Virtual Private LAN Service (VPLS) Interoperability with Provider Backbone Bridges

Internet Engineering Task Force (IETF)                        A. Sajassi
Request for Comments: 7080                                      S. Salam
Category: Informational                                            Cisco
ISSN: 2070-1721                                                 N. Bitar
                                                                 Verizon
                                                                F. Balus
                                                          Nuage Networks
                                                           December 2013


          Virtual Private LAN Service (VPLS) Interoperability
                     with Provider Backbone Bridges

Abstract

   The scalability of Hierarchical Virtual Private LAN Service (H-VPLS)
   with Ethernet access networks (RFC 4762) can be improved by
   incorporating Provider Backbone Bridge functionality in the VPLS
   access.  Provider Backbone Bridging has been standardized as IEEE
   802.1ah-2008.  It aims to improve the scalability of Media Access
   Control (MAC) addresses and service instances in Provider Ethernet
   networks.  This document describes different interoperability
   scenarios where Provider Backbone Bridge functionality is used in
   H-VPLS with Ethernet or MPLS access network to attain better
   scalability in terms of number of customer MAC addresses and number
   of service instances.  The document also describes the scenarios and
   the mechanisms for incorporating Provider Backbone Bridge
   functionality within H-VPLS with existing Ethernet access and
   interoperability among them.  Furthermore, the document discusses the
   migration mechanisms and scenarios by which Provider Backbone Bridge
   functionality can be incorporated into H-VPLS with existing MPLS
   access.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7080.

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Table of Contents

   1. Introduction ....................................................3
   2. Terminology .....................................................3
   3. Applicability ...................................................5
   4. H-VPLS with Homogeneous PBBN Access .............................6
      4.1. Service Interfaces and Interworking Options ................8
      4.2. H-VPLS with PBBN Access: Type I Service Interface .........10
      4.3. H-VPLS with PBBN Access: Type II Service Interface ........11
   5. H-VPLS with Mixed PBBN Access and PBN Access ...................14
      5.1. H-VPLS with Mixed PBBN and PBN Access: Modified PBN PE ....15
      5.2. H-VPLS with Mixed PBBN and PBN Access: Regular PBN PE .....16
   6. H-VPLS with MPLS Access ........................................17
      6.1. H-VPLS with MPLS Access: PBB U-PE .........................17
      6.2. H-VPLS with MPLS Access: PBB N-PE .........................19
   7. H-VPLS with MPLS Access: PBB Migration Scenarios ...............21
      7.1. 802.1ad Service Frames over VPLS Core .....................21
      7.2. PBB Service Frames over VPLS Core .........................22
      7.3. Mixed 802.1ad and PBB over VPLS Core ......................23
   8. Acknowledgments ................................................24
   9. Security Considerations ........................................24
   10. References ....................................................24
      10.1. Normative References .....................................24
      10.2. Informative References ...................................25

1.  Introduction

   The scalability of Hierarchical Virtual Private LAN Service (H-VPLS)
   with Ethernet access networks [RFC4762] can be improved by
   incorporating Provider Backbone Bridge (PBB) functionality in the
   VPLS access.  Provider Backbone Bridging has been standardized as
   IEEE 802.1ah-2008 [802.1ah], which is an amendment to IEEE 802.1Q to
   improve the scalability of Media Access Control (MAC) addresses and
   service instances in Provider Ethernet networks.  This document
   describes interoperability scenarios where IEEE 802.1ah functionality
   is used in H-VPLS with Ethernet or MPLS access network to attain
   better scalability in terms of the number of customer MAC addresses
   and the number of services.

   This document also covers the interoperability scenarios for
   deploying H-VPLS with Provider Backbone Bridging Ethernet access when
   other types of access networks are deployed, including existing
   802.1ad Ethernet and MPLS access in either single or multiple service
   domains.  Furthermore, the document explores the scenarios by which
   an operator can gradually migrate an existing H-VPLS network to
   Provider Backbone Bridging over VPLS.

   Section 2 gives a quick terminology reference and Section 3
   highlights the applicability of Provider Backbone Bridging
   interoperation with VPLS.  Section 4 describes H-VPLS with
   homogeneous Provider Backbone Bridge Access Network.  Section 5
   discusses H-VPLS with mixed 802.1ah/802.1ad access.  Section 6
   focuses on Provider Backbone Bridging in H-VPLS with MPLS Access
   Network including PBB function on U-PE and on N-PE variants.
   Finally, Section 7 describes gradual migration scenarios from
   existing H-VPLS to Provider Backbone Bridging over H-VPLS.

2.  Terminology

   802.1ad: IEEE specification for "QinQ" encapsulation and bridging of
      Ethernet frames.

   802.1ah: IEEE specification for "MAC tunneling" encapsulation and
      bridging of frames across a Provider Backbone Bridged Network
      (PBBN).

   B-BEB: A backbone edge bridge positioned at the edge of a PBBN.  It
      contains a B-component that supports bridging in the provider
      backbone based on B-MAC and B-TAG information.

   B-MAC: The backbone source or destination MAC address fields defined
      in the 802.1ah provider MAC encapsulation header.

   BCB: A backbone core bridge running in the core of a provider
      backbone bridged network.  It bridges frames based on B-TAG
      information just as an 802.1ad provider bridge will bridge frames
      based on a Service VLAN (S-VLAN) identifier.

   B-Component: The backbone component of a Provider Backbone edge
      bridge as defined in [802.1ah].

   BEB: A backbone edge bridge positioned at the edge of a provider
      backbone bridged network.  It can contain an I-component,
      B-component, or both.

   B-MACs: Backbone MAC addresses -- outer MAC addresses of a PBB-
      encapsulated frame.

   B-TAG: A field defined in the 802.1ah provider MAC encapsulation
      header that conveys the backbone VLAN identifier information.  The
      format of the B-TAG field is the same as that of an 802.1ad S-TAG
      field.

   B-Tagged Service Interface: This is the interface between a BEB and
      BCB in a PBB network.  Frames passed through this interface
      contain a B-TAG field.

   B-VID: This is the specific VLAN identifier carried inside a B-TAG

   C-MACs: Customer MAC addresses are the inner MAC addresses of a PBB-
      encapsulated frame.

   H-VPLS: Hierarchical Virtual Private LAN Service.

   I-component: A bridging component contained in a backbone edge bridge
      that bridges in the customer space (customer MAC addresses,
      S-VLAN).

   IB-BEB: A backbone edge bridge positioned at the edge of a provider
      backbone bridged network.  It contains an I-component for bridging
      in the customer space (customer MAC addresses, S-VLAN IDs) and a
      B-component for bridging the provider's backbone space (B-MAC,
      B-TAG).

   I-BEB: A backbone edge bridge positioned at the edge of a provider
      backbone bridged network.  It contains an I-component for bridging
      in the customer space (customer MAC addresses, S-VLAN IDs).

   I-SID: The 24-bit service instance field carried inside the I-TAG.
      I-SID defines the service instance that the frame should be
      "mapped to".

   I-TAG: A field defined in the 802.1ah provider MAC encapsulation
      header that conveys the service instance information (I-SID)
      associated with the frame.

   I-Tagged Service Interface: This is the interface defined between the
      I-component and B-component inside an IB-BEB or between two
      B-BEBs.  Frames passed through this interface contain an I-TAG
      field.

   N-PE: Network-facing Provider Edge

   PBB: Provider Backbone Bridge

   PBBN: Provider Backbone Bridged Network

   PBN: Provider Bridged Network.  A network that employs 802.1ad (QinQ)
      technology.

   S-TAG: A field defined in the 802.1ad QinQ encapsulation header that
      conveys the Service VLAN (S-VLAN) identifier information.

   S-Tagged Service Interface: This the interface defined between the
      customer (CE) and the I-BEB or IB-BEB components.  Frames passed
      through this interface contain an S-TAG field.

   S-VLAN: The specific Service VLAN identifier carried inside an S-TAG

   U-PE: User-facing Provider Edge

   VPLS: Virtual Private LAN Service

3.  Applicability

   [RFC4762] describes a two-tier hierarchical solution for VPLS for the
   purpose of improved pseudowire (PW) scalability.  This improvement is
   achieved by reducing the number of PE devices connected in a full-
   mesh topology through connecting CE devices via the lower-tier access
   network, which in turn is connected to the top-tier core network.
   [RFC4762] describes two types of H-VPLS network topologies -- one
   with an MPLS access network and another with an IEEE 802.1ad (QinQ)
   Ethernet access network.  In both types of H-VPLS, the learning and
   forwarding of MAC addresses is based on customer MAC addresses
   (C-MACs), which poses scalability issues as the number of VPLS
   instances (and thus C-MACs) increases.  Furthermore, since a set of
   PWs is maintained on a per customer service instance basis, the
   number of PWs required at N-PE devices is proportional to the number
   of customer service instances multiplied by the number of N-PE
   devices in the full-mesh set.  This can result in scalability issues
   (in terms of PW manageability and troubleshooting) as the number of
   customer service instances grows.

   In addition to the above, H-VPLS with an 802.1ad Ethernet access
   network has another scalability issue in terms of the maximum number
   of service instances that can be supported in the access network as
   described in [RFC4762].  Since the number of provider VLANs (S-VLANs)
   is limited to 4094 and each S-VLAN represents a service instance in
   an 802.1ad network, then the maximum number of service instances that
   can be supported is 4094.  These issues are highlighted in [RFC6246].

   This document describes how IEEE 802.1ah (aka Provider Backbone
   Bridges) can be integrated with H-VPLS to address these scalability
   issues.  In the case of H-VPLS with 802.1ah Ethernet access, the
   solution results in better scalability in terms of both number of
   service instances and number of C-MACs in the Ethernet access network
   and the VPLS core network, as well as number of PWs in VPLS core
   network.  And in the case of H-VPLS with MPLS access, Provider
   Backbone Bridging functionality can be used at the U-PE or N-PE,
   which results in reduction of customer MAC addresses and the number
   of PWs in the VPLS core network.

   The interoperability scenarios depicted in this document fall into
   the following two categories:

   -  Scenarios in which Provider Backbone Bridging seamlessly works
      with current VPLS implementations (e.g., Section 4.2).

   -  Scenarios in which VPLS-PE implementations need to be upgraded in
      order to work with Provider Backbone Bridging (e.g., Sections 4.3
      and 5.1).

4.  H-VPLS with Homogeneous PBBN Access

   PBBN access offers MAC-address-table scalability for H-VPLS PE nodes.
   This is due to the MAC tunneling encapsulation scheme of PBB, which
   only exposes the provider's own MAC addresses to PE nodes (B-MACs of
   Provider's PBB-capable devices in the access network), as opposed to
   customers' MAC addresses in conventional H-VPLS with MPLS or 802.1ad
   access.

   PBBN access also offers service-instance scalability when compared to
   H-VPLS with 802.1Q/802.1ad access networks.  This is due to the new
   24-bit service identifier (I-SID) used in PBB encapsulation, which
   allows up to 16M services per PBB access network, compared to 4094
   services per 802.1Q/802.1ad access network.

   Another important advantage of PBBN access is that it offers clear
   separation between the service layer (represented by I-SID) and the
   network layer (represented by B-VLAN).  B-VLANs segregate a PBB
   access network into different broadcast domains and possibly unique
   spanning-tree topologies, with each domain being able to carry
   multiple services (i.e., I-SIDs).  In 802.1ad access networks, the
   network and service layers are the same (represented by S-VLAN).

   This separation allows the provider to manage and optimize the PBB
   access network topology independent of the number of service
   instances that are supported.

   In this section and those following, we look into different flavors
   of H-VPLS with PBBN access.  This section discusses the case in which
   H-VPLS is deployed with homogeneous PBBN access.  Section 5 describes
   the case in which at least one of the access networks has PBN access
   (QinQ/802.1ad) while the others are PBBNs.

   On a macro scale, a network that employs H-VPLS with PBBN access can
   be represented as shown in Figure 1 below.

                           +--------------+
                           |              |
           +---------+     |    IP/MPLS   |    +---------+
   +----+  |         |   +----+        +----+  |         |  +----+
   | CE |--|         |   |VPLS|        |VPLS|  |         |--| CE |
   +----+  |  PBBN   |---| PE |        | PE |--|  PBBN   |  +----+
   +----+  | 802.1ah |   +----+        +----+  | 802.1ah |  +----+
   | CE |--|         |     |   Backbone   |    |         |--| CE |
   +----+  +---------+     +--------------+    +---------+  +----+

                    Figure 1: H-VPLS with PBBN Access

   In the context of PBBN and H-VPLS interoperability, "I-SID Domain"
   and "B-VLAN Domain" can be defined as follows:

   -  "I-SID Domain" refers to a network administrative boundary under
      which all the PBB BEBs and VPLS-PE devices use the same I-SID
      space.  That is, the I-SID assignment is carried out by the same
      administration.  This effectively means that a given service
      instance has the same I-SID designation on all devices within an
      I-SID Domain.

   -  "B-VLAN Domain" refers to a network administrative boundary under
      which all the PBB BEBs and VPLS-PE devices employ consistent I-SID
      to B-VLAN bundling.  For example, the grouping of I-SIDs to
      B-VLANs is the same in that domain.  Although the two B-VLANs in
      two PBBNs that represent the same group of I-SIDs do not need to
      use the same B-VID value, in practice, they often use the same
      value because once the I-SID grouping is made identical in two
      PBBNs.  It is very easy to make the values of the corresponding
      B-VIDs identical also.

   Consequently, three different kinds of "Service Domains" are defined
   in the following manner:

   -  Tightly Coupled Service Domain - Different PBBNs' access belonging
      to the same I-SID Domain and B-VLAN Domain.  However, the network
      control protocols (e.g., xSTP) run independently in each PBBN
      access.

   -  Loosely Coupled Service Domain - Different PBBNs' access belonging
      to the same I-SID Domain.  However, each PBBN access maintains its
      own independent B-VLAN Domain.  Again, the network control
      protocols (e.g., xSTP) run independently in each PBBN access.

   -  Different Service Domain - In this case, each PBBN access
      maintains its own independent I-SID Domain and B-VLAN Domain, with
      independent network control protocols (e.g., xSTP) in each PBBN
      access.

   In general, correct service connectivity spanning networks in a
   Tightly Coupled Service Domain can be achieved via B-VID mapping
   between the networks (often even without B-VID translation).
   However, correct service connectivity spanning networks in a Loosely
   Coupled Service Domain requires I-SID to B-VID remapping (i.e.,
   unbundling and rebundling of I-SIDs into B-VIDs).  Furthermore,
   service connectivity spanning networks in Different Service Domains
   requires both I-SID translation and I-SID to B-VID remapping.

4.1.  Service Interfaces and Interworking Options

   Customer devices will interface with PBBN edge bridges using existing
   Ethernet interfaces including IEEE 802.1Q and IEEE 802.1ad.  At the
   PBBN edge, C-MAC frames are encapsulated in a PBB header that
   includes service provider source and destination MAC addresses
   (B-MACs) and are bridged up to the VPLS-PE.  The PBB-encapsulated
   C-MAC frame is then injected into the VPLS backbone network,
   delivered to the remote VPLS-PE node(s), and switched onto the remote
   PBBN access.  From there, the PBBN bridges the encapsulated frame to
   a PBBN edge bridge where the PBB header is removed and the customer
   frame is sent to the customer domain.

   Interoperating between PBBN devices and VPLS-PE nodes can leverage
   the BEB functions already defined in [802.1ah].  When I-SID
   visibility is required at the VPLS-PE nodes, a new service interface
   based on I-SID tag will need to be defined.

   Moreover, by mapping a bridge domain (e.g., B-VLAN) to a VPLS
   instance, and bundling multiple end-customer service instances
   (represented by I-SID) over the same bridge domain, service providers
   will be able to significantly reduce the number of full-mesh PWs
   required in the core.  In this case, I-SID visibility is not required
   on the VPLS-PE and the I-SID will serve as the means of
   multiplexing/de-multiplexing individual service instances in the PBBN
   over a bundle (e.g., B-VLAN).

   When I-SID visibility is expected across the service interface at the
   VPLS-PE, the VPLS-PE can be considered to offer service-level
   interworking between PBBN access and the IP/MPLS core.  Similarly,
   when the PE is not expected to have visibility of the I-SID at the
   service interface, the VPLS-PE can be considered to offer network-
   level interworking between PBBN access and the MPLS core.

   A VPLS-PE is always part of the IP/MPLS core, and it may optionally
   participate in the control protocols (e.g., xSTP) of the access
   network.  When connecting to a PBBN access, the VPLS-PE needs to
   support one of the following two types of service interfaces:

      -  Type I: B-Tagged Service Interface with B-VID as Service
         Delimiter

   The PE connects to a Backbone Core Bridge (BCB) in the PBBN access.
   The handoff between the BCB and the PE is B-Tagged PBB-encapsulated
   frames.  The PE is transparent to PBB encapsulations and treats these
   frames as 802.1ad frames since the B-VID EtherType is the same as the
   S-VID EtherType.  The PE does not need to support PBB functionality.
   This corresponds to conventional VPLS-PEs' tagged service interface.
   When using Type I service interface, the PE needs to support either
   raw mode or tagged mode Ethernet PW.  Type I service interface is
   described in detail in Section 4.2.

      -  Type II: I-Tagged Service Interface with I-SID as Service
         Delimiter

   The PE connects to a B-BEB (backbone edge bridge with B-component) in
   the PBBN access.  The PE itself also supports the B-BEB functionality
   of [802.1ah].  The handoff between the B-BEB in the PBBN access and
   the PE is an I-Tagged PBB-encapsulated frame.  With Type II service
   interface, the PE supports the existing raw mode and tagged mode PW
   types.  Type II service interface is described in detail in Section
   4.3.

4.2.  H-VPLS with PBBN Access: Type I Service Interface

   This is a B-Tagged service interface with B-VID as service delimiter
   on the VPLS-PE.  It does not require any new functionality on the
   VPLS-PE.  As shown in Figure 2, the PE is always part of the IP/MPLS
   core.  The PE may also be part of the PBBN access (e.g., VPLS-PE on
   right side of Figure 2) by participating in network control protocols
   (e.g., xSTP) of the PBBN access.

        PBBN Access       IP/MPLS Core      PBBN Access
                        +--------------+
        +---------+     |              | +---------------+
        |         |    +----+          | |               |
        |      +---+   |VPLS|   +-+    | |    +---+      |
        |      |BCB|---| PE |---|P|    | |    |BCB|      |
        |      +---+  /+----+  /+-+   | |   /+---+      |
        |+---+    |  / +----+ /     +----+ /       +---+|
   +--+ ||IB-| +---+/  |VPLS|/  +-+  |VPLS|/  +---+ |IB-|| +--+
   |CE|-||BEB|-|BCB|---| PE |---|P|--| PE |---|BCB|-|BEB|--|CE|
   +--+ |+---+ +---+ ^ +----+   +-+  +----+ ^ +---+ +---+| +--+
        |         |  |  |              | |  |            |
        +---------+  |  |              | +--|------------+
                     |  +--------------+    |
                     |                      |
                   Type I                  Type I

     Figure 2: H-VPLS with PBBN Access and Type I Service Interface

   Type I service interface is applicable to networks with Tightly
   Coupled Service Domains, where both I-SID Domains and B-VLAN Domains
   are the same across all PBBN access networks.

   The BCB and the VPLS-PE will exchange PBB-encapsulated frames that
   include source and destination B-MACs, a B-VID, and an I-SID.  The
   service delimiter, from the perspective of the VPLS-PE, is the B-VID;
   in fact, this interface operates exactly as a current 802.1Q/ad
   interface into a VPLS-PE does today.  With Type I service interface,
   the VPLS-PE can be considered to provide network-level interworking
   between PBBN and MPLS domains, since VPLS-PE does not have visibility
   of I-SIDs.

   The main advantage of this service interface, when compared to other
   types, is that it allows the service provider to save on the number
   of full-mesh PWs required in the core.  This is primarily because
   multiple service instances (I-SIDs) are bundled over a single full-
   mesh PW corresponding to a bridge domain (e.g., B-VID), instead of
   requiring a dedicated full-mesh PW per service instance.  Another
   advantage is the MAC address scalability in the core since the core
   is not exposed to C-MACs.

   The disadvantage of this interface is the comparably excessive
   replication required in the core: since a group of service instances
   share the same full-mesh of PWs, an unknown unicast, multicast, or
   broadcast on a single service instance will result in a flood over
   the core.  This, however, can be mitigated via the use of flood
   containment per I-SID (B-MAC multicast pruning).

   Three different modes of operation are supported by Type I service
   interface:

   -  Port Mode: All traffic over an interface in this mode is mapped to
      a single VPLS instance.  Existing PW signaling and Ethernet raw
      mode (0x0005) PW type, defined in [RFC4447] and [RFC4448], are
      supported.

   -  VLAN Mode: all traffic associated with a particular VLAN
      identified by the B-VID is mapped to a single VPLS instance.
      Existing PW signaling and Ethernet raw mode (0x0005) PW type,
      defined in [RFC4447] and [RFC4448], are supported.

   -  VLAN Bundling Mode: all traffic associated with a group or range
      of VLANs or B-VIDs is mapped to a single VPLS instance.  Existing
      PW signaling and Ethernet raw mode (0x0005) PW type, defined in
      [RFC4447] and [RFC4448], are supported.

   For the VLAN mode, it is also possible to use Ethernet tagged mode
   (0x0004) PW, as defined in [RFC4447] and [RFC4448], for
   interoperability with equipment that does not support raw mode.  The
   use of raw mode is recommended to be the default though.

4.3.  H-VPLS with PBBN Access: Type II Service Interface

   This is an I-Tagged service interface with I-SID as service delimiter
   on the VPLS-PE.  It requires the VPLS-PE to include the B-component
   of PBB BEB for I-SID processing in addition to the capability to map
   an I-SID Bundle to a VPLS instance.  As shown in Figure 3, the PE is
   always part of the IP/MPLS core and connects to one or more B-BEBs in
   the PBBN access.

        PBBN Access      IP/MPLS Core      PBBN Access
                       +--------------+
        +---------+    |              |    +---------+
        |         |    |              |    |         |
        |      +---+  +-----+         |    |  +---+  |
        |      |B- |  |PE w/| +-+     |    |  |BCB|  |
        |      |BEB|--|B-BEB|-|P|     |    |  +---+  |
        |      +---+ /+-----+ +-+     |    | /   |   |
        |+---+ +---+/ +-----+/    +-----+ +---+ +---+|
   +--+ ||IB-| |B- |  |PE w/| +-+ |PE w/| |B- | |IB-|| +--+
   |CE|-||BEB|-|BEB|--|B-BEB|-|P|-|B-BEB|-|BEB| |BEB|--|CE|
   +--+ |+---+ +---+ ^+-----+ +-+ +-----+^+---+ +---+| +--+
        |         |  |  |             |  | |         |
        +---------+  |  |             |  | +---------+
                     |  +-------------+  |
                     |                   |
                 Type II             Type II

   Figure 3: H-VPLS with PBBN Access and Type II Service Interface

   Type II service interface is applicable to Loosely Coupled Service
   Domains and Different Service Domains.  B-VLAN Domains can be
   independent and the B-VID is always locally significant in each PBBN
   access: it does not need to be transported over the IP/MPLS core.
   Given the above, it should be apparent that Type II service interface
   is applicable to Tightly Coupled Service Domains as well.

   By definition, the B-BEB connecting to the VPLS-PE will remove any
   B-VLAN tags for frames exiting the PBBN access.  The B-BEB and
   VPLS-PE will exchange PBB-encapsulated frames that include source and
   destination B-MACs and an I-SID.  The service delimiter, from the
   perspective of the VPLS-PE, is the I-SID.  Since the PE has
   visibility of I-SIDs, the PE provides service-level interworking
   between PBBN access and IP/MPLS core.

   Type II service interface may operate in I-SID Bundling Mode: all
   traffic associated with a group or range of I-SIDs is mapped to a
   single VPLS instance.  The PE maintains a mapping of I-SIDs to a PE
   local bridge domain (e.g., B-VID).  The VPLS instance is then
   associated with this bridge domain.  With Loosely Coupled service
   Domains, no I-SID translation needs to be performed.  Type II Service
   interface also supports Different Service Domains in this mode, since
   the B-BEB link in the PE connecting to the local PBBN can perform the
   translation of PBBN-specific I-SID to a local I-SID within the
   IP/MPLS core, which may then be translated to the other PBBN-specific
   I-SID on the egress PE.  Such translation can also occur in the B-BEB
   of PBBN access.  Existing PW signaling and Ethernet raw mode
   (0x0005), defined in [RFC4447] and [RFC4448], is supported.  It is
   also possible to use a tagged mode (0x0004) PW for purpose of
   interoperability with equipment that does not support raw mode.

   Type II service interface provides operators with the flexibility to
   trade off PW state for multicast flooding containment, since a full-
   mesh of PWs can be set up:

   a. per I-SID,
   b. per group of I-SIDs, or
   c. for all I-SIDs.

   For (a) and (b), the advantage that Type II service interface has
   compared to Type I is that it can reduce replication in the core
   without the need for a mechanism that provides flood containment per-
   I-SID (B-MAC multicast pruning).  This is mainly due to the increased
   segregation of service instances over disjoint full meshes of PWs.
   For (c), both Type II and Type I service interfaces are at par with
   regard to flood containment.

   For (a) and (b), the disadvantage of this service interface, compared
   to Type I, is that it may require a larger number of full-mesh PWs in
   the core.  For (c), both Type II and Type I service interfaces are at
   par with regard to PW state.  However, for all three scenarios, the
   number of full-mesh PWs can still be fewer than the number required
   by H-VPLS without PBBN access, since an I-SID can multiplex many
   S-VLANs.

   It is expected that this interface type will be used for customers
   with significant multicast traffic (but without multicast pruning
   capability in the VPLS-PE) so that a separate VPLS instance is set up
   per group of customers with similar geographic locality (per I-SID
   group).

   Note: Port mode is not called out in Type II service interface since
   it requires the mapping of I-SIDs to be identical on different
   I-Tagged interfaces across VPLS network.  If this is indeed the case,
   Port mode defined in Type I service interface (Section 4.2) can be
   used.

5.  H-VPLS with Mixed PBBN Access and PBN Access

   It is foreseeable that service providers will want to interoperate
   their existing Provider Bridged Networks (PBNs) with Provider
   Backbone Bridged Networks (PBBNs) over H-VPLS.  Figure 4 below shows
   the high-level network topology.

                           +--------------+
                           |              |
           +---------+     |    IP/MPLS   |    +---------+
   +----+  |         |   +----+        +----+  |         |  +----+
   | CE |--|   PBN   |   |VPLS|        |VPLS|  |         |--| CE |
   +----+  |  (QinQ) |---| PE1|        | PE2|--|  PBBN   |  +----+
   +----+  | 802.1ad |   +----+        +----+  | 802.1ah |  +----+
   | CE |--|         |     |   Backbone   |    |         |--| CE |
   +----+  +---------+     +--------------+    +---------+  +----+

       Figure 4: H-VPLS with Mixed PBN and PBBN Access Networks

   Referring to Figure 4 above, two possibilities come into play
   depending on whether the interworking is carried out at PE1 or PE2.
   These are described in the following subsections.

5.1.  H-VPLS with Mixed PBBN and PBN Access: Modified PBN PE

   As shown in Figure 5, the operation of VPLS-PE2 (connecting to the
   PBBN access on the right) is no different from what was discussed in
   Section 4.  Type II service interface, as discussed in the above
   section, is applicable.  It is the behavior of VPLS-PE1 (connecting
   to the PBN access on the left) that is the focus of this section.

         PBN Access       IP/MPLS Core      PBBN Access
          (802.1ad)     +--------------+     (802.1ah)
                        |              |    +---------+
         +---------+    |              |    |         |
         |         |   +-----+         |    |  +---+  |
         |      +---+  |PE w/| +-+     |    |  |BCB|  |
         |      |PCB|--|IBBEB|-|P|     |    |  +---+  |
         |      +---+ /+-----+ +-+     |    | /   |   |
         |         | / +-----+/    +-----+ +---+ +---+|
    +--+ |+---+ +---+  |PE w/| +-+ |PE w/| |B- | |IB-|| +--+
    |CE|-||PEB|-|PCB|--|IBBEB|-|P|-|B-BEB|-|BEB| |BEB|--|CE|
    +--+ |+---+ +---+ ^+-----+ +-+ +-----+^+---+ +---+| +--+
         |         |  |  |PE1       PE2|  | |         |
         +---------+  |  |             |  | +---------+
                      |  +-------------+  |
                      |                   |
                  S-Tagged           Type II (I-Tagged)

   Figure 5: H-VPLS with Mixed PBN and PBBN Access: Modified PBN PE

   Some assumptions made for this topology include:

   -  CE is directly connected to PBBN via S-Tagged or port-based
      interface.

   -  I-SID in PBBN access represents the same customer as S-VID in PBN
      access.

   -  At S-Tagged service interface of PE with IB-BEB functionality
      (e.g., PE1 in Figure 5), the only viable service is 1:1 mapping of
      S-VID to I-SID.  However, towards the core network side, the same
      PE can support I-SID bundling into a VPLS instance.

   -  PE1 participates in the local I-SID Domain of the IP/MPLS core so
      the model accommodates for the rest of the PBB network any of the
      three domain types described in Section 4 -- Tightly Coupled,
      Loosely Coupled, and Different Service Domains.

   -  For ease of provisioning in these disparate access networks, it is
      recommended to use the same I-SID Domain among the PBBN access
      networks and the PEs with IB-BEB functionality (those connecting
      to PBN).

   This topology operates in I-SID Bundling Mode: at a PE connecting to
   PBN access, each S-VID is mapped to an I-SID and subsequently a group
   of I-SIDs is mapped to a VPLS instance.  Similarly, at a PE
   connecting to PBBN access, each group of I-SIDs is mapped to a VPLS
   instance.  Similar to Type II service interface, no I-SID translation
   is performed for the I-SID bundling case.  Existing PW signaling and
   Ethernet raw mode (0x0005) PW type, defined in [RFC4447] and
   [RFC4448], are supported.  It is possible to use tagged mode (0x0004)
   PW for backward compatibility as well.

5.2.  H-VPLS with Mixed PBBN and PBN Access: Regular PBN PE

   As shown in Figure 6, the operation of VPLS-PE1 (connecting to the
   PBN access on the left) is no different from existing VPLS-PEs.  It
   is the behavior of VPLS-PE2 (connecting to the PBBN access on the
   right) that is the focus of this section.

         PBN Access       IP/MPLS Core      PBBN Access
          (802.1ad)     +--------------+     (802.1ah)
                        |              |    +---------+
         +---------+    |              |    |         |
         |         |   +-----+         |    |  +---+  |
         |      +---+  |  PE | +-+     |    |  |BCB|  |
         |      |PCB|--|     |-|P|     |    |  +---+  |
         |      +---+ /+-----+ +-+     |    | /   |   |
         |         | / +-----+/    +-----+ +---+ +---+|
    +--+ |+---+ +---+  |  PE | +-+ |PE w/| |B- | |IB-|| +--+
    |CE|-||PEB|-|PCB|--|     |-|P|-|IBBEB|-|BEB| |BEB|--|CE|
    +--+ |+---+ +---+ ^+-----+ +-+ +-----+^+---+ +---+| +--+
         |         |  |  |PE1       PE2|  | |         |
         +---------+  |  |             |  | +---------+
                      |  +-------------+  |
                      |                   |
                  S-Tagged           Type II (I-Tagged)

   Figure 6: H-VPLS with Mixed PBN and PBBN Access: Regular PBN PE

   Some assumptions made for this topology include:

   -  The CE is directly connected to the PBBN access via an S-Tagged or
      port-based Interface.

   -  The I-SID in the PBBN access represents the same customer as the
      S-VID in the PBN access.

   -  There is 1:1 mapping between the I-SID and the VPLS instance.

   -  At the S-Tagged service interface of the PE connecting to PBN
      (e.g., PE1 in Figure 6), the PE only provides 1:1 mapping of S-VID
      to the VPLS instance.  S-VID bundling is not a viable option since
      it does not correspond to anything in the PBBN access.

   -  The PE connecting to the PBBN access (e.g., PE2 in Figure 6),
      supports IB-BEB functionality and the I-component is connected to
      the VPLS Forwarder (i.e., the I-component faces the IP/MPLS core
      whereas the B-component faces the PBBN access network).  One or
      more I-SIDs can be grouped into a B-VID in the PBBN access.

   -  Since C-VID grouping in different PBBN access networks must be
      consistent, it is assumed that same I-SID Domain is used across
      these PBBN access networks.

   Unlike the previous case, I-SID bundling mode is not supported in
   this case.  This is primarily because the VPLS core operates in the
   same manner as today.  The PE with IB-BEB functionality connecting to
   PBBN access performs the mapping of each VPLS instance to an I-SID
   and one or more of these I-SIDs may be mapped onto a B-VID within the
   PBBN access network.

6.  H-VPLS with MPLS Access

   In this section, the case of H-VPLS with MPLS access network is
   discussed.  The integration of PBB functionality into VPLS-PE for
   such access networks is described to improve the scalability of the
   network in terms of the number of MAC addresses and service instances
   that are supported.

   For this topology, it is possible to embed PBB functionality in
   either the U-PE or the N-PE.  Both of these cases are described in
   the following subsections.

6.1.  H-VPLS with MPLS Access: PBB U-PE

   As stated earlier, the objective for incorporating PBB function at
   the U-PE is to improve the scalability of H-VPLS networks in terms of
   the number of MAC addresses and service instances that are supported.

   In current H-VPLS, the N-PE must learn customer MAC addresses
   (C-MACs) of all VPLS instances in which it participates.  This can
   easily add up to hundreds of thousands or even millions of C-MACs at
   the N-PE.  When the U-PE performs PBB encapsulation, the N-PE only
   needs to learn the MAC addresses of the U-PEs, which is a significant
   reduction.  Furthermore, when PBB encapsulation is used, many I-SIDs
   are multiplexed within a single bridge domain (e.g., B-VLAN).  If the
   VPLS instance is set up per B-VLAN, then one can also achieve a
   significant reduction in the number of full-mesh PWs.  It should be
   noted that this reduction in full-mesh PWs comes at the cost of
   potentially increased replication over the full-mesh of PWs: customer
   multicast and/or broadcast frames are effectively broadcasted within
   the B-VLAN.  This may result in additional frame replication because
   the full-mesh PWs corresponding to a B-VLAN are most likely bigger
   than the full-mesh PWs corresponding to a single I-SID.  However,
   flood containment per I-SID (B-MAC multicast pruning) can be used to
   remedy this drawback and have multicast traffic replicated
   efficiently for each customer (i.e., for each I-SID).

   Figure 7 below illustrates the scenario for H-VPLS with MPLS access.
   As illustrated, customer networks or hosts (CE) connect into the U-PE
   nodes using standard Ethernet interfaces [802.1D-REV], [802.1Q], or
   [802.1ad].  The U-PE is connected upstream to one or more VPLS N-PE
   nodes by MPLS PWs (per VPLS instance).  These, in turn, are connected
   via a full mesh of PWs (per VPLS instance) traversing the IP/MPLS
   core.  The U-PE is outfitted with PBB Backbone Edge Bridge (BEB)
   functions where it can encapsulate/decapsulate customer MAC frames in
   provider B-MACs and perform I-SID translation if needed.

        PBB                                                PBB
        BEB                  +----------+                  BEB
         |                   |          |                   |
         |   +-----------+   |    IP    |   +-----------+   |
         |   | MPLS      |   |   MPLS   |   |    MPLS   |   |
         V   | Access +----+ |   Core   | +----+ Access |   V
   +--+  +----+       |VPLS|-|          |-|VPLS|       +----+  +--+
   |CE|--|U-PE|       |N-PE| |          | | PE |       |U-PE|--|CE|
   +--+  +----+       +----+ |          | +----+       +----+  +--+
             |           |   |          |   |           |
             +-----------+   +----------+   +-----------+

          Figure 7: H-VPLS with MPLS Access Network and PBB U-PE

   The U-PE still provides the same type of services toward its
   customers as before and they are:

      -  Port mode (either 802.1D, 802.1Q, or 802.1ad)
      -  VLAN mode (either 802.1Q or 802.1ad)
      -  VLAN-bundling mode (either 802.1Q or 802.1ad)
   By incorporating a PBB function, the U-PE maps each of these services
   (for a given customer) onto a single I-SID based on the configuration
   at the U-PE.  Many I-SIDs are multiplexed within a single bridge
   domain (e.g., B-VLAN).  The U-PE can then map a bridge domain onto a
   VPLS instance and the encapsulated frames are sent over the PW
   associated with that VPLS instance.  Furthermore, the entire Ethernet
   bridging operation over the VPLS network is performed as defined in
   [RFC4762].  In other words, MAC forwarding is based on the B-MAC
   address space and service delimiter is based on VLAN ID, which is
   B-VID in this case.  There is no need to inspect or deal with I-SID
   values in the VPLS N-PEs.

   In the case of PBB U-PEs in a single I-SID Domain, I-SID assignment
   is performed globally across all MPLS access networks and therefore
   there is no need for I-SID translation.  This scenario supports I-SID
   bundling mode, and it is assumed that the mapping of the I-SIDs to
   the bridge domain (e.g., B-VLAN) is consistent across all the
   participating PE devices.  In the case of the I-SID bundling mode, a
   bridge domain (e.g., B-VLAN) is mapped to a VPLS instance and an
   existing Ethernet raw mode (0x0005) or tagged mode (0x0004) PW type
   is used as defined in [RFC4447] and [RFC4448].

   I-SID mode can be considered to be a degenerate case of I-SID
   bundling where a single bridge domain is used per I-SID.  However,
   that results in an increased number of bridge domains and PWs in the
   PEs.  PBB flood containment (B-MAC multicast pruning) per I-SID can
   be used in conjunction with I-SID bundling mode to limit the scope of
   flooding per I-SID thus removing the need for I-SID mode.

6.2.  H-VPLS with MPLS Access: PBB N-PE

   In this case, the PBB function is incorporated at the N-PE to improve
   the scalability of H-VPLS networks in terms of the numbers of MAC
   addresses and service instances that are supported.

   Customer networks or hosts (CE) connect into the U-PE nodes using
   standard Ethernet interfaces [802.1D-REV], [802.1Q], or [802.1ad].
   The U-PE is connected upstream to one or more VPLS N-PE nodes by MPLS
   PWs (per customer).  These, in turn, are connected via a full mesh of
   PWs (per customer or group of customers) traversing the IP/MPLS core.

   The U-PE still provides the same type of services toward its
   customers as before and they are:

      -  Port mode (either 802.1D, 802.1Q, or 802.1ad)
      -  VLAN mode (either 802.1Q or 802.1ad)
      -  VLAN-bundling mode (either 802.1Q or 802.1ad)
   The spoke PW from the U-PE to the N-PE is not service multiplexed
   because there is no PBB functionality on the U-PE, i.e., one service
   per PW.

                         PBB              PBB
                         BEB +----------+ BEB
                           | |          | |
             +-----------+ | |    IP    | | +-----------+
             | MPLS      | V |   MPLS   | V |    MPLS   |
             | Access +----+ |   Core   | +----+ Access |
   +--+  +----+       |VPLS|-|          |-|VPLS|       +----+  +--+
   |CE|--|U-PE|       |N-PE| |          | | PE |       |U-PE|--|CE|
   +--+  +----+       +----+ |          | +----+       +----+  +--+
             |           |   |          |   |           |
             +-----------+   +----------+   +-----------+

       Figure 8: H-VPLS with MPLS Access Network and PBB N-PE

   By incorporating a PBB function, the N-PE maps each of these services
   (for a given customer) onto a single I-SID based on the configuration
   at the N-PE.  Many I-SIDs can be multiplexed within a single bridge
   domain (e.g., B-VLAN).  The N-PE can, then, either map a single I-SID
   into a VPLS instance or map a bridge domain (e.g., B-VLAN) onto a
   VPLS instance, according to its configuration.  Next, the
   encapsulated frames are sent over the set of PWs associated with that
   VPLS instance.

   In the case of PBB N-PEs in a single I-SID Domain, I-SID assignment
   is performed globally across all MPLS access networks and therefore
   there is no need for I-SID translation.  This scenario supports I-SID
   bundling mode, and it is assumed that the mapping of the I-SIDs to
   the bridge domain (e.g., B-VLAN) is consistent across all the
   participating PE devices.  In the case of the I-SID bundling mode, a
   bridge domain (e.g., B-VLAN) is mapped to a VPLS instance and an
   existing Ethernet raw mode (0x0005) or tagged mode (0x0004) PW type
   as defined in [RFC4447] and [RFC4448], can be used.

   I-SID mode can be considered to be a degenerate case of I-SID
   bundling where a single bridge domain is used per I-SID.  However,
   that results in an increased number of bridge domains and PWs in the
   PE.  PBB flood containment (B-MAC multicast pruning) per I-SID can be
   used in conjunction with I-SID bundling mode to limit the scope of
   flooding per I-SID thus removing the need for I-SID mode.

7.  H-VPLS with MPLS Access: PBB Migration Scenarios

   Operators and service providers that have deployed H-VPLS with either
   MPLS or Ethernet are unlikely to migrate to PBB technology over night
   because of obvious cost implications.  Thus, it is imperative to
   outline migration strategies that will allow operators to protect
   investments in their installed base while still taking advantage of
   the scalability benefits of PBB technology.

   In the following subsections, we explore three different migration
   scenarios that allow a mix of existing H-VPLS access networks to
   coexist with newer PBB-based access networks.  The scenarios differ
   in whether or not the Ethernet service frames passing over the VPLS
   core are PBB-encapsulated.  The first scenario, in Section 7.1,
   involves passing only frames that are not PBB-encapsulated over the
   core.  The second scenario, in Section 7.2, stipulates passing only
   PBB-encapsulated frames over the core.  Whereas, the final scenario,
   in Section 7.3, depicts a core that supports a mix of PBB-
   encapsulated and non-PBB-encapsulated frames.  The advantages and
   disadvantages of each scenario will be discussed in the respective
   sections.

7.1.  802.1ad Service Frames over VPLS Core

   In this scenario, existing access networks are left unchanged.  All
   N-PEs would forward frames based on C-MACs.  In other words, Ethernet
   frames that are traversing the VPLS core (within PWs) would use the
   802.1ad frame format, as in current VPLS.  Hence, the N-PEs in
   existing access networks do not require any modification.  For new
   MPLS access networks that have PBB functions on the U-PE, the
   corresponding N-PE must incorporate built-in IB-BEB functions in
   order to terminate the PBB encapsulation before the frames enter the
   core.  A key point here is that while both the U-PE and N-PE nodes
   implement PBB IB-BEB functionality, the former has the I-component
   facing the customer (CE) and the B-component facing the core; whereas
   the latter has the I-component facing the core and the B-component
   facing the customer (i.e., access network).

                                          PBB            PBB
                             +----------+ IB-BEB         IB-BEB
                             |          | |               |
             +-----------+   |    IP    | | +-----------+ |
             | MPLS      |   |   MPLS   | V |    MPLS   | |
             | Access +----+ |   Core   | +----+ Access | V
   +--+  +----+       |VPLS|-|          |-|VPLS|       +----+  +--+
   |CE|--|U-PE|       |N-PE| |          | | PE |       |U-PE|--|CE|
   +--+  +----+       +----+ |          | +----+       +----+  +--+
             | (Existing)|   |          |   |  (New)    |
             +-----------+   +----------+   +-----------+

   Figure 9: Migration with 802.1ad Service Frames over VPLS Core

   The main advantage of this approach is that it requires no change to
   existing access networks or existing VPLS N-PEs.  The main
   disadvantage is that these N-PEs will not leverage the advantages of
   PBB in terms of MAC address and PW scalability.  It is worth noting
   that this migration scenario is an optimal option for an H-VPLS
   deployment with a single PBB-capable access network.  When multiple
   PBB-capable access networks are required, then the scenario in
   Section 7.3 is preferred, as it provides a more scalable and optimal
   interconnect amongst the PBB-capable networks.

7.2.  PBB Service Frames over VPLS Core

   This scenario requires that the VPLS N-PE connecting to existing MPLS
   access networks be upgraded to incorporate IB-BEB functions.  All
   Ethernet service frames passing over the VPLS core would be PBB-
   encapsulated.  The PBB over MPLS access networks would require no
   special requirements beyond what is captured in Section 6 of this
   document.  In this case, both the U-PE and N-PE, which implement
   IB-BEB functionality, have the I-component facing the customer and
   the B-component facing the core.

                         PBB                             PBB
                      IB-BEB +----------+              IB-BEB
                           | |          |                 |
             +-----------+ | |    IP    |   +-----------+ |
             | MPLS      | V |   MPLS   |   |    MPLS   | |
             | Access +----+ |   Core   | +----+ Access | V
   +--+  +----+       |VPLS|-|          |-|VPLS|       +----+  +--+
   |CE|--|U-PE|       |N-PE| |          | | PE |       |U-PE|--|CE|
   +--+  +----+       +----+ |          | +----+       +----+  +--+
             | (Existing)|   |          |   |  (New)    |
             +-----------+   +----------+   +-----------+

    Figure 10: Migration with PBB Service Frames over VPLS Core
   The main advantage of this approach is that it allows better
   scalability of the VPLS N-PEs in terms of MAC address and pseudowire
   counts.  The disadvantage is that it requires upgrading the VPLS
   N-PEs of all existing MPLS access networks.

7.3.  Mixed 802.1ad and PBB over VPLS Core

   In this scenario, existing access networks are left unchanged, and
   they exchange Ethernet frames with 802.1ad format over the PWs in the
   core.  The newly added access networks, which incorporate PBB
   functionality exchange Ethernet frames that are PBB-encapsulated
   amongst each other over core PWs.  For service connectivity between
   existing access network (non-PBB-capable) and new access network (PBB
   based), the VPLS N-PE of the latter network employs IB-BEB
   functionality to decapsulate the PBB header from frames outbound to
   the core and encapsulate the PBB header for frames inbound from the
   core.  As a result, a mix of PBB-encapsulated and 802.1ad Ethernet
   service frames are exchanged over the VPLS core.

   This mode of operation requires new functionality on the VPLS N-PE of
   the PBB-capable access network, so that the PE can send frames in
   802.1ad format or PBB format, on a per PW basis, depending on the
   capability of the destination access network.  Effectively, the PE
   would have to incorporate B-BEB as well as IB-BEB functions.

   A given PE needs to be aware of the capability of its remote peer in
   order to determine whether it connects to the right PW Forwarder.
   This can be achieved either via static configuration or by extending
   the VPLS control plane (BGP-based auto-discovery and LDP Signaling)
   discussed in [RFC6074].  The latter approach and the details of the
   extensions required are out of scope for this document.

                                          PBB
                                          B-BEB          PBB
                             +----------+ IB-BEB         IB-BEB
                             |          | |               |
             +-----------+   |    IP    | | +-----------+ |
             | MPLS      |   |   MPLS   | V |    MPLS   | |
             | Access +----+ |   Core   | +----+ Access | V
   +--+  +----+       |VPLS|-|          |-|VPLS|       +----+  +--+
   |CE|--|U-PE|       |N-PE| |          | |N-PE|       |U-PE|--|CE|
   +--+  +----+       +----+ |          | +----+       +----+  +--+
             | (Existing)|   |          |   |  (New)    |
             +-----------+   +----------+   +-----------+

                Figure 11: Migration with Mixed 802.1ad and
                     PBB Service Frames over VPLS Core

   The U-PE and N-PE of the PBB-capable access network both employ BEB
   functionality.  The U-PE implements IB-BEB functionality where the
   I-component faces the customer (CE) and the B-component faces the
   core.  The N-PE, on the other hand, implements IB-BEB functionality
   with the I-component facing the core and the B-component facing the
   customer (access network).  In addition, the N-PE implements
   standalone B-BEB functionality.

   This scenario combines the advantages of both previous scenarios
   without any of their shortcomings, namely: it does not require any
   changes to existing access networks and it allows the N-PE to
   leverage the scalability benefits of 802.1ah for PBBN to PBBN
   connectivity.  The disadvantage of this option is that it requires
   new functionality on the N-PE of the PBBN access.  A second
   disadvantage is that this option requires two P2MP LSPs to be set up
   at the ingress N-PE: one for the N-PEs that support PBB encapsulation
   and another one for the N-PEs that don't support PBB encapsulation.

8.  Acknowledgments

   The authors would like to thank Chris Metz and Dinesh Mohan for their
   valuable feedback and contributions.

9.  Security Considerations

   This document does not introduce any additional security aspects
   beyond those applicable to VPLS/H-VPLS.  VPLS/H-VPLS security
   considerations are already covered in [RFC4111] and [RFC4762].

10.  References

10.1.  Normative References

   [802.1ad]    "IEEE Standard for and metropolitan area networks --
                Virtual Bridged Local Area Networks -- Provider
                Bridges", 802.1ad-2005, August 2005.

   [802.1ah]    "IEEE Standard for Local and metropolitan area networks
                -- Virtual Bridged Local Area Networks Amendment 7:
                Provider Backbone Bridges", IEEE Std. 802.1ah-2008,
                August 2009.

   [RFC4447]    Martini, L., Ed., Rosen, E., El-Aawar, N., Smith, T.,
                and G. Heron, "Pseudowire Setup and Maintenance Using
                the Label Distribution Protocol (LDP)", RFC 4447, April
                2006.

   [RFC4448]    Martini, L., Ed., Rosen, E., El-Aawar, N., and G. Heron,
                "Encapsulation Methods for Transport of Ethernet over
                MPLS Networks", RFC 4448, April 2006.

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

   [RFC6074]    Rosen, E., Davie, B., Radoaca, V., and W. Luo,
                "Provisioning, Auto-Discovery, and Signaling in Layer 2
                Virtual Private Networks (L2VPNs)", RFC 6074, January
                2011.

10.2.  Informative References

   [802.1Q]     "IEEE Standard for Local and metropolitan area networks
                - Media Access Control (MAC) Bridges and Virtual Bridged
                Local Area Networks", IEEE Std 802.1Q(tm), 2012 Edition,
                October 2012.

   [802.1D-REV] "IEEE Standard for Local and metropolitan area networks
                Media Access Control (MAC) Bridges", IEEE Std. 802.1D,
                June 2004.

   [RFC6246]    Sajassi, A., Ed., Brockners, F., Mohan, D., Ed., and Y.
                Serbest, "Virtual Private LAN Service (VPLS)
                Interoperability with Customer Edge (CE) Bridges", RFC
                6246, June 2011.

   [RFC4111]    Fang, L., Ed., "Security Framework for Provider-
                Provisioned Virtual Private Networks (PPVPNs)", RFC
                4111, July 2005.

Authors' Addresses

   Ali Sajassi
   Cisco
   EMail: sajassi@cisco.com


   Samer Salam
   Cisco
   EMail: ssalam@cisco.com


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


   Florin Balus
   Nuage Networks
   EMail: florin.balus@nuagenetworks.net