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Versions: 00 01                                                         
Networking Working Group                                         R. Chen
Internet-Draft                                                   Y. Wang
Intended status: Standards Track                         ZTE Corporation
Expires: September 15, 2011                                       L. Guo
                                                           China Telecom
                                                          March 14, 2011


  LDP Extensions for Optimized MAC Address Withdrawal in VPLS model 3
                     supporting Qualified learning
               draft-chen-l2vpn-vpls-mac-opt-qualified-01

Abstract

   This draft defines a method for optimized MAC Address Withdrawal in
   VPLS model 3 ([RFC4664]) supporting qualified learning ([RFC4762]).
   Some extensions are made based on the MAC Address Withdrawal
   procedures defined in [RFC4762] and
   [I-D.ietf-l2vpn-vpls-ldp-mac-opt], in order to enable a PE to remove
   only the MAC addresses, which belong to MAC address space affected by
   topology change.

Status of this Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   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."

   This Internet-Draft will expire on September 15, 2011.

Copyright Notice

   Copyright (c) 2011 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



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   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.


Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Conventions used in this document . . . . . . . . . . . . . . . 3
     2.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . 4
   3.  Problem Description . . . . . . . . . . . . . . . . . . . . . . 5
   4.  Optimized MAC Flush Mechanism . . . . . . . . . . . . . . . . . 6
     4.1.  MAC Address Space TLV . . . . . . . . . . . . . . . . . . . 6
     4.2.  MAC Address Space TLV Processing Rules  . . . . . . . . . . 7
     4.3.  Optimized MAC Flush Procedures  . . . . . . . . . . . . . . 8
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 8
   6.  Security Considerations . . . . . . . . . . . . . . . . . . . . 8
   7.  Normative references  . . . . . . . . . . . . . . . . . . . . . 8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 9






























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1.  Introduction

   There are operators deploying VPLS with qualified learning mode
   [RFC4762], so as to reduce the number of VPLS instance.  By using
   VLAN within VPLS and qualified learning mode to separate customer
   internally, current defined VPLS MAC address withdraw mechanism will
   flush MAC addresses VLAN space which are not affected due to topology
   change.

   [RFC4762] defines a basic MAC Address Withdrawal mechanism to remove
   or unlearn MAC addresses for faster convergence on topology change.
   It defines MAC List TLV which contains a list of MAC addresses to be
   flushed in LDP Address Withdraw Message, and when a MAC List TLV
   contains a large number of MAC addresses, it would be preferable to
   send a LDP Address Withdraw Message with an empty MAC List.

   As per the rules in [RFC4762], on receiving a MAC Address Withdrawal
   Message with MAC List TLV, a PE removes the association between the
   MAC address and the AC or PW over which this message is received.
   For a MAC Address Withdraw message with empty MAC list, a PE removes
   all MAC addresses except the MAC addresses learned over the newly
   activated PW.  The PE further transmits a MAC Address Withdrawal
   message to each remote PE in the VPLS network.  The problem is that
   it will flush MAC addresses which are not affected due to topology
   change, thus leading to unnecessary flooding and relearning.

   Draft [I-D.ietf-l2vpn-vpls-ldp-mac-opt] defines an extension to the
   MAC Address Withdrawal procedure with empty MAC List ([RFC4762]).  It
   is accomplished by sending an LDP Address Withdraw Message with the
   empty MAC addresses and PE-ID TLV.  When a PE device receives a MAC
   Address Withdrawal message with a PE-ID TLV, it SHOULD flush all the
   MAC addresses learned from the PW, which terminates in the remote VSI
   identified by the PE-ID element.  Comparing with [RFC4762], this
   mechanism narrows the scope of MAC address flush to PE-ID elements.
   But if this mechanism is used in VPLS model 3 ([RFC4664]) supporting
   qualified learning ([RFC4762]), it also flushes MAC addresses
   belonging to MAC address space which are not affected due to topology
   change.

   This draft describes the problem and a solution to optimize the MAC
   flush procedure in [RFC4762] and [I-D.ietf-l2vpn-vpls-ldp-mac-opt],
   and enable it to flush only the MAC addresses belonging to the MAC
   address space affected by topology change.


2.  Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",



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   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC2119.

2.1.  Terminology

   AC: Attachment Circuit

   CE: Customer Edge device

   LDP: Label Distribution Protocol

   PE: Provider Edge

   PW: Pseudowire

   MTU-s: Multi-Tenant Unit switch



































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3.  Problem Description


                                                                          VLAN1
                                               VLAN2                      VLAN2
                                               CE-2                       CE-3
                                              /                           /
                                    PE-1     /                  PE-3     /
                                  +--------+/                 +--------+/
                                  |        |                  |        |
                                  |   --   |      PW2         |   --   |
      VLAN1                       |  /  \  |------------------|  /  \  |
        CE-1               /------|  \ s/  |                  |  \S /  |
          \     primary spoke PW  |   --   |           /------|   --   |
           \             /        +--------+          /       +--------+
            \    (MTU-s)/              |    \ PW3    /          PW6|
             +--------+/               |     \      /              |
             |        |                |      \    /               |
             |   --   |            PW1 |       \  /                |
             |  /  \  |                |      H-VPLS Full Mesh Core|
             |  \S /  |                |       / \                 |
             |   --   |                |      /   \                |
             +--------+\               |  PW4/     \               |
                 backup spoke PW       |    /       \              |
                         \        +--------+         \--------+--------+
                          \       |        |                  |        |
                           \------|  --    |     PW5          |  --    |
                                  | /  \   |------------------| /  \   |
                                  | \s /   |                  | \S /   |
                                  |  --    |                  |  --    |
                                 /+--------+                  +--------+
                                /   PE-2                         PE-4
                               /
                              CE-4
                             VLAN1
                             VLAN2


          Figure 1: Dual homed MTU-s in two tier hierarchy H-VPLS

   Figure 1 is an example for the dual-homing access topology in VPLS
   model 3 supporting qualified learning.

   There are four VLANs in Figure 1, and each customer VLAN has its own
   broadcast domain and MAC address space.  CE-1 and CE-3 belong to
   VLAN1, CE-2 and CE-4 belong to VLAN2.

   CE-1, CE-2, CE-3 and CE-4 connect with MTU-S, PE-1, PE-4 and PE-2



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   respectively.  The MTU-S is dual-homed to PE-1 and PE-2.  Only the
   primary spoke PW is active at MTU-s, thus PE-1 is acting as the
   active device to reach the full mesh in the VPLS instance.

   When MTU-s switches to the backup spoke PW and activates it, PE-2
   becomes the active device to reach the full mesh core.  Traffic
   entering the H-VPLS from CE-1 is diverted by the MTU-s to the backup
   spoke PW.  For faster convergence MTU-s may desire to unlearn or
   remove the MAC addresses belonging to VLAN1 and learned from the PW
   that terminates at PE-1 MUST be removed.  Once the backup PW has been
   made active, MTU-s may send a MAC flush message to PE-2.

   As per the rules defined in [RFC4762], PE-2 flushes all of the MAC
   addresses learned in the VPLS from the PWs terminating at PE-1, PE-3
   and PE-4.  PE-2 further relays MAC flush messages to PE-1, PE-3 and
   PE-4.  Same processing rule applies at all those PE.

   As per the rules defined in [I-D.ietf-l2vpn-vpls-ldp-mac-opt], PE-2
   flushes all of the MAC addresses learned in the VPLS from the PWs
   terminating at PE-1.  In fact, PE2 need not flush the MAC addresses
   belonging to VLAN2 and learned over PW1.There are multi-Mac addresses
   spaces in a single VPLS, and the affected Mac addresses spaces is
   only VLAN1.  PE-2 only need flush and relearn MAC addresses belong to
   VLAN1 and learned over PW1.

   With the number of PE in the full-mesh increases, the number of
   unaffected MAC addresses flushed in a VPLS instance also increases,
   thus leading to unnecessary flooding and relearning.


4.  Optimized MAC Flush Mechanism

4.1.   MAC Address Space TLV

   This draft proposes a MAC Address Space TLV, it is carried in the LDP
   Address Withdraw Message.  The MAC Address Space TLV carries a MAC
   address Space which are affected due to topology change.  When a PE
   receives a LDP Address Withdraw message with MAC Address Space TLV,
   then the PE only flushes the suspect MAC addresses belonging to the
   MAC Address Space elements.

   The new MAC Address Space TLV format is as follows:









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        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |U|F| MAC Address Space TLV(TBD)|            Length             |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                      MAC address space                        |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



                  Figure 2: MAC Address Space TLV format

   U bit: Unknown bit.  This bit MUST be set to 1.  If the MAC address
   Space format is not understood, then it MUST be ignored.

   F bit: Forward bit.  This bit MUST be set to 0.  Since the LDP
   mechanism used here is targeted, the TLV MUST NOT be forwarded.

   Type: Type field.  This identifies the TLV type as MAC Address Space
   TLV.

   Length: Length field.  This field specifies the total length in
   octets of value in MAC Address Space TLV.

   MAC Address Space: This identifies the MAC addresses Space which are
   affected due to topology change.

   The MAC address space TLV should immediately be after the MAC address
   list TLV.  It is used to indicate MAC address space that these MAC
   address list belongs to.

4.2.  MAC Address Space TLV Processing Rules

   If a PE receives a MAC Address Withdraw with MAC Address Space TLV
   and empty MAC list, it SHOULD remove all the MAC addresses belonging
   to the MAC Address Spaces in a VPLS instance, except the MAC
   addresses learned over the PW associated with this signaling session
   over which the message was received.

   If a PE receives a MAC Address Withdraw with MAC Address Space TLV
   and MAC list TLV, it SHOULD remove the MAC address belonging to the
   MAC Address Space in a VPLS instance.

   If a PE receives a MAC Address Withdraw with MAC Address Space TLV
   and PE-ID TLV, from the specified MAC Address Space which is
   identified by MAC Address Space TLV, it SHOULD remove all the MAC
   addresses learned from the PW, which terminates at the PE identified
   by the PE-ID.



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   If a PE that doesn't support MAC Address Space TLV, receives a MAC
   flush message with this option, it MUST ignore the option and follow
   the processing rules as per [RFC4762] and
   [I-D.ietf-l2vpn-vpls-ldp-mac-opt].

4.3.  Optimized MAC Flush Procedures

   This section explains the optimized MAC flush procedure in the
   scenario shown in Figure 1.

   When the backup PW is activated by MTU-s, it may send MAC Address
   Withdraw message to PE-2 with the optional PE-ID TLV and MAC Address
   Space TLV.  Upon receipt of the MAC Address Withdraw message, PE-2
   identifies the VPLS instance that requires MAC Address Withdraw from
   the FEC element in the FEC TLV.  From the PE-ID TLV, PE-2 identifies
   the PW in the VPLS that terminates in PE-1.  From the MAC Address
   Space TLV, PE-2 identifies MAC addresses Space which are affected due
   to topology change.  PE-2 removes all MAC addresses belong to VLAN1
   and learned over PW1.

   PE-2 relays MAC Address Withdraw messages with the received MAC
   Address Space TLV and PE-ID to all its peer PE devices.  When the
   message is received at PE-3/PE-4, MAC addresses belonging to VLAN1
   and learned over the PW that terminates at PE1 MUST be removed.


5.   IANA Considerations

   The type field in the MAC List TLV is defined as 0x406 and is subject
   to IANA approval


6.  Security Considerations

   Security considerations discussed in [RFC4762] and [I-D.ietf-l2vpn-
   vpls-ldp-mac-opt] apply to this document.


7.  Normative references

   [I-D.ietf-l2vpn-vpls-ldp-mac-opt]
              Dutta, P., Balus, F., Calvignac, G., and O. Stokes, "LDP
              Extensions for Optimized MAC Address Withdrawal in
              H-VPLS", draft-ietf-l2vpn-vpls-ldp-mac-opt-03 (work in
              progress), October 2010.

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



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

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

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

   [RFC5036]  Andersson, L., Minei, I., and B. Thomas, "LDP
              Specification", RFC 5036, October 2007.


Authors' Addresses

   Ran Chen
   ZTE Corporation
   4F,RD Building 2,Zijinghua Road
   Yuhuatai District,Nanjing 210012
   P.R.China

   Phone: +86 025 52878135
   Email: chen.ran@zte.com.cn


   Yubao Wang
   ZTE Corporation
   4F,RD Building 2,Zijinghua Road
   Yuhuatai District,Nanjing 210012
   P.R.China

   Phone: +86 025 52872130
   Email: wang.yubao2@zte.com.cn


   Liang Guo
   China Telecom
   26/F,109 Zhongshan Ave
   Tianhe District,Guangzhou 510630
   P.R.China

   Phone: +86 020 38639595
   Email: guoliang@gsta.com






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