPN instance.
   The P-Tunnel attribute specifies the P2MP LSP identifier. This is the
   equivalent of an Inclusive tree in [VPLS-MCAST].  Note that multiple
   MAC-VPNs can 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.



8.2. Forwarding packets received from a CE

   When a MES receives a packet from a CE 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 from one or more other MESes, for this destination MAC
   address, 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



raggarwa                                                       [Page 13]


Internet Draft        draft-raggarwa-mac-vpn-00.txt           March 2010


   LSP label stack to reach the remote MES.

   If the MAC address is unknown then, if the admnistrative policy on
   the MES requires flooding of unknown unicast traffic:
       - The MES floods the packet to other MESes. The MES first
   encapsulates the packet in the ESI MPLS label as described in section
   4.  If P2MP LSPs are being used the packet is sent on the P2MP LSP
   that the MES is the root of for that MAC-VPN, with all the other
   MESes as the leaves.  The packet is encapsulated in the P2MP LSP
   label stack. If ingress replication is used the packet is replicated
   once for each remote MES with the bottom label of the stack being the
   MPLS label advertised by the remote MES in the P-Tunnel attribute.

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


8.3. Forwarding packets received from a remote MES

   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 8:

        - If the MES is the designated forwarder of unknown unicast,
   broadcast or multicast traffic, the default behavior is for the MES
   to flood the packet to all the host interfaces. 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 an option the MES
   may do a destination MAC lookup to flood the packet to only a subset
   of the host interfaces.
       - If the MES is not the designated forwarder, the default
   behavior is for it to drop the packet.

   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.









raggarwa                                                       [Page 14]


Internet Draft        draft-raggarwa-mac-vpn-00.txt           March 2010


9. 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 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 an
   "ESI MPLS label" in the DF route as described in section 6. This
   label is upstream assigned by the MES that advertises the DF 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 discarding packets received with this label.

   Further the MES that advertises the "ESI MPLS label" MUST program in
   its platform MPLS forwarding table a forwarding entry for this label
   which results in sending packets to the ESI.

   Consider MES1 and MES2 that are multi-homed to CE1 on ES1. 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. The resulting packet is
   further encapsulated in the MPLS label stack necessary to transmit
   the packet to the other MESes. Penultimate hop popping MUST be
   disabled on the P2P or 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 drop the packet.



10. 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.









raggarwa                                                       [Page 15]


Internet Draft        draft-raggarwa-mac-vpn-00.txt           March 2010


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

   Whenever a remote MES imports a MAC advertisement for a given ESI, in
   a MAC VPN instance, it MUST consider the MAC as reachahable via all
   the MESes from which it has imported DF routes for that ESI.

   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.
   Based on MAC-VPN extensions described in sections 5 and 6, 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 DF route for
   ES1.

   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 DF route
   advertised by MES2 for ES1, 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



raggarwa                                                       [Page 16]


Internet Draft        draft-raggarwa-mac-vpn-00.txt           March 2010


   that it is multi-homed to fails, the MES MUST withdraw the MAC
   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.

   Load balancing requires that the MESes that the CE is multi-homed to
   are configured with different Route-Distinguishers (RDs).


10.2. 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.


10.2.1. 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.


10.2.2. 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.













raggarwa                                                       [Page 17]


Internet Draft        draft-raggarwa-mac-vpn-00.txt           March 2010


11. 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 9. This
   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.

   This specification requires that when MES1 learns MAC1 from MES2, and
   MAC1 as learned by MES1 from the local CE, is not on the same
   ethernet segment as the one associated with MAC1 by MES2, MES1 must
   withdraw its own MAC address advertisement from BGP. Further if MES1
   receives traffic destined for MAC1 it must send the traffic to MES2.
   This procedure reduces the duration of traffic loss associated with
   MAC moves.


12. Multicast

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


12.1. Ingress Replication

   The MESes may use ingress replication for flooding unknown unicast,
   multicast or broadcast traffic as described in section 7.1. 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



raggarwa                                                       [Page 18]


Internet Draft        draft-raggarwa-mac-vpn-00.txt           March 2010


   receivers for a given multicast flow is done using explicit tracking
   described below.


12.2. 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.


12.2.1. 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 DF route.
   The  P-Tunnel attribute [VPLS-MCAST] for an Inclusive tree is
   advertised in the DF route as described in section 5.  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 DF routes.






raggarwa                                                       [Page 19]


Internet Draft        draft-raggarwa-mac-vpn-00.txt           March 2010


12.2.2. 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 <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 the same as those of the VPLS S-PMSI A-D route with
   the following difference. 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].


12.3. 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
   the procedures in [VPLS-MCAST] do not describe how explicit tracking



raggarwa                                                       [Page 20]


Internet Draft        draft-raggarwa-mac-vpn-00.txt           March 2010


   is performed if the CEs are enabled with join suppression. The
   procedures for this case will be described in a future version.


13. Convergence

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


13.1. 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.


13.2. 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.


13.2.1. Local Repair

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


13.3. MES to CE Network Failures

   Deatils will be described in the future.












raggarwa                                                       [Page 21]


Internet Draft        draft-raggarwa-mac-vpn-00.txt           March 2010


14. 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.


15. 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] "Multi-homing in BGP-based Virtual Private LAN
   Service", K. Kompella et.al., draft-kompella-l2vpn-vpls-
   multihoming-01.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,


16. 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




raggarwa                                                       [Page 22]


Internet Draft        draft-raggarwa-mac-vpn-00.txt           March 2010


   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








































raggarwa                                                       [Page 23]


Html markup produced by rfcmarkup 1.129c, available from https://tools.ietf.org/tools/rfcmarkup/