Network Working Group                         Rafi Ram, Orckit-Corrigent
Internet Draft                           Amir Halperin, Orckit-Corrigent
Category: Standard Track                            Raymond Key, Telstra
Expires: April 2011



                                                         October 4, 2010


             Extension to LDP-VPLS for E-Tree Using Two PW
               draft-ram-l2vpn-ldp-vpls-etree-2pw-00.txt


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   This Internet-Draft will expire on April 4, 2011.


Abstract

   This document proposes a solution for Metro Ethernet Forum (MEF)
   Ethernet Tree (E-Tree) support in Virtual Private LAN Service using
   LDP Signaling (LDP-VPLS) [RFC4762]. The proposed solution is
   characterized by the use of two PWs between a pair of PEs. This
   solution is applicable for both VPLS and H-VPLS.









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Table of Contents

   1. Introduction....................................................3
   2. The Problem.....................................................3
   3. The 2-PW Solution...............................................3
   4. Extension to VPLS for E-Tree....................................4
   4.1. AC E-Tree Type................................................4
   4.2. PW VSI Type..................... .............................4
   4.3. Additional Filtering in Data Forwarding.......................4
   4.4. Root/Leaf PWs Signaling.......................................5
   4.5. Supporting Remote ACs.........................................5
   5. Backward Compatibility..........................................6
   6. Compliance with Requirements....................................6
   7. Security Considerations.........................................6
   8. IANA Considerations.............................................6
   9. Acknowledgements................................................6
   10. References.....................................................7
   10.1. Normative References.........................................7
   10.2. Informative References.......................................7
   Authors' Addresses.................................................7
   Copyright Notice...................................................7


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].


























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1. Introduction

   This document proposes a solution for Metro Ethernet Forum (MEF)
   Ethernet Tree (E-Tree) support in Virtual Private LAN Service using
   LDP Signaling (LDP-VPLS) [RFC4762].

   [Draft ETree VPLS Req] is used as requirement specification.

   The proposed solution is characterized by the use of two PWs between
   a pair of PEs, which requires extension to the currnet VPLS standard
   [RFC4762].

   This solution is applicable for both VPLS and H-VPLS.

   The proposed solution is composed of three main components:
     - Current standard LDP-VPLS [RFC4762]
     - Extension to LDP-VPLS specified in this document
     - PE local split horizon mechanism

2. The Problem

   [Draft ETree VPLS Req] identifies the problem when there are two or
   more PEs with both Root AC and Leaf AC.

                   <--------------E-Tree-------------->
                   +---------+              +---------+
                   |   PE1   |              |   PE2   |
   +---+           |  +---+  |              |  +---+  |           +---+
   |CE1+----AC1----+--+   |  |              |  |   +--+----AC3----+CE3|
   +---+ (Root AC) |  | V |  |              |  | V |  | (Root AC) +---+
                   |  | S +--+------PW------+--+ S |  |
   +---+           |  | I |  |              |  | I |  |           +---+
   |CE2+----AC2----+--+   |  |              |  |   +--+----AC4----+CE4|
   +---+ (Leaf AC) |  +---+  |              |  +---+  | (Leaf AC) +---+
                   +---------+              +---------+

   Figure 1: Problem Scenario for Leaf-to-Leaf Communication Restriction

   When PE2 receives a frame from PE1 via the Ethernet PW,
     - PE2 does not know whether the ingress AC is a Leaf AC or not
     - PE2 does not have sufficient information to enforce the
       Leaf-to-Leaf communication restriction

3. The 2-PW Solution

   A simple fix is to carry additional information with each frame on
   the PW, indicating whether the frame is originated from a Leaf AC or
   a Root AC on the ingress PE.

   This solution uses a pair of PWs between a pair of VPLS PEs.
     - First PW is used for frames originated from Root ACs
     - Second PW is used for frames originated from Leaf ACs


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                   <--------------E-Tree-------------->
                   +---------+              +---------+
                   |   PE1   |              |   PE2   |
   +---+           |  +---+  |              |  +---+  |           +---+
   |CE1+----AC1----+--+   |  |              |  |   +--+----AC3----+CE3|
   +---+ (Root AC) |  | V +--+-VSI Root PW -+--+ V |  | (Root AC) +---+
                   |  | S |  |              |  | S |  |
   +---+           |  | I +--+-VSI Leaf PW -+--+ I |  |           +---+
   |CE2+----AC2----+--+   |  |              |  |   +--+----AC4----+CE4|
   +---+ (Leaf AC) |  +---+  |              |  +---+  | (Leaf AC) +---+
                   +---------+              +---------+

   Figure 2: Two-PW Solution for Leaf-to-Leaf Communication Restriction

   Extension to current VPLS standard [RFC4762] is required.

4. Extension to VPLS for E-Tree

4.1. AC E-Tree Type

   Each AC connected to a specific VPLS instance on a PE MUST have an AC
   E-Tree Type attribute, either Leaf AC or Root AC. For backward
   compatibility, the default AC E-Tree Type MUST be Root.

   This AC E-Tree Type is locally configured on a PE and no signaling is
   required between PEs.

4.2. PW VSI Type

   Use a pair of PWs to interconnect between a pair of VPLS PEs:
     - Root PW use VSI Root PW type
     - Leaf PW use VSI Leaf PW type

   Both PWs SHALL use the same PW-id. This is for indicating in the
   local node that a pair of such PWs are part of the same logical VSI
   interface.

   On reception, the two PWs SHALL be handled as the same logical VSI
   interface with respect to MAC address learning/forwarding, e.g.
   traffic SHALL not forwarded between such PWs, MAC addresses arrives
   from one of the PWs SHALL be learnt with a common logical VSI
   interface.

   The VPLS processing entity SHALL send Root originated traffic via
   the Root PW, and SHALL send Leaf originated traffic via the Leaf PW.

4.3. Additional Filtering in Data Forwarding

   An egress PE SHALL NOT deliver a frame originated from a Leaf AC to
   another Leaf AC.




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   The following specifies how AC E-Tree type per frame is determined:
     - A frame received from a root PW indicates that the frame was
       originated from a Root AC.
     - A frame received from a leaf PW indicates that the frame was
       originated from a Leaf AC.
     - For the case where both ingress AC and egress AC are on the same
       PE, local split horizon implementation on the PE will be
       sufficient, and is not further discussed in this document.

4.4. Root/Leaf PWs Signaling

   Signaling of root and leaf PWs is require only when two PWs are used
   for interconnecting between pair of VSIs. For this purpose a new PW
   types SHALL be used:
     - VSI Root PW type SHALL be used to signal a root PW.
     - VSI Leaf PW type SHALL be used to signal a leaf PW.

   PW type signaling rules remains as defined in [RFC4447].

4.5. Supporting Remote AC

   When PW is used to interconnect between VSI and a remote AC (e.g. the
   PW1, PW2 in Figure 3), a Ethernet Raw or Ethernet tagged PW types
   SHALL be used as defined in [RFC4762].

               <----------------------E-Tree------------>
                          +-------+             +-------+
               +----+     |  PE1  |             |  PE2  |
 +---+         |    |     | +---+ |             | +---+ |
 |CE1+---AC1---+----+-PW1-+-+   | |             | |   | |           +---+
 +---+(Root AC)|    |     | |   | |             | |   +-+----AC4----+CE4|
               |PE-r|     | | V +-+-VSI Root PW-+-+ V | | (Root AC) +---+
 +---+         |    |     | |   | |             | |   | |
 |CE2+---AC2---+----+-PW2-+-+ S | |             | | S | |
 +---+(Leaf AC)|    |     | |   | |             | |   | |
               +----+     | | I +-+-VSI Leaf PW-+-+ I | |
 +---+                    | |   | |             | |   | |           +---+
 |CE3+--------AC3---------+-+   | |             | |   +-+----AC5----+CE5|
 +---+     (Leaf AC)      | +---+ |             | +---+ | (Leaf AC) +---+
                          +-------+             +-------+

   Figure 3: VPLS with Remote AC Connectivity

   In addition, the AC type i.e. Root or leaf, SHALL be locally
   provisioned on the VSI side to specifies the remote AC E-Tree Type per
   PW. Moreover, such PWs that are used for interconnecting between a remote
   AC and a VSI SHALL considered as separate logical VSI interfaces with
   respect to MAC address learning/forwarding e.g. traffic forwarding between
   such PWs is allowed as long as they are not both defined as Leaf.




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   In Figure 3, AC1 is remotely interconnected to the VPLS service via
   PW1, and AC2 is remotely interconnected to the VPLS service via PW2.

   AC1 is a Root AC and therefore the local type for PW1 in PE1 SHALL be
   Root.

   AC2 is a Leaf AC and therefore the local type for PW2 in PE1 SHALL be
   Leaf.

5. Backward Compatibility

   VSI root or VSI leaf PW type SHALL be used only in cases where both
   PEs are VPLS capable and both supports E-Tree root/leaf.

   In a case where one of the peers do not support E-Tree, an Ethernet
   Raw or Ethernet tagged PW types SHALL be used as defined in
   [RFC4762].

6. Compliance with Requirements

   This refers to [Draft ETree VPLS Req] Section 5. Requirements.

   The solution prohibits communication between any two Leaf ACs in a
   VPLS instance.

   The solution allows multiple Root ACs in a VPLS instance.

   The solution allows Root AC and Leaf AC of a VPLS instance co-exist
   on any PE.

   The solution is applicable to LDP-VPLS [RFC4762].

   The solution is applicable to Case 1: Single technology "VPLS Only".

7. Security Considerations

   This will be added in later version.

8. IANA Considerations

   Additional assignments will be required for the new MPLS PW types
   introduced in Section 4.2. Details will be added in later version.

9. Acknowledgements

   This will be added in later version.








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10. References

10.1. 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 al, Pseudowire Setup and Maintenance
                Using the Label Distribution Protocol (LDP), April 2006

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

10.2. Informative References

   [Draft VPLS ETree Req]
                Key, et al., Requirements for MEF E-Tree Support in
                VPLS, draft-key-l2vpn-vpls-etree-reqt-01.txt,
                September 2010


Authors' Addresses

   Rafi Ram
   Orckit-Corrigent
   126 Yigal Alon st.
   Tel Aviv, Israel
   Email: rafir@orckit.com

   Amir Halperin
   Orckit-Corrigent
   126 Yigal Alon st.
   Tel Aviv, Israel
   Email: amirh@orckit.com

   Raymond Key
   Telstra
   242 Exhibition Street, Melbourne
   VIC 3000, Australia
   Email: raymond.key@team.telstra.com

Copyright Notice

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

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (http://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.


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