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Versions: (draft-ietf-l2vpn-vpls-pbb-interop) 00 01 02 03 04 05 06 RFC 7080

INTERNET-DRAFT                                               Ali Sajassi
L2VPN Working Group                                          Samer Salam
Intended Status: Informational                                     Cisco

                                                             Nabil Bitar
                                                                 Verizon

                                                            Florin Balus
                                                          Alcatel-Lucent


Expires: January 10, 2014                                  July 10, 2013


        VPLS Interoperability with Provider Backbone Bridges
                 draft-ietf-l2vpn-pbb-vpls-interop-05



Abstract

   The scalability of H-VPLS with Ethernet access networks can be
   improved by incorporating Provider Backbone Bridge functionality in
   the VPLS access. Provider Backbone Bridging has been standardized as
   IEEE 802.1ah-2008, and aims to improve the scalability of 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 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.




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   Internet-Drafts are draft documents valid for a maximum of six months
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Copyright and License Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors. All rights reserved.

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



Table of Contents

   1. Introduction  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3. Applicability . . . . . . . . . . . . . . . . . . . . . . . . .  6
   4. H-VPLS with Homogeneous PBBN Access . . . . . . . . . . . . . .  7
     4.1 Service Interfaces and Interworking Options  . . . . . . . .  9
     4.2 H-VPLS with PBBN Access: Type I Service Interface  . . . . . 10
     4.3 H-VPLS with PBBN Access: Type II Service Interface . . . . . 12
   5. H-VPLS with Mixed PBBN Access and PBN Access  . . . . . . . . . 14
     5.1 H-VPLS with Mixed PBBN & PBN Access: Modified PBN PE . . . . 15
     5.2 H-VPLS with Mixed PBBN & PBN Access: Regular PBN PE  . . . . 16
   6. H-VPLS with MPLS Access . . . . . . . . . . . . . . . . . . . . 18
     6.1 H-VPLS with MPLS Access: PBB U-PE  . . . . . . . . . . . . . 18
     6.2 H-VPLS with MPLS Access: PBB N-PE  . . . . . . . . . . . . . 20
   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



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   8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 24
   9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 24
   10. Security Considerations  . . . . . . . . . . . . . . . . . . . 24
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 25
     11.1 Normative References  . . . . . . . . . . . . . . . . . . . 25
     11.2 Informative References  . . . . . . . . . . . . . . . . . . 25
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 25












































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1. Introduction

   The scalability of Hierarchical-VPLS (H-VPLS) with Ethernet access
   networks can be improved by incorporating Provider Backbone Bridge
   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 Provider Backbone Bridge 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.

   B-BEB: A backbone edge bridge positioned at the edge of a provider
   backbone bridged network. 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



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   backbone bridged network. It bridges frames based on B-TAG
   information just as an 802.1ad provider bridge will bridge frames
   based on a VLAN identifier (S-VLAN)

   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 I and B components.

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

   B-TAG:  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 provider backbone bridged network. Frames passed through
   this interface contain a B-TAG field.

   B-VID: The specific VLAN identifier carried inside a B-TAG

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

   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, service 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, service 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.



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   I-Tagged Service Interface: This the interface defined between the I
   and B components inside an IB-BEB or between two B-BEB. 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 identifier information (S-VLAN).

   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


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, MAC address
   learning and forwarding are based on customer MAC addresses (C-MACs),
   which poses scalability issues as the number of VPLS instances (and
   thus customer MAC addresses) 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 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



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   described in [RFC4762]. Since the number of provider VLANs (S-VLANs)
   is limited to 4K 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 4K. 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 number of PWs in
   the VPLS core network.

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

   - Scenarios where Provider Backbone Bridging seamlessly works with
   current VPLS implementations (e.g. section 4.2).

   - Scenarios where VPLS PE implementations need to be upgraded in
   order to work with Provider Backbone Bridging (e.g. sections 4.3,
   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 4K
   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



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   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 and the following sections we look into different flavors of
   H-VPLS with PBBN access. This section discusses the case where H-
   VPLS is deployed with homogenous PBBN access networks. Section 5
   describes the case where at least one of the access networks is PBN
   access (QinQ/802.1ad) while others are PBBN access.

   At 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,
   i.e. 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 - e.g., grouping of I-SIDs to B-VLANs are 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 also identical.

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



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

   - Loosely Coupled Service Domain - Different PBB access networks
   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 PBB 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 re-mapping (i.e unbundling and
   re-bundling 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 re-mapping.

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, customer MAC frames are encapsulated in a PBB header that
   includes a service provider source and destination MAC addresses (B-
   MACs) and are bridged up to the VPLS PE. The PBB encapsulated
   customer 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-SIDs, 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



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

   A VPLS PE is always part of the IP/MPLS core, and 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 PE's 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.






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             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 & 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 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 as providing 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 corresponding to a bridge domain (e.g. B-VID), instead of
   requiring a dedicated full-mesh 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



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   the core. This, however, can be mitigated via the use of per I-SID
   flood containment (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] [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] [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] [RFC4448], are supported.

   For the VLAN mode, it is also possible to use Ethernet tagged mode
   (0x0004) PW, as defined in [RFC4447] [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 B-Component of PBB
   BEB for I-SID processing in addition to the capability to map I-SID
   Bundle to VPLS instance. As shown in Figure 3, the PE is always part
   of the IP/MPLS core and connects to one or more B-BEB in the PBBN
   access.


















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             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 & 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 and 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 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 Tightly and 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] [RFC4448], is supported. It is



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   also possible to use 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 vs. 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 the Type II service interface has
   compared to Type I is that it can reduce replication in the core
   without the need for a per I-SID flood containment (B-MAC multicast
   pruning) mechanism. 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 regards 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 regards to PW state. However, for all three scenarios, the
   number of full-mesh PWs can still be less than those 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 PBN (QinQ) access networks with PBBN access networks
   over H-VPLS. Figure 4 below shows the high-level network topology.







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                                +--------------+
                                |              |
                +---------+     |    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 sub-Sections.

5.1 H-VPLS with Mixed PBBN & 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



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   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, 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 interface, no I-SID translation is performed for
   I-SID bundling case. Existing PW signaling and Ethernet raw mode
   (0x0005) PW type, defined in [RFC4447] [RFC4448], are supported. It
   is possible to use tagged mode (0x0004) PW for backward compatibility
   as well.

5.2 H-VPLS with Mixed PBBN & 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.















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             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:

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

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

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

   - At S-Tagged Service Interface of PE connecting to PBN (e.g. PE1 in
    Figure 6), the PE only provides 1:1 mapping of S-VID to 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



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   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 sub-sections.

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 that it participates in. 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 is most likely bigger
   than the full-mesh PWs corresponding to a single I-SID. However, per
   I-SID flood containment (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 it can be seen, customer networks or hosts (CE) connect into the
   U-PE nodes using standard Ethernet interfaces [802.1D], [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



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   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/de-encapsulate 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 support 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
   existing Ethernet raw mode (0x0005) or tagged mode (0x0004) PW type
   is used as defined in [RFC4447] [RFC4448].




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   I-SID mode can be considered as 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], [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



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   into a VPLS instance or it can 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
   existing Ethernet raw mode (0x0005) or tagged mode (0x0004) PW type
   as defined in [RFC4447] [RFC4448], can be used.

   I-SID mode can be considered as 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 overnight
   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 sub-sections, we explore three different migration
   scenarios which allow a mix of existing H-VPLS access networks to co-
   exist with newer PBB-based access networks. The scenarios differ in
   whether the Ethernet service frames passing over the VPLS core are
   PBB-encapsulated or not. The first scenario in section 7.1 involves
   passing only non PBB-encapsulated frames 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 its respective section.

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 which are traversing the VPLS core (within PWs) would use the



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   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.






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                           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
   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 de-capsulate 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.






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                                            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 &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 function 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 stand-alone 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 PBB to PBB access
   network connectivity. The disadvantage of this option is that it
   requires new functionality on the N-PE of the PBB-capable access
   network. A second disadvantage is that this option requires two P2MP
   LSPs to be setup 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. IANA Considerations

   This document has no actions for IANA.

10. Security Considerations

   This document does not introduce any additional security aspects



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   beyond those applicable to VPLS/H-VPLS. VPLS/H-VPLS security
   considerations are already covered in [RFC4762].


11. References

11.1 Normative References

   [802.1ad] "Virtual Bridged Local Area Networks, Amendment 4: Provider
   Bridges", IEEE Std. 802.1ad-2005, May 2006

   [802.1ah] "Virtual Bridged Local Area Networks Amendment 7: Provider
   Backbone Bridges", IEEE Std. 802.1ah-2008, August 2008

   [RFC4447] "Pseudowire Setup and Maintenance using LDP", RFC4447,
   April 2006

   [RFC4448] "Encapsulation Methods for Transport of Ethernet over MPLS
   Networks", RFC4448, April 2006

   [RFC4762] "Virtual Private LAN Service (VPLS) Using Label
   Distribution Protocol (LDP) Signaling", RFC4762, January 2007

   [RFC6074] E. Rosen, et al., "Provisioning, Autodiscovery and
   Signaling in L2VPNs", RFC6074, January 2011

11.2 Informative References

   [802.1Q] "Virtual Bridged Local Area Networks", IEEE Std. 802.1Q-
   2005

   [802.1D-REV] "Media Access Control (MAC) Bridges", IEEE Std. 802.1D-
   2003

   [RFC6246] A. Sajassi, et al., "VPLS Interoperability with CE
   Bridges", RFC6246, June 2011


Authors' Addresses

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


      Samer Salam



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


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


      Florin Balus
      Alcatel-Lucent
      701 E. Middlefield Road
      Mountain View, CA, USA 94043
      Email: florin.balus@alcatel-lucent.com



































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