[Docs] [txt|pdf] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits] [IPR]

Versions: (draft-jiang-l2vpn-vpls-pe-etree) 00 01 02 03 04 05 06 07 08 09 10 11 RFC 7796

Internet Working Group                                        Y. Jiang
                                                               L. Yong
Internet Draft                                                  Huawei

Intended status: Standards Track                               M. Paul
                                                      Deutsche Telekom

                                                             F. Jounay
                                                             Orange CH

                                                              F. Balus
                                                         W. Henderickx
                                                        Alcatel-Lucent

                                                            A. Sajassi
                                                                 Cisco

Expires: March 2015                                 September 30, 2014



    Ethernet-Tree (E-Tree) Support in Virtual Private LAN Service (VPLS)
                   draft-ietf-l2vpn-vpls-pe-etree-04.txt


Status of this Memo

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

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

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

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

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

   This Internet-Draft will expire on March 30, 2015.





Jiang, et al           Expires March 30, 2015                 [Page 1]


Internet-Draft         E-Tree Support in VPLS           September 2014

Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors. All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Abstract

   A generic Virtual Private LAN Service (VPLS) solution is proposed for
   Ethernet-Tree (E-Tree) services which uses VLANs to indicate root or
   leaf traffic. A VPLS Provider Edge (PE) model is illustrated as an
   example for the solution. In the solution, E-Tree VPLS PEs are
   interconnected by PWs which carry the VLAN indicating the E-Tree
   attribute, the MAC address based Ethernet forwarding engine and the
   PW work in the same way as before. A signaling mechanism for E-Tree
   capability and VLAN mapping negotiation is further described.

Table of Contents

   1.   Conventions used in this document ......................... 3
   2.   Terminology ............................................... 3
   3.   Introduction .............................................. 4
   4.   PE Model with E-Tree Support .............................. 5
      4.1. Existing PE Models ..................................... 5
      4.2. A New PE Model with E-Tree Support ..................... 8
   5.   PW for E-Tree Support ..................................... 9
      5.1. PW Encapsulation ....................................... 9
      5.2. VLAN Mapping ........................................... 9
      5.3. PW Processing ......................................... 11
         5.3.1.  PW Processing in the VLAN Mapping Mode .......... 11
         5.3.2.  PW Processing in the Compatible Mode ............ 12
         5.3.3.  PW Processing in the Optimized Mode ............. 13
   6.   Signaling for E-Tree Support ............................. 14
      6.1. LDP Extensions for E-Tree Support ..................... 14
      6.2. BGP Extensions for E-Tree Support ..................... 16
   7.   OAM Considerations ....................................... 18
   8.   Applicability ............................................ 18
   9.   Security Considerations .................................. 18
   10.  IANA Considerations ...................................... 19


Jiang, et al           Expires March 30, 2015                 [Page 2]


Internet-Draft         E-Tree Support in VPLS           September 2014

   11.  References ............................................... 19
      11.1.   Normative References ............................... 19
      11.2.   Informative References ............................. 20
   12.  Acknowledgments .......................................... 20
   Appendix A. Other PE Models for E-Tree ........................ 21
      A.1. A PE Model With a VSI and No bridge ................... 21
      A.2. A PE Model With external E-Tree interface ............. 22



1. Conventions used in this document

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

2. Terminology

   E-Tree: Ethernet Tree, a Rooted-Multipoint EVC service as defined in
   MEF 6.1

   EVC: Ethernet Virtual Connection, as defined in MEF 4.0

   FIB: Forwarding Information Base, or forwarding table

   T-VSI: Tree VSI, a VSI with E-Tree support

   Root AC, an AC attached with a root

   Leaf AC, an AC attached with a leaf

   C-VLAN, Customer VLAN

   S-VLAN, Service VLAN

   B-VLAN, Backbone VLAN

   Root VLAN, a VLAN ID used to indicate all the frames that are
   originated at a root AC

   Leaf VLAN, a VLAN ID used to indicate all the frames that are
   originated at a leaf AC

   I-SID, Backbone Service Instance Identifier, as defined in IEEE
   802.1ah





Jiang, et al           Expires March 30, 2015                 [Page 3]


Internet-Draft         E-Tree Support in VPLS           September 2014

3. Introduction

   The Ethernet-Tree (E-Tree) service is defined in Metro Ethernet Forum
   (MEF) as a Rooted-Multipoint Ethernet Virtual Connection (EVC)
   service. It is a multipoint Ethernet service with special
   restrictions: the frames from a root may be received by any other
   root or leaf, and the frames from a leaf may be received by any root,
   but MUST not be received by a leaf. Further, an E-Tree service may
   include multiple roots and multiple leaves. Although VPMS or P2MP
   multicast is a somewhat simplified version of this service, in fact,
   there is no exact corresponding terminology in IETF.

   [Etree-req] gives the requirements for providing E-Tree solutions in
   the VPLS and the need to filter leaf-to-leaf traffic.

   [Vpls-etree] describes a PW control word based E-Tree solution, where
   a bit in the PW control word is used to indicate the root/leaf
   attribute for a packet. The Ethernet forwarder in the VPLS is also
   extended to filter the leaf-to-leaf traffic based on the <ingress
   port, egress port, CW L-bit> tuple.

   [Etree-2PW] proposes another E-Tree solution where root and leaf
   traffic are classified and forwarded in the same VSI but with two
   separate PWs.

   Both solutions are only applicable to "VPLS only" networks.

   In fact, VPLS PE usually consists of a bridge module itself (see
   [RFC4664] and [RFC6246]); moreover, E-Tree services may cross both
   Ethernet and VPLS domains. Therefore, it is necessary to develop an
   E-Tree solution both for "VPLS only" scenarios and for interworking
   between Ethernet and VPLS.

   IEEE 802.1 has incorporated the generic E-Tree solution in the latest
   version of 802.1Q [802.1Q-2011], which is just an improvement on the
   traditional asymmetric VLAN mechanism (the use of different VLANs to
   indicate E-Tree root/leaf attributes and prohibiting leaf-to-leaf
   traffic with the help of VLANs was first standardized in IEEE 802.1Q-
   2003). In the solution, VLANs are used to indicate root/leaf
   attribute of a packet: one VLAN ID is used to indicate the frames
   originated from the roots and another VLAN ID is used to indicate the
   frames originated from the leaves. At a leaf port, the bridge can
   then filter out all the frames from other leaf ports based on the
   VLAN ID. It is better to reuse the same mechanism in VPLS than to
   develop a new mechanism. The latter will introduce more complexity to
   interwork with IEEE 802.1Q solution.




Jiang, et al           Expires March 30, 2015                 [Page 4]


Internet-Draft         E-Tree Support in VPLS           September 2014

   This document introduces how the Ethernet VLAN solution can be used
   to support generic E-Tree services in VPLS. The solution proposed
   here is fully compatible with the IEEE bridge architecture and the
   IETF PWE3 technology, thus it will not change the FIB (such as
   installing E-Tree attributes in the FIB), or need any specially
   tailored implementation. Furthermore, VPLS scalability and simplicity
   is also well kept. With this mechanism, it is also convenient to
   deploy a converged E-Tree service across both Ethernet and MPLS
   networks.

   Firstly, a typical VPLS PE model is introduced as an example; the
   model is then extended in which a Tree VSI is connected to a VLAN
   bridge with a dual-VLAN interface.

   This document then discusses the PW encapsulation and PW processing
   such as VLAN mapping options for transporting E-Tree services in
   VPLS.

   Finally, it describes the signaling extensions and processing
   procedures for E-Tree support in VPLS.



4. PE Model with E-Tree Support

   Problem scenario of E-Tree as shown in Fig. 1 of [Etree-req] is a
   simplification of the L2VPN architecture, several common VPLS PE
   architectures are discussed in more details in [RFC4664] and
   [RFC6246].

   Therefore, E-Tree solution in VPLS is demonstrated with the help of a
   typical VPLS PE model. It can also be used by other PE models which
   are discussed in Appendix A.

4.1. Existing PE Models

   According to [RFC4664], there are at least three models possible for
   a VPLS PE, including:

   o A single bridge module, a single VSI;

   o A single bridge module, multiple VSIs;

   o Multiple bridge modules, each attaches to a VSI.

   The second PE model is commonly used. A typical example is further
   depicted in Fig. 1 and Fig. 2 [RFC6246], where an S-VLAN bridge



Jiang, et al           Expires March 30, 2015                 [Page 5]


Internet-Draft         E-Tree Support in VPLS           September 2014

   module is connected to multiple VSIs each with a single VLAN virtual
   interface.

                      +-------------------------------+
                      |  802.1ad Bridge Module Model  |
                      |                               |
           +---+      |  +------+      +-----------+  |
           |CE |---------|C-VLAN|------|           |  |
           +---+      |  |bridge|------|           |  |
                      |  +------+      |           |  |
                      |     o          |   S-VLAN  |  |
                      |     o          |           |  |
                      |     o          |   Bridge  |  |
           +---+      |  +------+      |           |  |
           |CE |---------|C-VLAN|------|           |  |
           +---+      |  |bridge|------|           |  |
                      |  +------+      +-----------+  |
                      +-------------------------------+

                 Figure 1  A model of 802.1ad Bridge Module


           +----------------------------------------+
           |           VPLS-capable PE model        |
           |   +---------------+          +------+  |
           |   |               |          |VSI-1 |------------
           |   |               |==========|      |------------ PWs
           |   |     Bridge    ------------      |------------
           |   |               | S-VLAN-1 +------+  |
           |   |     Module    |             o      |
           |   |               |             o      |
           |   |   (802.1ad    |             o      |
           |   |    bridge)    |             o      |
           |   |               |             o      |
           |   |               | S-VLAN-n +------+  |
           |   |               ------------VSI-n |-------------
           |   |               |==========|      |------------- PWs
           |   |               |     ^    |      |-------------
           |   +---------------+     |    +------+  |
           |                         |              |
           +-------------------------|--------------+
                            LAN emulation Interface

                     Figure 2  A VPLS-capable PE Model

   In this PE model, Ethernet frames from Customer Edges (CEs) will
   cross multiple stages of bridge modules (i.e., C-VLAN and S-VLAN
   bridge) and a VSI in a PE before being sent on the PW to a remote PE.


Jiang, et al           Expires March 30, 2015                 [Page 6]


Internet-Draft         E-Tree Support in VPLS           September 2014

   Therefore, the association between an AC port and a PW on a VSI is
   difficult, sometimes even impossible.

   This model could be further enhanced: When Ethernet frames arrive at
   a PE, a root VLAN or a leaf VLAN tag is added. Then the frames with
   the root VLAN tag are transmitted both to the roots and the leaves,
   while the frames with the leaf VLAN tag are transmitted to the roots
   but dropped for the leaves (these VLAN tags are removed before the
   frames are transmitted over the wire). It was demonstrated in
   [802.1Q-2011] that the E-Tree service in Ethernet networks can be
   well supported with this mechanism.

   Assuming this mechanism is implemented in the bridge module, it is
   quite straightforward to infer a VPLS PE model with two VSIs to
   support the E-Tree (as shown in Fig. 3). But this model will require
   two VSIs per PE and two sets of PWs per E-Tree service, which is
   poorly scalable in a large MPLS/VPLS network; in addition, both these
   VSIs have to share their learned MAC addresses.



           +----------------------------------------+
           |           VPLS-capable PE model        |
           |   +---------------+          +------+  |
           |   |               |          |VSI-1 |------------
           |   |               |==========|      |------------ PWs
           |   |     Bridge    ------------      |------------
           |   |               | Root     +------+  |
           |   |     Module    | S-VLAN             |
           |   |               |                    |
           |   |   (802.1ad    |                    |
           |   |    bridge)    |                    |
           |   |               | Leaf               |
           |   |               | S-VLAN   +------+  |
           |   |               ------------VSI-2 |-------------
           |   |               |==========|      |------------- PWs
           |   |               |     ^    |      |-------------
           |   +---------------+     |    +------+  |
           |                         |              |
           +-------------------------|--------------+
                            LAN emulation Interface

              Figure 3  A VPLS PE Model for E-Tree with 2 VSIs







Jiang, et al           Expires March 30, 2015                 [Page 7]


Internet-Draft         E-Tree Support in VPLS           September 2014

4.2. A New PE Model with E-Tree Support

   In order to support the E-Tree in a more scalable way, a new VPLS PE
   model with a single Tree VSI (T-VSI, a VSI with E-Tree support) is
   proposed. As depicted in Fig. 4, the bridge module is connected to
   the T-VSI with a dual-VLAN virtual interface, i.e., both the root
   VLAN and the leaf VLAN are connected to the same T-VSI, and they
   share the same FIB and work in shared VLAN learning. In this way,
   only one VPLS instance and one set of PWs is needed per E-Tree
   service, and the scalability of VPLS is improved.

           +----------------------------------------+
           |           VPLS-capable PE model        |
           |   +---------------+          +------+  |
           |   |               |==========|TVSI-1|------------
   +---+AC |   |               ------------      |------------ PWs
   |CE |-------|     Bridge    ------------      |------------
   +---+   |   |               | Root &   +------+  |
           |   |     Module    | Leaf VLAN   o      |
           |   |               |             o      |
           |   |               |             o      |
           |   |               |             o      |
           |   |               |             o      |
   +---+AC |   |               |   VLAN-n +------+  |
   |CE |-------|               ------------VSI-n |-------------
   +---+   |   |               |==========|      |------------- PWs
           |   |               |     ^    |      |-------------
           |   +---------------+     |    +------+  |
           |                         |              |
           +-------------------------|--------------+
                            LAN emulation Interface

          Figure 4  A VPLS PE Model for E-Tree with a Single T-VSI

   For an untagged port (frames over this port are untagged) or VLAN-
   unaware port (VLAN tags in the frames are ignored), the Ethernet
   frames received from the root ACs SHOULD be tagged with a root C-VLAN,
   and optionally MAY be added with another root S-VLAN.

   For a C-VLAN tagged port, the Ethernet frames received from the root
   ACs SHOULD be added with a root S-VLAN.

   For an S-VLAN tagged port, the S-VLAN tag in the Ethernet frames
   received from the root ACs SHOULD be translated to the root S-VLAN in
   the VPLS network domain. Alternatively, the PBB VPLS PE model (where
   an IEEE 802.1ah bridge module is embedded in the PE) as described in
   [PBB-VPLS] MAY be used, and a root B-VLAN or leaf B-VLAN MAY be added
   in this case (the E-Tree attribute may also be indicated with two I-


Jiang, et al           Expires March 30, 2015                 [Page 8]


Internet-Draft         E-Tree Support in VPLS           September 2014

   SID tags in the bridge module, and the frames are further
   encapsulated and transported transparently over a single B-VLAN, thus
   the PBB VPLS works just in the same way as described in [PBB-VPLS]
   and will be discussed no more in this document). When many S-VLANs
   are multiplexed in a single AC, the 2nd option has an advantage of
   both VLAN scalability and MAC address scalability.

   In a similar way, the traffic from the leaf ACs is tagged and
   transported on the leaf C-VLAN, S-VLAN or B-VLAN.

   In all cases, the outermost VLAN in the resulted Ethernet header is
   used to indicate the E-Tree attribute of an Ethernet frame; this
   document will use VLAN to refer to this outermost VLAN for simplicity
   in the latter sections.



5. PW for E-Tree Support

5.1. PW Encapsulation

   To support an E-Tree service, T-VSIs in a VPLS must be interconnected
   with a bidirectional Ethernet PW. The Ethernet PW may work in the
   tagged mode (PW type 0x0004) as described in [RFC4448], and a VLAN
   tag must be carried in each frame in the PW to indicate the frame
   originated from either root or leaf (the VLAN tag indicating the
   frame originated from either root or leaf can be translated by a
   bridge module in the PE or added by an outside Ethernet edge device,
   even by a customer device). In the tagged PW mode, two service
   delimiting VLANs must be allocated in the VPLS domain for an E-Tree.
   PW processing for the tagged PW will be described in Section 5.3 of
   this document.

   Raw PW (PW type 0x0005 in [RFC4448]) may be used to carry E-Tree
   service for a PW in Compatible mode as shown in Section 5.3.2.

5.2. VLAN Mapping

   There are two ways of manipulating VLANs for an E-Tree in VPLS:

   o Global VLAN based, that is, provisioning two global VLANs (Root
      VLAN, Leaf VLAN) across the VPLS network, thus no VLAN mapping is
      needed at all, or the VLAN mapping is done completely in the
      Ethernet domains.

   o Local VLAN based, that is, provisioning two local VLANs for each
      PE (which participates in the E-Tree) in the VPLS network
      independently.


Jiang, et al           Expires March 30, 2015                 [Page 9]


Internet-Draft         E-Tree Support in VPLS           September 2014

   The first method requires no VLAN mapping in the PW, but two unique
   service delimiting VLANs must be allocated across the VPLS domain.

   The second method is more scalable in the use of VLANs, but needs a
   VLAN mapping mechanism in the PW similar to what is already described
   in Section 4.3 of [RFC4448].

   Global or local VLANs can be manually configured or provisioned by an
   OSS system. Alternatively, some automatic VLAN allocation algorithm
   may be provided in the management plane, but it is out scope of this
   document.

   For both methods, VLAN mapping parameters from a remote PE can be
   provisioned or determined by a signaling protocol as described in
   Section 6 when a PW is being established.


































Jiang, et al           Expires March 30, 2015                [Page 10]


Internet-Draft         E-Tree Support in VPLS           September 2014

5.3. PW Processing

5.3.1.PW Processing in the VLAN Mapping Mode

   In the VLAN Mapping mode, two VPLS PEs with E-Tree capability are
   inter-connected with a PW (For example, the scenario of Fig. 5
   depicts the interconnection of two PEs miscellaneously attached with
   both root and leaf nodes).

                  +------------------------+
                  |  VPLS PE with T-VSI    |
                  |                        |
        +----+    | +------+       +-----+ |  PW
        |Root|------| VLAN |-------|T-VSI|----------
        +----+    | | BRG  |       |     |----------
        +----+    | |      |-------|     |----------
        |Leaf|------|      |       |     |---------+
        +----+    | +------+       +-----+ |       |
                  |                        |       |
                  +------------------------+       |
                                                   |
                  +------------------------+       |
                  |  VPLS PE with T-VSI    |       |
                  |                        |       |
        +----+    | +------+       +-----+ |  PW   |
        |Root|------| VLAN |-------|T-VSI|---------+
        +----+    | | BRG  |       |     |----------
        +----+    | |      |-------|     |----------
        |Leaf|------|      |       |     |----------
        +----+    | +------+       +-----+ |
                  |                        |
                  +------------------------+

              Figure 5 T-VSI Interconnected in the Normal Mode

   If a PE is in the VLAN mapping mode for a PW, then in the data plane
   the PE MUST map the VLAN in each frame as follows:

    o Upon transmitting frames on the PW, map from local VLAN to remote
    VLAN (i.e., the local leaf VLAN in a frame is translated to the
    remote leaf VLAN; the local root VLAN in a frame is translated to the
    remote root VLAN).

    o Upon receiving frames on the PW, map from remote VLAN to local VLAN,
    and the frames are further forwarded or dropped in the egress bridge
    module using the filtering mechanism as described in [802.1Q-2011].

    The signaling for VLANs used by E-Tree is specified in Section 6.


Jiang, et al           Expires March 30, 2015                [Page 11]


Internet-Draft         E-Tree Support in VPLS           September 2014

5.3.2.PW Processing in the Compatible Mode

   The new VPLS PE model can work in a traditional VPLS network
   seamlessly in the compatibility mode. As shown in Fig. 6, the VPLS PE
   with T-VSI can be attached with root and/or leaf nodes, while the
   VPLS PE with a traditional VSI can only be attached with root nodes.
   A raw PW should be used to connect them.


                  +------------------------+
                  |  VPLS PE with T-VSI    |
                  |                        |
        +----+    | +------+       +-----+ |  PW
        |Root|------| VLAN |-------|T-VSI|----------
        +----+    | | BRG  |       |     |----------
        +----+    | |      |-------|     |----------
        |Leaf|------|      |       |     |---------+
        +----+    | +------+       +-----+ |       |
                  |                        |       |
                  +------------------------+       |
                                                   |
                  +------------------------+       |
                  |  VPLS PE with VSI      |       |
                  |                        |       |
        +----+    | +------+       +-----+ |  PW   |
        |Root|------| VLAN |-------|VSI  |---------+
        +----+    | | BRG  |       |     |----------
        +----+    | |      |       |     |----------
        |Root|------|      |       |     |----------
        +----+    | +------+       +-----+ |
                  |                        |
                  +------------------------+

             Figure 6 T-VSI interconnected with Traditional VSI

   If a PE is in the Compatible mode for a PW, then in the data plane
   the PE MUST process the frame as follows:

    o Upon transmitting frames on the PW, remove the root or leaf VLAN in
    the frames.

    o Upon receiving frames on the PW, add a VLAN tag with a value of the
    local root VLAN to the frames.







Jiang, et al           Expires March 30, 2015                [Page 12]


Internet-Draft         E-Tree Support in VPLS           September 2014

5.3.3.PW Processing in the Optimized Mode

   When two PEs (both have E-Tree capability) are inter-connected and
   one of them (e.g., PE2) is attached with only leaf nodes, as shown in
   the scenario of Fig. 7, its peer PE (e.g., PE1) should then work in
   the optimized mode. In this case, PE1 should not send the frames
   originated from the local leaf VLAN to PE2, i.e., these frames are
   dropped rather than transported over the PW. The bandwidth efficiency
   of the VPLS can thus be improved. The signaling for the PE attached
   with only leaf nodes is specified in Section 6.
                  +------------------------+
                  |VPLS PE with T-VSI (PE1)|
                  |                        |
        +----+    | +------+       +-----+ |  PW
        |Root|------| VLAN |-------|T-VSI|----------
        +----+    | | BRG  |       |     |----------
        +----+    | |      |-------|     |----------
        |Leaf|------|      |       |     |---------+
        +----+    | +------+       +-----+ |       |
                  |                        |       |
                  +------------------------+       |
                                                   |
                  +------------------------+       |
                  |VPLS PE with T-VSI (PE2)|       |
                  |                        |       |
        +----+    | +------+       +-----+ |  PW   |
        |Leaf|------| VLAN |-------|T-VSI|---------+
        +----+    | | BRG  |       |     |----------
        +----+    | |      |-------|     |----------
        |Leaf|------|      |       |     |----------
        +----+    | +------+       +-----+ |
                  |                        |
                  +------------------------+

     Figure 7 T-VSI interconnected with PE attached with only leaf nodes

   If a PE is in the Optimized Mode for a PW, upon transmit, the PE
   SHOULD first operate as follows:

   o Drop a frame if its VLAN ID matches the local leaf VLAN ID.









Jiang, et al           Expires March 30, 2015                [Page 13]


Internet-Draft         E-Tree Support in VPLS           September 2014

6. Signaling for E-Tree Support

6.1. LDP Extensions for E-Tree Support

   In addition to the signaling procedures as specified in [RFC4447],
   this document proposes a new interface parameter sub-TLV to provision
   an E-Tree service and negotiate the VLAN mapping function, as follows:

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |  E-Tree       |   Length=8    |           Reserved        |P|V|
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |          Root VLAN ID         |          Leaf VLAN ID         |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                          Figure 8  E-Tree Sub-TLV

   Where:

   o E-Tree is the sub-TLV identifier to be assigned by IANA.

   o Length is the length of the sub TLV in octets.

   o Reserved bits MUST be set to zero on transmit and be ignored on
      receive.

   o P is a Leaf-only bit, it is set to 1 to indicate that the PE is
      attached with only leaf nodes, and set to 0 otherwise.

   o V is a bit indicating the sender's VLAN mapping capability. A PE
      capable of VLAN mapping MUST set this bit, and clear it otherwise.

   o Root VLAN ID is the value of the local root VLAN.

   o Leaf VLAN ID is the value of the local leaf VLAN.

   When setting up a PW for the E-Tree based VPLS, two PEs negotiate the
   E-Tree support using the above E-Tree sub-TLV. Note PW type of 0x0004
   should be used during the PW negotiation.

   A PE that wishes to support E-Tree service MUST include an E-Tree
   Sub-TLV in its PW label mapping message and include its local root
   VLAN ID and leaf VLAN ID in the TLV.  A PE that has the VLAN mapping
   capability MUST set the V bit to 1, and a PE is attached with only
   leaf nodes SHOULD set the P bit to 1.





Jiang, et al           Expires March 30, 2015                [Page 14]


Internet-Draft         E-Tree Support in VPLS           September 2014

   In default, for each PW, VLAN-Mapping-Mode, Compatible-Mode, and
   Optimized-Mode are all set to FALSE.

   A PE that receives a PW label mapping message with an E-Tree Sub-TLV
   from its peer PE, after saving the VLAN information for the PW, must
   process it as follows:

   1) if the root and leaf VLAN ID in the message match the local root
      and leaf VLAN ID, then continue to 3);

   2) else {

          if the bit V is cleared, then {

                if the PE is capable of VLAN mapping, then it MUST set
                VLAN-Mapping-Mode to TRUE;

                else {

                     A label release message with the error code "E-Tree
                     VLAN mapping not supported" is sent to the peer PE
                     and exit the process;

                     }

          }

          if the bit V is set, and the PE is capable of VLAN mapping,
          then the PE with the minimum IP address MUST set VLAN-Mapping-
          Mode to TRUE;

      }

   3) If the P bit is set, then:

      {

          If the PE is a leaf-only node itself, then a label release
      message with a status code "Leaf to Leaf PW released" is sent to
      the peer PE and exit the process;

          Else the PE SHOULD set the Optimized-Mode to TRUE.

      }

   If a PE has sent an E-Tree Sub-TLV but does not receive any E-Tree
   Sub-TLV in its peer's PW label mapping message, The PE SHOULD then



Jiang, et al           Expires March 30, 2015                [Page 15]


Internet-Draft         E-Tree Support in VPLS           September 2014

   establish a raw PW with this peer as in traditional VPLS and set
   Compatible-Mode to TRUE for this PW.

   Data plane processing for this PW is as following:

   If Optimized-Mode is TRUE, then data plane processing as described in
   Section 5.3.3 applies.

   If VLAN-Mapping-Mode is TRUE, then data plane processing as described
   in Section 5.3.1 applies.

   If Compatible-Mode is TRUE, then data plane processing is as
   described in Section 5.3.2.

   PW processing as described in [RFC4448] proceeds as usual for all
   cases.

6.2. BGP Extensions for E-Tree Support

   A new E-Tree extended community is proposed for E-Tree signaling in
   BGP VPLS:

                   +------------------------------------+
                   | Extended community type (2 octets) |
                   +------------------------------------+
                   |  Root VLAN (2 octets)              |
                   +------------------------------------+
                   |  Leaf VLAN (2 octets)              |
                   +------------------------------------+
                   |  Reserved                      |P|V|
                   +------------------------------------+


                     Figure 9 E-Tree Extended Community


   Where:

   o Root VLAN ID is the value of the local root VLAN.

   o Leaf VLAN ID is the value of the local leaf VLAN.

   o Reserved, 14 bits MUST be set to zero on transmit and be ignored
      on receive.

   o P is a Leaf-only bit, it is set to 1 to indicate that the PE is
      attached with only leaf nodes, and set to 0 otherwise.



Jiang, et al           Expires March 30, 2015                [Page 16]


Internet-Draft         E-Tree Support in VPLS           September 2014

   o V is a bit indicating the sender's VLAN mapping capability. A PE
      capable of VLAN mapping MUST set this bit, and clear it otherwise.

   The PEs attached with both leaf and root nodes MUST support BGP E-
   Tree signaling as described in this document, and SHOULD support VLAN
   mapping in their data planes. The traditional PE attached with only
   root nodes may also participate in an E-Tree service. If some PEs
   don't support VLAN mapping, global VLANs as per Section 5.2 MUST be
   provisioned for an E-Tree service.

   In BGP VPLS signaling, besides attaching a Layer2 Info Extended
   Community as detailed in [RFC4761], an E-Tree Extended Community MUST
   be further attached if a PE wishes to participate in an E-Tree
   service. The PE MUST include its local root VLAN ID and leaf VLAN ID
   in the E-Tree Extended Community. A PE attached with only leaf nodes
   of an E-Tree SHOULD set the P bit in the E-Tree Extended Community to
   1.

   A PE that receives a BGP UPDATE message with an E-Tree Extended
   Community from its peer PE, after saving the VLAN information for the
   PW, must process it as follows (after processing procedures as
   specified in Section 3.2 of [RFC4761]):

   1) if the root and leaf VLAN ID in the E-Tree Extended Community
      match the local root and leaf VLAN ID, then continue to 3);

   2) else {

          if the bit V is cleared, then {

                if the PE is capable of VLAN mapping, then it MUST set
                VLAN-Mapping-Mode to TRUE;

                else {

                     Log with a message "E-Tree VLAN mapping not
                     supported" and exit the process;

                     }

          if the bit V is set, and the PE is capable of VLAN mapping,
          the PE with the minimum IP address MUST set VLAN-Mapping-Mode
          to TRUE;

      }

   3) If the P bit is set {



Jiang, et al           Expires March 30, 2015                [Page 17]


Internet-Draft         E-Tree Support in VPLS           September 2014

          If the PE is a leaf-only PE itself, then forbids any traffic on
          the PW;

          Else the PE SHOULD set the Optimized-Mode to TRUE.

      }

   A PE which does not recognize this attribute shall ignore it silently.
   If a PE has sent an E-Tree Extended Community but does not receive
   any E-Tree Extended Community from its peer, the PE SHOULD then
   establish a raw PW with this peer as in traditional VPLS, and set
   Compatible-Mode to TRUE for this PW.

   Data plane in the VPLS is the same as described in Section 4.2 of
   [RFC4761], and data plane processing for a PW is the same as
   described at the end of Section 6.1.

7. OAM Considerations

   VPLS OAM requirements and framework as specified in [RFC6136] are
   applicable to E-Tree, as both Ethernet OAM frames and data traffic
   are transported over the same PW.

   Ethernet OAM for E-Tree including both service OAM and segment OAM
   frames shall undergo the same VLAN mapping as the data traffic; and
   root VLAN SHOULD be applied to segment OAM frames so that they are
   not filtered.

8. Applicability

   The solution is applicable to both LDP VPLS [RFC4762] and BGP VPLS
   [RFC4761].

   The solution is applicable to both "VPLS Only" networks and VPLS with
   Ethernet aggregation networks.

   The solution is also applicable to PBB VPLS networks.

9. Security Considerations

   Besides security considerations as described in [RFC4448], [RFC4761]
   and [RFC4762], this solution prevents leaf to leaf communication in
   the data plane of VPLS when its PEs are interconnected with PWs. In
   this regard, security can be enhanced for customers with this
   solution.





Jiang, et al           Expires March 30, 2015                [Page 18]


Internet-Draft         E-Tree Support in VPLS           September 2014

10.  IANA Considerations

   IANA is requested to allocate a value for E-Tree in the registry of
   Pseudowire Interface Parameters Sub-TLV type.

   Parameter ID   Length       Description
   =======================================
   TBD            8            E-Tree


   IANA is requested to allocate two new LDP status codes from the
   registry of name "STATUS CODE NAME SPACE". The following values are
   suggested:


   Range/Value     E     Description
   ------------- -----   ----------------------
   TBD             1     E-Tree VLAN mapping not supported
   TBD             0     Leaf to Leaf PW released

   IANA is requested to allocate a value for E-Tree in the registry of
   BGP Extended Community.

   Type Value          Name
   =======================================
   TBD                 E-Tree Info

11.  References

11.1.  Normative References

   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC4447] Martini, L., and et al, "Pseudowire Setup and Maintenance
             Using Label Distribution Protocol (LDP)", RFC 4447, April
             2006.

   [RFC4448] Martini, L., and et al, "Encapsulation Methods for
             Transport of Ethernet over MPLS Networks", RFC 4448, April
             2006.

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

   [RFC4762] Lasserre, M. and Kompella, V., "Virtual Private LAN
             Services using LDP", RFC 4762, January 2007.


Jiang, et al           Expires March 30, 2015                [Page 19]


Internet-Draft         E-Tree Support in VPLS           September 2014

   [RFC6136] Sajassi, A. and Mohan, D., "L2VPN OAM Requirements and
             Framework", RFC 6136, March 2011

11.2. Informative References

   [RFC3985] Bryant, S., and Pate, P., "Pseudo Wire Emulation Edge-to-
             Edge (PWE3) Architecture", RFC 3985, March 2005.

   [RFC4664] Andersson, L., and Rosen, E., "Framework for Layer 2
             Virtual Private Networks (L2VPNs)", RFC 4664, September
             2006.

   [RFC6246] Sajassi, A., and et al, "Virtual Private LAN Service (VPLS)
             Interoperability with Customer Edge (CE) Bridges", RFC 6246,
             June 2011

   [ETree-req] Key, R., et al, "Requirements for Metro Ethernet Forum
             (MEF) Ethernet-Tree (E-Tree) Support in Layer 2 Virtual
             Private Network (L2VPN)", RFC 7152, March 2014

   [ETree-frwk] Key, R., and et al, "A Framework for E-Tree Service over
             MPLS Network", draft-ietf-l2vpn-etree-frwk-10, Work in
             Progress

   [802.1Q-2011] IEEE 802.1Q, Media Access Control (MAC) Bridges and
             Virtual Bridge Local Area Networks, August 2011

   [PBB-VPLS] Balus, F., and et al., Extensions to VPLS PE model for
             Provider Backbone Bridging, RFC 7041, November 2013



12.  Acknowledgments

   The authors would like to thank Adrian Farrel, Susan Hares and Shane
   Amante for their valuable advices, thank Ben Mack-crane, Edwin
   Mallette, Donald Fedyk, Dave Allan, Giles Heron, Raymond Key, Josh
   Rogers, Sam Cao and Daniel Cohn for their valuable comments and
   discussions.










Jiang, et al           Expires March 30, 2015                [Page 20]


Internet-Draft         E-Tree Support in VPLS           September 2014

Appendix A. Other PE Models for E-Tree

A.1. A PE Model With a VSI and No bridge

   If there is no bridge module in a PE, the PE may consist of Native
   Service Processors (NSPs) as shown in Figure A.1 (adapted from Fig. 5
   of [RFC3985]) where  any transformation operation for VLANs (e.g.,
   VLAN insertion/removal or VLAN mapping) may be applied. Thus a root
   VLAN or leaf VLAN can be added by the NSP depending on the UNI type
   (root/leaf) associated with the AC over which the packet arrives.

   Further, when a packet with a leaf VLAN exits a forwarder and arrives
   at the NSP, the NSP must drop the packet if the egress AC is
   associated with a leaf UNI.

   Tagged PW and VLAN mapping work in the same way as in the typical PE
   model.

           +----------------------------------------+
           |                PE Device               |
   Multiple+----------------------------------------+
   AC      |      |          |        Single        | PW Instance
   <------>o  NSP #          +      PW Instance     X<---------->
           |      |          |                      |
           |------|  VSI     |----------------------|
           |      |          |        Single        | PW Instance
   <------>o  NSP #Forwarder +      PW Instance     X<---------->
           |      |          |                      |
           |------|          |----------------------|
           |      |          |        Single        | PW Instance
   <------>o  NSP #          +      PW Instance     X<---------->
           |      |          |                      |
           +----------------------------------------+

        Figure A.1  A PE model with a VSI and no bridge module

   This PE model may be used by an MTU-s in an H-VPLS network, or an N-
   PE in an H-VPLS network with non-bridging edge devices, wherein a
   spoke PW can be treated as an AC in this model.










Jiang, et al           Expires March 30, 2015                [Page 21]


Internet-Draft         E-Tree Support in VPLS           September 2014

A.2. A PE Model With external E-Tree interface


           +----------------------------------------+
           |                PE Device               |
   Root    +----------------------------------------+
   VLAN    |                 |        Single        | PW Instance
   <------>o                 +      PW Instance     X<---------->
           |                 |                      |
           |       VSI       |----------------------|
           |                 |        Single        | PW Instance
           |    Forwarder    +      PW Instance     X<---------->
           |                 |                      |
   Leaf    |                 |----------------------|
   VLAN    |                 |        Single        | PW Instance
   <------>o                 +      PW Instance     X<---------->
           |                 |                      |
           +----------------------------------------+

         Figure A.2  A PE model with external E-Tree interface

   A more simplified PE model is depicted in A.2, where Root/Leaf VLANs
   are directly or indirectly over a single PW connected to a same VSI
   forwarder in a PE, any transformation of E-Tree VLANs, e.g., VLAN
   insertion/removal or VLAN mapping, can be performed by some outer
   equipments, and the PE may further translate these VLANs into its own
   local VLANs. This PE model may be used by an N-PE in an H-VPLS
   network with bridging-capable devices, or scenarios such as providing
   E-Tree Network-to-Network (NNI) interfaces.




















Jiang, et al           Expires March 30, 2015                [Page 22]


Internet-Draft         E-Tree Support in VPLS           September 2014

   Authors' Addresses

   Yuanlong Jiang
   Huawei Technologies Co., Ltd.
   Bantian, Longgang district
   Shenzhen 518129, China
   Email: jiangyuanlong@huawei.com

   Lucy Yong
   Huawei USA
   207 Estrella Xing
   Georgetown TX, USA 78628
   Email: lucyyong@huawei.com

   Manuel Paul
   Deutsche Telekom
   Winterfeldtstr. 21
   10781 Berlin, Germany
   Email: manuel.paul@telekom.de

   Frederic Jounay
   Orange CH
   4 rue caudray 1020 Renens, Switzerland
   Email: frederic.jounay@orange.ch

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

   Wim Henderickx
   Alcatel-Lucent
   Copernicuslaan 50
   2018 Antwerp, Belgium
   Email: wim.henderickx@alcatel-lucent.com

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








Jiang, et al           Expires March 30, 2015                [Page 23]


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